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Figure

A computer tracks sperm movements. In semen, sperm swim in a straight line (a), but as they are activated by biochemicals normally found in the woman's body, their trajectories widen (b). The sperm in (c) are in the mucus of a woman's cervix, and the sperm in (d) are attempting to penetrate the structures surrounding an egg cell.

glands is expelled first. This is followed by the release of fluid from the prostate gland, the passage of the sperm cells, and finally, the ejection of fluid from the seminal vesicles (fig. 22.17).

Immediately after ejaculation, sympathetic impulses constrict the arteries that supply the erectile tissue, reducing the inflow of blood. Smooth muscles within the walls of the vascular spaces partially contract again, and the veins of the penis carry the excess blood out of these spaces. The penis gradually returns to its flaccid state, and usually an other erection and ejaculation cannot be triggered for a period of ten to thirty minutes or longer. Table 22.1 summarizes the functions of the male reproductive organs.

Spontaneous emission and ejaculation commonly occur in adolescent males during sleep. Changes in hormonal concentrations that accompany adolescent development and sexual maturation cause these nocturnal emissions.

Figure 22.17

Mechanism of emission and ejaculation.

Functions of the Male Reproductive Organs

Figure 22.17

Mechanism of emission and ejaculation.

What controls blood flow into the erectile tissues of the penis?

Distinguish among orgasm, emission, and ejaculation.

Review the events associated with emission and ejaculation.

Hormonal Control of Male Reproductive Functions

Hormones secreted by the hypothalamus, the anterior pituitary gland, and the testes control male reproductive functions. These hormones initiate and maintain sperm cell production and oversee the development and maintenance of male sex characteristics.

Organ

Function

Testis

Essentials of Human Physiology

Essentials of Human Physiology

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