Q5 LONG ANSWER 10M ★ High-yield

Describe the histology of the testis and the ovary. Add a note on the genital ducts and the endometrium.

Anatomy · 1st Professional — Pre-Clinical

Covered by the tunica albuginea, which sends septa dividing it into about 250 lobules
Each lobule contains 1 to 4 seminiferous tubules

Cell	Position	Function
Sertoli cell	Tall, resting on the basal lamina, extending to the lumen; pale nucleus with a prominent nucleolus	Support and nutrition of germ cells; forms the blood–testis barrier by tight junctions; secretes inhibin and androgen-binding protein; phagocytoses residual bodies
Spermatogonia	On the basal lamina	Stem cells
Primary spermatocyte	The largest germ cell; nucleus shows condensed chromosomes	Undergoes the first meiotic division
Spermatids	Near the lumen; small, with dense nuclei	Transform into spermatozoa by spermiogenesis
LEYDIG (interstitial) cell	Between the tubules, in clusters near vessels; eosinophilic, with lipid droplets and crystals OF REINKE	Secretes testosterone under LH

Structure	Epithelium	Distinguishing feature
Rete testis	Simple cuboidal	Irregular channels in the mediastinum
Efferent ductules	Alternating tall ciliated and short non-ciliated cells	Scalloped (wavy) lumen
Epididymis	Pseudostratified columnar with stereocilia	Smooth, regular lumen packed with spermatozoa
Vas deferens	Pseudostratified columnar with stereocilia	Very thick three-layered muscular wall with a small, star-shaped lumen
Seminal vesicle	Pseudostratified columnar	Honeycomb of interconnecting mucosal folds
Prostate	Simple to pseudostratified columnar	Fibromuscular stroma with corpora amylacea in the acini

Germinal epithelium — a misnomer; a simple cuboidal covering, beneath which lies the tunica albuginea
Cortex contains the follicles in a cellular stroma; medulla contains vessels

Follicle	Features
Primordial	Oocyte surrounded by a single layer of flat cells
Primary	Cuboidal granulosa cells; the zona pellucida appears
Secondary (preantral)	Several layers of granulosa; theca interna and externa form
Antral (vesicular)	A fluid-filled antrum appears
Graafian (mature)	Large antrum; the oocyte sits on the cumulus oophorus with the corona radiata
Corpus luteum	Large pale granulosa lutein cells centrally and smaller darker theca lutein cells peripherally; folded outline
Corpus albicans	A white fibrous scar

Theca interna secretes androgen; granulosa cells aromatise it to oestrogen — the two-cell, two-gonadotrophin theory

Endometrium — simple columnar epithelium with tubular glands in a cellular stroma; a functional layer that is shed and a basal layer that regenerates it
Proliferative phase — straight, narrow glands; mitoses in the stroma
Secretory phase — tortuous, "saw-tooth" glands with subnuclear vacuoles and a coiled spiral artery
Myometrium — thick, interlacing smooth muscle
Uterine tube — a highly folded (labyrinthine) mucosa lined by ciliated and secretory (peg) cells, most complex in the ampulla

Stage	Testis — what is seen	Ovary and endometrium
Basal	Spermatogonia on the basal lamina	Primordial follicles in the cortex
Mid	Primary spermatocytes — the largest cells, with visible chromosomes	Growing and antral follicles; proliferative endometrium with straight glands
Late	Spermatids near the lumen, small and dense	Graafian follicle; ovulation
After	Spermatozoa in the lumen, tails projecting	Corpus luteum; secretory endometrium with tortuous saw-tooth glands

Spermatogenesis takes about 64 days and proceeds in waves, so a single tubule shows only certain stages — which is why adjacent tubules in one section look different
The presence of a corpus luteum dates an ovary to the second half of the cycle, and secretory endometrium dates the uterus to the same period

Structure	Resting state	Active state
Breast lobule	Ducts predominate; few and small acini; abundant fibrofatty stroma	In pregnancy and lactation the acini enlarge greatly and the stroma is reduced
Breast secretion	—	Apocrine for lipid, merocrine for protein — both in the same cell
Endocervix	Simple columnar mucus-secreting; deep clefts	Mucus becomes thin and stretchy at ovulation
Ectocervix	Stratified squamous non-keratinised, rich in glycogen	—
Transformation zone	Where the two meet; the site of squamous metaplasia	The site of cervical carcinoma and of the Pap smear

Blocked cervical gland ducts form nabothian cysts, a normal finding
The squamocolumnar junction moves with age — outward at puberty and in pregnancy, inward after the menopause, which is why sampling becomes more difficult in older women

Endometrial dating — a biopsy can be assigned to a day of the cycle from the appearance of the glands, and is used in the investigation of infertility
Cryptorchidism — the undescended testis is at a higher temperature; spermatogenesis fails but Leydig cells survive, so testosterone is normal while the man is infertile. The risk of malignancy is raised
Vasectomy divides the vas; spermatogenesis continues and the sperm are phagocytosed — testosterone and libido are unaffected
Benign prostatic hyperplasia shows nodules of glands and stroma with abundant corpora amylacea; carcinoma shows small crowded glands with loss of the basal cell layer, which is the diagnostic criterion
Polycystic ovary syndrome — multiple peripheral cysts with a thickened tunica albuginea and hyperplastic theca
The corpus luteum of pregnancy persists under hCG and secretes progesterone until the placenta takes over at about 10 weeks

All questions in Systemic Histology