Sperm Production: Spermatogenesis

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Spermatogenesis• Sperm produced in testes which are located

outside the body in order to help in temperature regulation (~3° lower temperature)

• In each testis are seminiferous tubules; near outer wall of tubules are germinal epithelial cells (cells of an organism whose function is to reproduce its kind) called spermatogonia

Note: It takes 64-74 days for sperm to develop and every day ~100 million sperm are produced

Spermatogonia either go through mitosis to replace cells becoming sperm (type A) or go through meiosis to form 4 spermatozoa (type B)

Leydig cells – found in-between the tubules; after pituitary gland secretes LH, these cells respond by producing testosterone (key to sperm production)

Sertoli cells – cells in the seminiferous tubules that assist in the development of sperm cells (Nurse cells)

Testis Tissue

Pseudo-colored scanning electron micrograph of seminiferous tubule

Process of Making Sperm: Spermatogenesis

1. Mitosis of Type A spermatogonia takes place to form a Type B spermatogonia

2. Type B spermatogonia then grows and becomes a primary spermatocyte

3. Primary spermatocyte undergos Meiosis I (forming the secondary spermatocyte) and Meiosis II (forming spermatids); both result in haploid cells

4. The spermatids then differentiate into spermatozoa (flagellum/acrosome)

Function of Hormones in spermatogenesis:

• LH – produced by pituitary gland; stimulates Leydig cells to produce testosterone

• Testosterone – produced by Leydig cells; promotes spermiogenesis (maturation of spermatids into spermatozoa)

• FSH – produced by pituitary gland; stimulates sperm production in seminiferous tubules; stimulates division and maturation of Sertoli cells

Head: Acrosome (organelle that contains enzymes necessary to penetrate the egg); Nucleus (haploid)

Midpiece: Mitochondria (provide ATP for swimming)

Tail: Flagellum (movement)