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Male Reproductive System. Overview. Physiologic anatomy Spermatogenesis Endocrine function of testes Regulation of sex hormones Control of testicular function. Physiologic Anatomy. Male reproductive system include Two testes System of ducts that store and transport sperms to exterior
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Male Reproductive System Male Reproductive System
Overview • Physiologic anatomy • Spermatogenesis • Endocrine function of testes • Regulation of sex hormones • Control of testicular function Male Reproductive System
Physiologic Anatomy • Male reproductive system include • Two testes • System of ducts that store and transport sperms to exterior • Epididymis, vas deferens, ejaculatory ducts • Glands that empty into these ducts • Seminal vesicles, prostate, bulbo-urethral glands Male Reproductive System
Physiologic Anatomy Ureter Urinary bladder Prostate Seminal vesicle Urethra Ejaculatory duct Bulbourethral gland (Cowper’s) Epididymis Penis Testes Scrotum Male Reproductive System
Physiologic Anatomy • The duct system, glands and penis • Male accessory reproductive system • Testes • Located in abdomen • During embryonic development • At 7th month of development • Descend into scrotum Male Reproductive System
Physiologic Anatomy • Suspended outside the body in the scrotum • Temperature regulation • Special requirement for spermatogenesis Male Reproductive System
Epididymis Ductuli efferents Head of epididymis Ductus deferens Seminiferous tubules Tail (trilaminar smooth muscle investment) Tunica albuginea Male Reproductive System
Seminiferous Tubules Sertoli cell • Seminiferous tubules • Convoluted tubules length approx 250 meters • Site for sperm formation Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Seminiferous Tubules Sertoli cell • Each seminiferous tubule bound by • Basement membrane • Layer of smooth muscle like cells • Responsible for peristaltic movement of tubules • Which propels spermatids Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Seminiferous Tubules Sertoli cell • Each seminiferous tubule bound by • Germ cells (spermatogonia) • Sertoli cells • The centre of the tubules (lumen) • Filled with fluid rich in • Androgens, estrogens, K+, Inositol, glutamic acid Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Seminiferous Tubules Sertoli cell • Both ends of the seminiferous tubules • Drain through networks of ducts • Into head of epididymis • From there spermatozoa pass through the tail of the epididymis into vas deferens Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Seminiferous Tubules Sertoli cell • Between the seminiferous tubules there are • Leydig cells • Secrete testosterone into blood stream • The spermatic arteries to testes • Run counter current to veins • Allow counter current exchange of heat and testosterone Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Seminiferous Tubules Sertoli cell • Blood-testes-barrier • Walls of seminiferous tubules are lined by • Primitive germ cells • Sertoli cells • Sertoli cells • Large & complex cells containing glycogen • Stretches from basal lamina to the lumen Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Seminiferous Tubules Sertoli cell • Near the basal lamina there are tight junctions between adjacent sertoli cells • Form blood-testes-barrier • Blood-testes-barrier • Prevent molecules from basal compartment into lumen and vice versa • But allow some molecules to penetrate • Like steroids Basement membrane Blood vessel Spermatogonia Leydig cells Lumen Male Reproductive System
Sertoli Cells Spermatids (late) Spermatids (early) Spermatogonia Male Reproductive System
Sertoli Cells • Other functions of Sertoli cells. • Surround developing sperm cells • Synchronize the events of spermatogenesis • Secrete critical proteins • Growth factors • Androgen binding proteins (ABP) • Inhibin Male Reproductive System
Spermatogenesis • Occur in the seminiferous tubules during active sexual life • Stimulated by pituitary Gonadotropins beginning at puberty • Spermatogonia the primitive germ cells • Continually proliferate to replenish themselves • Also differentiate to form sperms Male Reproductive System
Spermatogenesis • Spermatogonia • Mature into primary spermatocyte • Mitosis (46 chromosome) • Primary spermatocyte undergo meiosis • Reducing the number of chromosomes • Two stage process Male Reproductive System
Spermatogenesis • Secondary spermatocyte (23 chromosomes) • Spermatid (23 chromosomes) • Spermatozoa Male Reproductive System
Spermatozoa Acrosome Condensed chromatin Connecting piece Mitochondrial sheath Tail End piece Male Reproductive System
Spermatozoa • Acrosome contain the following enzymes • Hyaluronidase enzyme • Digest proteoglycan filaments of tissue • Proteolytic enzymes • Digest protein • These enzymes play important role in • Allowing sperms to penetrate the ovum for fertilization Male Reproductive System
Hormonal Factors for Spermatogenesis • Testosterone • Secreted by leydig cells • Essential for growth & division of testicular germinal cells • Lutenizing hormone (LH) • Secreted by ant. Pituitary • Stimulate leydig cells to produce testosterone Male Reproductive System
Hormonal Factors for Spermatogenesis • Follicle – stimulating hormone (FSH) • Secreted by anterior pituitary • Stimulate Sertoli cells • Enable the process of spermiogenesis to occur Male Reproductive System
Hormonal Factors for Spermatogenesis • Estrogens • Formed from testosterone by • The sertoli cells when stimulated by FSH • Essential for spermiogenesis • Growth hormone • Control background metabolic process of the testes • Promote division of spermatogonia Male Reproductive System
Composition of Semen • Fluid and sperms from vas deferens (10% of total vol) • Fluid from seminal vesicle(60% of total) • Fructose, phosphorylcholine, flavin, ergothioneine, ascorbic acid, prostaglands • Fluid from prostate gland (30% of total) • Spermine, citric acid, cholesterol phospholipids,fibrinolysin, fibrinogenase, zinc, acid phosphatase Male Reproductive System
Composition of Semen • Small amount from mucus glands • Bulblourethral glands • Colour of semen • White, opalescent ph 7.5 • Sperm count • 100million/ml Male Reproductive System
Endocrine Function of Testes • Testes secrete the following hormones • Steroid hormones • Testosterone • Androstendedione • Estrogen • Dihydrotestosterone • Inhibin Male Reproductive System
Testosterone • Testosterone • Produced by the leydig cells • 19 carbon (C19) steroid • Has an – OH group at position 17 18 OH 19 12 17 11 13 16 1 14 9 2 10 15 8 3 5 O 4 7 6 Male Reproductive System
Synthesis Cholestryl ester Cholesterol Pregnenolone 17 - Dehydroxy Pregnenolone Dehydroepiandrosterone Androstenedione Testosterone Male Reproductive System
Secretion • Normal man secretes 4 – 9mg/d (13.9 – 31.3 mol/d) • Small amounts are also secreted • Adrenals Male Reproductive System
Secretion • 98% of secreted testosterone is bound to plasma proteins • 65 bound to - globulin(Gonadal steroid binding globulin) • 33% bound to albumin • A very small % of testosterone is not bound Male Reproductive System
Androstenedione • Also secrete by the testis • About 2.5mg/d • Important precursor of estrogen in man • Non endocrine tissue convert • Androgen → estrogen • Brain, skin, liver have the enzyme Aromatase Male Reproductive System
Dihydrotestosterone (DHT) • Synthesized by testis Sertoli cells • Testosterone → Dihydrotestosterone • By 5 reductase • Only 20% of plasma Dihydrotestosterone is from testis origin Male Reproductive System
Dihydrotestosterone (DHT) • Remainder comes from peripheral tissues • Conversion of testosterone → DHT • DHT has twice the biological activity of testosterone Male Reproductive System
Estrogens • Major portion of plasma estradiol, estrogen are • Derived from testosterone and androstenedione • Sertoli & leydig cells secretes small amounts of estrogens Male Reproductive System
Estrogens • Brain, skin, liver, mammary glands adipose tissue • Have aromatase enzyme • Can convert • Testosterone & androstenedione to • Estradiol • Estrogen Male Reproductive System
Estrogens • Thus estrogen in males are derived from • Testes • From peripheral conversion of testosterone & androstenedione Male Reproductive System
Effects of Testosterone in the Male • Testosterone • Is essential for spermatogenesis • Leydig cells secrete testosterone • Enters the sertoli cells • Facilitate spermatogenesis • It induces differentiation of • Male accessory reproductive organs and maintain their functions • Morphology & function of entire male duct systems, glands and penis Male Reproductive System
Effects of Testosterone in the Male • Induces male secondary sex characteristics • Growth and distributions of hair • External genitalia • Penis, scrotum • Internal genitalia • Seminal vesicle, prostate, bulbo-urethral glands Male Reproductive System
Effects of Testosterone in the Male • Testosterone • Stimulate protein anabolism, bone growth and cessation of bone growth • Maintain sex drive, libido and enhances aggressiveness Male Reproductive System
Effects of Testosterone in the Male • Testosterone • Production of GnRH by hypothalamus • LH, FSH secretion by pit • Directly inhibits LH secretion via action on the ant. Pit Male Reproductive System
Mechanisms of Action • Testosterone cross plasma membrane readily • Combine with specific receptors • Influence transcriptions of genes → RNA • Result in synthesis of new proteins which underlie the overall responses to the hormone Male Reproductive System
Mechanisms of Action • Testosterone receptor complex responsible for: • Maturation of wolffian duct structure • Increase in muscle mass • Development of male sex drive, libido • Spermatogenesis Male Reproductive System
Mechanisms of Action • Dihydrotestosterone – receptor complex responsible for • 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
Feed Back Control Limbic system • Hypothalamus • Releases gonatotrophin releasing hormone (GnRH) • GnRH acts on the anterior pituitary • Release LH & FSH Hypothalamus GnRH Negative feed bacvk Adeno-hypophysis LH FSH Inhibin Plasma testosterone Testis Leydig cells Sertoli cells Spermatogenesis Male Reproductive System
Sex Hormones Limbic system • LH acts on leydig cells • To produce testosterone • FSH acts on sertoli cells • Carry out normal spermatogenesis Hypothalamus GnRH Negative feed bacvk Adeno-hypophysis LH FSH Inhibin Plasma testosterone Testis Leydig cells Sertoli cells Spermatogenesis Male Reproductive System
Sex Hormones Limbic system • The level of androgens in plasma • Inhibit further production of the hormones via • Anterior pituitary • Hypothalamus • Sertoli cells produce inhibin • Inhibits FSH Hypothalamus GnRH Negative feed bacvk Adeno-hypophysis LH FSH Inhibin Plasma testosterone Testis Leydig cells Sertoli cells Spermatogenesis Male Reproductive System
