Testis and duct system.pptx

the above lecture explains the anatomy of male reproductive system.

1. TESTIS AND DUCT SYSTEM Presenter Name: Dr. Kashif Hussain Alvi Awan

2. INTRODUCTION The Male Reproductive system is responsible for the production of spermatozoa, and it comprises of 4 components: Paired testes or male gonads. Male genital duct. Accessory sex gland. Penis- a copulatory organ.

3. The Testes or Male Gonads , a paired organs lying in the scrotal sac are responsible for production of the male gametes, spermatozoa and secretion of male sex hormones, principally Testosterone . A System of Ducts consisting of ductuli efferentes, epididymis, ductus (vas) deferens and ejaculatory duct collects, stores and carries spermatozoa from each testis. Two Exocrine Glands , the paired seminal vesicles and the single prostate gland, secrete a nutritive and lubricating fluid medium called seminal fluid in which spermatozoa are conveyed to the female reproductive tract. The Penis is the organ of copulation

4. TESTIS The Testes perform both Exocrine And Endocrine functions. The Exocrine function is to produce Male gametes. The Endocrine function is the secretion of Testosterone , the chief male sex hormones. The Testis is covered by a thick capsule of dense irregular connective tissue called the Tunica Albungenia which gives rise to numerous incomplete collagenous septa. These divide the testis into about 250 testicular lobules. Each testicular lobule contains 1 to 4 highly convoluted Seminiferous Tubules . Beneath the Tunica Albugenia , there is a layer of loose connective tissue containing network of blood vessels known as Tunica vasculosa .

5. SEMINIFEROUS TUBULES Each Seminiferous tubules is intricately coiled and average about 0.2 mm in diameter and 50 cm in length usually commence as free blind ends but neighbouring tubules may form anastomosing loops. At the apex of the testicular lobules, seminiferous tubules lose their convolution and becomes straight. These straight segments is known as Tubuli recti . The Tubuli recti passes into the mediastinum testis and join a network of anastomosing channels called Rete testis . From the Rete testis arises 10 to 20 spirally structure ‘efferent ducutles’ which leaves the testis and open into the duct of the epididymis. The seminiferous tubules is lined by a complex seminiferous epithelium, a modified stratified cuboidal epithelium .

6. The Seminiferous tubules are highly convoluted and are lined by: • Germ cells in various stages of spermatogenesis which are collectively referred to as the spermatogenic series. • Non–germ cells , called Sertoli cells , which support and nourish the developing spermatozoa are also found within the Seminiferous tubules. • In the interstitial spaces between the tubules, endocrine cells called Leydig cell are found either singly or in groups in the supporting tissue.

7. SPERMATOGENIC CELLS These cells lie between the Sertoli cells and forms a Stratified epithelium consisting of several layers of cell which occupy the space between the lamina and lumen of the seminiferous tubules. In the testis of a child, only the primitive germ cells called spermatogonia are present. However, with the onset of sexual maturity the process of spermatogenesis starts and the spermatogenic cells are seen in various stages of differentiation, arrange in an orderly manner. Usually 4 to 5 concentric layers of morphologically distinct spermatogenic cells representing generations of cell at various stages of development can be identified in the adult seminiferous epithelium.

8. The process of Spermatogenesis consist of: Spermatogonium Primary spermatocyte Secondary spermatocyte Spermatids The spermatogonia are located directly inside the basal lamina of the seminiferous epithelium. Depending on the nuclear structure, the spermatogonia can be classified into three types in an adult person. These three types are: The type A Dark spermatogonia The type A Pale spermatogonia The type B Spermatogonia

9. The type A Dark spermatogonia contains an oval , darkly staining nucleus. The are the reserve cells and divide occasionally to maintain their own number and to give rise to type A pale spermatogonia. The type A Pale spermatogonia contain a lightly staining nucleus. These cells divide mitotically to give rise to other type A pale spermatogonia as well as type B spermatogonia. The type B Spermatogonia have a spherical nucleus . Mitotic division of the type B spermatogonia produce daughter cell, all of which differentiate into Primary spermatocytes . The Primary spermatocytes lie next to the spermatogonia. They are large cells having vesicular nuclei. The secondary spermatocytes are smaller cells that arise from a primary spermatocytes as a result of the first meiotic division. The Spermatids are produced from the secondary spermatocytes by the second meiotic division. Spermatids does not divide further but is transformed into a spermatozoon by a series of morphological changes which are collectively known as Spermatogenesis.

10. SERTOLI CELLS The Sertoli cells are tall, columnar cells that extends from the basal lamina to the lumen of the seminiferous tubules. Each Sertoli cells is 70 to 90 um and nearly 30um wide. Due to their close association with the spermatogenic cells, the lateral margins of the Sertoli cells are irregular and cannot easily be distinguished under LM. Each Sertoli cells has a large, pale staining nucleus which is located in then bas al portion of the cells. The nucleus exhibits two distinctive features: The Nuclear envelop shows many folding The Nucleus is very prominent. Luminal surface of the Sertoli cell shows many grooves in which head of the mature in spermatozoa are embedded.

11. FUNCTION OF SERTOLI CELLS The Sertoli cell provide physical and nutritional support to the germ cells. They established the important blood testis barrier, which prevents a immune response against the developing germ cells. They carry out phagocytosis of then excess cytoplasm that is shed by the spermatids during the process of spermatogenesis. The Sertoli cells secretes AMH which promotes regression of the paramesonephric ducts. It secretes a hormone called Inhibin that inhibits the production of FSH by the anterior pituitary.

12. LEYDIG CELLS The Leydig cells are large ovoid cells that are arranged as group in close association to blood capillaries. Leydig cells are found in the interstitial supporting tissue between the seminiferous tubules, synthesise and secrete the male sex hormones and other non-steroid substances. The Leydig cell secretes the Male sex Hormone Testosterone . This Hormone is released into the blood capillaries as it is synthesized and therefore they do not exhibit any secretory vesicles. Testosterone is not only responsible for the development of male secondary sexual characteristics at puberty but is also essential for the continued function of the seminiferous Epithelium.

13. MALE GENITAL DUCT The Male genital duct system comprises of: Tubuli recti Rete testis Ductuli efferentes Epididymis Ductus deferens

14. Tubuli recti The seminiferous tubules at the apex of the testicular lobule joins to form straight tubules called Tubuli recti . The proximal part of the straight tubules is lined by Sertoli cells while the distal part is lined by simple cuboidal epithelium. Rete testis A highly anastomotic network of channel lying in the dense connective tissue of the mediastinum testis. The rete testis is lined by simple cuboidal epithelium . Ductuli efferentes from each testis arise 12 or more ductuli efferentes . These efferentes ductules emerge from the superior part of the posterior border of testis. The ductuli efferentes are lined by simple columnar epithelium . The lining epithelium consists of group of tall columnar ciliated cells alternating with groups of tall columnar ciliated cells alternating with groups of non ciliated, low columnar cells called Principal Cell . The principal cells are absorptive in function. They absorb most of the fluid secreted in the seminiferous tubules.

15. EPIDIDYMIS Epididymis is a comma shaped body that overlies the posterior surface of the testis. Epididymis is divided into 3 part: Head body and Tail The Epididymis consist almost entirely of a single, complex convoluted duct called Ductus Epididymis. This duct is 6 to 7 metres long and begins in the head of the epididymis. Cross section examination reveals that the duct duct of epididymis is lined by a Pseudostratified columnar epithelium , composed of tall columnar cells and basal cells.

16. FUNCTION OF EPIDIDYMIS Storage of spermatozoa Transportation of spermatozoa Reabsorption of most of the fluid the leave the testis Spermatozoa develops the motility, ability and maturity to fertilize the ova.

17. DUCTUS DEFERENS It is a narrow luminal structure and a thick muscular wall structure which consist of the following 3 coats: Mucosa Muscularis Adventitia The Mucosa is thrown into longitudinal folds due to which the lumen appears star shaped in a cross section. The lining epithelium of the ductus deferens closely resembles to that of the epididymis. It is a pseudostratified columnar epithelium in which the tall columnar cells bears the stereocilia on their free luminal surfaces. The Muscularis is very thick. It is composed of 3 layers of smooth muscles. The Adventitia surrounds the muscularis and consists of a thin layer of connective tissue containing blood vessels and nerves.

18. The distal end of the ductus deferens is dilated to form the ampulla. It is characterized by the presence of tall, highly branched mucosal folds with glandular diverticula. The mucosa of the ampulla is lined by simple columnar epithelium which is secretory in nature .

19. ACCESSORY GLANDS The Accessory glands of the male reproductive system consist of: Paired Seminal Vesicles The Prostate Paired Bulbourethral Glands

20. SEMINAL VESICLES Each seminal vesicles is a highly tortuous tube which is about 15 cm long. It consists of 3 coats: Mucosa Muscularis Adventitia It is lined by Pseudostratified columnar epithelium that contains two types of cells i.e. Principal Cells and Basal Cells . The seminal vesicles secretes 70% of the volume of the semen. The secretory products of the seminal vesicles is rich in fructose that serves as a nutritive material for the spermatozoa.

21. PROSTATE GLANDS The prostate surrounds the initial part of the male urethra and is the largest accessory sex gland of the male reproductive system. It is covered by a thin capsule of richly vascularized, dense irregular connective tissue interspersed with smooth muscle cells. The secretion of then prostate gland are discharged into the urethra by contraction of the muscular stroma at the time of ejaculation. The prostate gland secretes PSA . Depending upon the incident of disease in different part of the prostate, it is divided into three zones : The peripheral zone constitute 70% of the glandular mass. It is most susceptible to prostatic cancer. The transitional zone is the common site for BPH which occurs in the middle age. The central zone is resistant to hyperplasia as well as malignancy.

22. BULBOURETHRAL GLANDS The bulbourethral glands are 2 Pea Sized bodies located posterolateral to the membranous urethra. Each gland is compound Tubuloacinar gland whose ducts drain into the proximal part of the penile urethra. During erotic stimulation, the bulbourethral glands secretes a clear mucous like fluid that serves to lubricate the lumen of the urethra.

23. SEMEN The Semen consist of seminal plasma and spermatozoa. The seminal plasma constitute about 95% of the volume. It serves as an energy source and vehicle for the spermatozoa. The Density of the Spermatozoa is highly variable i.e.,100 Million/ml. The normal volume of semen from a single ejaculation varies from 2 to 6 ml.

24. PENIS The penis consist of 3 cylindrical masses of erectile tissue. The paired Corpora cavernosa lies dorsally while the single Corpus spongium lies ventrally . The paired Corpora cavernosa are fused together in the body of penis but diverge in the perineum to form crura of the penis. The Corpus spongiosum enlarges proximally to form the bulb of the penis. Distally, it expands to form a cup shaped enlargement, the glans penis which forms conical cap over the conical ends of the corpora cavernosa. In the Un-circumcised males, the glans penis is covered by a fold of skin called Prepuce . The outer surface of the prepuce is covered by the ordinary epidermis consisting of stratified squamous keratinized epithelium . However, its inner surface is lined by stratified squamous non-keratinized epithelium. The skin of the inner surface of the also contains a large number of sebaceous glands secretion of which keeps the surface moist.

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