Quiz on Testis and Spermatogenesis

Testis

• Each testis is an oval structure.
• Located in the scrotum, they are about 5cm long and 3cm in diameter.
• Covered by the tunica albuginea, a fibrous capsule that covers each testis.
• The tunica albuginea gives rise to septa that divide the testis into lobules.
• Each lobule contains 3 or 4 highly coiled seminiferous tubules.
• The seminiferous tubules converge to form the rete testis which transports sperm to the epididymis.

Seminiferous Tubules

• Lined by germ cells in various stages and non-germ cells called Sertoli cells.
• Germ cells are referred to as the spermatogenic series.
• Sertoli cells support and nourish developing spermatozoa.

Spermatogenesis

• A tightly regulated developmental process.
• Involves sequential mitotic and meiotic cellular divisions.
• Occurs within seminiferous tubules and is orchestrated by Sertoli cells.
• Differentiating germ cells must migrate through the lumen as they develop.
• There are typically 4-5 concentric layers of spermatogenic cells at different developmental stages.
• Cells move from the basement membrane (BM) of the seminiferous tubule towards the lumen.

Interstitial Cells of Leydig

• Principal cell type found in interstitial tissue between seminiferous tubules.

Epididymis

• Consists of three parts: the head, body, and tail.
• The head is composed of a series of highly coiled tubules.
• The body and tail are less coiled.
• Principal cells of the epididymis have stereocilia.
• The epididymis is lined by epithelium.
• The inner lumen is lined by basal cells and principal cells.

Vas (Ductus) Deferens

• Conducts spermatozoa from the epididymis to the seminal vesicles.
• Thick-walled muscular tube with inner & outer longitudinal layers and a thick intermediate circular layer.
• Innervated by the sympathetic nervous system which produces strong peristaltic contractions to expel contents into the urethra during ejaculation.
• Lined by pseudostratified columnar epithelium with stereocilia.

Seminal Vesicles

• Secrete 50-70% of the total volume of seminal fluid.
• Have a pseudostratified tall columnar epithelium.
• Contain secretory cells with lipid droplets, giving a foamy appearance.
• The lumen is highly irregular.
• Produce a yellowish viscid alkaline fluid containing fructose, fibrinogen, Vitamin C and prostaglandins.
• Prominent muscular wall arranged into inner circular and outer longitudinal layers.
• Supplied by sympathetic nervous system to contract during ejaculation.

Prostate Gland

• Secretory product makes up 30-50% of the seminal fluid volume.
• Composed of glands and stroma.
• Stroma is a mixture of collagenous fibrous tissue and smooth muscle fibers.
• The glands show a convoluted pattern.
• Epithelium contains tall columnar secretory cells with prominent round basal nuclei and pale-staining cytoplasm.
• Scanty population of small, flat, basal cells at the base of the gland in contact with the basement membrane.

Penis

• Erectile tissues arranged into three columns: two dorsal (corpora cavernosa) and one ventral (corpus spongiosum).
• Penile urethra runs through the center of the corpus spongiosum, which expands distally to form the glans penis.
• Erectile corpora are enclosed within and separated by a fibrocollagenous capsule.
• A sheath of skin encloses the erectile center of the penis.
• Erectile tissues consist of lacunae, spaces surrounded by collagenous connective tissue.

Penile Urethra

• Lined by stratified or pseudostratified columnar epithelium.
• May contain small areas of stratified squamous epithelium.
• The external opening, the urethral meatus is lined by stratified squamous epithelium.
• Lubricated by mucous secretions from para-urethral glands and bulbo-urethral glands of Cowper.

Ovary

• Review the basic structure of the ovary and the stages of follicular development.

Follicle Development - Primordial Follicles

• Undeveloped follicles, inactive structures awaiting stimulation from FSH before re-entering their developmental pathway.
• Composed of a primary oocyte surrounded by a single layer of flattened follicular cells.

Follicle Development - Primary Follicles

• Once stimulated by FSH, 30-50 primordial follicles become primary follicles.
• The primary follicle oocyte has enlarged, and the follicular cells (now called granulosa cells) have multiplied.
• A zona pellucida layer develops between the oocyte and the granular cells.

Follicle Development - Secondary Follicle

• The zona granulosa continues to proliferate.
• Small fluid-filled spaces develop between the granulosa cells, fusing to form the follicular antrum.
• The oocyte is situated eccentrically within a thickened area of the zona granulosa called the cumulus oophorus.
• Stroma around the developing follicle differentiates into thecal cells with two layers: theca interna and theca externa.

Follicle Development - Graafian Follicle

• The oocyte at this stage is called the secondary oocyte.
• The follicular antrum is markedly enlarged.
• The zona granulosa forms a layer of even thickness around the periphery.
• The maturing follicle has reached 1.5-2.5 cm in diameter.

Uterus (Proliferative)

• Stratum basalis regrows the stratum functionalis.
• Long and straight non-functional uterine glands are present.

Uterus (Secretory)

• Uterine glands of the stratum functionalis become functional.
• Uterine glands produce glycogen.
• Curvy, serrated-looking glands are present.

Uterus (Menstrual)

• Stratum functionalis dies and loses its anatomical integrity.
• The stratum functionalis sheds from the stratum basalis.

Vagina

• Consists of three layers: mucosal, muscular, and adventitial layer.
• The mucosal layer is lined by stratified squamous epithelium.
• The muscular layer has smooth muscle bundles arranged as inner circular and outer longitudinal layers.
• The adventitial layer contains elastin fibers, a rich plexus of small veins, and is devoid of glands.
• Lubricated by cervical mucus.