Histology                                                                                                                     Stanley Shostak
BioSc 1450                                                                                                                  Spring 03

Lecture 19. Male Reproductive System

Testis

tunica vaginalis: serosal lining; both parietal and visceral layers; contains fibroblast and myocytes (muscle-like cells); contract rhythmically; covers loose, vascular ct.

tunica albuginea (white tunic): capsule of dense fibrous tissue; delicate collagenous septa divide testis into about 250 testicular lobules

interstitial endocrinocytes = Leydig cells singly or in groups within ct; secrete androgens.

seminiferous tubules: 250 to 1000 per testis; 1 to 4 per testicular lobule; supportive or sustentacular cells = Sertoli cells; cells of the spermatogenic series; possibly blind end; opening into tubuli recti

tubuli recti (straight): sustentacular cells (sans spermatogenic cells); dense ct sheath

rete testis (net): collecting tubules for seminiferous tubules; usually no spermatozoa; low cuboidal epithelium; no muscle; contained in mediastinum testis (thickening of tunica albuginea at hilum)

ductuli efferentes: 15 to 20 small ducts conduct spermatozoa and condense into single epididymal tube in body of epididymis; upper, posterior pole of testis; usually no spermatozoa; epithelium: juxtaposition of tall ciliated and low absorptive cells gives corrugated appearance; smooth muscle

epididymis: compact mass extending down over posterior aspect of testis; extremely tortuous, tightly coiled tube; first part of ductus deferens; usually filled with decapacitated spermatozoa; lined by columnar, pseudostratified epithelium bearing stereocilia (large, branched microvilli)

ductus (vas as in vasectomy) deferens: inner and outer layers of longitudinally oriented smooth muscle, intermediate layer of circular muscle; sympathetic nervous innervation; strong peristaltic contractions expel ejaculum; lined by pseudostratified epithelium thrown into folds (containing lamina propria); dilated distal portion = ampulla: receives short ducts from seminal vesicle to become ejaculatory ducts

ejaculatory ducts: combining ducts from seminal vesicles and ductus deferens; converge to join urethra (prostatic urethra: passes through prostate gland)

 spermatogenesis: entire process leading to spermatozoa (male gametes)

spermiogenesis ( = spermioteleosis): follows development of haploid cell; differentiation spermatids into spermatozoa

final maturation = decapacitation: occurs within epididymis; inhibits motility during passage into female genital tract.

Germinal or seminiferous epithelium (misnomer): Note: germinal epithelium was earlier thought to give rise to germ cells; primordial germ cells arise in hind gut of mammals and infiltrate (colonize) germinal ridge early in embryology.

Supportive or sustentacular cells: comprise simple, columnar epithelium; highly infiltrated with germ cells of the spermatogenic series: function as follicle cells; under influence of FSH, secrete androgen binding protein (transports dihydrotestosterone to lumen of seminiferous tubule); phagocytize excess cytoplasm cast off by spermatids; nuclei usually found toward basement membrane; frequently triangular or ovoid; oriented at right angles to basement membrane; may be deeply indented; prominent nucleolus; dispersed chromatin; prominent chromatin bodies associated with nucleolus; sER; extensive cytoplasm ramifies throughout whole germinal epithelium, enclosing all the spermatogenic series; supported by basement membrane

junctional complexes containing extensive tight  (occluding) junctions; separate basal compartment containing spermatogonia from adluminal compartment containing spermatocytes and spermatids behind a blood-testis barrier

lamina propria contains several layers of spindle-shaped fibromyocytes (myoid cells) responsible for movement of spermatozoa along tubules (?).
 
 


Spermatogenic series: move toward lumen.

spermatogonia: basal layer; Type A (dark): typically in G0, a reserve population that is called back into play if testis is traumatized
Type A (pale) divide mitotically to become Type A pale (self-renewing)  and Type B. Characterized by a large, oval to round nucleus with condensed chromatin associated with nuclear membrane; may have a prominent nuclear vacuole; sparse, poorly stained cytoplasm.
Type B: mitosis limited; committed to enter meiosis; dispersed chromatin, centrally located nucleoli, and no nuclear vacuole; sparse, poorly stained cytoplasm. spermatocytes: in some stage of meiosis preleptotene primary spermatocytes: in S or G-2 phases of meiosis

primary spermatocytes: in any stage of meiosis I; identified by condition of chromosomes; copious cytoplasm; large nuclei containing coarse clumps or thin threads of chromatin; dividing cells

secondary spermatocytes: in any stage of meiosis II; smaller than primary spermatocytes; much less common.
 

 spermatids: round phase: become smaller, more condensed, less granular;
elongation phase: assume small pointed form; develop acrosomal vesicles elaborated from golgi apparatus; mid- and tail piece. spermatozoa: require capacitation within female genital tract (or tissue culture medium) to become motile Semen (Latin: liquid seed): product of ejaculuation; spermatozoa, seminal fluid (principally from seminal vesicle and prostate gland) & desquamated cells from tract; fructose and citrate metabolites;

Accessory glands

Seminal vesicle: glandular diverticulum of ductus deferens; secrete more than half volume seminal fluid; honeycombed appearance; pseudostratified epithelium, secretory (low cuboidal); brown lipofuscin granules; produce yellowish viscid alkaline fluid containing fructose, fibrinogen, vitamin C and prostaglandins; prominent muscular wall inner circular and outer longitudinal layers; innervated by sympathetic nervous system

Prostate gland: surrounded by thick, fibro-elastic capsule; bilobed gland; lobes separated by thick central stroma also containing bladder neck and prostatic urethra, ejaculatory ducts , urethral sinuses & urethral crest; separated by septa (arising from capsule and containing smooth muscle innervated by sympathetic neurons) into 50 or so poorly defined lobules; pseudostratified columnar epithelium (much higher than epi of SV); basally located nuclei; forms branching folds with central core of lamina propria = papillary appearance; lamellated glycoprotein masses = corpora amylacea increase with age; calcify as prostatic concretions; thin, milky secretory product rich in citric acid and hydrolytic enzymes: fibrinolysin.

3 separate groups of compound tubulo-acinar glands arranged concentrically around urethra

main prostatic glands (bulk of organ) peripheral 2/3rds; drain via about 20 long (arching) ducts into distal urethra on either side of the urethral crest; give rise to prostatic cancer

submucosal (outer periurethral) glands: drain via short ducts into urethral sinuses; tend to become enlarged leading to benign prostatic hyperplasia

mucosal (inner periurethral) glands: open directly into urethra; tend to become enlarged leading to benign prostatic hyperplasia
 

 prostatic urethra: lined by transitional epithelium Penis: Note: sympathetic nervous system > evacuation; parasympathetic nervous system > engorgement 3 cylindrical masses of erectile tissue: paired corpora cavernosa penis (dorsal); corpora carvernosum urethrae (or corpora spongiosum) surrounding penile urethra and forming glans penis.

tunica albuginea: condensed fibro-elastic tissue invests cavernous bodies; continuous with loose ct of hypodermis (allows thin penile skin to move) containing prominent blood vessels

penile erectile tissue (of cavernous bodies): broad vascular lacunae or cavernous sinuses supported by trabeculae of fibro-elastic tissue and smooth muscle; non-fenestrated vascular endothelium.

vascular sinuses: become engorged during erection; enlargement compresses venous outflow; thick-walled, anastomosing arteries and arterioles - helicine arteries (as in helix); spiral in flaccid state; veins in dense fibro-elastic investments; dilation of helicine arteries mediated by parasympathetic nervous system; smooth muscle of trabeculae relax penile urethra: deep outpocketings continuous with ducts of simple acinar glands = paraurethral glands; lined by stratified or pseudostratified columnar epithelium (within areas of stratified squamous) paraurethral glands and bulbo-urethral glands (of Cowper) lubricate; mucoid secretion urethral meatus: external opening lined by stratified squamous epithelium continuous with skin of glans. last revised: 03-27-03