Male reproductive system. Female reproductive system

Usinglectures(on theweb-page of the departmentpostedthe presentationtextandlectures), books,additional literatureand other sources, students must to preparethe following theoreticalquestions:

1.                General structure and function of the testis.

2.                Description of the spermatogenesis and structural peculiarities of the spermatogenetic cells at different stages of their development.

3.                Structure and function of the testis seminiferous tubules, microscopic and ultramicroscopic structure of the Sertoli cells.

4.                Structure and significance of the haemotesticular barrier.

5.                Morphofunctional characteristic of Leydig cells.

6.                Structure of the wall of the tubuli recti, the rete testis and the mediastinum testis.

7.                Structure of the wall of the ductus efferents and the ductus epididimus.

8.                Morphology of the ductus deferents, the ductus ejaculatorius and the urine.

9.                General structure and function of the prostate gland.

10.           Structure of the paraurethral gland of the prostate.

11.           Seminal vesicles and bulbourethral glands, their fine structure.

12.           Hormonal interaction of the hypophysis and the male reproductive system.

13.           Development and general structure of the ovary. The role of the interstitium.

14.           Incretory function of the ovary and correlation with the other endocrine glands.

15.           Thin structure of the cortex of the ovary.

16.           Ovogenesis (main stages and their morphofunctional characteristics). Comparison of the stages of the ovogenesis and spermatogenesis.

17.           Dynamics of the development of the follicles of the ovary. (Structure of the primordial, primary, secondary and mature folliculi).

18.           Ovulation, its biological essence and hormonal regulation of this process.

19.           Stages of the formation of the Corpus luteum, its endocrine function.

20.           Artesia of the folliculi. Atretic body, its main differences from Corpus albicans and Corpus luteum.

21.           Uterine tube structure and functions.

22.           Uterus structure.

23.           General description of some cyclic changes in the uterus and ovary. Periods of the menstrual (sexual cycle).

24.           Morphological and functional changes of the endometrium in the menstrual phase.

25.           Histological changes of the endometrium that cause the uterine bleeding.

26.           Histophysiology of the endometrium in the postmenstrual phase.

27.           Hormonal adjusting of the cyclic changes in the uterus.

28.           Cyclic changes in the vagina.

29.           Development and a general structure of the mammary gland.

30.           Fine structure of the secretory portion of the mammary gland before lactation.

31.           Structural features of the parenchyma of the active and inactive mammary gland.

32.           Description of the secretory process and hormonal regulation of the function of mammary gland.

The male reproductive system consists of internal and external genitalia. Penis belong to external ones. The internal male genitalia consist of the testes with the adjoining epididymis, the vas deferens and the accessory sex glands, namely the seminal vesicles, the prostrate and the bulbourethral glands (the latter sometimes are included in the external genitalia).

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The male genital system. The testis and the epididymis are shown in different scales than the other parts of the reproductive system. Note the communication between the testicular lobules.

TESTES

The testes have, like the ovaries, two functions: they produce the male gametesor spermatozoa, and they produce male sexual hormone, testosterone, which stimulates the accessory male sexual organs and causes the development of the masculine extragenital sex characteristics.

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The testis is encapsulated by a dense, fibrous, connective tissue layer, the tunica albuginea, from which, at the posterior aspect, numerous ill-defined connective tissue septa divide the testis into about 250-300 testicular lobules, which communicate peripherally. Testicular lobule is the parenchimal unit of testis. Within each lobule there are from one to four highly convoluted loops, the seminiferous tubules, in which spermatozoa are produced. The seminiferous tubules are about 150-300 µm in diameter, 30-80 cm long. They converge upon a plexus of spaces, the rete testis. The testis is packed with numerous, coiled, seminiferous tubules that can be clearly seen. Groups of about four seminiferous tubules are segregated into testicular lobules; the connective tissue septa are so delicate to be distinctly seen at low magnification. The dense fibrous capsule which invests the testis, and that is continuous with many of the interlobular septa, is called the tunica albuginea.

Interstitial tissue between the convoluted tubules is continuous with a layer of loose vascular connective tissue, the tunica vasculosa testis, which is found beneath the tunica albuginea.Each seminiferous tubule continues near the mediastinum into a straight tubule, a tubulus rectus. The straight tubules continue into the rete testis, a labyrinthine system of cavities in the mediastinum.

Germ cells production or spermatogenesis is principal function of testis which occurs in spermatogenic epithelium of testis. The cells of spermatogenic lineage are stacked in 4-8 layers that occupy the space between the basal lamina and the lumen of tubule. These cells devide several times and finally differentiate, producing spermatozoa. They represent various stages in the continuous process of differentiation of the male germ cells. This phenomenon, from start to finish, is called spermatogenesis and can be devided into three phases: reproduction, growth and maturation.

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 Diagram showing the clonal nature of the germ cells. Only the initial spermatogonia divide and produce separate daughter cells. Once committed to differentiation, the cells of all subsequent divisions stay connected by intercellular cytoplasmic bridges. Only after they are separated from the residual bodies can the spermatozoa be considered isolated cells.

Spermatogenesis is regulated by follicle stimulating hormone (FSH), which in males stimulates the spermatogenic epithelium, and luteinizing-hormone (LH), which in males stimulates testosterone production by Leydig cells in the interstitial tissue.

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Hypophyseal control of male reproduction. Luteinizing hormone (LH) acts on the Leydig cells, and follicle-stimulating hormone (FSH) acts on the seminiferous tubules. A testicular hormone, inhibin, inhibits FSH secretion in the pituitary. ABP, androgen-binding protein.

The Convoluted Seminiferous Tubules

The seminiferous tubules are highly convoluted tubules lined by a stratified epithelium. These tubules are enclosed by a thick basal lamina and surrounded by 3-4 layers of smooth muscle cells (or myoid cells) The insides of the tubules are lined with seminiferous epithelium (germinal or spermatogenic), which consist of two distinct cellular populations: 1. Cells in various stages of spermatogenesis and spermiogenesis, collectively referred to as the spermatogenic series; 2. Non-spermatogenic cells, called Sertoli cells, that support and nourish developing spermatozoa.

In the interstitial spaces between the tubules, cells with an endocrine function, called Leyding cells, are found either singly or in clumps in the supporting connective tissue. They secrete testicular androgens (testosterone).

 

Spermatogenic cells:

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Spermatogoniaare the first cells of spermatogenesis. They originate in the 4th week of foetal development in the endodermal walls of the yolk sac and migrate to the primordium of the testis, where they differentiate into spermatogonia. Spermatogonia remain dormant until puberty. They are always in contact with the basal lamina of the tubule.

Two types of spermatogonia can be distinguished in the human seminiferous epithelium:

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Type A spermatogonia have a rounded nucleus with very fine chromatin grains and one or two nucleoli. They are stem cells which divide to form new generations of both type A and type B spermatogonia.

Type B spermatogonia have rounded nuclei with chromatin granules of variable size, which often attach to the nuclear membrane, and one nucleolus. Although type B spermatogonia may divide repeatedly, they do not function as stem cells and their final mitosis always results in the formation of

Primary spermatocytes which lie in the cell layer luminal to the spermatogonia. They appear larger than spermatogonia. They immediately enter the prophase of the first meiotic division, which is extremely prolonged (about 22 days!). A large number of primary spermatocytes is always visible in cross-sections through seminiferous tubules. Cell divisions, from the formation of primary spermatocytes and onwards, to the production of the spermatocytes, are incomplete. The cells remain connected by bridges of cytoplasm. The completion of the first meiotic division results in the formation of

Secondary spermatocytes, which are smaller than primary spermatocytes. They rapidly enter and complete the second meiotic division and are therefore seldom seen in histological preparations. Their division results in the formation of

Spermatids, which lie in the luminal part of the seminiferous epithelium. They are small (about 10 µm in diameter) with an initially very light (often eccentric) nucleus. The chromatin condenses during the maturation of the spermatids into spermatozoa, and the nucleus becomes smaller and stains darker.

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The terminal phase of spermatogenesis is called spermiogenesis and consists of the differentiation of the newly formed spermatids intoSpermatozoa

The mature human spermatozoon is about 60 µm long and actively motile. It is divided into head, neck and tail.

The head (flattened, about 5 µm long and 3 µm wide) chiefly consists of the nucleus (greatly condensed chromatin!). The anterior 2/3 of the nucleus is covered by the acrosome, which contains enzymes important in the process of fertilisation. The posterior parts of the nuclear membrane forms the so-called basal plate.

The neck is short (about 1 µm) and attached to the basal plate. A transversely oriented centriole is located immediately behind the basal plate. The neck also contains nine segmented columns of fibrous material, which continue as the outer dense fibres into the tail.

The tail is further divided into a middle piece, a principal piece and an end piece. The axonema (the generic name for the arrangement of microtubules in all cilia) begins in the middle piece. It is surrounded by nine outer dense fibres, which are not found in other cilia. In the middle piece (about 5 µm long), the axonema and dense fibres are surrounded by a sheath of mitochondria. The middle piece is terminated by a dense ring, the annulus. The principal piece is about 45 µm long. It contains a fibrous sheath, which consists of dorsal and ventral longitudinal columns interconnected by regularly spaced circumferential hoops. The fibrous sheath and the dense fibres do not extend to the tip of the tail. Along the last part (5 µm) of the tail, called the end piece, the axonema is only surrounded by a small amount of cytoplasm and the plasma membrane.

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It takes about 48 days from the time cells enter meiosis until morphologically mature spermatozoa are formed. Depending on the length of reproduction of spermatogonia (which is not precisely determined) it takes approximately 64-72 days to complete spermatogenesis.

SERTOLI CELLS

are far less numerous than the spermatogenic cells and are evenly distributed between them. Their shape is highly irregular - columnar is the best approximation. Sertoli cells extend from the basement membrane to the luminal surface of the seminiferous epithelium. Processes of the Sertoli cells extend in between the spermatogenic cells (cell limits are therefore not clearly visible in the LM). The nucleus of Sertoli cells is ovoid or angular, large and lightly stained and often contains a large nucleolus. The long axis of the nucleus is oriented perpendicular to wall of the tubule. A fold in the nuclear membrane is characteristic for Sertoli cells but not always visible in the LM. These cells contain abundant smooth endoplasmic reticulum, some rough endoplasmic reticulum, a well developed Golgi complex, and numerous mitochondria and lysosomes. Lateral processes of Sertoli cells are interconnected by tight junctions, which are likely to be the structural basis for the blood-testis barrier, which includes Sertoli cells, basement membrane of seminiferous tubule, myoid and fibrous layer of seminiferous tubule wall, perivascular space rich with macrophages and hemocapillary wall (basement membrane and endothelium).

Spermatogonia and primary spermatocytes are located in the basal compartment, other cellular stages of spermatogenesis are located in the adluminal compartment. Tight junctions may temporarily open to permit the passage of spermatogenic cells from the basal into the adluminal compartment. Sertoli cells provide mechanical and nutritive support for the spermatogenic cells. Sertoli cells also secrete two hormones - inhibin and activin - which provide positive and negative feedback on FSH secretion from the pituitary.

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Interstitial tissue

The spaces between seminiferous tubules in the testis are filled with accumulation of connective tissue, nerves, blood, and lymphatic vessels. The connective tissue consists of various cell types, including fibroblasts, undifferentiated connective cells, mast cells, and macrophages.

Leydig cells (15-20 µm), located in the interstitial tissue between the convoluted seminiferous tubules, constitute the endocrine component of the testis. They synthesise and secrete testosterone, which is responsible for the development of the secondary male sex characteristics. Leydig cells occur in clusters, which are variable in size and richly supplied by capillaries. They have the characteristics of steroid –secreting cells. The cytoplasm is strongly acidophilic and finely granular. The nucleus is large, round and often located eccentric in the cell.

 

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Electron micrograph of a section of an interstitial cell. There is abundant smooth endoplasmic reticulum as well as mitochondria. Medium magnification.

EXCRETORY GENITAL DUCTS

Spermatozoa pass via the tubuli recti (low columnar epithelium) and the rete testis (flattened or cuboidal epithelium) into numerous ductuli efferentes, which are lined by a columnar epithelium, which consists of both absorptive and ciliated cells. The height of the two cells types which form the epithelium of the ductuli efferentes is variable which gives the lumen a characteristic wavy outline.

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The ductuli efferentes leave the testis and open into a common duct, the ductus epididymidis(about 6 m long!).

The epididymis is a long, extremely convoluted duct extending down the posterior aspect of the testis to the lower pole where it becomes the ductus deferens. The major function of the epididymis is thought to be the accumulation and storage of spermatozoa when the spermatozoa develop motility. The epididymis is a tube of smooth muscle lined by a pseudostratified epithelium. From the proximal to the distal end of the epididymis, the muscular wall increases from a single, circular layer as in these micrographs to three layers organized in the same manner as in the ductus deferens. The smooth muscle at the proximal end exhibits slow, rhythmic contractility; this activity gently moves spermatozoa towards the ductus deferens. Distally, the smooth muscle is richly innervated by the sympathetic nervous system which produces intense contractions of the lower part of the epididymis during ejaculation.

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The epithelial lining of the epididymis shows a gradual transition from a tall, pseudostratified columnar form proximally to a shorter pseudostratified form distally. The principal cells of the epididymal epithelium bear tufts of very long microvilli, inappropriately called stereocilia; stereocilia are thought to be involved in absorption of a vast excess of fluid accompanying the spermatozoa from the testis. Stereocilia are non-motile structures, which in the EM resemble large microvilli. Towards the basal lamina a number of small nuclei could be seen, which belong to the basal cells of the ductus epididymidis. These cells regenerate the epithelium.

Peristaltic contractions of smooth muscle cells surrounding the ductus epididymidis move the spermatozoa towards the middle segment of the duct, which is the site of final functional maturation of the spermatozoa - now they are motile. The terminal segment of the ductus epididymidis is the site of storage of the mature spermatozoa. Smooth muscle fibres of the terminal part of the ductus epididymidis do not contract spontaneously. They contract during sexual stimulation concurrently with the contraction of the musculature of the duct into which it opens, the vas deferens.

Note that ductuli efferentes are located mainly in the head of the epididymis, whereas the ductus epididymidis forms the body and tail of the epididymis. Sections of epididymis may therefore not contain both types of ducts.

DUCTUS DEFERENS

Ductus deferens is a straight tube with thick, muscular wall. It continues from epididymis toward the prostatic urethra and empties into it. It is characterized by a narrow lumen and a thick layer of smooth muscle. The wall of ductus deferens consists of three tunices: mucosa, muscularis and adventitia.The mucosaof the vas deferens forms low longitudinal folds. It is lined by a pseudostratified columnar epithelium. Similar to the epididymis, cells have long stereocilia. The lamina propria is unusually rich in elastic fibres. The muscularis is well developed (up to 1.5 mm thick) and consists of a thick circular layer of smooth muscle between thinner inner and outer longitudinal layers. The muscularis is the structure which makes the vas deferens palpable in the spermatic cord. The vas deferens is surrounded by an adventitia, which is slightly denser than usual. Before it enters the prostate, the vas deferens dilates, forming a region called the ampulla. In this area, the epithelium becomes thicker and extensively folded. At the final portion of the ampulla, the seminal vesicles join the duct. From there on, the ductus deferens enters the prostate, opening into the prostatic urethra.the segment entering the prostate is called the ejaculatory duct. The mucous layer of the ductus deferens continues through the ampulla into the ejaculatory duct, but the muscle layer ends after ampulla.

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ACCESSORY GENITAL GLANDS

The accessory (or secondary) male sex glands consist of the seminal vesicles, the prostrate and the bulbourethral glands.

Prostateis the largest accessory sex gland in men (about 2 × 3 × 4 cm). It contains 30 - 50 tubuloalveolar glands, which empty into 15 - 25 independent excretory ducts. These ducts open into the urethra. The glands are embedded into a fibromuscular stroma, which mainly consists of smooth muscle separated by strands of connective tissue rich in collagenous and elastic fibres. The muscle forms a dense mass around the urethra and beneath the fairly thin capsule of the prostrate.

The secretory alveoli of the prostate are very irregularly shaped because of papillary projections of the mucosa into the lumen of the gland. The epithelium is cuboidal or columnar. Basal cells are again present, and the epithelium may look pseudostratified where they are found. The secretory cells are slightly acidophilic and secretory granules may be visible in the cytoplasm. Small extensions of the apical cytoplasm into the lumen of the alveoli may represent cells which  release their secretory products (secretion is apocrine/merocine). The secretion of the prostate contains citric acid, the enzyme fibrinolysin (liquefies the semen), acid phosphatase, a number of other enzymes and lipids. The secretion of the prostate is the first fraction of the ejaculate. The secretory ducts of the prostate are lined by a simple columnar epithelium, which changes to a transitional epithelium near the openings of the ducts into the urethra.

A characteristic feature of the prostate is the appearance of corpora amylacea in the secretory alveoli. They are rounded eosinophilic bodies. Their average diameter is about 0.25 mm (up to 2 mm). They appear already in the seventh month of foetal development. Their number increases with age - in particular past 50. They may undergo calcification. Corpora amylacea may appear in semen.

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Macroscopically the prostrate can be divided into lobes, but they are inconspicuous in histological sections. In good histological sections it is possible to distinguish three concentric zones, which surround the prostatic part of the urethra.

The peripheral zone(70 %) contains large, so-called main glands, whose ducts run posteriorly to open into the urethra.

The internal zone consists of the so-called submucosal glands, whereas

the innermostcentral zone (25% of gland’s volume) containsmucosal glands.

This subdivision of the prostate is of clinical importance. With age the prostate becomes enlarged due to benign nodular hyperplasia. The onset age of these hyperplastic changes is 45. About 3/4 of the males above 60 are affected of which half will be symptomatic. This condition affects the mucosal glands. Cancer of the prostate, which is the second most common malignant tumor in western males, involves the peripheral zone.

Have a look at the epithelium and the interstitial tissue. It is quite cellular (smooth muscle).

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Seminal Vesicles. The seminal vesicles develop from the vas deferens. Their histological organisation resembles to some extent that of the vas deferens. They are elongated sacs (about 4 cm long and 2 cm wide), which taper where they unite with the vas deferens. Each seminal vesicle consists of one coiling tube (about 15cm long). All the lumina visible in sections of the seminal vesicle are in continuity in the intact organ.   The mucosa shows thin, branched, anastomosing folds. The structure of the epithelium is variable appearing columnar or pseudostratified columnar (columnar cells and basal cells). The lamina propria of the mucosa is fairly thin and loose. The muscularis consists of inner circular and outer longitudinal layers of smooth muscle.

Seminal vesicles were thought to store semen - hence there name. This turned out to be wrong. They are glands, whose secretion constitutes 60-70 % of the ejaculate. The secretory product of the columnar cell, which may be seen in the lumen of the seminal vesicles, is strongly acidophilic. It contains large amounts of fructose which the spermatozoa utilise as a source of energy. Furthermore, the secretion contains prostaglandins, flavins (yellow fluorescing pigment - of use in forensic medicine to detect semen stains) and several other proteins and enzymes.

The cocktail of compounds which is released by the seminal vesicles in addition to fructose has three main functions:

the formation of the sperm coagulum,

the regulation of sperm motility and

the suppression of immune function in the female genital tract.

The secretion of the seminal vesicles is the third fraction of the ejaculate (the spermatozoa are released with the second fraction - the contents of the vas deferens).

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Secretory vesicles may be visible in the apical cytoplasm of the columnar cells. The lumen of the seminal vesicles is often filled with the their acidophilic secretion. Try to understand the appearance of the epithelium by looking at spots where it is cut parallel or perpendicular to its surface. Sections passing tangentially through the anastomosing epithelial folds of the mucosa will often show a honeycomb-like structure.

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Contraction of the seminal vesicles smooth muscle propels accumulated secretion into the ejaculatory duct.

The ejaculatory duct is formed by the merging of the short duct from the seminal vesicle with the vas deferens distal to the ampulla. Each ejaculatory duct is only 1 cm long and is lined by an epithelium of tall columnar and small round cells identical to that of ampulla; there is no smooth myocytes in its wall. The right and left ejaculatory ducts run through the prostate gland and open into the prostatic urethra at the prostatic utricle.

PENIS

The penis is composed of erectile tissue and contains part of the male urethra. The erectile tissue is arranged into two dorsal cylinders (corpora cavernosa) and a smaller central one (corpus spongiosum) through which the penile urethra runs. The cylinders are each surrounded by dense fibrocollagenous sheath, the tunica albuginea, which also holds them together. The erectile tissues are essentially interconnecting vascular spaces which are empty when penis is flaccid but fill with blood during erection to gorm an enlarged rigid organ. The blood supply to the penis is provided by the dorsal and the deep arteries. From the last ones arise srteries supplying the tunica albuginea, and the helicine arteries, which supply the erectiole tissue. The helicine arteries are spiral in the flaccid penis but during erection they straighten and dilate, filling the corpora with blood.

The erectile component of the penis is surrounded by skin, which has a very loose subcutis, permitting it to move considerably during intercourse. At the distal end of the penis the corpus spongiosum terminates on the glans penis, which is covered with nonkeratinizing squamous epithelium containing sebaceous glands.

The penile urethra opens at the meatus at the centre of the glans penis. For the most of its length the penile urethra is lined by nonsecreting columnar epithelium into which small mucus glands are embedded in the corpus spongiosum drain. Within the glans penis the urethra dilates and becomes lined by non-keratinizing stratified squamous epithelium identical to that covering the glans. The end of the penis is normally covered by an overlap of penile skin (the prepuce), which is rich in elastic fibers permitting it to retract over the glans penis during intercource.

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OVARIES

The paired ovaries are small flattened ovoid organs lying in the right and left lateral pelvic cavities. They have two major functions: germ cells production (exocrine) and hormones secretion (endocrine).

 

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The ovaries are encapsulated in a fibrous connective tissue layer called the tunica albuginea, named for its white appearance at gross examination. The surface of the ovary is covered by a single layer of epithelium. Usually it is cuboidal or low columnar im type, but commonly flattens with increasing age and when the ovary is enlarged. The epithelium is continuous with the pelvic peritoneum at the hilum of ovary (though the cells differ structurally from the peritoneal mesothelial cells).

The ovary can be devided into three components: hilum, medulla and cortex.

The body of the ovary consists of spindle-shaped cells, reticular fibres and ground substance which together constitute the ovarian stroma. In the peripheral zone of the stroma, known as the cortex, are numerous follicles which contain female gametes in various stages of development. In addition, there may also be postovulatory follicles of various kinds, i.e. corpora lutea or degenerativefollicles i.e. corpora albicantes and atretic follicles.

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Ovary of a woman of reproductive age showing its main components: germinal epithelium, tunica albuginea, cortical region, and medullary region.

The central zone of the ovarian stroma, the medulla is highly vascular. The blood vessels of the ovary, together with autonomic nerves and lymphatics, pass in the broad ligament into the ovary at the hilum.

During early fetal development, primordial germ cells called oogonia migrate into the ovarian cortex where they multiply by mitosis. By the fourth and fifth months of fetal development in the human, some oogonia enlarge and assume the potential for development into mature gametes.

 

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At this stage they become known as primary oocytes and commence the first stage of meiotic division. By the seventh month of fetal development, the primary oocytes become encapsulated by a single layer of flattened follicular cells, of epithelial origin, to form primordial follicles. This encapsulation arrests the first meiotic division and no further development of the primordial follicle then occurs until after the female reaches sexual maturity. The remaining phases of meiotic division occur during a final phase of follicular maturation leading to ovulation and fertilization. Thus all the female germ cells are present at birth and the process of meiotic division is completed between 15 and 50 years later. In contrast, in males, meiotic division of germ cells commences only after sexual maturity and sperm formation is accomplished within about 2 months.

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During each ovarian cycle, up to 20 primordial follicles are in some way activated to undergo the maturation process; nevertheless, usually only one follicle reaches full maturity and is ovulated whilst the remainder undergo atresia before the point of ovulation. The reason for this apparent wastage is unclear; during maturation, however, the follicles have an endocrine function which may be far beyond the capacity of a single follicle and the primary purpose of the other follicles may be to act as an endocrine gland

Approaching maturity, further growth of the oocyte ceases and the first meiotic division is completed just before ovulation. At this stage the oocyte becomes known as the secondary oocyte and commences the second meiotic division. The first polar body, containing very little cytoplasm, remains inconspicuously within the zona pellucida. The follicular antrum enlarges markedly and the zona granulosa forms a layer of even thickness around the periphery of the follicle. The cumulus oophorus diminishes leaving the oocyte surrounded by a layer several cells thick, the corona radiata, which remains attached to the zona granulosa by thin bridges of cells. Before ovulation these bridges break down and the oocyte, surrounded by the corona radiata, floats free inside the follicle.

 

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Photomicrograph of part of an antral follicle. Cavities (A) that appear in the granulosa layer will fuse and form one large cavity, the antrum. The oocyte is surrounded by the zona pellucida. Granulosa cells (G) surround the oocyte and cover the wall of the follicle. A theca can be seen around the follicle. H&E. Medium magnification.

During the process of follicular maturation the amount of estrogen-secreting tissue, the theca interna, increases progressively and there is a corresponding rise in the level of circulating estrogens. Atresia of all but the follicle destined to ovulate probably accounts for the fall in circulating estrogens which occurs just prior to ovulation.

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Photomicrograph of a small part of the wall of an antral follicle, showing the antrum, the layer of granulosa cells, and the thecas. The theca interna surrounds the follicle, and its cells appear lightly stained because their cytoplasm contains lipid droplets, a characteristic of steroid-producing cells. The theca interna is surrounded by the theca externa, which merges with the stroma of the ovary. Theca externa consists of two layers: inner vascular layer and outer fibrous one. Cell of theca later they will be transformed into thecoluteocytes. A basement membrane separates the granulosa layer from the theca interna. PT stain. High magnification.

 

At ovulation, the mature follicle ruptures and the ovum, comprising the secondary oocyte, zona pellucida and corona radiata, is expelled into the peritoneal cavity near the entrance to the uterine tube. The second meiotic division of the oocyte is not completed until after penetration of the ovum by a spermatozoon.

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Photomicrograph of the atresia of a follicle characterized by: (1) the death of granulosa cells, many of which are seen loose in the antrum; (2) loss of the cells of the corona radiata; and (3) the oocyte floating free within the antrum. PT stain. Medium magnification.

Usually ovulation occurs right at the middle of menstrual-ovarial cycle (14th day). After that the rmnant of follicle is transmorming into corpus luteum which undergos next stages during two-three weeks:

1.     bleeding, vascularization and prolipheration;

2.     glandular methamorphosis;

3.     secretion;

4.     involution.

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Part of a corpus luteum. Granulosa lutein cells, which constitute the majority of the cells, derive from the granulosa layer. They are larger and stain more lightly than the theca lutein cells, which originate from the theca interna. The remnant of the blood clot is seen in the centre of the corpus luteum, surrounded by a broad zone of granulose luteal cells. Peripherally, a thin zone of theca luteal (paraluteal) cells T can be seen. The corpus luteum is bounded by a connective tissue zone representing the theca externa of the antecedent Graafian follicle. Granulose luteocytes may be compared with theca luteocytes (paraluteal) cells T. Granulose luteal cells have a relatively large amount of pale-stained cytoplasm containing numerous lipid droplets which give rise to the vacuolated appearance seen in this preparation; lipid is utilized in the synthesis of the steroid hormone, progesterone.

Theca luteal (paraluteal) cells form a thin zone around the periphery of the granulose luteal layer with finger-like extensions of the theca luteal layer extending into the granulose luteal layer. Theca luteal cells are smaller, with a more densely staining, less vacuolated cytoplasm; these cells are responsible for the secretion of estrogens.

As a result of involution corpus albicans (connective tissue) appear in the ovary.

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Corpus albicans, the scar of connective tissue that replaces a corpus luteum after its involution

 

Menstrual  cycle.  Mammary  glands

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The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges (singularsalpinx) are two very fine tubes of great mobility leading from the ovaries into the uterus.

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Female genittalia blood supply

There are two Fallopian tubes, attached to either side of the cornual end of the uterus, and each terminating at or near one ovary forming a structure called the fimbria.

The Fallopian tubes are not directly attached to the ovaries, but open into the peritoneal cavity (essentially the inside of the abdomen); they thus form a direct communication between the peritoneal cavity and the outside via the vagina. In humans, the Fallopian tubes are about 7–14 cm long.

There are four regions of the fallopian tube from the ovary to the uterus:

Infundibulum - contains fimbriae (a fringe of finger-like extensions).

Ampulla - usual site of fertilization

Isthmus

Intramural oviduct - inside wall of uterus

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Oviduct with highly labyrinthine mucosa. Each piece of folded, branching mucosa is lined with simple columnar epithelium. The rest of the wall is rather thin and shows interlaced smooth muscle bundles.

 

Layers of the wall of the fallopian tube.

 

Layers of the fallopian tube wall.

 

There are three layers of the fallopian tube wall: mucosa, muscularis and serosa composed of visceral peritoneum.

 

Mucosahas  the distinctive branched folds of the mucosa are the most unusual feature. In cross sections, the lumen of the ampulla resembles a labyrinth. These folds become smaller in the segments of the tube that are closer to the uterus. In the intramural portion, the folds are reduced to small bulges in the lumen, so its internal surface is almost smooth.

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Photomicrograph of part of the wall of an oviduct. The highly folded mucosa indicates that this region is close to the ovary. PT stain. Low magnification.

 

Two layers are present in mucosa: epithelium and lamina propria. The epithelium lining the mucosa is simple columnar and contains two types of cells. One has cilia; the other is secretory.

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Photomicrograph of the epithelial lining of an oviduct. The epithelial lining is formed by ciliated and more darkly staining nonciliated secretory cells. Ciliated cells contribute to the movement of the oocyte or conceptus to the uterus. PT stain. High magnification.

 

A higher power of the fimbriated (finger-like) end of the oviduct. The surface epithelium is high cuboidal or low columnar and has a ciliated surface. Arrows indicate non-ciliated "peg" cells which are secretory in function and stand up higher than the other cells. (a = lamina propria core of fimbria.)

 

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Scanning electron micrograph of the lining of an oviduct. Note the abundant cilia. In the center is the apex of a secretory cell covered by short microvilli. X8000.

 

The cilia beat toward the uterus, causing movement of the viscous liquid film that covers the surface. This liquid consists mainly of products of the secretory cells interspersed between ciliated cells. This secretion has nutrient and protective functions for the ovum and promotes activation (capacitation) of spermatozoa. Movement of the film that covers the mucosa of the tube, in conjunction with contractions of the muscle layer, helps to transport the ovum or the conceptus toward the uterus. This movement also hampers the passage of  microorganisms from uterus to the peritoneal cavity. Transport of the ovum or conceptus to the uterus, however, is normal in female with immotile cilia syndrome, showing that ciliary activity is not essential for transport.

The lamina propria of the mucosa is composed of loose connective tissue and has decidual cells similar to uterine ones. This makes embryo implantation possible here. In cases of abnormal nidation (ectopic pregnancy), the lamina propria reacts like the endometrium, forming numerous decidual cells. Bbecause of its small diameter, the oviduct cannot contain these new cells and bursts, causing extensive hemorrhage that can be fatal if not treated immediately.

Muscularis externaconsists of smooth muscular tissue arranged in the inner circular and outer longitudinal layer.

Outermost tunica serosa are made up of peritoneum visceral layer (connective tissue with mesothelium).

The oviduct captures the ovum expelled by the ovary and carries it toward the uterus. Its lumen is an environment adequate for fertilization, and its secretions contribute to the nutrition of the embryo during the early phases of development

 (tubal period).

At the time of ovulation, the oviduct exhibits active movement. The fimbria of the infundibulum move closer to the surface of the ovary, and the funnel shape of the infundibulum facilitates the recovery of the liberated ovum.

The wall of the oviduct is richly vascularized, and its vessels become dilated at the time of ovulation. This dilatation gives rigidity and distension to the organ, facilitating its approximation to the ovary. Fertilization usually takes place in the lateral third of the oviduct.

The Fallopian tubes are mobile, and have been observed on time-lapse videography moving about the pelvis. Although anatomical illustrations have them proceeding from the uterine horns to the ovary, this is not the case for most of the menstrual cycle, and a tube may cross to the other side or lie on top of the uterus.

 

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Ampular, isthmic and uterine parts of Fallopian tube

The ostium of the Fallopian tube is the opening in the infundibulum of uterine tube into the abdominal cavity. In ovulation, the oocyte enters the Fallopian tube through this opening.

It is surrounded by fimbriae, which help in the collection of the oocyte. In the female reproductive system, the fimbria (plural, fimbriae) is a fringe of tissue around the ostium of the Fallopian tube, in the direction of the ovary.

An ovary is not directly connected to its adjacent Fallopian tube. When ovulation is about to occur, the sex hormones activate the fimbriae, causing it to hit the ovary in a gentle, sweeping motion. An oocyte is released from the ovary into the peritoneal cavity and the cilia of the fimbriae sweep the ovum into the Fallopian tube. Not all fimbriae, but only the ovarian fibria]][1] is long enough to reach to ovary.

The third part of the uterine tube is the the infundibulum. It terminates with the ostium of Fallopian tube, surrounded by fimbriae, one of which, the ovarian fimbria is attached to the ovary.

The first part of the uterine tube is the isthmus tubae uterinae. It is the medial third, and it is constricted.

The ampulla is the second portion of the uterine tube. It is an intermediate dilated portion, which curves over the ovary. It is the most common site of human fertilization.

Uterus

The uterus or womb is the major female reproductive organ of most mammals, including humans. One end, the cervix, opens into the vagina; the other is connected on both sides to the fallopian tubes. The term uterus is commonly used within the medical and related professions, whilst womb is in more common usage.

The bilateral Müllerian ducts form during early fetal life. In males, MIF secreted from the testes leads to their regression. In females these ducts give rise to the Fallopian tubes and the uterus. In humans the lower segments of the two ducts fuse to form a single uterus, however, in cases of uterine malformations this development may be disturbed. The different uterine forms in various mammals are due to various degrees of fusion of the two Müllerian ducts.

The main function of the uterus is to accept a fertilized ovum which becomes implanted into the endometrium, and derives nourishment from blood vessels which develop exclusively for this purpose. The fertilized ovum becomes an embryo, develops into a fetus and gestates until childbirth. Due to anatomical barriers such as the pelvis, the uterus is pushed partially into the abdomen due to its expansion during pregnancy. Even in pregnancy the mass of a human uterus amounts to only about a kilogram (2.2 pounds).

Regions

From outside to inside, the path to the uterus is as follows:

Vulva

Vagina

Cervix uteri - "neck of uterus"

External orifice of the uterus

Canal of the cervix

Internal orifice of the uterus

Сorpus uteri - "Body of uterus"

Cavity of the body of the uterus

Fundus (uterus)

Layers

The layers, from innermost to outermost, are as follows:

Endometrium The lining of the uterine cavity is called the "endometrium." In most mammals, including humans, the endometrium builds a lining periodically which, if no pregnancy occurs, is shed or reabsorbed. Shedding of the endometrial lining in humans is responsible for menstrual bleeding (known colloquially as a woman's "period") throughout the fertile years of a female and for some time beyond. In other mammals there may be cycles set as widely apart as six months or as frequently as a few days.

Myometrium The uterus mostly consists of smooth muscle, known as "myometrium." The innermost layer of myometrium is known as the junctional zone, which becomes thickened in adenomyosis.

Perimetrium The uterus is surrounded by "peritoneum."

Parametrium The loose surrounding tissue is called the "perimetrium."

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A panoramic view of the uterus showing the whole thickness of the wall.

Major ligaments

It is held in place by several peritonealligaments, of which the following are the most important (there are two of each):

Name

From

To

uterosacral ligament

the posterior cervix

the sacrum of pelvis

cardinal ligaments

the side of the cervix

the ischial spines

Other named ligaments near the uterus, i.e. the broad ligament, the round ligament, the suspensory ligament of the ovary, the infundibulopelvic ligament, have no role in the support of the uterus.

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Uterus general wiev

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Light microscopy of endometrium in different phases of menstrual cycle (prolipherative early and late secretory) and in pregnancy.

 

Photomicrograph of the superficial layer of the endometrium during the proliferative phase. The surface epithelium and the uterine glands are embedded in a lamina propria made of very loose connective tissue. PT stain. Medium magnification.

 

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Photomicrograph of straight uterine glands in the deep endometrium during the proliferative phase. Smooth muscle of the myometrium is also seen. H&E stain. Medium magnification.

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Photomicrograph of uterine glands. During the luteal phase, the uterine glands become tortuous and their lumen is filled with secretions. Some edema is present in the connective tissue. H&E stain. Medium magnification.

 

cervix

Mucosa of the cervix with its lumen to the left. (The uterus would lie above this region and the vagina below.) Notice how the mucosal glands slant upwards. They produce a mucoid secretion. Arrows = small blood vessels.

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Sharp transition from simple columnar epithelium of the endocervix to non-cornified stratified squamous epithelium of the ectocervix and vagina.

The vagina, (from Latin, literally "sheath" or "scabbard" ) is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the oviduct. The Latinate plural (rarely used in English) is vaginae.

In common speech, the term "vagina" is often used to refer to the vulva or female genitals generally; strictly speaking, the vagina is a specific internal structure and the vulva is the exterior genitalia only.

The human vagina is an elastic muscular canal that extends from the cervix to the vulva.Although there is wide anatomical variation, the length of the unaroused vagina is approximately 6 to 7.5 cm (2.5 to 3 in) across the anterior wall (front), and 9 cm (3.5 in) long across the posterior wall (rear).During sexual arousal the vagina expands in both length and width.Its elasticity allows it to stretch during sexual intercourse and during birth to offspring.The vagina connects the superficial vulva to the cervix of the deep uterus.

If the woman stands upright, the vaginal tube points in an upward-backward direction and forms an angle of slightly more than 45 degrees with the uterus. The vaginal opening is at the caudal end of the vulva, behind the opening of the urethra. The upper one-fourth of the vagina is separated from the rectum by the rectouterine pouch. Above the vagina is Mons Veneris. The vagina, along with the inside of the vulva, is reddish pink in color, as with most healthy internal mucous membranes in mammals.

Vaginal lubrication is provided by the Bartholin's glands near the vaginal opening and the cervix. The membrane of the vaginal wall also produces moisture, although it does not contain any glands. Before and during ovulation, the cervix's mucus glands secretes different variations of mucus, which provides a favorable alkaline environment in the vaginal canal to maximize the chance of surivival for sperm.

The hymen is a thin membrane of connective tissue which is situated at the opening of the vagina. As with many female animals, the hymen covers the opening of the vagina from birth until it is ruptured during activity. The hymen may rupture during sexual or non-sexual activity. Vaginal penetration may rupture the hymen. A pelvic examination, injury, or certain types of exercises, such as horseback riding or gymnastics may also rupture the hymen. Sexual intercourse does not always rupture the hymen.Therefore, the presence or absence of a hymen does not indicate virginity or prior sexual activity.

Physiological functions of the vagina

The vagina has several biological functions.

Uterine secretions

The vagina provides a path for menstrualblood and tissue to leave the body. In industrial societies, tampons, menstrual cups and sanitary napkins may be used to absorb or capture these fluids.

Sexual activity

The concentration of the nerve endings that lie close to the entrance of a woman's vagina can provide pleasurable sensation during sexual activity, when stimulated in a way that the particular woman enjoys. During sexual arousal and particularly stimulation of the clitoris, the walls of the vagina self-lubricate, reducing friction during sexual activity. Research has found that portions of the clitoris extend into the vulva and vagina.

With arousal, the vagina lengthens rapidly to an average of about 4 in.(8.5 cm), but can continue to lengthen in response to pressure.As the woman becomes fully aroused, the vagina tents (last ²⁄ expands in length and width) while the cervix retracts.The walls of the vagina are composed of soft elastic folds of mucous membrane skin which stretch or contract (with support from pelvic muscles) to the size of the penis. With proper arousal, the vagina may stretch/contract to accommodate virtually any penis size (or sex toy/object within reason).

An erogenous zone referred to commonly as the G-spot is located at the anterior wall of the vagina, about five centimeters in from the entrance. Some women experience intense pleasure if the G-spot is stimulated appropriately during sexual activity. A G-Spot orgasm may be responsible for female ejaculation, leading some doctors and researchers to believe that G-spot pleasure comes from the Skene's glands, a female homologue of the prostate, rather than any particular spot on the vaginal wall.[11][12][13] Some researchers deny the existence of the G-spot.

Childbirth

During childbirth, the vagina provides the channel to deliver the baby from the uterus to its independent life outside the body of the mother. During birth, the vagina is often referred to as the birth canal. The vagina is remarkably elastic and stretches to many times its normal diameter during vaginal birth.

Vagina with stratified squamous epithelial lining and a wide lamina propria (some people would call the deeper portion of this layer the submucosa. The two connective tissue Iayers merge because there is no muscularis mucosae to separate them.) Notice distended venules in the connective tissue and the way the smooth muscle of the muscularis externa lies in loose strands.

 

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Photomicrograph of stratified squamous epithelium of the vagina supported by a dense connective tissue. The cytoplasm of these epithelial cells is clear because of accumulated glycogen. PSH stain.Medium magnification.

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During the entire life of a woman, the structure and functions of the vaginal epithelium and of the endometrium depend on ovarian hormones.

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Changes in the uterine glands and in the gland cells during the menstrual cycle. In the proliferative stage the glands are straight tubules, and their cells show no secretory activity. In the initial secretory phase the glands begin to coil, and their cells accumulate glycogen in the basal region. In the late secretory phase the glands are highly coiled, and their cells present secretory activity at their apical portion.

 

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Schematic drawing of the female breast showing inactive and active mammary glands. Each lactiferous duct with its accompanying smaller ducts is a gland in itself and constitutes the lobes of the gland.

 

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Changes in the mammary gland. A: In nonpregnant women, the gland is quiescent and undifferentiated, and its duct system is inactive. B: During pregnancy, alveoli proliferate at the ends of the ducts and prepare for the secretion of milk. C: During lactation, alveoli are fully differentiated, and milk secretion is abundant. Once lactation is completed, the gland reverts to the nonpregnant condition.

 

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Photomicrograph of lactating mammary gland. Several alveoli are filled with milk, visible as granular material. The vacuoles in the lumen and in the alveolar cell cytoplasm represent the lipid portion of milk. PT stain. Medium magnification.

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Secreting cells from the mammary gland. From left to right, note the accumulation and extrusion of lipids and proteins. The proteins are released through exocytosis.

 

 

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Pituitary hormones control most ovarian functions. Follicle-stimulating hormone (FSH) stimulates follicular growth and synthesis of estrogen by the granulosa cells. Luteinizing hormone (LH) induces ovulation and transforms the granulosa layer and the theca interna into an actively secreting gland, the corpus luteum. Estrogen and progesterone produced in the ovary act on the hypothalamus, stimulating or inhibiting the liberation of gonadotropin-releasing hormone (GnRH).

 

References:

a) basic

1.     Practical classes materials.

2.     Lectury presentation.

3.     Stevens A. Human Histology / A.Stevens, J.Lowe. – [second edition]. Mosby, 2000. P. 309-324, 338-344/

4.     Wheter’s Functional Histology :A Text and Colour Atlas / [Young B., Lowe J., Stevens A., Heath J.]. Elsevier Limited, 2006. – P. 346-358, 360-367.

5.     Ross M. Histology : A Text and Atlas / M. Ross W.Pawlina. – [sixth edition]. – Lippincott Williams and Wilkins, 2011. – P. 784-845, 872-876.

b) additional

6. Eroschenko V.P. Atlas of Histology with functional correlations / Eroschenko V.P. [tenthedition]. – Lippincott Williams and Wilkins, 2008. – P. 409-453.

7. Charts:

http://intranet.tdmu.edu.ua/index.php?dir_name=kafedra&file_name=tl_34.php#n15

8. Volkov K. S. Ultrastructure of cells and tissues / K. S. Volkov, N. V. Pasechko. – Ternopil : Ukrmedknyha, 1997. – P. 94-99.

http://en.wikipedia.org/wiki/Histology

http://www.meddean.luc.edu/LUMEN/MedEd/Histo/frames/histo_frames.html

http://www.udel.edu/biology/Wags/histopage/histopage.htm