Notes on Histology of the Male Reproductive System
Rahul's Noteblog
Notes on Histology
Notes on Histology of the Male Reproductive System
Male reproductive system includes:
• Penis - intomittent organ
• Testis - site of genesis of sex cells
• Duct system - conduit to outside
• Accessory glands - nourish sperm & provide bulk of semen
Primordial germ cells (PGC) arise in the 3rd week from yolk sac endoderm. They migrate via ameboid locomotion to the genital ridge and arrive by end of the 4th or beginning of the 5th week.
Primordial germ cells proliferate via mitosis. Coelomic epithelium proliferates to form sex cords. The swellings produced are the genital ridges.
In the 2nd month, sex cords invest the Primordial germ cells. In females, cortical sex cords near the surface form follicle cells. In males, medullary sex cords form pre-Sertoli cells which at puberty will become Sertoli cells of the seminiferous tubules.
During:
• Meiosis I. homologous chromosomes pair and when they separate chiasma occur where blocks of genes are exchanged.
• Meiosis II. yields 2 secondary spermatocytes in males; 1 secondary oocyte & 1 polar body in females. The 2nd meiotic division yields 4 spermatids in males; 1 oocyte & 2 more polar bodies in females.
Meiosis halves the number of chromosomes & DNA in preparation for fertilization.
Significance of Meiosis: Chiasma allows genetic mixing & recombination of genetic material Constancy of chromosome number from generation to generation is maintained by producing haploid germ cells.
Prepuce with glands of Tyson which are sebaceous glands not associated with hairs. Contribute to smegma - thick, cheesy, odiferous material chiefly composed of desquamated cells around external genitalia, especially clitoris & under prepuce. Phimosis - if aperture of glans is too small for prepuce to be withdrawn easily to reveal glans.Penile raphe - remnants of urethral folds. Detumescence - loss of erection. Circumcision - both males & females
Duct System Tubulae recta
Testis is both endocrine (testosterone) & exocrine (spermatozoa) Accessory Glands: Prostate - secretions are more alkaline than the acid pH of the vagina Seminal vesicles - fructose & prostaglandins Cowper’s (bulbourethral) - mucous Glands of Littre - mucous glands in urethra
Ureter Seminal vesicle Prostate UG diaphragm Cowper’s or bulbourethral Right & left crus Epididymis Testis Urinary bladder Ductus deferens Corpus cavernosum Corpus spongiosum Glans
Urachus apex Bladder Ureter Ductus deferens Seminal vesicle Prostate Cowper’s Bulb Crus Corpus spongiosum Corpus cavernosum Testis Glans
3 parts of urethra: Prostatic Membranous Penile (spongy) with glands of Littre
Ureter Ductus defer. Seminal vesc. Prostate Mem. Urethra Cowper’s Bulb Bladder
Van Gieson to show collagen, (T) tunica albuginea is thickened posteriorly to form the mediastinum testis (M)Tunica vasculosa is inner layer next to tunica albuginea with many blood vessels
Spermatogonia - A & B differentiate. Primary spermatocytes - prolonged prophase followed by rapid completion of Meiosis I. Secondary spermatocytes - short lived, rarely seen. Spermatids - connected by cytoplasmic bridges. Spermatozoa - released from Sertoli cell, immature & flagellum cannot beat. Sertoli cell - tall & irregular in shape, blood-testis barrier, nourish, secrete serous fluid, phagocytose excess cytoplasm of spermatids.
Testosterone from interstitial cells of Leydig initiate puberty & cause seminiferous tubules to function. Primordial germ cells develop as : Spermatogonia A - mitotically active stem cell population. Spermatogonia B - differentiate into primary spermatocytes in a process called spermatocytogenesis.
Sertoli cells nourish sex cells. Phagocytose excess cytoplasm of spermatids. Secrete large volumes of fluid to wash non-motile sperm. Provide proper environment for development of sex cells. Blood-testis barrier Contains Charcot- Bottcher crystals, function unknown.
Lanthanum in seminiferous tubule, blood-testis barrier. Combined length is 275 yards.Prepubertal - solid. Senile tubules typically atrophy with loss of sex cells.
Spermatogenesis takes 64 days:
Spermiogenesis - maturation & transformation of spermatids into spermatozoa. Formation of acrosome from Golgi Condensation of nucleus Formation of neck, midpiece & tail Shedding excess cytoplasm as the residual body
Sertoli cells secrete: Androgen-binding protein (ABP) which binds testosterone in seminiferous tubules Inhibin which regulates FSH and aids in regulating the number of cells entering spermatogenesis A substance similar to LH-releasing factor that may function as intercellular messenger between Sertoli & Leydig cells Anti-Mullerian hormone which acts during embryonic development to promote regression of Mullerian ducts in males
Capacitation - obligate period of time sperm must spend in the female tract before they can fertilize an egg. Glycoproteins are removed from the acrosome & sperm become active (hyperactivated). Most likely occurs in the isthmic sperm reservoir. 200-300 million sperm in a 3.5 ml ejaculate 300-500 move through the cervix, uterus & oviduct
Leydig with Reinke crystalloids (RC)
Not found in other mammals, function unknown.
Leydig cells: Located between seminiferous tubules. Produce testosterone. Large, light & frothy. Occur in clumps. Target is seminiferous tubules.
Duct System Tubulae recta
Straight tubules drain (T) seminiferous tubules, sperm are immotile.(C) Anastomosing channels of rete testis with simple cuboidal to columnar epithelium and immotile sperm.
Efferent ductule, about 3 inches long with ciliated columnar cells alternating with cuboidal microvillar cells. A thin band of smooth muscle surrounds each ductule. This is the only place with motile ciliated cells.Epididymis
Efferent ductule Lumen cogwheel and sawtooth-like
Epididymis about 20 feet long with stereocilia on pseudostratified columnar epithelium.Sperm pass through slowly, about 6 weeks. 90% of all fluid from Sertoli cells resorbed here. Smooth muscle contracts during ejaculation. If ejaculation does not occur, sperm degenerate.
Epididymis
Vas (ductus) deferens with thick smooth muscle layers (3). Epithelium is pseudostratified columnar.
Ductus deferens
Pampiniform plexus: Temperature of blood entering testicular artery must be cooled below normal prior to entering the testis. Testicular artery is surrounded by Pampiniform plexus which cools the blood. Epithelium of prostatic urethra is transitional. Further down it is variable (stratified or pseudostratified). In penile urethra epithelium is stratified squamous.
Seminal vesicle with smooth muscle. Epithelium is honeycombed and irregular. Function is to supply viscous mucous with fructose. Supplied by sympathetic fibers that fire during ejaculation.
Prostate surrounds prostatic urethra. Smooth muscle and irregular epithelial lumen. Secretes serous material rich in acid phosphatase and makes up 70% of seminal fluid. Secretions are slightly acidic (ph 6.5) but are alkaline when compared with the vagina. Secretions liquefy coagulated sperm after it has been deposited in the female. Prostatic concretions, lamellar bodies, amyloid bodies or corpora amylacea are secretion deposits & sloughed epithelial cells. Can become calcified.
Benign prostatic hypertrophy (PUG) Periurethral glands are enlarged& compress the urethra (U).Present in 50% of males over 50 & 95% of men over 70. Clinical symptoms in 5-10%.
2 corpora cavernosa 1 corpus spongiosum All are surrounded by tunica albuginea.
Blood supply to the penis: Flaccid - supplied by dorsal artery. Erection - blood is supplied by deep arteries which give off helicine arteries that enter lacunae. In flaccid state helicine arteries have a longitudinal intimal pad of smooth muscle that closes the vessels. During excitation leading to erection, the muscles relax allowing blood to flow into the lacunae. This compresses the veins beneath the tunica albuginea that drain the penis and an erection is achieved. After ejaculation, the helicine muscles contract and the veins drain the blood from the lacunae.
Deep artery Lacuna
Tunica albuginea Lacuna Veins
Ejaculation: During erotic stimuli, glands of Littre adds mucous to the urethra. Bulbourethral (Cowper’s) secretes mucous to lubricate and clean out urethra. Friction on the glans reinforced by other afferent impulses results in discharge along sympathetic fibers to smooth muscle of epididymis, vas deferens, prostate and seminal vesicles. Smooth muscle contractions ejects sperm and matrix to prostatic urethra.
Bulbospongiosus muscle ejects fluid & sperm from prostatic urethra. Bulbospongiosus muscle is supplied by pudendal nerve, (S2, 3, 4 keeps the penis off the floor). Sphincters of the bladder contract & prevent reflux of sperm into the bladder. “Point and shoot” - arousal, erection = p = parasympathetic = point Ejaculation - s = sympathetic = shoot
Additional Reading:
Basic Histology
1. Introduction to Histology
2. Basic Cell Physiology
3. Actin, Microtubules, and Intermediate Filaments
4. Mitochondria, Nucleus, Endoplasmic Reticulum, Golgi
5. Epithelium (Epithelial Tissue)
6. Connective and Adipose Tissue
7. Types of Cartilage
8. Osteogenesis
9. Nervous Tissue
10. Muscle Tissue
11. Cardiovascular System
12. Blood and Hematopoiesis
13. Lymphoid Tissue
14. Digestive Tract I: Oral Cavity
15. Digestive Tract II: Esophagus through Intestines
16. Liver, Pancreas, and Gall Bladder
17. Respiratory System
18. Integument
19. Urinary System
20. Endocrine System
21. Male Reproductive System
22. Female Reproductive System
23. Eye and Ear
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