Male Reproductive System 11 Jan22 Male Reproductive System

Male Reproductive System 11 -Jan-22 Male Reproductive System 1

Overview n n n Physiologic anatomy Spermatogenesis Endocrine function of testes Regulation of sex hormones Control of testicular function 11 -Jan-22 Male Reproductive System 2

Physiologic Anatomy n Male reproductive system include 1. 2. Two testes System of ducts that store and transport sperms to exterior n 3. Glands that empty into these ducts n 11 -Jan-22 Epididymis, vas deferens, ejaculatory ducts Seminal vesicles, prostate, bulbourethral glands Male Reproductive System 3

Physiologic Anatomy Ureter Urinary bladder Prostate Seminal vesicle Urethra Ejaculatory duct Bulbourethral gland (Cowper’s) Penis Epididymis Testes Scrotum 11 -Jan-22 Male Reproductive System 4

Physiologic Anatomy n The duct system, glands and penis n n Male accessory reproductive system Testes n Located in abdomen n During n embryonic development At 7 th month of development n Descend 11 -Jan-22 into scrotum Male Reproductive System 5

Physiologic Anatomy n Suspended outside the body in the scrotum n Temperature n 11 -Jan-22 regulation Special requirement for spermatogenesis Male Reproductive System 6

Epididymis Ductuli efferents Head of epididymis Ductus deferens Seminiferou s tubules Tunica albuginea 11 -Jan-22 Tail (trilaminar smooth muscle investment) Male Reproductive System 7

Seminiferous Tubules Sertoli cell n Basement membrane Seminiferous tubules n Blood vessel n Convoluted tubules length approx 250 meters Site for sperm formation Spermatogonia Leydig cells Lumen 11 -Jan-22 Male Reproductive System 8

Seminiferous Tubules Sertoli cell n Basement membrane Each seminiferous tubule bound by n n Blood vessel Spermatogonia Leydig cells n Basement membrane Layer of smooth muscle like cells Responsible for peristaltic movement of tubules n Lumen 11 -Jan-22 Male Reproductive System Which propels spermatids 9

Seminiferous Tubules Sertoli cell n Basement membrane Each seminiferous tubule bound by n n Blood vessel n The centre of the tubules (lumen) n Spermatogonia Leydig cells Germ cells (spermatogonia) Sertoli cells Filled with fluid rich in n Androgens, estrogens, K+, Inositol, glutamic acid Lumen 11 -Jan-22 Male Reproductive System 10

Seminiferous Tubules Sertoli cell n Basement membrane Both ends of the seminiferous tubules n Blood vessel Drain through networks of ducts n n Spermatogonia Leydig cells Lumen 11 -Jan-22 Male Reproductive System Into head of epididymis From there spermatozoa pass through the tail of the epididymis into vas deferens 11

Seminiferous Tubules Sertoli cell n Basement membrane n Blood vessel Spermatogonia Leydig cells Between the seminiferous tubules there are n Leydig cells n Secrete testosterone into blood stream The spermatic arteries to testes n Run counter current to veins n Allow counter current exchange of heat and testosterone Lumen 11 -Jan-22 Male Reproductive System 12

Seminiferous Tubules Sertoli cell n Basement membrane n Blood-testes-barrier Walls of seminiferous tubules are lined by n n Blood vessel n Sertoli cells n n Spermatogonia Leydig cells Primitive germ cells Sertoli cells Large & complex cells containing glycogen Stretches from basal lamina to the lumen Lumen 11 -Jan-22 Male Reproductive System 13

Seminiferous Tubules Sertoli cell n Basement membrane Near the basal lamina there are tight junctions between adjacent sertoli cells n n Blood-testes-barrier n Blood vessel n Spermatogonia Form blood-testesbarrier Prevent molecules from basal compartment into lumen and vice versa But allow some molecules to penetrate Leydig cells n Like steroids Lumen 11 -Jan-22 Male Reproductive System 14

Sertoli Cells Spermatids (late) Spermatids (early) Spermatogonia 11 -Jan-22 Male Reproductive System 15

Sertoli Cells n Other functions of Sertoli cells. n n n Surround developing sperm cells Synchronize the events of spermatogenesis Secrete critical proteins n Growth factors n Androgen binding proteins (ABP) n Inhibin 11 -Jan-22 Male Reproductive System 16

Spermatogenesis n Occur in the seminiferous tubules during active sexual life n n Stimulated by pituitary Gonadotropins beginning at puberty Spermatogonia the primitive germ cells n n 11 -Jan-22 Continually proliferate to replenish themselves Also differentiate to form sperms Male Reproductive System 18

Spermatogenesis n Spermatogonia n Mature into primary spermatocyte n Mitosis n (46 chromosome) Primary spermatocyte undergo meiosis n Reducing the number of chromosomes n Two stage process 11 -Jan-22 Male Reproductive System 19

Spermatogenesis n Secondary spermatocyte (23 chromosomes) n n 11 -Jan-22 Spermatid (23 chromosomes) Spermatozoa Male Reproductive System 20

Spermatozoa Condensed chromatin Acrosome Connecting piece Mitochondrial sheath Tail End piece 11 -Jan-22 Male Reproductive System 21

Spermatozoa n Acrosome contain the following enzymes n Hyaluronidase enzyme n n Proteolytic enzymes n n Digest proteoglycan filaments of tissue Digest protein These enzymes play important role in n 11 -Jan-22 Allowing sperms to penetrate the ovum for fertilization Male Reproductive System 22

Hormonal Factors for Spermatogenesis n Testosterone n n n Secreted by leydig cells Essential for growth & division of testicular germinal cells Lutenizing hormone (LH) n n 11 -Jan-22 Secreted by ant. Pituitary Stimulate leydig cells to produce testosterone Male Reproductive System 23

Hormonal Factors for Spermatogenesis n Follicle – stimulating hormone (FSH) n n n 11 -Jan-22 Secreted by anterior pituitary Stimulate Sertoli cells Enable the process of spermiogenesis to occur Male Reproductive System 24

Hormonal Factors for Spermatogenesis n Estrogens n Formed from testosterone by n The sertoli cells when stimulated by FSH n n Essential for spermiogenesis Growth hormone n n 11 -Jan-22 Control background metabolic process of the testes Promote division of spermatogonia Male Reproductive System 25

Composition of Semen n n Fluid and sperms from vas deferens (10% of total vol) Fluid from seminal vesicle (60% of total) n n Fructose, phosphorylcholine, flavin, ergothioneine, ascorbic acid, prostaglands Fluid from prostate gland (30% of total) n 11 -Jan-22 Spermine, citric acid, cholesterol phospholipids, fibrinolysin, fibrinogenase, zinc, acid phosphatase Male Reproductive System 26

Composition of Semen n Small amount from mucus glands n n Colour of semen n n Bulblourethral glands White, opalescent ph 7. 5 Sperm count n 11 -Jan-22 100 million/ml Male Reproductive System 27

Endocrine Function of Testes n Testes secrete the following hormones n Steroid hormones n Testosterone n Androstendedione n Estrogen n Dihydrotestosterone n 11 -Jan-22 Inhibin Male Reproductive System 28

Testosterone n 18 19 11 12 13 n OH 17 16 1 2 O 3 10 4 n 14 9 8 5 Testosterone 15 n 7 6 11 -Jan-22 Male Reproductive System Produced by the leydig cells 19 carbon (C 19) steroid Has an – OH group at position 17 29

Synthesis Cholestryl ester Cholesterol Pregnenolone 17 - Dehydroxy Pregnenolone Dehydroepiandrosterone Androstenedione Testosterone 11 -Jan-22 Male Reproductive System 30

Secretion n n Normal man secretes 4 – 9 mg/d (13. 9 – 31. 3 mol/d) Small amounts are also secreted n 11 -Jan-22 Adrenals Male Reproductive System 31

Secretion n 98% of secreted testosterone is bound to plasma proteins n n n 11 -Jan-22 65 bound to - globulin(Gonadal steroid binding globulin) 33% bound to albumin A very small % of testosterone is not bound Male Reproductive System 32

Androstenedione n Also secrete by the testis n n About 2. 5 mg/d Important precursor of estrogen in man n Non endocrine tissue convert n Androgen → estrogen n Brain, skin, liver have the enzyme Aromatase 11 -Jan-22 Male Reproductive System 33

Dihydrotestosterone (DHT) n Synthesized by testis Sertoli cells n Testosterone → Dihydrotestosterone n By n 5 reductase Only 20% of plasma Dihydrotestosterone is from testis origin 11 -Jan-22 Male Reproductive System 34

Dihydrotestosterone (DHT) n Remainder comes from peripheral tissues n n Conversion of testosterone → DHT has twice the biological activity of testosterone 11 -Jan-22 Male Reproductive System 35

Estrogens n Major portion of plasma estradiol, estrogen are n n Derived from testosterone androstenedione Sertoli & leydig cells secretes small amounts of estrogens 11 -Jan-22 Male Reproductive System 36

Estrogens n Brain, skin, liver, mammary glands adipose tissue n n Have aromatase enzyme Can convert n Testosterone & androstenedione to n Estradiol n Estrogen 11 -Jan-22 Male Reproductive System 37

Estrogens n Thus estrogen in males are derived from n n 11 -Jan-22 Testes From peripheral conversion of testosterone & androstenedione Male Reproductive System 38

Effects of Testosterone in the Male n Testosterone n Is essential for spermatogenesis n n Leydig cells secrete testosterone Enters the sertoli cells Facilitate spermatogenesis It induces differentiation of n n 11 -Jan-22 Male accessory reproductive organs and maintain their functions Morphology & function of entire male duct systems, glands and penis Male Reproductive System 39

Effects of Testosterone in the Male n Induces male secondary sex characteristics n n Growth and distributions of hair External genitalia n Penis, n scrotum Internal genitalia n Seminal vesicle, prostate, bulbourethral glands 11 -Jan-22 Male Reproductive System 40

Effects of Testosterone in the Male n Testosterone n n 11 -Jan-22 Stimulate protein anabolism, bone growth and cessation of bone growth Maintain sex drive, libido and enhances aggressiveness Male Reproductive System 41

Effects of Testosterone in the Male n Testosterone n Production of Gn. RH by hypothalamus n n LH, FSH secretion by pit Directly inhibits LH secretion via action on the ant. Pit 11 -Jan-22 Male Reproductive System 42

Mechanisms of Action n n Testosterone cross plasma membrane readily Combine with specific receptors n n 11 -Jan-22 Influence transcriptions of genes → RNA Result in synthesis of new proteins which underlie the overall responses to the hormone Male Reproductive System 43

Mechanisms of Action n Testosterone receptor complex responsible for: n n 11 -Jan-22 Maturation of wolffian duct structure Increase in muscle mass Development of male sex drive, libido Spermatogenesis Male Reproductive System 44

Mechanisms of Action n Dihydrotestosterone – receptor complex responsible for n n n 11 -Jan-22 Formation of male external genitalia For enlargement of prostate & penis at puberty For facial hair, the acne temporal recession of hair line Male Reproductive System 45

Feed Back Control Limbic system n Negative feed bacvk LH FSH Adenohypophysis Inhibin Plasma testosteron e Leydig cells n Hypotha lamus Gn. RH Sertoli cells Testis Hypothalamus n Releases gonatotrophin releasing hormone (Gn. RH) Gn. RH acts on the anterior pituitary n Release LH & FSH Spermato genesis 11 -Jan-22 Male Reproductive System 46

Sex Hormones Limbic system n Hypotha lamus Gn. RH Negative feed bacvk LH FSH Adenohypophysis Inhibin Plasma testosteron e LH acts on leydig cells n n FSH acts on sertoli cells n Leydig cells Sertoli cells To produce testosterone Testis Carry out normal spermatogenesis Spermato genesis 11 -Jan-22 Male Reproductive System 47

Sex Hormones Limbic system n Hypotha lamus Gn. RH Negative feed bacvk LH FSH Leydig cells n Adenohypophysis Inhibin Plasma testosteron e The level of androgens in plasma Sertoli cells Testis n Inhibit further production of the hormones via n Anterior pituitary n Hypothalamus Sertoli cells produce inhibin n Inhibits FSH Spermato genesis 11 -Jan-22 Male Reproductive System 48