Histology                                                                                                                     Stanley Shostak
BioSc 1450                                                                                                                  Spring 02

Lecture 22. 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

seminiferous tubules: 1÷4 per testicular lobule; sustentacular cells = Sertoli cells; cells of the spermatogenic series; interstitial endocrinocytes = Leydig cells singly or in groups within ct; secrete androgens.

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

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

ductuli efferentes: 15÷20 small ducts conduct spermatozoa; upper, posterior pole of testis; usually no spermatozoa; tall ciliated and lo absorptive cells; 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

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; spermatids transformation into motile spermatozoa

final maturation = decapacitation: occurs within epididymis.

Germinal epithelium:
Sustentacular cells: comprise simple, columnar epithelium; highly infiltrated by 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 (?).

[Note: seminiferous (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.]


Spermatogenic series: move luminally.

spermatogonia: basal layer; Type A (dark): ypically in G0, a reserve population that is called back into play if testis is traumatized
Type A (pale) self-renewing; divide mitotically to become Type A pale and Type B. Characterized by a large, oval to roundnucleus 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: are in S phase of meiosis

primary spermatocytes: in some stage of meiosis I; copious cytoplasm; large nuclei containing coarse clumps or thin threads of chromatin; dividing cells

secondary spermatocytes: in some 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 Semen: 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 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 hyperplasic

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

 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 carernous bodies; continuous with loose ct of hypodermis (allows thin penile skin to move) containing prominent blood vessels

penile erectile tissue (of carvernous 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. modified: 04-09-01
last revised: 01-06-02