Embryology_Gametogenle_reproductive.pptx

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1. Lecture (2): Gametogenesis Male Reproductive System

2. Male reproductive system Male reproductive system is composed of the: A pair of tests. 2) Excretory genital ducts, these ducts are the Ductus epididymis, the ductus (vas) deferens, & the urethra. 3) Accessory genital glands, these are: The seminal vesicles, the prostate, & the bulbourethral glands. Penis

3. The testes: - The testes are paired organs that produce the male germ cells ( spermatozoa ) & the male sex hormones , the androgen . - In early fetal life, testes are situated in the abdominal cavity, near the kidney, just before birth, testes pass into the Scrotum . - The Scrotum temperature is about 1.5 – 3C˚less than body temperature & the development of spermatozoa does not take place at body temperature .

4. - Each testis is surrounded by a thick capsule of dense connective tissue, the tunica albuginea . - The tunica albuginea is thickened on the posterior surface of the testis to form the mediastinum testis. - The tunica albuginea is surrounded by mesothelial cells Tunica vaginalis.

5. Septa of connective tissue extend from the capsule that divide the testis into about 250 pyramidal compartments called the testicular lobules. Lying within the lobule about 3-4 seminiferous tubules in the form of loop which end by straight tubule or ( Tubuli recti ). The seminiferous tubules enmeshed in a web of loose connective tissue that is rich in blood & lymphatic vessels, nerves, & interstitial cells , also known as Leydig cells.

6. Seminiferous tubules produce male reproductive cells, the spermatozoa, whereas interstitial cells secrete testicular androgens. The straight tubule open into a network of channels within the mediastinum testis called Rete testis. The Rete testis open into 10-12 ductuli efferentes which connect the Rete testis to the cephalic portion of the epididymis that is situated on the posterior surface of the testis.

7. The mammalian testes are divided into many lobules, and each lobule contains many seminiferous tubules. Sperm develop in an ordered fashion in these tubules. The spermatozoa arise from the germinal epithelium of the testis. In the mammal this epithelium consists of two kinds of cells: (1) The supporting cells (Sertoli) these cells are supporting cells that stretch from the lumen to the edge of the tubule. They nourish the developing sperm. They form a blood-testis barrier to control spermatogenesis.

8. (2) The spermatogenic cells in various stages of development Of the latter the basal layer consists of small round or oval cells which are known as spermatogonia . - Internal to these are the larger spermatocytes having large vesicular nuclei with densely staining chromatin. - Between these and the lumen of the seminiferous tubule are several layers of small round or oval cells, the spermatids .

9. The spermatids have the reduced number of chromosomes, and by direct transformation give rise to the mature spermatozoa which may either lie free in the lumen of the tubule or have their heads embedded in the supporting cells. A section across a testis Many seminiferous tubules are shown. These make the spermatozoa One seminiferous tubule

10. Part of the wall of a seminiferous tubule. Observe flagella of spermatids (arrows) associated with Sertoli cells. Section of a testis showing seminiferous tubules and groups of pale-stained interstitial (Leydig) cells (arrowheads).

11. Spermatogenesis: Is the sequence of events by which spermatogonia are transformed into spermatozoa. The spermatogonia are stem cells situated along the basement membrane of the seminiferous tubule. They are large cells with rounded nuclei (Type A&B). Spermatogonia divided by mitosis into primary spermatocyte which are large, migrate toward the middle zone & pass into first meiotic division into secondary spermatocytes which soon divide (2 nd meiotic division ) into spermatids.

12. The Spermatids undergo a serial of morphological changes spermiogenesis leading to the formation of spermatozoa. The mature spermatozoon is smaller than ova, it consists of: Head, neck, body, & tail. Head is formed by the condensed nucleus & covered by basement membrane which covering the anterior 2/3 of the nucleus is the acrosomal cap , which contains several enzymes such as: hyaluronidase & protease that are involved in the penetration of the ovum . The principal changes occurring in spermatids during spermiogenesis. The basic structural feature of the spermatozoon is the head, which consists primarily of condensed nuclear chromatin. The reduced volume of the nucleus affords the sperm greater mobility and may protect the genome from damage while in transit to the egg. The rest of the spermatozoon is structurally arranged to promote motility. Bottom: The structure of a mature spermatozo on.

13. The axial filament arises from the centrioles in the neck. Mitochondria arranged spirally around the filament within the body ( middle piece ). The tail forms the greater part & is the motile part of the spermatozoon . Mature spermatozoon can live several weeks in the ♂ reproductive system & only 3-5 days in the duct of ♀.

14. SPERMATOGENESIS THREE PHASES Spermatogonial Phase (Mitosis) Spermatocyte Phase (Meiosis) Spermatid Phase (Spermiogenesis) Acrosome formation ; that contains hydrolytic enzymes which will enable the spermatozoa to move through the investing layers of the oocyte. - Flagellum formation ; centrioles and associate axoneme (arrangement of microtubules in cilia). - Changes in size and shape of nucleus; chromatin condenses and shedding of residual body (cytoplasm)

15. Maturation: Once the spermatozoon has been formed & lie free in the lumen, it is not motile. It is moved to the epididymis, by the contraction of smooth muscle of the tubules, within the epididymis, it undergo further maturation, resulting in increased motility & fertilizing power. At the time of ejaculation, they become very active due to the alkaline secretion of seminal vesicle, & prostate.

16. Sertoli cell: Sertoli cells lie on the basement membrane, they are few in number, they are columnar in shape with many invaginations in their apical surface. Nucleus is ovoid, cytoplasm contain RER, SER, GA, Mitochondria…….. Adjacent Sertoli cells are held together by gab junctions & multiple tight junction form the blood- testis barrier that protect spermatogenic cells from noxious substances that may present within the blood .

17. Function: Support, protection spermatogenic cell. Nourishment of spermatocytes , spermatids & spermatozoon. Phagocytosis of residual bodies derived from spermatids. Secretion of fluid into the lumen for transport of spermatozoa. Formation of small quantities of estrogen. Formation of androgen binding protein. Release inhibin .

18. The interstitial cells (Leydig cell): Are situated in group embedded in loose connective tissue, between seminiferous tubules, they are large polyhedral, with an eccentric nucleus & poorly staining cytoplasm. They secret the androgen (Testosterone; Dihydro testosterone & androstenediones'). The interstial cells are present in large number in fetus but atrophy by some extent after birth. In fetus it is stimulated by the gonadotropin of the placenta to stimulate the development of male genitalia & suppression of female genitalia formation & also bring the descent of the testes. Epithelium of seminiferous tubules surrounded by myoid cells. The spaces between the tubules contain connective tissue, blood and lymphatic vessels, and interstitial cells.

19. Excretory ducts: 1. Straight tubules: Lined with Sertoli cells with no spermatogenic cells. 2. Rete testis: Lined with simple squamous or low cuboidal epithelial tissue. 3. Efferent ductules: Lined with ciliated simple columnar, beneath the basement membrane there is a layer of smooth muscle.

20. 4. Epididymis: Lined with pseudostratified epithelial tissue with steriocilia (are long & branched microvilli). Functions: Absorption of fluid. Store spermatozoa. Release nutrient material for spermatozoa. 5. Vas deference: Lined with : Mucous membrane (pseudostratified epithelial tissue with steriocilia ) Muscular coat (thick 3 layers). Fibrous coat. Function: Convey spermatozoa by peristalsis.

21. 6. Ejaculatory ducts: Lined by pseudostratified epithelial tissue. There is no muscle. Function: Convey spermatozoa & secretion of seminal vesicles to the urethra.

22. Accessory glands: Seminal vesicles: Seminal vesicles are paired organ, each consists of coiled tube embedded in connective tissue. Seminal vesicles are lined by mucous membrane, thrown into folds lined with pseudostratified epithelial tissue that secret a yellowish viscous liquid. Muscular coat (inner circular & outer longitudinal). Fibrous coat (Loose connective tissue).

23. Its function is controlled by testosterone. Castration results in its atrophy. Their secretion contribute to seminal fluid & its contain important substances such as: Ascorbic acid & amino acid that are essential for nourishment of spermatozoa. Prostaglandins --- assist fertilization by making the cervix of uterus more receptive to spermatozoa. The wall of seminal vesicles contract during ejaculation.

24. 2. Prostate: This gland is large tubulo - alveolar gland that surround the prostatic urethra. Function: Its function is controlled by testosterone. Castration results in its atrophy. Their secretion is thin milky fluid contain citric acid & acid phosphatase & fructose The prostatic secretion is alkaline, help to neutralize the acidity in the vagina. The prostate contract during ejaculation.

25. 3. Bulbo-urethral glands (Cowper’s gland): Are small tubulo- alveolar gland & their simple columnar epithelial cells secrete mucus. Their secretion is poured into urethra as result of erotic stimulation. It is affected by testosterone. Castration result in its atrophy. 4. Penis: The body of penis composed of three cylindrical erectile tissue : 1. Two dorsally placed ( Corpora cavernosum) 2. Single corpus spongiosum in the ventral surface. Transverse section of the penis.

26. Semen: The male reproductive fluid, containing spermatozoa in suspension. Semen is the a viscid whitish fluid of the male reproductive tract consisting of spermatozoa suspended in secretions of accessory glands (as of the prostate and Cowper's glands). - A normal sperm count ranges from 15 million sperm to more than 200 million sperm per milliliter (mL) of semen. Anything less than 15 million sperm per milliliter, or 39 million sperm per ejaculate, is considered low. A low sperm count is often referred to as oligospermia. - Total sperm count in ejaculate: 39–928 million - Sperm concentration: 15–259 million per mL - Sperm morphology: 4–48 percent - Ejaculate volume: 1.5–7.6 mL

27. Motility: 50-70% of spermatozoa are motile (Less than 40% reduced fertility). 20% are morphologically abnormal. In frozen state, spermatozoa may be stored for years & still possess fertilizing capacity after thawing.

28. Sperm abnormalities : The classification of sperm cell defects may be subdivided into three categories: Primary sperm abnormalities which are due to disturbance of spermatogenesis by congenital or hereditary factors , high ambient temperature or scrotal insulation and diseases . 2) Secondary sperm abnormalities which occur only after spermatogenesis and during epididymal journey of spermatozoa . 3) Tertiary sperm abnormalities which arise from improper handling of semen sample.

29. Primary Abnormalities Normal   Decapitated   Macrocephalic   Microcephalic and Stump Tail Pyriform   Pyriform   Round and Double Tail Round head

30. Ruffled acrosome Tapered Craters (diadem) microcephalic

31. Secondary Abnormalities Proximal Cytoplasmic (Protoplasmic) Droplet Translocating Cytoplasmic Droplets Tail Opening following Droplet Translocation Tail Opening following Droplet Translocation

32.  A.  Coiled Tail with Droplet  B.  Coiled Double Tail  C.  "DAG" defect  D.  Folded tail  E.  Filamentous  F.  Double Tail  G.  Corkscrew Midpiece with Droplet  H.  Corkscrew Midpiece

33.   Bent Tail   Coiled Tail "DAG" defect Double Tail Folded tail with pyriform head

34. Morphology Normal Morphology Abnormal Morphology

35. Hormones in males - FSH stimulates maturation of the testes and sperm - LH stimulates release of testosterone (male sex hormone) from the testes Testosterone stimulates : Sperm production, erection, and ejaculation. Is responsible for growth & development of sex organs (Prostate, Seminal Vesicle, Cowper glands & Penis). It is also responsible for development of secondary sexual characteristic at puberty, e.g. Facial, chest , axillary & pubic hair, enlargement of larynx & muscle & bones, voice,……).

36. Sites of hormonal control - Anterior pituitary (endocrine gland in brain) produces: 1. Luteinizing hormone (LH) Follicle stimulating hormone (FSH) - Hypothalamus (in brain) 1. Regulates release of FSH and LH by acting on the pituitary 2. Controls blood pressure, body temp., emotions 3. Makes antidiuretic hormone (ADH) and oxytocin

37. Factors that influence Testicular function: Hormones exert the most important stimulatory effect on spermatogenesis, which depends on the action of follicle stimulating hormone (FSH) & Luteinizing hormone (LH) of the hypophysis on the testicular cells. The FSH acts on Sertoli cell to form a protein that bind to androgen called androgen binding protein (ABP) which stimulate spermatogenesis. Hypophyseal control of male reproduction. LH acts on the Leydig cells, and FSH acts on the seminiferous tubules. A testicular hormone, inhibin, inhibits FSH secretion in the pituitary. ABP, androgen-binding protein.

38. 2- Sertoli cells also release inhibin which inhibit the production of FSH . 3- LH acts on the interstitial cells, stimulating the production of testosterone necessary for the normal development of cells of the spermatogenic lineage. The testosterone (androgens) enter the tubules & bind to protein of Sertoli cells to stimulated spermatogenesis. Spermatogenesis is stimulated by testosterone & inhibited by estrogens & progesterone. Hypophyseal control of male reproduction. LH acts on the Leydig cells, and FSH acts on the seminiferous tubules. A testicular hormone, inhibin, inhibits FSH secretion in the pituitary. ABP, androgen-binding protein.