Spermatogenesis and male repro. Physiology

What is spermatogenesis?

The process of producing male gametes (sperm) in the seminiferous tubules of the testes. It takes ~65–75 days and begins at puberty.

Where does spermatogenesis occur?

In the seminiferous tubules of the testes.

What cell type initiates spermatogenesis?

Spermatogonia (diploid stem cells, 2n).

What happens to spermatogonia during spermatogenesis?

They undergo mitosis → some remain stem cells, others differentiate into primary spermatocytes.

What is the ploidy of primary spermatocytes?

Diploid (2n).

What occurs during meiosis I in spermatogenesis?

Primary spermatocytes → secondary spermatocytes (haploid, n; chromosomes still duplicated).

What occurs during meiosis II?

Secondary spermatocytes → spermatids (haploid, n; single chromatids).

Final output of one primary spermatocyte?

4 spermatids.

What is spermiogenesis?

Transformation of spermatids into mature sperm cells.

Key structural changes in spermiogenesis?

• Acrosome formation

• Nuclear condensation

• Flagellum development

• Mitochondrial increase

• Cytoplasm removal (by Sertoli cells)

Function of Sertoli (sustentacular) cells?

• Support developing sperm

• Remove excess cytoplasm

• Secrete androgen-binding protein (ABP)

• Release inhibin

Function of Leydig cells?

Produce testosterone in response to LH.

What hormone initiates spermatogenesis at puberty?

GnRH from hypothalamus.

Role of LH in males?

Stimulates Leydig cells → testosterone production.

Role of FSH in males?

Stimulates Sertoli cells → supports spermatogenesis.

What is inhibin?

Hormone from Sertoli cells that inhibits FSH release.

What is the function of the acrosome?

Contains enzymes (e.g., hyaluronidase) to penetrate the oocyte.

Function of the midpiece?

Contains mitochondria → ATP production for motility.

Why are sperm highly specialized?

Designed for motility and fertilization.

Pathway of sperm (SEVEn UP)?

Seminiferous tubules → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Penis

Where do sperm gain motility?

Epididymis.

What is semen composed of?

Sperm + accessory gland secretions.

Key functions of semen?

• Nutrient supply (fructose)

• Protection (alkaline pH)

• Transport medium

What causes erection?

Nitric oxide → vasodilation → increased blood flow.

What controls ejaculation?

Sympathetic nervous system.