Gametogenesis

Spermatogenesis

The biological process by which diploid germ cells develop into haploid mature male gametes called spermatozoa within the seminiferous tubules.

Spermatogonia

Diploid stem cells (2n) located at the basement membrane of the seminiferous tubules that undergo mitosis to maintain the cell line.

Type A Spermatogonia

A subset of spermatogonia that remain at the basement membrane to serve as a permanent pool of stem cells via mitosis.

Type B Spermatogonia

Differentiated daughter cells of Type A spermatogonia that move toward the lumen to become primary spermatocytes.

Primary Spermatocyte

A diploid cell (2n) that undergoes the first meiotic division (Meiosis I) to produce two secondary spermatocytes.

Secondary Spermatocytes

Haploid cells (n) formed after Meiosis I; they quickly undergo Meiosis II to produce four spermatids.

Spermatids

Small, round haploid cells (n) produced at the end of the second meiotic division; they are not yet motile or streamlined.

Spermiogenesis

The final phase of spermatogenesis involving the morphological transformation of round spermatids into elongated, flagellated spermatozoa.

Spermatozoa

The fully mature male gametes characterized by a head, a midpiece, and a flagellum (tail).

Sperm Head

The part of the sperm containing the haploid nucleus and the acrosome, responsible for delivering paternal genetic material.

Acrosome

A lysosome-like organelle at the tip of the sperm head containing proteolytic enzymes like \text{acrosin} to penetrate the ovum layers.

Sperm Midpiece

The central part of the sperm body containing many mitochondria arranged in a spiral to provide ATP for flagellar movement.

Sperm Tail

A long flagellum composed of a central axoneme which provides the propulsive force for sperm motility.

Sertoli Cells

Large columnar cells extending from the basement membrane to the lumen that nourish, support, and protect developing sperm cells.

Blood-Testis Barrier

A physical barrier created by tight junctions between Sertoli cells that prevents blood-borne substances and immune cells from attacking germ cells.

Leydig Cells

Interstitial cells located outside the seminiferous tubules that secrete testosterone when stimulated by Luteinizing Hormone (LH).

Luteinizing Hormone (LH)

A gonadotropin from the anterior pituitary that binds to Leydig cells to trigger testosterone production.

Follicle-Stimulating Hormone (FSH)

A gonadotropin that targets Sertoli cells to initiate spermatogenesis and produce androgen-binding protein (ABP).

Androgen-Binding Protein (ABP)

A protein secreted by Sertoli cells that binds testosterone to keep its concentration high within the seminiferous tubules.

Inhibin

A hormone released by Sertoli cells that provides negative feedback to the anterior pituitary to reduce the secretion of FSH.