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بسم الله الرحمن الرحيم. Male R eproductive Physiology . Dr.Mohammed Sharique Ahmed Quadri Assistant professor physiology Al M aarefa College. Objectives . Describe the structure of the testis physiological functions of the major components of the male reproductive tract.
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بسم الله الرحمن الرحيم Male Reproductive Physiology Dr.Mohammed Sharique Ahmed Quadri Assistant professor physiology Al Maarefa College
Objectives • Describe the structure of the testis physiological functions of the major components of the male reproductive tract. • Explain how the secretions of FSH and LH are regulated in the male and describe the actions of these hormones on the testis. • Describe spermatogenesis and the role of Sertoli cells, Leydig cells and the basement membrane in this process. • Explain the hormonal control of spermatogenesis and describe the effects of androgens on the male accessory sex organs. • Describe the composition of semen, • Discuss the various factors that affect male fertility.
Male Reproductive Physiology • Testes • Development of testis occurs in abdominal cavity, Descent is usually complete by seventh month of gestation. • Descend into scrotum • Location provides cooler environment essential for spermatogenesis • Perform dual function • Produce sperm • Occurs within seminiferous tubules • Secrete testosterone • Produced by Leydig (interstitial) cells that lie in connective tissue between seminiferous tubules
Male Reproductive Physiology • Testosterone • Steroid hormonederived from cholesterol precursor molecule • It is synthesized from the cholesterol in the Leydig cells and also from the androstenedione secreted by the adrenal cortex • Testosterone secretion rate is 4-9mg/dL in normal adults and very small amount is secreted in women
Male Reproductive Physiology • Testosterone • Five categories of testosterone effects • Effects on Reproductive system before birth • Effects on Sex-specific tissues after birth • Other reproductive-related effects • Effects on Secondary sexual characteristics • Non-reproductive actions
Effects of Testosterone • Effects before Birth • Masculinizes the reproductive tract and external genitalia • Promotes descent of the testes into the scrotum • Effects on Sex-Specific Tissues after Birth Promotes growth and maturation of the reproductive system at puberty • Enlargement and maturation of gonads, • Development of secondary sexual characteristics, • Achievement of fertility(Is essential for spermatogenesis) • Growth and maturation of the reproductive tract, and Maintains the reproductive tract throughout adulthood
Effects of Testosterone(continues) • Other Reproduction-Related Effects • Develops the sex drive at puberty • Controls gonadotropin hormone secretion by negative feedback • Effects on Secondary Sexual Characteristics • Induces the male pattern of hair growth (e.g., beard) • A deep voice because of thickening of the vocal folds. • Thick skin • Promotes muscle growth responsible for the male body configuration.( as a result of protein-anabolic affect)
Effects of Testosterone(continues) • Nonreproductive Actions • Exerts a protein anabolic (synthesis) effect • Promotes bone growth at puberty • Closes the epiphyseal plates after being converted to estrogen by aromatase • Stimulates oil secretion by sebaceous glands (results in development of acne). • May induce aggressive behavior
Does males also have Estrogen? • Small amount produce by adrenal cortex • A portion of the testosterone secreted by the testes is converted to estrogen outside the testes by the enzyme aromatase, which is widely distributed but most abundant in adipose tissue
Spermatogenesis • Complex process by which diploid primordial germ cells (spermatogonia) are converted into motile haploid spermatozoa (sperm). • It takes 64 days for development of mature sperm from spermatogonium (several hundred million sperm may reach maturity daily)
Spermatogenesis • Three major stages • Mitotic proliferation • Spermatogonia divide mitotically to give rise to two daughter cells • Sperm-forming daughter cell divides mitotically twice more to form four identical primary spermatocytes • Meiosis • Each primary spermatocyte forms two secondary spermatocytes yielding four spermatids after the second meiotic division • Theoretically, sixteen spermatozoa result from each spermatogonium that goes through process • Packaging • Production of motile spermatozoa from spermatids (Spermiogenesis).
Spermatozoa Consists of four parts • Head • Consists primarily of the nucleus (contains DNA) • Acrosome • containing hydrolytic enzymes that allow the sperm to penetrate and enter the egg • Midpiece • Area where mitochondria are concentrated • Tail • Provides mobility for spermatozoa
Functions of Sertoli cellslocated in seminiferous tubules • Form blood-testes barrier • Provide nourishment • Phagocytic function • Secrete seminiferous tubule fluid which flushes released sperm from tubule into epididymis for storage and additional processing • Secrete androgen-binding protein • Site of action for testosterone & FSH to control spermatogenesis • Release inhibin,Acts in negative-feedback fashion to regulate FSH secretion • Also released Mullerian inhibiting factor ( fetal development)
Role of Accessory Sex Glans & Reproductive Tract • Epididymis and ductus deferens • Store and concentrate sperm • Increase sperm motility and fertility prior to ejaculation • Secret defensin , protect sperm from microorganisms
Role of Accessory Sex Glans & • Seminal vesicles • Sperm and seminal fluid mix in the ejaculatory duct and enter the prostatic urethra during ejaculation • Supply fructose f(energy source for sperms) • Contribute to 60% of the semen volume • Secrete fibrinogen • Supply prostaglandins • Promote smooth muscle contraction in both male and female reproductive tracts (enhances sperm transport)
Role of Accessory Sex Glans • Prostate gland • Contributes alkaline fluid that neutralizes acidic vaginal secretions( sperms are more viable in slightly alkaline environment) • Provides clotting enzymes and prostate-specific antigen(PSA)-fibrin degrading enzyme • Bulbourethral glands • Release lubricating mucus
Semen • Milky white, sticky mixture of sperm and accessory gland secretions • Viscous alkaline fluid containing fructose, coagulating enzyme , and prostaglandins • Provides a transport medium and nutrients (fructose), protects and activates sperm, and facilitates their movement • Average volume is 2.5-3.5 ml per ejaculate • Normally 100 million sperm/ml of semen
Location and Functions of the Components of the Male Reproductive System
Abnormalities of testicular function Cryptorchidism – descent of testes is incomplete one or less commonly both side, testes remain in the abdomen Male hypogonadism: Clinical picture depends on whether testicular deficiency develops before or after puberty. causes: • Testicular disease(Hypergonadotrophic Hypogonadism) • Disorder of hypothalamus or pituitary (HypogonadotrophicHypogonadism) Androgen secreting tumors :Leydig cell tumors (a rare condition) leads to precocious pseudopuberty in prepubertal boys
References • Human physiology by Lauralee Sherwood, seventh edition • Text book physiology by Guyton &Hall,11th edition • Text book of physiology by Linda .s contanzo,third edition