Male reproductive system The physiology of sexual act

Transcription

1 Male reproductive system The physiology of sexual act Gabriella Kékesi 65. The development and physiology of the male reproductive system. The physiology of the sexual act Define chromosomal, gonadal and somatic sex. Describe the physiological functions of the major components (testis, epididymis, ductus deferens, seminal vesicle, prostate) of the male reproductive tract. Describe spermatogenesis and the role of Sertoli cells, Leydig cells and the basement membrane in this process. Describe the blood-testis barrier. Describe the endocrine regulation of testicular function: the role of the GnRH pulse generator, FSH, LH, testosterone, and inhibin. Describe the, biosynthesis, mechanism of transport within the blood of testosterone and related androgens. List the major target organs and cell types for testosterone and other androgens. Describe the effects and cellular action mechanisms of testosterone and related androgens. Identify the consequences of over-secretion and under-secretion of testosterone for a) prepubertal and b) postpubescent males. Describe the neural, vascular, and endocrine components of the erection, emission and ejaculation response. Normal values: volume of semen: ml, sperm concentration >15 (20-40) million/ml, >60% motile 1

2 I. Male reproductive system II. Endocrine control III. Spermatogenesis IV. Andogenes V. Sexual intercourse GENDER Genetic (chromosomal) XX or XY Gonadal In order to predominate the chromosomal gender, the appropriate development of gonads are necessary. Phenotypic Prenatal internal and external genital differentiation Embrional sexual hormone production (testosterone, antimullerian hormone) Ratio of androgenes and estrogenes 2

3 External and internal genital organs Anatomy and organization of testis Scrotum Skin + subcutaneous tissue Two parts two testicles Smooth muscle wrinkled appearance Skeletal musle controls its position Testis Fibrous connective tissue capsule (tunica albugines) extends inward to form lobules Lobules contain seminiferous tubules that concverge to form tubulus rectus, which leads into the rete testis Efferent ductule head of epididymis body of epididymis tail of epididymis ductus (vas) deferens 3

4 Testis Leydig cells (interstitial) - hormone production testosterone, 5α-dihydrotestosterone, androsterone, androstendion, progesterone, pregnenolone Sertoli cells (seminiferous tubules) spermatogenesis (+ inhibin) I. Male reproductive system II. Andogenes III. Endocrine control IV. Spermatogenesis V. Sexual intercourse 4

5 No storage 2% free, 98 % binded: ABG (50%), albumin IC receptor Gene transcription 5

6 Androgene hormons effects Androgene effects (development of the reproductive system) Anabolic effects (growth of the muscular tissue and bones, dopping) Sexual organs & secondary sex characteristic growth of testis, penis, scrotum spermatogenesis prostate, epididymis and seminal vesicle secretion hair Libido Nycturnal erection Capability to sexual intercourse Growth acceleration (testosteron GH) Increase the size and mass of muscle Proper bone density Size of larynx increases, expansion of vocal cords change of voice 6

7 I. Male reproductive system II. Andogenes III. Endocrine control IV. Spermatogenesis V. Sexual intercourse Regulation of hormone secretion PRL GnRH (LHRH) Limbic s. Smell Visual s. intermittent!!! LH & FSH Leydig cells Sertoli cells Testosterone Dihydrotestosterone Estrogens Inhibin Activin inhibition stimulation 7

8 Age-related testosterone secretion Fetal life First year Adrenarche (age 6-7; adrenal gland cortex hormon, DHEA-SO 4 ) At puberty GnRH production Age 12 androgens secretion induced by GnRH I. Male reproductive system II. Androgenes III. Endocrine control IV. Spermatogenesis V. Sexual intercourse 8

9 Sertoli s cells: blood-testis barrier protection zonula occludens communication with germ cells paracrin secretion, ABG synthesis nourish & support Spermatogenesis Packed with cells in various stages of development Dormant until puberty Each successive stage in spermatogenesis is pushed toward the center of the tubule so that the more immature cells are at the periphery and the more differentiated cells are nearer the center. between age is stable vitamin A countercurrent exhange kryptorchism takes about 70 days 9

10 Seminiferous epithelium. Note that maturing germ cells remain connected by cytoplasmic bridges through the early spermatid stage and that these cells are closely invested by Sertoli cell cytoplasm as they move from the basal lamina to the lumen. (Reproduced with permission from Junqueira LC, Carneiro J: Basic Histology: Text & Atlas, 10th ed. McGraw-Hill, 2003.) Hormonal background of spermatogenesis LH, FSH Androgenic steroids Results of spermatogenesis: detached from Sertoli-cells plasma-bridge disappear tubuli seminiferi rete testis (myoid cells, smooth muscle around the testis) Role of epididymis: fluid secretion day spermium motility capability of fertilization 10

11 I. Male reproductive system II. Androgenes III. Endocrine control IV. Spermatogenesis V. Sexual intercourse Sexual intercourse 1. erection 2. ejaculation 3. relaxation 11

12 1. Erection changes in blood content, pressure and size erectile tissues: corpus cavernosum (2), corpus spongiosum, glans penis sinusoids, trabecular structure (connective tissue and smooth muscle) blood flow stimuli (tactile, visual, auditory, psychic; REM phase) efferents: S2-4 (PSY), Th10-12 (SY), somatomotor (S2-4) neurogenic relaxation: NO!!! (PDE5 Viagra ); VIP, Ach cavernous nerve 2. Ejection emission (prox. urethra); ejaculation spinal reflex originated from mechanoreceptors Emission to the proximal urethra NA, ATP vas deferens contraction D. deferens contraction, m. ischiocavernosus and bulbocavernosus contraction ejaculation (4 ml, 200 milion) 3. Relaxation SY trabecular smooth muscle and arteries contraction 12

13 Accessory glands secrete fluids that enter the urethra Seminal vesicles posterior to the urinary bladder viscous fluid: fructose, PGs and proteins Prostate inferior to the bladder, encircles the urethra thin, milky colored, alkaline secretion Bulbourethral glands near the base of penis alkaline mucus-like secretion Seminal fluid (semen) ml / ejection, seminal fluid & sperms only ONE sperm actually penetrates and fertilizes the ovum 13