Systemic and pulmonary veins
HEPATIC PORTAL VEIN
Veins collect blood from the body's tissues and organs by means of an elaborate venous network that drains into the right atrium of the heart via the superior and inferior venae cavae (Figure 21-30 ). The branching pattern of peripheral veins is much more variable than that of arteries. The discussion that follows is based on the most common arrangement of veins. Complementary arteries and veins commonly run side by side, and in many cases they have comparable names.
One significant difference between the arterial and venous systems concerns the distribution of major veins in the neck and limbs. Arteries in these areas are located deep beneath the skin, protected by bones and surrounding soft tissues. In contrast, the neck and limbs generally have two sets of peripheral veins, one superficial and the other deep. This dual venous drainage is important for controlling body temperature. In hot weather, venous blood flows in superficial veins, where heat loss can occur; in cold weather, blood is routed to the deep veins to minimize heat loss.
The Superior Vena Cava
All the body's systemic veins (except the cardiac veins) drain into either the superior vena cava or the inferior vena cava. The superior vena cava (SVC) receives blood from the tissues and organs of the head, neck, chest, shoulders, and upper limbs (Figure 21-30).
Venous Return from the Cranium. Numerous superficial cerebral veins and internal cerebral veins drain the cerebral hemispheres. The superficial cerebral veins and small veins of the brain stem, such as the pontal and petrosal veins, empty into a network of dural sinuses. These sinuses include the superior and inferior sagittal sinuses, the petrosal sinuses, the occipital sinus, the left and right transverse sinuses, and the straight sinus (Figure 21-31 b ). The largest sinus, the superior sagittal sinus, is in the falx cerebri (see Figure 14-4b). The majority of the internal cerebral veins collect inside the brain to form the great cerebral vein, which collects blood from the interior of the cerebral hemispheres and the choroid plexus and delivers it to the straight sinus. Other cerebral veins drain into the cavernous sinus in company with numerous small veins from the orbit.
The venous sinuses converge within the dura mater in the region of the lambdoidal suture. The left and right transverse sinuses converge at the base of the petrous portion of the temporal bone, forming the sigmoid sinus, which penetrates the jugular foramen and leaves the skull as the internal jugular vein. The internal jugular vein descends parallel to the common carotid artery in the neck.
Vertebral veins drain the cervical spinal cord and the posterior surface of the skull. These vessels descend within the transverse foramina of the cervical vertebrae, in company with the vertebral arteries. The vertebral veins empty into the brachiocephalic veins of the chest (discussed later in the chapter).
Superficial Veins of the Head and Neck. Superficial veins of the head collect to form the temporal, facial, and maxillary veins (Figure 21-31ab). The temporal and maxillary veins drain into the external jugular vein. The facial vein drains into the internal jugular vein. A broad anastomosis between the external and internal jugular veins at the angle of the mandible provides dual venous drainage of the face, scalp, and cranium. The external jugular vein descends toward the chest just beneath the skin on the anterior surface of the sternocleidomastoid muscle. Posterior to the clavicle, the external jugular empties into the subclavian vein. In healthy individuals, the external jugular vein is easily palpable, and a jugular venous pulse (JVP) can sometimes be seen at the base of the neck.
Venous Return from the Upper Limbs. The digital veins empty into the superficial and deep palmar veins of the hand, which are interconnected to form the palmar venous arches. The superficial arch empties into the cephalic vein, which ascends along the radial side of the forearm, the median antebrachial vein, and the basilic vein, which ascends on the ulnar side (Figure 21-32 ). Anterior to the elbow is the superficial median cubital vein. This vein passes from the cephalic vein, medially and at an oblique angle, to connect to the basilic vein. (The median cubital is the vein from which venous blood samples are typically collected.) From the elbow, the basilic vein passes superiorly along the median surface of the biceps brachii.
The deep palmar veins drain into the radial vein and the ulnar vein. After crossing the elbow, these veins fuse to form the brachial vein. The brachial vein lies parallel to the brachial artery. As the brachial vein continues toward the trunk, it receives blood from the basilic vein before entering the axilla as the axillary vein.
Formation of the Superior Vena Cava. The cephalic vein joins the axillary vein on the lateral surface of the first rib, forming the subclavian vein, which continues into the chest. The subclavian vein passes superior to the first rib and along the superior margin of the clavicle. The vein then meets and merges with the external and internal jugular veins of that side. This fusion creates the brachiocephalic vein, or innominate vein, which penetrates the body wall and enters the thoracic cavity.
Each brachiocephalic vein receives blood from the vertebral vein of the same side, which drains the back of the skull and spinal cord. Near the heart, at the level of the first and second ribs, the left and right brachiocephalic veins combine, creating the superior vena cava. Close to the point of fusion, the internal thoracic vein empties into the brachiocephalic vein.
The azygos vein is the major tributary of the superior vena cava. This vessel ascends from the lumbar region over the right side of the vertebral column to invade the thoracic cavity through the diaphragm. The azygos joins the superior vena cava at the level of vertebra T2. On the left side, the azygos receives blood from the smaller hemiazygos vein, which in many people also drains into the left brachiocephalic through the highest intercostal vein.
The azygos and hemiazygos veins are the chief collecting vessels of the thorax. They receive blood from (1) numerous intercostal veins, which receive blood from the chest muscles, (2) esophageal veins, which drain blood from the esophagus, and (3) smaller veins draining other mediastinal structures.
SYSTEM of internal jugular vein and SUPERIOR VENA CAVA
Superior vena cava is generated by reason of confluence of right and left brachiocephalic veins behind joint of cartilage of first right rib with sternum. Superior vena cava on level of third right cartilage empties into right atrium. Azygos vein empties into superior vena cava from right side.
Brachiocephalic veins form by the confluence of subclavian vein, internal jugular and sometimes External jugular vein. This place is called as venous angle, where thoracic lymphatic duct empties (left side), and right lymphatic duct (right side). Inferior thyroid veins from thyroid plexus, inferior laryngeal vein and thymic vein, pericardial veins from pericardium, bronchic veins and esophageal veins from esophagus fall into brachiocephalic veins.
Azygos vein continues into thoracic cavity from right ascending lumbar vein. Azygos vein receives posterior intercostal veins, esophageal veins, bronchic veins, pericardial veins and mediastinal veins, also hemizygos vein.
Internal jugular vein is a largest vessel, which drainage blood from area of head and neck. Internal jugular vein originates from sygmoid sinus of dura mater encephali, where it begins on level of jugular foramen by superior bulb and lies behind internal carotid artery and vagus nerve. Inferior jugular bulb is situated near the confluence with subclavian vein.
Internal jugular has the following extracranial influxes:
• pharyngeal veins;
• lingual vein;
• superior thyroid vein;
• facial vein, which receives retromandibular vein
• retromandibular vein empties into facial vein, or into internal jugular vein.
Follow vessels belong to intracranial tributaries of internal jugular vein:
• venous sinuses of dura mater encephali and veins of brain:
The veins of the brain possess no valves, and their walls, owing to the absence of muscular tissue, are extremely thin. They pierce the arachnoid membrane and the inner or meningeal layer of the dura mater, and open into the cranial venous sinuses. They may be divided into two sets, cerebral and cerebellar.
The cerebral veins (vv. cerebri) are divisible into external and internal groups according as they drain the outer surfaces or the inner parts of the hemispheres.
The external veins are the superior, inferior, and middle cerebral.
The Superior Cerebral Veins (vv. cerebri superiores), eight to twelve in number, drain the superior, lateral, and medial surfaces of the hemispheres, and are mainly lodged in the sulci between the gyri, but some run across the gyri. They open into the superior sagittal sinus; the anterior veins runs nearly at right angles to the sinus; the posterior and larger veins are directed obliquely forward and open into the sinus in a direction more or less opposed to the current of the blood contained within it.
The Middle Cerebral Vein (v. cerebri media; superficial Sylvian vein) begins on the lateral surface of the hemisphere, and, running along the lateral cerebral fissure, ends in the cavernous or the sphenoparietal sinus. It is connected (a) with the superior sagittal sinus by the great anastomotic vein of Trolard, which opens into one of the superior cerebral veins; (b) with the transverse sinus by the posterior anastomotic vein of Labbé, which courses over the temporal lobe.
The Inferior Cerebral Veins (vv. cerebri inferiores), of small size, drain the under surfaces of the hemispheres. Those on the orbital surface of the frontal lobe join the superior cerebral veins, and through these open into the superior sagittal sinus; those of the temporal lobe anastomose with the middle cerebral and basal veins, and join the cavernous, sphenoparietal, and superior petrosal sinuses.
The basal vein is formed at the anterior perforated substance by the union of (a) a small anterior cerebral vein which accompanies the anterior cerebral artery, (b) the deep middle cerebral vein (deep Sylvian vein), which receives tributaries from the insula and neighboring gyri, and runs in the lower part of the lateral cerebral fissure, and (c) the inferior striate veins, which leave the corpus striatum through the anterior perforated substance. The basal vein passes backward around the cerebral peduncle, and ends in the internal cerebral vein (vein of Galen); it receives tributaries from the interpeduncular fossa, the inferior horn of the lateral ventricle, the hippocampal gyrus, and the mid-brain.
The Internal Cerebral Veins (vv. cerebri internæ; veins of Galen; deep cerebral veins) drain the deep parts of the hemisphere and are two in number; each is formed near the interventricular foramen by the union of the terminal and choroid veins. They run backward parallel with one another, between the layers of the tela chorioidea of the third ventricle, and beneath the splenium of the corpus callosum, where they unite to form a short trunk, the great cerebral vein; just before their union each receives the corresponding basal vein.
The terminal vein (v. terminalis; vena corporis striati) commences in the groove between the corpus striatum and thalamus, receives numerous veins from both of these parts, and unites behind the crus fornicis with the choroid vein, to form one of the internal cerebral veins. The choroid vein runs along the whole length of the choroid plexus, and receives veins from the hippocampus, the fornix, and the corpus callosum.
The Great Cerebral Vein (v. cerebri magna [Galeni]; great vein of Galen) (565), formed by the union of the two internal cerebral veins, is a short median trunk which curves backward and upward around the splenium of the corpus callosum and ends in the anterior extremity of the straight sinus.
The cerebellar veins are placed on the surface of the cerebellum, and are disposed in two sets, superior and inferior. The superior cerebellar veins (vv. cerebelli superiores) pass partly forward and medialward, across the superior vermis, to end in the straight sinus and the internal cerebral veins, partly lateralward to the transverse and superior petrosal sinuses. The inferior cerebellar veins (vv. cerebelli inferiores) of large size, end in the transverse, superior petrosal, and occipital sinuses.
The sinuses of the dura mater are venous channels which drain the blood from the brain; they are devoid of valves, and are situated between the two layers of the dura mater and lined by endothelium continuous with that which lines the veins. They may be divided into two groups: (1) a postero-superior, at the upper and back part of the skull, and (2) an antero-inferior, at the base of the skull.
The postero-superior group comprises the
Superior sagittal sinus laid open after remova of the skull cap. The chordæ Willisii are clearly seen. The venous lacunæ are also well shown; from two of them probes are passed into the superior sagittal sinus.
The superior sagittal sinus (sinus sagittalis superior; superior longitudinal sinus) (566, 567) occupies the attached or convex margin of the falx cerebri. Commencing at the foramen cecum, through which it receives a vein from the nasal cavity, it runs from before backward, grooving the inner surface of the frontal, the adjacent margins of the two parietals, and the superior division of the cruciate eminence of the occipital; near the internal occipital protuberance it deviates to one or other side (usually the right), and is continued as the corresponding transverse sinus. It is triangular in section, narrow in front, and gradually increases in size as it passes backward. Its inner surface presents the openings of the superior cerebral veins, which run, for the most part, obliquely forward, and open chiefly at the back part of the sinus, their orifices being concealed by fibrous folds; numerous fibrous bands (chordæ Willisii) extend transversely across the inferior angle of the sinus; and, lastly, small openings communicate with irregularly shaped venous spaces (venous lacunæ) in the dura mater near the sinus. There are usually three lacunæ on either side of the sinus: a small frontal, a large parietal, and an occipital, intermediate in size between the other two (Sargent 106). Most of the cerebral veins from the outer surface of the hemisphere open into these lacunæ, and numerous arachnoid granulations (Pacchionian bodies) project into them from below. The superior sagittal sinus receives the superior cerebral veins, veins from the diploë and dura mater, and, near the posterior extremity of the sagittal suture, veins from the pericranium, which pass through the parietal foramina.
The numerous communications exist between this sinus and the veins of the nose, scalp, and diploë.
The inferior sagittal sinus (sinus sagittalis inferior; inferior longitudinal sinus) (567) is contained in the posterior half or two-thirds of the free margin of the falx cerebri. It is of a cylindrical form, increases in size as it passes backward, and ends in the straight sinus. It receives several veins from the falx cerebri, and occasionally a few from the medial surfaces of the hemispheres.
The straight sinus (sinus rectus; tentorial sinus) (567, 569) is situated at the line of junction of the falx cerebri with the tentorium cerebelli. It is triangular in section, increases in size as it proceeds backward, and runs downward and backward from the end of the inferior sagittal sinus to the transverse sinus of the opposite side to that into which the superior sagittal sinus is prolonged. Its terminal part communicates by a cross branch with the confluence of the sinuses. Besides the inferior sagittal sinus, it receives the great cerebral vein (great vein of Galen) and the superior cerebellar veins. A few transverse bands cross its interior.
The transverse sinuses (sinus transversus; lateral sinuses) (569, 570) are of large size and begin at the internal occipital protuberance; one, generally the right, being the direct continuation of the superior sagittal sinus, the other of the straight sinus. Each transverse sinus passes lateralward and forward, describing a slight curve with its convexity upward, to the base of the petrous portion of the temporal bone, and lies, in this part of its course, in the attached margin of the tentorium cerebelli; it then leaves the tentorium and curves downward and medialward to reach the jugular foramen, where it ends in the internal jugular vein. In its course it rests upon the squama of the occipital, the mastoid angle of the parietal, the mastoid part of the temporal, and, just before its termination, the jugular process of the occipital; the portion which occupies the groove on the mastoid part of the temporal is sometimes termed the sigmoid sinus. The transverse sinuses are frequently of unequal size, that formed by the superior sagittal sinus being the larger; they increase in size as they proceed from behind forward. On transverse section the horizontal portion exhibits a prismatic, the curved portion a semicylindrical form. They receive the blood from the superior petrosal sinuses at the base of the petrous portion of the temporal bone; they communicate with the veins of the pericranium by means of the mastoid and condyloid emissary veins; and they receive some of the inferior cerebral and inferior cerebellar veins, and some veins from the diploë. The petrosquamous sinus, when present, runs backward along the junction of the squama and petrous portion of the temporal, and opens into the transverse sinus.
The occipital sinus (sinus occipitalis) (570) is the smallest of the cranial sinuses. It is situated in the attached margin of the falx cerebelli, and is generally single, but occasionally there are two. It commences around the margin of the foramen magnum by several small venous channels, one of which joins the terminal part of the transverse sinus; it communicates with the posterior internal vertebral venous plexuses and ends in the confluence of the sinuses.
The Confluence of the Sinuses (confluens sinuum; torcular Herophili) is the term applied to the dilated extremity of the superior sagittal sinus. It is of irregular form, and is lodged on one side (generally the right) of the internal occipital protuberance. From it the transverse sinus of the same side is derived. It receives also the blood from the occipital sinus, and is connected across the middle line with the commencement of the transverse sinus of the opposite side.
The antero-inferior group of sinuses comprises the
Two Superior Petrosal.
Two Inferior Petrosal.
The cavernous sinuses (sinus cavernosus) (570, 571) are so named because they present a reticulated structure, due to their being traversed by numerous interlacing filaments. They are of irregular form, larger behind than in front, and are placed one on either side of the body of the sphenoid bone, extending from the superior orbital fissure to the apex of the petrous portion of the temporal bone. Each opens behind into the petrosal sinuses. On the medial wall of each sinus is the internal carotid artery, accompanied by filaments of the carotid plexus; near the artery is the abducent nerve; on the lateral wall are the oculomotor and trochlear nerves, and the ophthalmic and maxillary divisions of the trigeminal nerve (571). These structures are separated from the blood flowing along the sinus by the lining membrane of the sinus. The cavernous sinus receives the superior ophthalmic vein through the superior orbital fissure, some of the cerebral veins, and also the small sphenoparietal sinus, which courses along the under surface of the small wing of the sphenoid. It communicates with the transverse sinus by means of the superior petrosal sinus; with the internal jugular vein through the inferior petrosal sinus and a plexus of veins on the internal carotid artery; with the pterygoid venous plexus through the foramen Vesalii, foramen ovale, and foramen lacerum, and with the angular vein through the ophthalmic vein. The two sinuses also communicate with each other by means of the anterior and posterior intercavernous sinuses.
The ophthalmic veins (572), two in number, superior and inferior, are devoid of valves.
The Superior Ophthalmic Vein (v. ophthalmica superior) begins at the inner angle of the orbit in a vein named the nasofrontal which communicates anteriorly with the angular vein; it pursues the same course as the ophthalmic artery, and receives tributaries corresponding to the branches of that vessel. Forming a short single trunk, it passes between the two heads of the Rectus lateralis and through the medial part of the superior orbital fissure, and ends in the cavernous sinus.
The Inferior Ophthalmic Vein (v. ophthalmica inferior) begins in a venous net-work at the forepart of the floor and medial wall of the orbit; it receives some veins from the Rectus inferior, Obliquus inferior, lacrimal sac and eyelids, runs backward in the lower part of the orbit and divides into two branches. One of these passes through the inferior orbital fissure and joins the pterygoid venous plexus, while the other enters the cranium through the superior orbital fissure and ends in the cavernous sinus, either by a separate opening, or more frequently in common with the superior ophthalmic vein.
The intercavernous sinuses (sini intercavernosi) (570) are two in number, an anterior and a posterior, and connect the two cavernous sinuses across the middle line. The anterior passes in front of the hypophysis cerebri, the posterior behind it, and they form with the cavernous sinuses a venous circle (circular sinus) around the hypophysis. The anterior one is usually the larger of the two, and one or other is occasionally absent.
The superior petrosal sinus (sinus petrosus superior) (570) small and narrow, connects the cavernous with the transverse sinus. It runs lateralward and backward, from the posterior end of the cavernous sinus, over the trigeminal nerve, and lies in the attached margin of the tentorium cerebelli and in the superior petrosal sulcus of the temporal bone; it joins the transverse sinus where the latter curves downward on the inner surface of the mastoid part of the temporal. It receives some cerebellar and inferior cerebral veins, and veins from the tympanic cavity.
The inferior petrosal sinus (sinus petrosus inferior) (570) is situated in the inferior petrosal sulcus formed by the junction of the petrous part of the temporal with the basilar part of the occipital. It begins in the postero-inferior part of the cavernous sinus, and, passing through the anterior part of the jugular foramen, ends in the superior bulb of the internal jugular vein. The inferior petrosal sinus receives the internal auditory veins and also veins from the medulla oblongata, pons, and under surface of the cerebellum.
The exact relation of the parts to one another in the jugular foramen is as follows: the inferior petrosal sinus lies medially and anteriorly with the meningeal branch of the ascending pharyngeal artery, and is directed obliquely downward and backward; the transverse sinus is situated at the lateral and back part of the foramen with a meningeal branch of the occipital artery, and between the two sinuses are the glossopharyngeal, vagus, and accessory nerves. These three sets of structures are divided from each other by two processes of fibrous tissue. The junction of the inferior petrosal sinus with the internal jugular vein takes place on the lateral aspect of the nerves.
The basilar plexus (plexus basilaris; transverse or basilar sinus) (571) consists of several interlacing venous channels between the layers of the dura mater over the basilar part of the occipital bone, and serves to connect the two inferior petrosal sinuses. It communicates with the anterior vertebral venous plexus.
Emissary Veins (emissaria).—The emissary veins pass through apertures in the cranial wall and establish communication between the sinuses inside the skull and the veins external to it. Some are always present, others only occasionally so. The principal emissary veins are the following: (1) A mastoid emissary vein, usually present, runs through the mastoid foramen and unites the transverse sinus with the posterior auricular or with the occipital vein. (2) A parietal emissary vein passes through the parietal foramen and connects the superior sagittal sinus with the veins of the scalp. (3) A net-work of minute veins (rete canalis hypoglossi) traverses the hypoglossal canal and joins the transverse sinus with the vertebral vein and deep veins of the neck. (4) An inconstant condyloid emissary vein passes through the condyloid canal and connects the transverse sinus with the deep veins of the neck. (5) A net-work of veins (rete foraminis ovalis) unites the cavernous sinus with the pterygoid plexus through the foramen ovale. (6) Two or three small veins run through the foramen lacerum and connect the cavernous sinus with the pterygoid plexus. (7) The emissary vein of the foramen of Vesalius connects the same parts. (8) An internal carotid plexus of veins traverses the carotid canal and unites the cavernous sinus with the internal jugular vein. (9) A vein is transmitted through the foramen cecum and connects the superior sagittal sinus with the veins of the nasal cavity.
• diploic veins from skull bones:
The diploic veins (564) occupy channels in the diploë of the cranial bones. They are large and exhibit at irregular intervals pouch-like dilatations; their walls are thin, and formed of endothelium resting upon a layer of elastic tissue.
So long as the cranial bones are separable from one another, these veins are confined to the particular bones; but when the sutures are obliterated, they unite with each other, and increase in size. They communicate with the meningeal veins and the sinuses of the dura mater, and with the veins of the pericranium. They consist of (1) the frontal, which opens into the supraorbital vein and the superior sagittal sinus; (2) the anterior temporal, which is confined chiefly to the frontal bone, and opens into the sphenoparietal sinus and into one of the deep temporal veins, through an aperture in the great wing of the sphenoid; (3) the posterior temporal, which is situated in the parietal bone, and ends in the transverse sinus, through an aperture at the mastoid angle of the parietal bone or through the mastoid foramen; and (4) the occipital, the largest of the four, which is confined to the occipital bone, and opens either externally into the occipital vein, or internally into the transverse sinus or into the confluence of the sinuses (torcular Herophili).
• meningeal veins are from cranial dura mater;
• superior ophthalmic vein and inferior ophtalmic vein is from sight organ;
• labyrinthic veins - from internal ear;
• emissary veins from intracranial veins and sinuses of dura mater and communicate with extracranial veins.
External jugular vein is generated by the confluence of occipital vein and posterior auricular vein, which accompany same name arteries. External jugular vein receives anterior jugular vein, which collect blood from anterior neck area and, anastomosing each other, form jugular venous arc.
The veins of the head and neck may be subdivided into three groups: (1) The veins of the exterior of the head and face. (2) The veins of the neck. (3) The diploic veins, the veins of the brain, and the venous sinuses of the dura mater.
1. The Veins of the Exterior of the Head and Face—The veins of the exterior of the head and face (557) are:
The frontal vein (v. frontalis) begins on the forehead in a venous plexus which communicates with the frontal branches of the superficial temporal vein. The veins converge to form a single trunk, which runs downward near the middle line of the forehead parallel with the vein of the opposite side. The two veins are joined, at the root of the nose, by a transverse branch, called the nasal arch, which receives some small veins from the dorsum of the nose. At the root of the nose the veins diverge, and, each at the medial angle of the orbit, joins the supraorbital vein, to form the angular vein. Occasionally the frontal veins join to form a single trunk, which bifurcates at the root of the nose into the two angular veins.
The supraorbital vein (v. supraorbitalis) begins on the forehead where it communicates with the frontal branch of the superficial temporal vein. It runs downward superficial to the Frontalis muscle, and joins the frontal vein at the medial angle of the orbit to form the angular vein. Previous to its junction with the frontal vein, it sends through the supraorbital notch into the orbit a branch which communicates with the ophthalmic vein; as this vessel passes through the notch, it receives the frontal diploic vein through a foramen at the bottom of the notch.
The angular vein (v. angularis) formed by the junction of the frontal and supraorbital veins, runs obliquely downward, on the side of the root of the nose, to the level of the lower margin of the orbit, where it becomes the anterior facial vein. It receives the veins of the ala nasi, and communicates with the superior ophthalmic vein through the nasofrontal vein, thus establishing an important anastomosis between the anterior facial vein and the cavernous sinus.
The anterior facial vein (v. facialis anterior; facial vein) commences at the side of the root of the nose, and is a direct continuation of the angular vein. It lies behind the external maxillary (facial) artery and follows a less tortuous course. It runs obliquely downward and backward, beneath the Zygomaticus and zygomatic head of the Quadratus labii superioris, descends along the anterior border and then on the superficial surface of the Masseter, crosses over the body of the mandible, and passes obliquely backward, beneath the Platysma and cervical fascia, superficial to the submandibular gland, the Digastricus and Stylohyoideus. It unites with the posterior facial vein to form the common facial vein, which crosses the external carotid artery and enters the internal jugular vein at a variable point below the hyoid bone. From near its termination a communicating branch often runs down the anterior border of the Sternocleidomastoideus to join the lower part of the anterior jugular vein. The facial vein has no valves, and its walls are not so flaccid as most superficial veins.
Tributaries.—The anterior facial vein receives a branch of considerable size, the deep facial vein, from the pterygoid venous plexus. It is also joined by the superior and inferior palpebral, the superior and inferior labial, the buccinator and the masseteric veins. Below the mandible it receives the submental, palatine, and submandibular veins, and, generally, the vena comitans of the hypoglossal nerve.
The superficial temporal vein (v. temporalis superficialis) begins on the side and vertex of the skull in a plexus which communicates with the frontal and supraorbital veins, with the corresponding vein of the opposite side, and with the posterior auricular and occipital veins. From this net-work frontal and parietal branches arise, and unite above the zygomatic arch to form the trunk of the vein, which is joined in this situation by the middle temporal vein, from the substance of the Temporalis. It then crosses the posterior root of the zygomatic arch, enters the substance of the parotid gland, and unites with the internal maxillary vein to form the posterior facial vein.
Tributaries.—The superficial temporal vein receives in its course some parotid veins, articular veins from the temporomandibular joint, anterior auricular veins from the auricula, and the transverse facial from the side of the face. The middle temporal vein receives the orbital vein, which is formed by some lateral palpebral branches, and passes backward between the layers of the temporal fascia to join the superficial temporal vein.
The pterygoid plexus (plexus pterygoideus) is of considerable size, and is situated between the Temporalis and Pterygoideus externus, and partly between the two Pterygoidei. It receives tributaries corresponding with the branches of the internal maxillary artery. Thus it receives the sphenopalatine, the middle meningeal, the deep temporal, the pterygoid, masseteric, buccinator, alveolar, and some palatine veins, and a branch which communicates with the ophthalmic vein through the inferior orbital fissure. This plexus communicates freely with the anterior facial vein; it also communicates with the cavernous sinus, by branches through the foramen Vesalii, foramen ovale, and foramen lacerum.
The internal maxillary vein (v. maxillaris interna) is a short trunk which accompanies the first part of the internal maxillary artery. It is formed by a confluence of the veins of the pterygoid plexus, and passes backward between the sphenomandibular ligament and the neck of the mandible, and unites with the temporal vein to form the posterior facial vein.
The posterior facial vein (v. facialis posterior; temporomaxillary vein), formed by the union of the superficial temporal and internal maxillary veins, descends in the substance of the parotid gland, superficial to the external carotid artery but beneath the facial nerve, between the ramus of the mandible and the Sternocleidomastoideus muscle. It divides into two branches, an anterior, which passes forward and unites with the anterior facial vein to form the common facial vein and a posterior, which is joined by the posterior auricular vein and becomes the external jugular vein.
The posterior auricular vein (v. auricularis posterior) begins upon the side of the head, in a plexus which communicates with the tributaries of the occipital, and superficial temporal veins. It descends behind the auricula, and joins the posterior division of the posterior facial vein to form the external jugular. It receive the stylomastoid vein, and some tributaries from the cranial surface of the auricula.
The occipital vein (v. occipitalis) begins in a plexus at the back part of the vertex of the skull, From the plexus emerges a single vessel, which pierces the cranial attachment of the Trapezius and, dipping into the suboccipital triangle, joins the deep cervical and vertebral veins. Occasionally it follows the course of the occipital artery and ends in the internal jugular; in other instances, it joins the posterior auricular and through it opens into the external jugular. The parietal emissary vein connects it with the superior sagittal sinus; and as it passes across the mastoid portion of the temporal bone, it receives the mastoid emissary vein which connects it with the transverse sinus. The occipital diploic vein sometimes joins it.
The veins of the neck (558), which return the blood from the head and face, are:
Posterior External Jugular.
The external jugular vein (v. jugularis externa) receives
the greater part of the blood from the exterior of the cranium and the deep
parts of the face, being formed by the junction of the posterior division of
the posterior facial with the posterior auricular vein. It commences in the
substance of the parotid gland, on a level with the angle of the mandible, and
runs perpendicularly down the neck, in the direction of a line drawn from the
angle of the mandible to the middle of the clavicle at the posterior border of
the Sternocleidomastoideus. In its course it crosses
the Sternocleidomastoideus obliquely, and in the subclavian triangle perforates the deep fascia, and ends in
the subclavian vein, lateral to or in front of the Scalenus anterior. It is separated from the Sternocleidomastoideus by the investing layer of the deep
cervical fascia, and is covered by the Platysma, the
superficial fascia, and the integument; it crosses the cutaneous cervical
nerve, and its upper half runs parallel with the great auricular nerve. The
external jugular vein varies in size, bearing an inverse proportion to the
other veins of the neck, it is occasionally double. It is provided with two
pairs of valves, the lower pair being placed at its entrance into the subclavian vein, the upper in most cases about
Tributaries.—This vein receives the occipital occasionally, the posterior external jugular, and, near its termination, the transverse cervical, transverse scapular, and anterior jugular veins; in the substance of the parotid, a large branch of communication from the internal jugular joins it.
The posterior external jugular vein (v. jugularis posterior) begins in the occipital region and returns the blood from the skin and superficial muscles in the upper and back part of the neck, lying between the Splenius and Trapezius. It runs down the back part of the neck, and opens into the external jugular vein just below the middle of its course.
The anterior jugular vein (v. jugularis anterior) begins near the hyoid bone by the confluence of several superficial veins from the submandibular region. It descends between the median line and the anterior border of the Sternocleidomastoideus, and, at the lower part of the neck, passes beneath that muscle to open into the termination of the external jugular, or, in some instances, into the subclavian vein (557, 558). It varies considerably in size, bearing usually an inverse proportion to the external jugular; most frequently there are two anterior jugulars, a right and left; but sometimes only one. Its tributaries are some laryngeal veins, and occasionally a small thyroid vein. Just above the sternum the two anterior jugular veins communicate by a transverse trunk, the venous jugular arch, which receive tributaries from the inferior thyroid veins; each also communicates with the internal jugular. There are no valves in this vein.
The internal jugular vein (v. jugularis interna) collects
the blood from the brain, from the superficial parts of the face, and from the
neck. It is directly continuous with the transverse sinus, and begins in the
posterior compartment of the jugular foramen, at the base of the skull. At its
origin it is somewhat dilated, and this dilatation is called the superior
bulb. It runs down the side of the neck in a vertical direction, lying at
first lateral to the internal carotid artery, and then lateral to the common
carotid, and at the root of the neck unites with the subclavian
vein to form the innominate vein; a little above its termination is a second
dilatation, the inferior bulb. Above, it lies upon the Rectus capitis lateralis, behind the
internal carotid artery and the nerves passing through the jugular foramen;
lower down, the vein and artery lie upon the same plane, the glossopharyngeal
and hypoglossal nerves passing forward between them; the vagus
descends between and behind the vein and the artery in the same sheath, and the
accessory runs obliquely backward, superficial or deep to the vein. At the root
of the neck the right internal jugular vein is placed at a little distance from
the common carotid artery, and crosses the first part of the subclavian artery, while the left internal jugular vein
usually overlaps the common carotid artery. The left vein is generally smaller
than the right, and each contains a pair of valves, which are placed about
Tributaries.—This vein receives in its course the inferior petrosal sinus, the common facial, lingual, pharyngeal, superior and middle thyroid veins, and sometimes the occipital. The thoracic duct on the left side and the right lymphatic duct on the right side open into the angle of union of the internal jugular and subclavian veins.
The Inferior Petrosal Sinus (sinus petrosus inferior) leaves the skull through the anterior part of the jugular foramen, and joins the superior bulb of the internal jugular vein.
The Lingual Veins (vv. linguales) begin on the dorsum, sides, and under surface of the tongue, and, passing backward along the course of the lingual artery, end in the internal jugular vein. The vena comitans of the hypoglossal nerve (ranine vein), a branch of considerable size, begins below the tip of the tongue, and may join the lingual; generally, however, it passes backward on the Hyoglossus, and joins the common facial.
The Pharyngeal Veins (vv. pharyngeæ) begin in the pharyngeal plexus on the outer surface of the pharynx, and, after receiving some posterior meningeal veins and the vein of the pterygoid canal, end in the internal jugular. They occasionally open into the facial, lingual, or superior thyroid vein.
The Superior Thyroid Vein (v. thyreoidea superioris) (560) begins in the substance and on the surface of the thyroid gland, by tributaries corresponding with the branches of the superior thyroid artery, and ends in the upper part of the internal jugular vein. It receives the superior laryngeal and cricothyroid veins.
The Middle Thyroid Vein (561, 562) collects the blood from the lower part of the thyroid gland, and after being joined by some veins from the larynx and trachea, ends in the lower part of the internal jugular vein.
The common facial and occipital veins have been described.
The vertebral vein (v. vertebralis) is formed in the suboccipital triangle, from numerous small tributaries which spring from the internal vertebral venous plexuses and issue from the vertebral canal above the posterior arch of the atlas. They unite with small veins from the deep muscles at the upper part of the back of the neck, and form a vessel which enters the foramen in the transverse process of the atlas, and descends, forming a dense plexus around the vertebral artery, in the canal formed by the foramina transversaria of the cervical vertebræ. This plexus ends in a single trunk, which emerges from the foramen transversarium of the sixth cervical vertebra, and opens at the root of the neck into the back part of the innominate vein near its origin, its mouth being guarded by a pair of valves. On the right side, it crosses the first part of the subclavian artery.
Tributaries.—The vertebral vein communicates with the transverse sinus by a vein which passes through the condyloid canal, when that canal exists. It receives branches from the occipital vein and from the prevertebral muscles, from the internal and external vertebral venous plexuses, from the anterior vertebral and the deep cervical veins; close to its termination it is sometimes joined by the first intercostal vein.
The Anterior Vertebral Vein commences in a plexus around the transverse processes of the upper cervical vertebræ, descends in company with the ascending cervical artery between the Scalenus anterior and Longus capitis muscles, and opens into the terminal part of the vertebral vein.
The Deep Cervical Vein (v. cervicalis profunda; posterior vertebral or posterior deep cervical vein) accompanies its artery between the Semispinales capitis and colli. It begins in the suboccipital region by communicating branches from the occipital vein and by small veins from the deep muscles at the back of the neck. It receives tributaries from the plexuses around the spinous processes of the cervical vertebræ, and terminates in the lower part of the vertebral vein.
The inferior Vena Cava
The inferior vena cava (IVC) collects most of the venous blood from organs inferior to the diaphragm. (A small amount reaches the superior vena cava via the azygos and hemiazygos veins.) Figure 21-33 diagrams the tributaries of the inferior vena cava.
Veins Draining the Lower Limb. Blood leaving capillaries in the sole of each foot collects into a network of plantar veins, which supply the plantar venous arch. The plantar network provides blood to the deep veins of the leg: the anterior tibial vein, the posterior tibial vein, and the peroneal vein (Figure 21-34 ). The dorsal venous arch collects blood from capillaries on the superior surface of the foot and the digital veins of the toes. There are extensive interconnections between the plantar arch and the dorsal arch, and the path of blood flow can easily shift from superficial to deep veins.
The dorsal venous arch is drained by two superficial veins, the great saphenous vein (saphenes, prominent) and the small saphenous vein. The great saphenous vein ascends along the medial aspect of the leg and thigh, draining into the femoral vein near the hip joint. The small saphenous vein arises from the dorsal venous arch and ascends along the posterior and lateral aspect of the calf. This vein then enters the popliteal fossa, where it meets the popliteal vein, formed by the union of the tibial and peroneal veins. The popliteal vein is easily palpated in the popliteal fossa adjacent to the adductor magnus muscle (Figure 21-34). Once it reaches the femur, the popliteal vein becomes the femoral vein, which ascends along the thigh, next to the femoral artery. Immediately before penetrating the abdominal wall, the femoral vein receives blood from the great saphenous vein and the deep femoral vein, which collects blood from the thigh. The femoral vein then penetrates the body wall and emerges in the pelvic cavity as the external iliac vein.
Veins Draining the Pelvis. The external iliac veins receive blood from the lower limbs, pelvis, and lower abdomen. As the left and right external iliacs travel across the inner surface of the ilium, they are joined by the internal iliac veins, which drain the pelvic organs. The union of external and internal iliac veins results in the common iliac vein. The right and left common iliacs ascend at an oblique angle, and anterior to vertebra L5 they unite to form the inferior vena cava (Figure 21-32).
Veins Draining the Abdomen. The inferior vena cava ascends posterior to the peritoneal cavity, parallel to the aorta. The abdominal portion of the inferior vena cava collects blood from six major veins (Figures 21-32 and 21-33):
1. Lumbar veins drain the lumbar portion of the abdo-men, including the spinal cord and body wall muscles. Superior branches of these veins are connected to the azygos vein (right side) and hemiazygos vein (left side), which empty into the superior vena cava.
2. Gonadal (ovarian or testicular) veins drain the ovaries or testes. The right gonadal vein empties into the inferior vena cava; the left gonadal generally drains into the left renal vein.
3. Hepatic veins leave the liver and empty into the inferior vena cava at the level of vertebra T10.
4. Renal veins collect blood from the kidneys. These are the largest tributaries of the inferior vena cava.
5. Suprarenal veins drain the adrenal glands. Generally, only the right suprarenal vein drains into the inferior vena cava, and the left drains into the left renal vein.
6. Phrenic veins drain the diaphragm. Only the right phrenic vein drains into the inferior vena cava; the left drains into the left renal vein.
The liver is the only digestive organ drained by
the inferior vena cava. Instead of traveling directly to the inferior vena
cava, blood leaving the capillaries supplied by the celiac, superior, and
inferior mesenteric arteries flows into the hepatic portal system. As we noted
The hepatic portal system begins in the capillaries of the digestive organs and ends as the hepatic portal vein discharges blood into sinusoids in the liver. The tributaries of the hepatic portal vein (Figure 21-35a, b) include the following:
· The inferior mesenteric vein, which collects blood from capillaries along the lower portion of the large intestine. Its tributaries include the left colic vein and the superior rectal veins, which drain the descending colon, sigmoid colon, and rectum.
· The splenic vein, formed by the union of the inferior mesenteric vein and veins from the spleen, the lateral border of the stomach (left gastroepiploic), and the pancreas (pancreatic).
· The superior mesenteric vein, which collects blood from veins draining the stomach (right gastroepiploic), the small intestine (intestinal), and two-thirds of the large intestine (ileocolic, right colic, and middle colic).
The hepatic portal vein forms through the fusion of the superior mesenteric and splenic veins. Of the two, the superior mesenteric normally contributes the greater volume of blood and most of the nutrients. As it proceeds toward the liver, the hepatic portal receives blood from the gastric veins, which drain the medial border of the stomach, and the cystic vein from the gallbladder.
System of inferior vena cava. System of hepatic portal vein
Venae cavae are the two largest veins in the body. These blood vessels carry de-oxygenated blood from various regions of the body to the right atrium of the heart. As the de-oxygenated blood is returned to the heart and continues to flow through the cardiac cycle, it is transported to the lungs where it becomes oxygenated. The blood then travels back to the heart and is pumped out to the rest of the body via the aorta. Oxygen depleted blood is returned to the heart again via the venae cavae.
The superior vena cava is located in the upper chest region and is formed by the joining of the brachiocephalic veins. It is bordered by heart structures such as the aorta and pulmonary artery. The inferior vena cava is formed by the joining of the common iliac veins which meet a little below the small of the back. The inferior vena cava travels along the spine and transports blood from the lower extremities of the body to the posterior region of the right atrium.
Function of the Venae Cavae
· Superior Vena Cava: Brings de-oxygenated blood from the head, neck, arm and chest regions of the body to the right atrium.
· Inferior Vena Cava: Brings de-oxygenated blood from the lower body regions (legs, back, abdomen and pelvis) to the right atrium.
It is posterior to the abdominal cavity and runs alongside of the vertebral column on its right side (i.e. it is a retroperitoneal structure). It enters the right atrium at the lower right, back side of the heart.
The IVC is formed by the joining of the left and right common iliac veins and brings blood into the right atrium of the heart. It also anastomoses with the azygos vein system (which runs on the rght side of the vertebral column) and venous plexuses next to the spinal cord.
The tributaries of Inferior vena cava can be remembered using the mnemonic, "I Like To Rise So High", for Illiac vein (common), Lumbar vein, Testicular vein, Renal vein, Suprarenal vein and Hepatic vein.
Note that the vein that carries de-oxygenated blood from the upper half of the body is the superior vena cav
Inferior vena cava starts on level IV-V lumbar vertebrae by the confluence of left common iliac vein and right common iliac vein, to the right and beneath from bifurcation of aorta. It passes through special foramen in centrum tendineum of diaphragm into mediastinum and empties into right atrium.
There are parietal and visceral influxes of inferior vena cava.
The venæ cavæ and azygos veins, with their tributaries.
Parietal tributaries of inferior vena cava:
· lumbar veins are 3-4 pairs, which collect blood from areas according with ramification of lumbar arteries, they anastomose by right and left ascending lumbar veins;
· inferior phrenic veins collect blood from areas according with ramification same name arteries.
Follow veins are the visceral tributaries of inferior vena cava:
· in male - right testicular vein starts from posterior testicle margin. Testicular vein forms pampiniform plexus which enters to composition of spermatic cord. Left testicular vein (also left ovaricа vein in famile) empties by right angle into left renal vein;
· in famile - right ovaric
· vein begins from ovary hilus;
· renal veins, pair, pass from kidney hilus and, anastomosing with lumbar veins, emptiy into inferior vena cava between lumbar vertebrae first and second;
· right suprarenal vein, exits from hilus of adrenal gland. Left suprarenal vein falls into left renal vein;
· hepatic veins (3-4) veins fall into inferior vena cava in area of same name sulcus in liver.
The inferior vena cava (v. cava inferior) (577), returns to the heart the blood from the parts below the diaphragm. It
is formed by the junction of the two common iliac veins, on the right side of
the fifth lumbar vertebra. It ascends along the front of the vertebral column,
on the right side of the aorta, and, having reached the liver, is continued in
a groove on its posterior surface. It then perforates the diaphragm between the
median and right portions of its central tendon; it subsequently inclines
forward and medialward for about
Relations.—The abdominal portion of the inferior vena cava is in relation in front, from below upward, with the right common iliac artery, the mesentery, the right internal testicular artery, the inferior part of the duodenum, the pancreas, the common bile duct, the portal vein, and the posterior surface of the liver; the last partly overlaps and occasionally completely surrounds it; behind, with the vertebral column, the right Psoas major, the right crus of the diaphragm, the right inferior phrenic, suprarenal, renal and lumbar arteries, right sympathetic trunk and right celiac ganglion, and the medial part of the right suprarenal gland; on the right side, with the right kidney and ureter; on the left side, with the aorta, right crus of the diaphragm, and the caudate lobe of the liver.
The thoracic portion is only about
Peculiarities.—In Position.—This vessel is sometimes placed on the left side of the aorta, as high as the left renal vein, and, after receiving this vein, crosses over to its usual position on the right side; or it may be placed altogether on the left side of the aorta, and in such a case the abdominal and thoracic viscera, together with the great vessels, are all transposed.
Point of Termination.—Occasionally the inferior vena cava joins the azygos vein, which is then of large size. In such cases, the superior vena cava receives the whole of the blood from the body before transmitting it to the right atrium, except the blood from the hepatic veins, which passes directly into the right atrium.
Tributaries.—The inferior vena cava receives the following veins:
Right Spermatic or Ovarian.
The Lumbar Veins (vv. lumbales) four in number on each side, collect the blood by dorsal tributaries from the muscles and integument of the loins, and by abdominal tributaries from the walls of the abdomen, where they communicate with the epigastric veins. At the vertebral column, they receive veins from the vertebral plexuses, and then pass forward, around the sides of the bodies of the vertebræ, beneath the Psoas major, and end in the back part of the inferior cava. The left lumbar veins are longer than the right, and pass behind the aorta. The lumbar veins are connected together by a longitudinal vein which passes in front of the transverse processes of the lumbar vertebræ, and is called the ascending lumbar; it forms the most frequent origin of the corresponding azygos or hemiazygos vein, and serves to connect the common iliac, iliolumbar, and azygos or hemiazygos veins of its own side of the body.
The Testicular veins (vv. spermaticæ) (590) emerge from the back of the testis, and receive tributaries from the epididymis; they unite and form a convoluted plexus, called the pampiniform plexus, which constitutes the greater mass of the spermatic cord; the vessels composing this plexus are very numerous, and ascend along the cord, in front of the ductus deferens. Below the subcutaneous inguinal ring they unite to form three or four veins, which pass along the inguinal canal, and, entering the abdomen through the abdominal inguinal ring, coalesce to form two veins, which ascend on the Psoas major, behind the peritoneum, lying one on either side of the internal testicular artery. These unite to form a single vein, which opens on the right side into the inferior vena cava, at an acute angle; on the left side into the left renal vein, at a right angle. The testicular veins are provided with valves. 107 The left testicular vein passes behind the iliac colon, and is thus exposed to pressure from the contents of that part of the bowel.
The Ovarian Veins (vv. ovaricæ) correspond with the spermatic in the male; they form a plexus in the broad ligament near the ovary and uterine tube, and communicate with the uterine plexus. They end in the same way as the testicular veins in the male. Valves are occasionally found in these veins. Like the uterine veins, they become much enlarged during pregnancy.
The Renal Veins (vv. renales) are of large size, and placed in front of the renal arteries. The left is longer than the right, and passes in front of the aorta, just below the origin of the superior mesenteric artery. It receives the left testicular and left inferior phrenic veins, and, generally, the left suprarenal vein. It opens into the inferior vena cava at a slightly higher level than the right.
The Suprarenal Veins (vv. suprarenales) are two in number: the right ends in the inferior vena cava; the left, in the left renal or left inferior phrenic vein.
The Inferior Phrenic Veins (vv. phrenicæ inferiores) follow the course of the inferior phrenic arteris; the right ends in the inferior vena cava; the left is often represented by two branches, one of which ends in the left renal or suprarenal vein, while the other passes in front of the esophageal hiatus in the diaphragm and opens into the inferior vena cava.
The Hepatic Veins (vv. hepaticæ) commence in the substance of the liver, in the terminations of the portal vein and hepatic artery, and are arranged in two groups, upper and lower. The upper group usually consists of three large veins, which converge toward the posterior surface of the liver, and open into the inferior vena cava, while that vessel is situated in the groove on the back part of the liver. The veins of the lower group vary in number, and are of small size; they come from the right and caudate lobes. The hepatic veins run singly, and are in direct contact with the hepatic tissue. They are destitute of valves.
The hepatic portal vein is a blood vessel that conducts blood from the gastrointestinal tract and spleen to the liver. This blood is rich in nutrients that were extracted from food, and the liver processes these nutrients; it also filters toxins that may have been ingested with the food. The liver receives about 75% of its blood through the hepatic portal vein, with the remainder coming from the hepatic artery proper. The blood leaves the liver to the heart in the hepatic veins.
The hepatic portal vein is not a true vein, because it conducts blood to capillary beds in the liver and not directly to the heart. It is a major component of the hepatic portal system, one of only two portal venous systems in the body. The other is the hypophyseal portal system.
Conditions involving the hepatic portal vein cause considerable illness and death. An important example of such a condition is elevated blood pressure in the hepatic portal vein. This condition, called portal hypertension, is a major complication of cirrhosis.
In most individuals, the hepatic portal vein is formed by the union of the superior mesenteric vein and the splenic vein. For this reason, the hepatic portal vein is occasionally called the splenic-mesenteric confluence. Occasionally, the hepatic portal vein also directly communicates with the inferior mesenteric vein, although this is highly variable. Other tributaries of the hepatic portal vein include the cystic and gastric veins.
Immediately before reaching the liver, the portal vein divides into right and left. It ramifies further, forming smaller venous branches and ultimately portal venules. Each portal venule courses alongside a hepatic arteriole and the two vessels form the vascular components of the portal triad. These vessels ultimately empty into the hepatic sinusoids to supply blood to the liver.
The portal venous system has several anastomoses with the systemic venous system. In cases of portal hypertension these anastamoses may become engorged, dilated, or varicosed and subsequently rupture.
Accessory hepatic portal veins are those veins that drain directly into the liver without joining the hepatic portal vein. These include the paraumbilical veins as well as veins of the lesser omentum, falciform ligament, and those draining the gallbladder wall.
Vena portae hepatis is situated in thickness of hepatoduodenal ligament between ductus choledochus and proper hepatic artery (formula of their position DVA – from right to left). It originates behind head of pancreas by the confluence of superior, inferior mesenteric veinc and splenic vein. It collects venous blood from odd organs of abdominal cavity, except liver. Vena portae receives cystic vein, right and left gastric veins and prepyloric vein closely to liver hilus. Paraumbilical veins fall into portal vein in liver hilus.
There are cava-caval and porto-caval anastomoses between systems of portal vein, superior and inferior vanea cavae (see table on the next page).
The portal system (591) includes all the veins which drain the blood from the abdominal part of the digestive tube (with the exception of the lower part of the rectum) and from the spleen, pancreas, and gall-bladder. From these viscera the blood is conveyed to the liver by the portal vein. In the liver this vein ramifies like an artery and ends in capillary-like vessels termed sinusoids, from which the blood is conveyed to the inferior vena cava by the hepatic veins. From this it will be seen that the blood of the portal system passes through two sets of minute vessels, viz., (a) the capillaries of the digestive tube, spleen, pancreas, and gall-bladder; and (b) the sinusoids of the liver. In the adult the portal vein and its tributaries are destitute of valves; in the fetus and for a short time after birth valves can be demonstrated in the tributaries of the portal vein; as a rule they soon atrophy and disappear, but in some subjects they persist in a degenerate form.
The portal vein (vena portæ)
Tributaries.—The tributaries of the portal vein are:
The Lienal Vein (v. lienalis; splenic vein) commences by five or six large branches which return the blood from the spleen. These unite to form a single vessel, which passes from left to right, grooving the upper and back part of the pancreas, below the lineal artery, and ends behind the neck of the pancreas by uniting at a right angle with the superior mesenteric to form the portal vein. The lienal vein is of large size, but is not tortuous like the artery.
Tributaries.—The lineal vein receives the short gastric veins, the left gastroepiploic vein, the pancreatic veins, and the inferior mesenteric veins.
The short gastric veins (vv. gastricæ breves), four or five in number, drain the fundus and left part of the greater curvature of the stomach, and pass between the two layers of the gastrolienal ligament to end in the lienal vein or in one of its large tributaries.
The left gastroepiploic vein (v. gastroepiploica sinistra) receives branches from the antero-superior and postero-inferior surfaces of the stomach and from the greater omentum; it runs from right to left along the greater curvature of the stomach and ends in the commencement of the lienal vein.
The pancreatic veins (vv. pancreaticæ) consist of several small vessels which drain the body and tail of the pancreas, and open into the trunk of the lienal vein.
The inferior mesenteric vein (v. mesenterica inferior) returns blood from the rectum and the sigmoid, and descending parts of the colon. It begins in the rectum as the superior hemorrhoidal vein, which has its origin in the hemorrhoidal plexus, and through this plexus communicates with the middle and inferior hemorrhoidal veins. The superior hemorrhoidal vein leaves the lesser pelvis and crosses the left common iliac vessels with the superior hemorrhoidal artery, and is continued upward as the inferior mesenteric vein. This vein lies to the left of its artery, and ascends behind the peritoneum and in front of the left Psoas major; it then passes behind the body of the pancreas and opens into the lienal vein; sometimes it ends in the angle of union of the lienal and superior mesenteric veins.
Tributaries.—The inferior mesenteric vein receives the sigmoid veins from the sigmoid colon and iliac colon, and the left colic vein from the descending colon and left colic flexure.
The Superior Mesenteric Vein (v. mesenterica superior) returns the blood from the small intestine, from the cecum, and from the ascending and transverse portions of the colon. It begins in the right iliac fossa by the union of the veins which drain the terminal part of the ileum, the cecum, and vermiform process, and ascends between the two layers of the mesentery on the right side of the superior mesenteric artery. In its upward course it passes in front of the right ureter, the inferior vena cava, the inferior part of the duodenum, and the lower portion of the head of the pancreas. Behind the neck of the pancreas it unites with the lienal vein to form the portal vein.
Tributaries.—Besides the tributaries which correspond with the branches of the superior mesenteric artery, viz., the intestinal, ileocolic, right colic, and middle colic veins, the superior mesenteric vein is joined by the right gastroepiploic and pancreaticoduodenal veins.
The right gastroepiploic vein (v. gastroepiploica dextra) receives branches from the greater omentum and from the lower parts of the antero-superior and posteroinferior surfaces of the stomach; it runs from left to right along the greater curvature of the stomach between the two layers of the greater omentum.
The pancreaticoduodenal veins (vv. pancreaticoduodenales) accompany their corresponding arteries; the lower of the two frequently joins the right gastroepiploic vein.
The Coronary Vein (v. coronaria ventriculi; gastric vein) derives tributaries from both surfaces of the stomach; it runs from right to left along the lesser curvature of the stomach, between the two layers of the lesser omentum, to the esophageal opening of the stomach, where it receives some esophageal veins. It then turns backward and passes from left to right behind the omental bursa and ends in the portal vein.
The Pyloric Vein is of small size, and runs from left to right along the pyloric portion of the lesser curvature of the stomach, between the two layers of the lesser omentum, to end in the portal vein.
The Cystic Vein (v. cystica) drains the blood from the gall-bladder, and, accompanying the cystic duct, usually ends in the right branch of the portal vein.
Parumbilical Veins (vv. parumbilicales).—In the course of the ligamentum teres of the liver and of the middle umbilical ligament, small veins (parumbilical) are found which establish an anastomosis between the veins of the anterior abdominal wall and the portal, hypogastric, and iliac veins. The best marked of these small veins is one which commences at the umbilicus and runs backward and upward in, or on the surface of, the ligamentum teres between the layers of the falciform ligament to end in the left portal vein.
Collateral venous circulation to relieve portal obstruction in the liver may be effected by communications between (a) the gastric veins and the esophageal veins which often project as a varicose bunch into the stomach, emptying themselves into the hemiazygos vein; (b) the veins of the colon and duodenum and the left renal vein; (c) the accessory portal system of Sappey, branches of which pass in the round and falciform ligaments (particularly the latter) to unite with the epigastric and internal mammary veins, and through the diaphragmatic veins with the azygos; a single large vein, shown to be a parumbilical vein, may pass from the hilus of the liver by the round ligament to the umbilicus, producing there a bunch of prominent varicose veins known as the caput medusæ; (d) the veins of Retzius, which connect the intestinal veins with the inferior vena cava and its retroperitoneal branches; (e) the inferior mesenteric veins, and the hemorrhoidal veins that open into the hypogastrics; (f) very rarely the ductus venosus remains patent, affording a direct connection between the portal vein and the inferior vena cava.
Theme 2. Cava-caval and porto-caval anastomoses. Circulation of blood of foetus and new-born
Position of anastomose
V. cava superior
v. cava inferior
v. epigastrica superior (tributary of the internal thoracic vein) and v. Thoracoepigastrica (tributary of the subclavian vein)
v. epigastrica inferior (tributary of the external iliac vein) and v. Epigastrica superficialis (tributary of the femoral vein)
In anterior abdominal wall round the navel
V. cava superior
And v. Cava inferior
vv. azygos and hemiazygos
On posterior abdominal wall
V. cava superior
And v. Cava inferior
Rr. spinales (tributary of the vv. Intercostales posteriores)
Rr. spinales (tributary of the vv. Lumbales)
Form internal and external vertebral plexus
V. cava superior and v. Portae
v. epigastrica superior (tributary of the internal thoracic vein)
In anterior abdominal wall round the navel
V. cava superior and v. Portae
Vv. esophageales (tributary of the azygos vein)
v. gastrica sinistra
Near gastric cardia
V. cava inferior and v. Portae
v. epigastrica inferior (tributary of the external iliac vein)
In anterior abdominal wall
V. cava inferior and v. Portae
V. rectalis media (tributary of the internal iliac vein)
V. rectalis superior (tributary of the inferior mesenteric vein)
Plexus venosus rectalis
V. cava inferior and v. Portae
Vv. mesenterica superior and inferior
In thickness of ascending and descending colon
Circulatory system of the foetus has a row of peculiarities that differ from adult one:
- arterial blood reaches the foetus through umbilical vein from placenta;
- exclusive of umbilical vein, a blood in vessels is mixed;
- venous (Аranti) duct functions between umbilical and inferior vena cava by veins;
- blood from inferior vena cava gets from right atrium through the ovale foramen into left atrium;
- pulmonary circulation does not function;
- arterial (Botalova) duct functions between aortic arch and pulmonary trunk, through the which blood from pulmonary blood circle passes in systemic circulation;
- more oxygenated blood supplies head, neck, upper limbs and superior part of torso. Inferior part of trunk and lower limbs supplied by mixed blood, which is insufficiently saturated by oxygen, that's why these body portions of foetus fall behind in development in compare of head and upper part of torso.
After birth breath starts and pulmonary circulation begins to function. Umbilical vessels overgrow in 6-7 days, Botali duct - in 9-10 days and oval foramen in interatrial wall – in 30 days after birth
Peculiarities in the Vascular System in the Fetus The chief peculiarities of the fetal heart are the direct communication between the atria through the foramen ovale, and the large size of the valve of the inferior vena cava. Among other peculiarities the following may be noted. (1) In early fetal life the heart lies immediately below the mandibular arch and is relatively large in size. As development proceeds it is gradually drawn within the thorax, but at first it lies in the middle line; toward the end of pregnancy it gradually becomes oblique in direction. (2) For a time the atrial portion exceeds the ventricular in size, and the walls of the ventricles are of equal thickness: toward the end of fetal life the ventricular portion becomes the larger and the wall of the left ventricle exceeds that of the right in thickness. (3) Its size is large as compared with that of the rest of the body, the proportion at the second month being 1 to 50, and at birth, 1 to 120, while in the adult the average is about 1 to 160.
The foramen ovale, situated at the lower part of the atrial septum, forms a free communication between the atria until the end of fetal life. A septum (septum secundum) grows down from the upper wall of the atrium to the right of the primary septum in which the foramen ovale is situated; shortly after birth it fuses with the primary septum and the foramen ovale is obliterated.
The valve of the inferior vena cava serves to direct the blood from that vessel through the foramen ovale into the left atrium.
The peculiarities in the arterial system of the fetus are the communication between the pulmonary artery and the aorta by means of the ductus arteriosus, and the continuation of the hypogastric arteries as the umbilical arteries to the placenta.
The ductus arteriosus is a short tube, about
The hypogastric arteries run along the sides of the bladder and thence upward on the back of the anterior abdominal wall to the umbilicus; here they pass out of the abdomen and are continued as the umbilical arteries in the umbilical cord to the placenta. They convey the fetal blood to the placenta.
The peculiarities in the venous system of the fetus are the communications established between the placenta and the liver and portal vein, through the umbilical vein; and between the umbilical vein and the inferior vena cava through the ductus venosus.
Fetal Circulation (502).
—The fetal blood is returned from the placenta to the fetus by the umbilical vein. This vein enters the abdomen at the umbilicus, and passes upward along the free margin of the falciform ligament of the liver to the under surface of that organ, where it gives off two or three branches, one of large size to the left lobe, and others to the lobus quadratus and lobus caudatus. At the porta hepatis (transverse fissure of the liver) it divides into two branches: of these, the larger is joined by the portal vein, and enters the right lobe; the smaller is continued upward, under the name of the ductus venosus, and joins the inferior vena cava. The blood, therefore, which traverses the umbilical vein, passes to the inferior vena cava in three different ways. A considerable quantity circulates through the liver with the portal venous blood, before entering the inferior vena cava by the hepatic veins; some enters the liver directly, and is carried to the inferior cava by the hepatic veins; the remainder passes directly into the inferior vena cava through the ductus venosus.
In the inferior vena cava, the blood carried by the ductus venosus and hepatic veins becomes mixed with that returning from the lower extremities and abdominal wall. It enters the right atrium, and, guided by the valve of the inferior vena cava, passes through the formen ovale into the left atrium, where it mixes with a small quantity of blood returned from the lungs by the pulmonary veins. From the left atrium it passes into the left ventricle; and from the left ventricle into the aorta, by means of which it is distributed almost entirely to the head and upper extremities, a small quantity being probably carried into the descending aorta. From the head and upper extremities the blood is returned by the superior vena cava to the right atrium, where it mixes with a small portion of the blood from the inferior vena cava. From the right atrium it descends into the right ventricle, and thence passes into the pulmonary artery. The lungs of the fetus being inactive, only a small quantity of the blood of the pulmonary artery is distributed to them by the right and left pulmonary arteries, and returned by the pulmonary veins to the left atrium: the greater part passes through the ductus arteriosus into the aorta, where it mixes with a small quantity of the blood transmitted by the left ventricle into the aorta. Through this vessel it descends, and is in part distributed to the lower extremities and the viscera of the abdomen and pelvis, but the greater amount is conveyed by the umbilical arteries to the placenta.
From the preceding account of the circulation of the blood in the fetus the following facts will be evident: (1) The placenta serves the purposes of nutrition and excretion, receiving the impure blood from the fetus, and returning it purified and charged with additional nutritive material. (2) Nearly the whole of the blood of the umbilical vein traverses the liver before entering the inferior vena cava; hence the large size of the liver, especially at an early period of fetal life. (3) The right atrium is the point of meeting of a double current, the blood in the inferior vena cava being guided by the valve of this vessel into the left atrium, while that in the superior vena cava descends into the right ventricle. At an early period of fetal life it is highly probable that the two streams are quite distinct; for the inferior vena cava opens almost directly into the left atrium, and the valve of the inferior vena cava would exclude the current from the right ventricle. At a later period, as the separation between the two atria becomes more distinct, it seems probable that some mixture of the two streams must take place. (4) The pure blood carried from the placenta to the fetus by the umbilical vein, mixed with the blood from the portal vein and inferior vena cava, passes almost directly to the arch of the aorta, and is distributed by the branches of that vessel to the head and upper extremities. (5) The blood contained in the descending aorta, chiefly derived from that which has already circulated through the head and limbs, together with a small quantity from the left ventricle, is distributed to the abdomen and lower extremities.
Changes in the Vascular System at Birth.—At birth, when respiration is established, an increased amount of blood from the pulmonary artery passes through the lungs, and the placental circulation is cut off. The foramen ovale is closed by about the tenth day after birth: the valvular fold above mentioned adheres to the margin of the foramen for the greater part of its circumference, but a slit-like opening is left between the two atria above, and this sometimes persists.
The ductus arteriosus begins to contract immediately after respiration is established, and is completely closed from the fourth to the tenth day; it ultimately degenerates into an impervious cord, the ligamentum arteriosum, which connects the left pulmonary artery to the arch of the aorta.
Of the hypogastric arteries, the parts extending from the sides of the bladder to the umbilicus become obliterated between the second and fifth days after birth, and project as fibrous cords, the lateral umbilical ligaments, toward the abdominal cavity, carrying on them folds of peritoneum.
The umbilical vein and ductus venosus are completely obliterated between the second and fifth days after birth; the former becomes the ligamentum teres, the latter the ligamentum venosum, of the liver.
There are significant differences between the fetal and adult circulatory systems that reflect differing sources of respiratory and nutritional support. The embryonic lungs are collapsed and nonfunctional, and the digestive tract has nothing to digest. All the embryonic nutritional and respiratory needs are provided by diffusion across the placenta.
Fetal circulation is diagrammed in Figure 21-36. Blood flow to the placenta is provided by a pair of umbilical arteries, which arise from the internal iliac arteries and enter the umbilical cord. Blood returns from the placenta in the single umbilical vein, bringing oxygen and nutrients to the developing fetus. The umbilical vein drains into the ductus venosus, which is connected to an intricate network of veins within the developing liver. The ductus venosus collects blood from the veins of the liver and from the umbilical vein and empties into the inferior vena cava. When the placental connection is broken at birth, blood flow ceases along the umbilical vessels, and they soon degenerate.
One of the most interesting aspects of circulatory development reflects the differences between the life of an embryo or fetus and that of an infant. Throughout embryonic and fetal life, the lungs are collapsed; yet, after delivery, the newborn infant must be able to extract oxygen from inspired air rather than across the placenta.
Although the interatrial and interventricular septa develop early in fetal life, the interatrial partition remains functionally incomplete up to the time of birth. The foramen ovale, or interatrial opening, is associated with a long flap that acts as a valve. Blood can flow freely from the right atrium to the left atrium, but any backflow will close the valve and isolate the two chambers. Thus blood can enter the heart at the right atrium and bypass the pulmonary circuit. A second short-circuit exists between the pulmonary and aortic trunks. This connection, the ductus arteriosus, consists of a short, muscular vessel.
With the lungs collapsed, the capillaries are compressed, and little blood flows through the lungs. During diastole, blood enters the right atrium and flows into the right ventricle, but it also passes into the left atrium through the foramen ovale. About 25 percent of the blood arriving at the right atrium bypasses the pulmonary circuit in this way. In addition, over 90 percent of the blood leaving the right ventricle passes through the ductus arteriosus and enters the systemic circuit rather than continuing to the lungs.
At birth, dramatic changes occur. When the infant takes the first breath, the lungs expand, and so do the pulmonary vessels. The resistance in the pulmonary circuit declines suddenly, and blood rushes into the pulmonary vessels. Within a few seconds, rising O2 levels stimulate constriction of the ductus arteriosus, isolating the pulmonary and aortic trunks. As pressures rise in the left atrium, the valvular flap closes the foramen ovale and completes the circulatory remodeling. In the adult, the interatrial septum bears a shallow depression, the fossa ovalis, that marks the site of the foramen ovale. The remnants of the ductus arteriosus persist as a fibrous cord, the ligamentum arteriosum.
If the proper circulatory changes do not occur at birth or shortly thereafter, problems will eventually develop. The severity of the problem depends on which connection remains open and on the size of the opening. Treatment may involve surgical closure of the foramen ovale, the ductus arteriosus, or both. Other forms of congenital heart defects result from abnormal cardiac development or inappropriate connections between the heart and major arteries and veins.