Male Reproduction terms to memorize

 

SRY gene

The gene on the Y chromosome which causes the embryo’s gonads to develop into testes

Testis determining factor

The protein coded for by the SRY gene

Pronephros

The first kidneys; reabsorbed early in the embryo’s development

Mesonephros

The middle kidneys – colonized by germ cells to become the gonads

Mesonephric ducts or Wolffian ducts

These carried urine from the mesonephros to the bladder. In males, they will become the vas deferens.

Paramesonephric ducts or Mullerian ducts

These ducts lie beside the mesonephros. In females they will become the oviducts and uterus.

Mullerian inhibiting factor

A compound produced by the embryo’s testes, it causes the mullerian ducts to be reabsorbed so the male embryo does not develop oviducts and a uterus

Testosterone

Produced by the developing testes. It causes the wolffian ducts to develop into the vas deferens. Later, a larger amount is produced by the adrenal cortex and causes the external genitalia to develop.

5-alpha-hydroxylase

An enzyme that converts testosterone into a form (dihydrotestosterone) which is very active in the external tissues. This allows development of the external genitalia.

Gonadotropin releasing hormone (GnRH)

Released from the hypothalamus at puberty. Causes the pituitary to release FSH and LH

Follicle Stimulating Hormone (FSH)

Causes the male testes to begin producing sperm

Luteinizing hormone (LH)

Causes the testes to produce testosterone

Negative feedback control

Testosterone has a negative feedback effect on the hypothalamus (stops GnRH release) and pituitary (stops FSH and LH release).

Acetylcholine (Ach)

Neurotransmitter that causes erection

G-protein

A protein in the membrane of the smooth muscle cells, that is activated when Ach attaches to the Ach receptor. It then causes smooth muscle relaxation leading to vasodilation

NO (nitric oxide)

A vasodilating substance released from the same nerve fibers that release Ach

Guanylate cyclase

An enzyme in the smooth muscle cell membrane that is stimulated by NO. It then produces cyclic GMP, a second messenger which moves down inside the cell and causes it to relax.

Parasympathetic system

The major system causing release of Ach and NO in the penis

Sympathetic system

Can cause Ach and NO release, but is more usually involved with emission and ejaculation by causing peristaltic contractions of the vas deferens. It also closes the urinary sphincters so urine and semen do not mix.