📝 STANDARD DESCRIPTION:
MALE:
• Testis: Seminiferous tubules (with spermatogenic cells + Sertoli cells) + interstitial Leydig cells (testosterone).
• Epididymis: Pseudostratified columnar with stereocilia; sperm storage.
• Ductus Deferens: Thick muscular wall; pseudostratified epithelium.
• Accessory Glands: Seminal/vesicular, prostate, bulbourethral.
• Penis: Erectile tissue (corpus cavernosum + spongiosum) + urethra.
FEMALE:
• Ovary: Cortex with follicles at all stages + corpus luteum; medulla with vessels.
• Oviduct: Simple ciliated columnar with mucosal folds.
• Uterus: Endometrium + Myometrium + Perimetrium. Cyclic changes.
• Cervix, Vagina, Vulva: Stratified squamous epithelium (vaginal cyclic changes).
📚 DETAILED DESCRIPTION:
REPRODUCTIVE SYSTEM HISTOLOGY
I. MALE REPRODUCTIVE TRACT:
1. Testis:
• Capsule = tunica albuginea (dense CT) sends septa dividing testis into lobules.
• Each lobule contains seminiferous tubules (highly coiled).
• Tubule wall:
– Spermatogenic cells: at multiple stages from base to lumen — spermatogonia (basal) → primary spermatocytes → secondary spermatocytes → spermatids → spermatozoa (luminal).
– Sertoli cells: tall columnar 'nurse' cells extending from base to lumen; tight junctions form blood-testis barrier; secrete inhibin, ABP, anti-Müllerian hormone.
• Between tubules: Leydig (interstitial) cells with abundant SER + lipid → secrete testosterone.
2. Epididymis:
• Pseudostratified columnar epithelium with STEREOCILIA (long microvilli, despite the name).
• Smooth muscle increases distally.
• Sperm acquire motility + maturation here; stored in tail (cauda).
3. Ductus Deferens:
• Pseudostratified columnar (with stereocilia) lining a stellate (star-shaped) lumen.
• Very thick muscular wall — three layers (inner longitudinal + middle circular + outer longitudinal). Smooth muscle propels sperm during ejaculation.
4. Accessory Sex Glands (vary by species):
• Seminal/Vesicular gland: lobulated; high columnar epithelium with secretory granules; provides bulk of seminal fluid (fructose, prostaglandins). Lobulated in BULL; smooth-walled in stallion.
• Prostate: Tubuloalveolar gland with thick fibromuscular stroma; secretes alkaline fluid. Concretions (corpora amylacea) common in older animals.
• Bulbourethral (Cowper's): Compound tubular mucous gland; secretes pre-ejaculate.
5. Penis:
• Corpus cavernosum penis (paired) + corpus spongiosum penis (single, around urethra) — erectile tissues with vascular sinuses.
• Bull/Ram/Boar: fibroelastic penis — small cavernous spaces, mostly dense CT.
• Stallion/Dog: musculocavernous penis — large erectile spaces.
• Os penis in dog (and a few others).
II. FEMALE REPRODUCTIVE TRACT:
1. Ovary:
• Surface = germinal (surface) epithelium = simple cuboidal (NOT really germinal — misnomer).
• Tunica albuginea just under it.
• Cortex: stroma + follicles at every stage:
– Primordial: oocyte + flat follicular cells.
– Primary: cuboidal follicular cells; zona pellucida appears.
– Secondary: multiple layers of granulosa + theca interna/externa.
– Tertiary (antral): with antrum; cumulus oophorus.
– Mature (Graafian): ready to ovulate.
– Atretic follicles: degenerating.
– Corpus haemorrhagicum (after ovulation, with blood) → Corpus luteum (lutein cells secreting progesterone) → Corpus albicans (white scar).
• Medulla: loose CT + vessels + nerves.
• Mare ovary has a single ovulation fossa (only ovulation site).
2. Uterine Tube (Oviduct):
• Mucosa highly folded.
• Simple columnar epithelium with ciliated + secretory (peg) cells.
• Smooth muscle (inner circular + outer longitudinal).
3. Uterus:
• Endometrium: simple columnar epithelium + lamina propria with simple tubular uterine glands; estrous-cycle changes under estrogen and progesterone; human menstrual 'proliferative/secretory phase' terminology should not be applied unchanged across domestic species.
• In ruminants — caruncles (non-glandular elevations) for placental attachment.
• Myometrium: thick smooth muscle (inner circular + middle vascular + outer longitudinal).
• Perimetrium: serosa.
4. Cervix:
• Heavy fibromuscular wall; mucosal folds, crypts and glandular development vary by species; mucus production and a pregnancy plug are functional features.
• Mucous plug in pregnancy.
5. Vagina:
• Stratified squamous epithelium — KEY for vaginal cytology in cycle staging:
– Proestrus/oestrus (oestrogen high) — superficial cornified cells (anuclear, large flat).
– Diestrus — parabasal + intermediate cells.
• Lamina propria + smooth muscle + adventitia.
6. Mammary Gland:
• Compound tubuloalveolar gland.
• Lactating: many large alveoli with milk inside; cuboidal-columnar epithelium; myoepithelial cells outside (oxytocin contracts them → milk ejection).
• Non-lactating: mostly fat + ducts; few/no alveoli.
• Apocrine + merocrine secretion (lipid pinches off; protein by exocytosis).
// COMPARATIVE ANALYSIS
| OX |
Vesicular glands lobulated; uterine caruncles for cotyledonary placenta. Vaginal smear cytology used in cycle monitoring. |
| HORSE |
Mare ovary has single ovulation fossa — most peculiar shape. Microcotyledonary diffuse placenta. |
| BITCH |
Vaginal cytology = THE standard tool for breeding management; a high proportion of cornified superficial cells supports estrus staging, but precise breeding time should be refined with serial progesterone with or without LH testing and clinical context. |
CLINICAL RELEVANCE
Cryptorchidism: An undescended testis has impaired spermatogenesis and increased neoplasia risk; bilateral cryptorchids are infertile, while unilateral animals may remain fertile. Cystic Endometrial Hyperplasia / Pyometra (Bitch): Common, life-threatening. Mammary Tumours (Bitch): ~50% malignant. Mastitis: Bacterial inflammation of mammary alveoli.
