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8 Cards in this Set

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  • Back

How many sperm are produced a day, and how long does it take?

100 million

64 days

What do sperm start out from?

At puberty, spermatagonia (2n diploid cells) located in the basal compartment of the wall of the seminiferous tubule will be initiated and divide mitotically

Describe what initial division of germ cells produces?

Type A and Type B cells

**Dark type A cells replenish spermatagonia stores

**Light type A cells become type B cells

**Type B cells move into the adluminal compartment and become primary spermatocytes

Describe the types of division the germ cell undergoes

Spermatagonia A (mitosis)

Spermatagonia B (mitosis)

Primary spermatocyte. Migrates to adluminal compartment. (1st meiosis)

Secondary spermatocyte (2nd meiosis)

Spermatids (mature)


During development the cells of the spermatogenic series are supported by Sertoli cells

What is spermiogenesis?

The process by which spermotids are transformed into mature spermatozoa

No further division, only differentiation

Describe the main changes of spermiogenesis

1. Golgi apparatus makes large, membrane-bound vesicle

2. Acrosomal vesicle is applied to pole of developing nucleus to become the acrosomal head cap.

3. Both centrioles migrate to opposite end to acrosomal head cap.

4. One centriole elongates to form flagellum

5. Cytoplasm migrates to surround first part of flagellum

6. Any excess cytoplasm phagocytosed by Sertoli cells

What then happens to mature spermatozoa?

Lack of motility renders them sterile.

Released from Sertoli cells by spermiation.
Transported to epididymis in testicular fluid secreted by Sertoli cells with the aid of peristaltic contraction

In the epididymis, the spermatazoa gain motility and become capable of fertilisation

Outline the regulation of spermatogenesis

GnRH is released from hypothalamus via hypophyseal portal tract

GnRH acts on anterior pituitary to stimulate release of FSH and LH

LH acts on Leydig cells, bringing about synthesis of testosterone

Testosterone and FSH act on Sertoli cells to aid development of gametes

Once spermatogenesis reaches sufficient levels, Sertoli cells produce inhibin which has a negative feedback effect on FSH secretion.