Histology of Reproductive System

Histology of Reproductive System

• The female reproductive system includes primary sex organs (gonads), the genital tract, external genitalia, and accessory organs.
• The primary sex organs (gonads) are the ovaries, which have an endocrine function (hormone secretion) and an exocrine function (ova production).
• The genital tract includes the uterine tubes, uterus, and vagina.
• The external genitalia include the clitoris, labia minora, and labia majora.
• Accessory organs include the placenta and mammary glands.

The Ovary

• Paired, almond-shaped organ in the pelvic cavity.
• Covered with germinal epithelium (simple cuboidal).
• Underlying the epithelium is the tunica albuginea (dense connective tissue).
• The ovary is composed of a wide outer cortex and a small central medulla.
• The cortex contains ovarian follicles at various stages of development.
• The medulla contains loose connective tissue and highly vascularized structures.

Ovarian Follicles

• Present in the ovarian cortex under the tunica albuginea.
• Different types: primordial, unilaminar primary, multilaminar primary, secondary (antral), and mature (graafian).
• FSH stimulates primordial follicles to grow at puberty, initiating ovarian cycles.

Primordial Follicle

• A primary oocyte (immature ovum), surrounded by a single layer of flat follicular cells.
• The primary oocyte is 25 µm in diameter, with a large eccentric pale nucleus.

Unilaminar Primary Follicle

• The primary oocyte enlarges.
• The surrounding follicular cells become cuboidal.

Multilaminar Primary Follicle

• The oocyte continues to grow in size.
• The surrounding follicular cells proliferate to multiple layers forming granulosa cells.
• A zona pellucida forms between the granulosa cells and the oocyte.
• Theca folliculi form from stroma cells.

Secondary (Antral) Follicle

• A fluid-filled cavity (antrum) forms within the granulosa cells.
• The theca folliculi differentiates into an inner theca interna and an outer theca externa.

Mature (Graafian) Follicle

• The primary oocyte reaches its maximum size (150 µm).
• The ovum is pushed to one side by the surrounding follicular cells and granulosa cells.
• A corona radiata forms around the ovum.

Ovulation

• The rupture of a mature graafian follicle.
• Release of the secondary oocyte with its corona radiata and cumulus oophorus.
• Occurs in the middle of the menstrual cycle (around day 14).
• Induced by an LH surge from the anterior pituitary.

Corpus Luteum

• A yellow body formed in the ovarian cortex after ovulation.
• A remnant of the mature follicle.
• Collapses and infolds, becoming a temporary endocrine gland.
• Functions: secreting progesterone and estrogen; preventing further follicle development.

Atretic Follicle

• Ovarian follicles that undergo atresia (degeneration).
• Atresia can occur at any stage of follicle development.
• Atresia is characterized by oocyte death and degeneration of surrounding cells.
• A scar of fibrous tissue remains in the ovary (following atresia of large follicles).

The Uterus

• Pear-shaped muscular organ that receives the fallopian tubes.
• Lower part opens into the vagina.
• Anatomical parts: fundus, body, cervix.
• Structure of the body and fundus: endometrium (mucosa), myometrium (muscularis), perimetrium (serosa).
• Endometrium: simple columnar epithelium, lamina propria, uterine glands.
• Myometrium: composed of three poorly-defined layers of smooth muscle (stratum submucosum, stratum vasculare, stratum supravasculare).
• Perimetrium: loose connective tissue covered by mesothelium.

Cervix of the Uterus

• Lower cylindrical part of the uterus that protrudes into the vagina.
• Internal os: junction between the cervix and the uterine body.
• External os: point where the cervical lumen opens into the vaginal cavity.
• External aspect covered by non-keratinizing stratified squamous epithelium.
• Composed of mucosa (mucous-secreting cervical glands) and stroma (dense connective tissue with few smooth muscle fibers).

Male Genital System

• Includes primary sex organs (testes), excretory ducts, accessory glands, and external genitalia (penis and scrotum).

Testes

• Ovoid organs (4–5 cm long).
• Covered by three layers: tunica vaginalis, tunica albuginea, tunica vasculosa.
• Consist of lobules containing seminiferous tubules (ST).

Seminiferous Tubules (ST)

• Highly convoluted tubules.
• Approximately 0.2 mm in diameter and 50 cm long.
• Lined by stratified germinal epithelium (spermatogenic cells) and Sertoli cells.
• Surrounded by myoid cells and a basement membrane.

Spermatogenic Cells

• Germ cells in ST lining.
• Differentiate from the basal region of ST to its lumen.
• Sequence of events called spermatogenesis (forming spermatozoa from spermatogonia).
• Stages: spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa.

Sertoli Cells

• Pyramidal cells in ST.
• Extend from the basement membrane to the lumen of ST.
• Lateral borders contain pockets for proliferating spermatogenic cells.
• Tight junctions form the blood-testis barrier.
• Functions: secreting testicular fluid, ABP, inhibin; supporting and nourishing spermatogenic cells; phagocytosis of residual bodies; forming the blood-testis barrier.

Interstitial Cells of Leydig

• Located in the connective tissue between seminiferous tubules.
• Polygonal shape with pale, acidophilic, vacuolated cytoplasm.
• Function: secreting testosterone.