Lec62 (reproductive system male)

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Lec62 (reproductive system male)

  1. 1. Male Reproductive System<br />spermatogenesis, which means simply the formation of sperm<br />(2) regulation of male reproductive functions by the various hormones<br />(3) performance of the male sexual act<br />
  2. 2. MALE REPRODUCTIVE SYSTEM<br />THE ORGANS AND THEIR FUNCTIONS:-<br />SCROTUM:- TEMPERATURE REGULATION AND PROTECTION OF THE TESTES<br />TESTES:- SPERMS PRODUCTION & THE SECRETION OF MALE SEX HORMONES<br />DUCTS:- STORE & TRANSPORT SPERMS<br />ACCESSORY GLANDS:- SECRETION OF THE FLUID PART OF THE SEMEN<br />PENIS:- MALE ORGAN OF COPULATION<br />
  3. 3. 3<br />MALE REPRODUCTIVE SYSTEM<br />
  4. 4. The testis is composed of seminiferous tubules, in which the sperm are formed<br />The sperm then empty into the epididymis<br />The epididymis leads into the vas deferens<br />Two seminal vesicles, one located on each side of the prostate, empty into the prostatic end of the ampulla, pass into an ejaculatory duct<br />The urethra is the last connecting link from the testis to the exterior<br />The urethra is supplied with mucus derived from urethral glandsand also from bilateralbulbourethral glands (Cowper's glands) located near the origin of the urethra <br />Physiologic Anatomy of the Male Sexual Organs<br />
  5. 5. 5<br />TESTES<br />SEMINEFEROUS TUBULES<br />INTERSTITIAL CELLS <br />
  6. 6. Spermatogenesis<br />Sequence of events by which spermatogonia are transformed into <br />mature sperm orspermatozoa<br />
  7. 7. Spermatogenesis<br />Spermatogonia that cross the barrier into the Sertoli cell layer become progressively modified and enlarged to form large primary spermatocytes<br />Each of these, in turn, undergoes meiotic division to form two secondary spermatocytes<br />After another few days, these too divide to form spermatidsthat are eventually modified to become spermatozoa (sperm)<br />
  8. 8. Spermatogenesis<br />SPERMATOGENESIS: Occurs in the seminiferous tubules during active sexual life<br />1º SPERMATOCYTE<br />2º SPERMATOCYTE<br />SPERMATIDS<br />SPERMATOGONIA<br />SPERMATIDS<br />2º SPERMATOCYTE<br />1º SPERMATOCYTE<br />- The first stage is the spermatogonia migrate among Sertoli cells toward the central lumen of the seminiferous tubule<br />SERTOLI CELLS: are large cells that surround the developing spermatogonia<br />SERTOLI CELLS<br />SPERMATOGONIA<br />
  9. 9. The Seminiferous Tubules<br />
  10. 10. Spermiogenesis<br />The process by which thespermatidsalter their shape and differentiateinto sperm cellsisspermiogenesis<br />
  11. 11. Spermatogenesis & Spermiogenesis<br />Takes about 2 months(64-74 days) <br />Everyday a healthy adult male produces about 400 million sperms<br />Sperm are mostly stored in the vas deferens. They can remain stored, maintaining their fertility, for at least a month<br />
  12. 12. Functions of Sertoli cells:<br />1)Tight junctions between Sertoli cells form blood-testes barrier which maintains critical composition of tubular fluid for sperm maturation<br />2) Secrete fluid for carrying sperm into the epididymis<br />3) Provide nutrients for maturing sperm<br />4) Secrete ABP (androgen-binding protein) that functions to maintain high levels of androgens in the tubular fluid<br />5) Contain aromatase which converts androgens to estrogens<br />6) Secrete inhibin<br />
  13. 13. 13<br />THE SPERM<br />
  14. 14. The anterior 2/3 of the head is covered by theacrosome<br />Acrosome:cap at top of sperm head, contains hyaluronidase and proteolytic enzymes, important in penetration into ovum<br />Mitochondria – arranged around body<br />Tail, or flagellum, undergoes whip-like movements that propel the spermthrough the female reproductive tract<br />Spermatozoa - head<br />
  15. 15. Physiology of the Mature Sperm<br />The activity of sperm is greatly enhanced in a neutral and slightly alkaline medium<br />The activity of sperm increases with increasing temperature<br />Life expectancy of ejaculated sperm in the female genital tract is only 1 to 2 days <br />
  16. 16. Function of the Seminal Vesicles<br />Secretes a mucoid material containing an abundance of fructose, citric acid, large quantities of prostaglandins and fibrinogen<br />The fructose considerable nutrient value for the ejaculated sperm until one of the sperm fertilizes the ovum<br />Prostaglandinsare important in fertilization<br />
  17. 17. Function of the Prostate Gland<br />Secretes a milky fluid that contains calcium, citrate ion, phosphate ion, a clotting enzyme, and a profibrinolysin<br />A slightly alkaline characteristic of the prostatic fluid important for successful fertilization of the ovum <br />
  18. 18. Semen<br />Semen is composed of the fluid and sperm <br />Sperm from the vas deferens resemble about 10 per cent of the total<br />Fluid from the seminal vesicles (almost 60 per cent)<br />Fluid from the prostate gland (about 30 per cent)<br />Small amounts from the mucous glands, especially the bulbourethral glands<br />The average pH= 7.5<br />Each ejaculation contains approximately 3.5 ml, about 120 million sperm/ml <br />
  19. 19. Capacitation<br />Freshly ejaculated sperm do not possess the capacity to fertilize ovum<br />This capacity to fertilize is acquired in the female genital tract, and, appears to involve a reversal of inhibitory factors secreted by the epididymis<br />
  20. 20. Acrosome Reaction<br />Upon contact with the ovum, the acrosomal cap binds with the cell membrane of the ovum<br />This allows release of digestive enzymes, which digest the cell membrane of the ovum allowing the sperm contents to enter<br />
  21. 21. Hormonal Factors That Stimulate Spermatogenesis<br />Testosterone: secreted by the Leydig cellsis essential for growth and division of the testicular germinal cells, which is the first stage in forming sperm <br />Luteinizing hormone: secreted by the anterior pituitary gland, stimulates the Leydig cells to secrete testosterone <br />Follicle-stimulating hormone: stimulates the Sertoli cells; which stimulate the conversion of the spermatids to sperm <br />Estrogens: formed from testosterone by the Sertoli cells when they are stimulated by follicle-stimulating hormone<br />Growth hormone: Growth hormone promotes early division of the spermatogonia themselves<br />
  22. 22. Hormonal Feedback and the Regulation of the Male Reproductive Function<br />
  23. 23.
  24. 24. Testosterone Secretion and Other Male Sex Hormones<br />The testes secrete several male sex hormones, which are collectively called androgens, including testosterone, dihydrotestosterone, and androstenedione. <br />Testosterone is formed by the interstitial cells of Leydig<br />Leydig cells are almost nonexistent in the testes during childhood <br />Leydig cells numerous in the newborn male infant for the first few months of life and in the adult male any time after puberty<br />
  25. 25. Different stages of male sexual functions: plasma testosterone and sperm production<br />
  26. 26. Functions of Testosterone<br />1. fetal development:present at 2nd month of embryonic life<br /> presence or absence of testosterone determines <br />development of genital organs and characteristics<br />2. causes descent of testes into scrotum during last 2-3 months of <br /> pregnancy<br />
  27. 27. Functions of Testosterone<br />adult primary and secondary characteristics: <br />1)body hair distribution <br /> (pubis, face, chest, back, etc)<br />2) voice: hypertrophy of laryngeal mucosa and larynx <br />3) skin: thickens skin and<br /> increases ruggedness of subcutaneous tissues, <br /> sebaceous glands and oil production<br />4) muscle development<br />
  28. 28. Functions of Testosterone<br />5) bone growth and calcium retention: thought to inhibit production of osteoclasts <br />6) red blood cells – causes increases in erythropoeitin –stimulates RBC production<br />7) stimulates sodium and water reabsorption in DT of kidney <br />
  29. 29. BODY OF PENIS IS MADE FROM THREE COLUMNS OF ERECTILE TISSUE:-<br />TWO CORPORA CAVERNOSA<br />ONE CORPUS SPONGIOSUM<br />GLANS PENIS IS MADE BY EXPANSION OF THE CORPUS SPONGIOSUM.<br />PREPUCE IS A SKIN SHEATH COVERING THE GLANS PENIS.<br />PENIS<br />
  30. 30. Male Sexual Response<br />Erection: controlled by parasympathetic nervous system<br />activity to penile arterioles = vasodilation of the <br /> arterioles and erection<br />Parasympathetic release NO in addition to Ach<br />- NO relaxes the arteries of the penis<br />- relaxes the trabecular meshwork of smooth muscle<br /> fibre in the erectile tissue <br />Of the corpora cavernosa and corpus spongiosum<br />–veins are compressed causing reduction in venous <br /> return<br />
  31. 31. Male Sexual Response<br />Emission: movement of ejaculate into proximal part of urethra<br /> under sympathetic control – causes sequential peristaltic <br /> contraction of smooth muscle of vas deferens<br />–closing of bladder sphincter<br />Ejaculation: spinal reflex – triggered by entry of semen into <br />urethra causes nerve impulses to activate perineal muscles <br />– forcibly expel semen from urethra <br />Orgasm: culmination of sexual excitation<br />At its termination, the male sexual excitement disappears entirely <br />Within 1 – 2 minutes<br />
  32. 32. The Penis<br />

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