Chapter 17

Male Reproductive System

Each testis contains about 250 meters of seminiferous tubule

• Testes: produce sperm (spermatogenesis)

– Production Site: seminiferous tubules

– About 250 meters of tubule/testis

– 100 – 300 million sperm/day produced

• Testes also produce male hormones

(testosterone)

Two Major Functions of Testes

Delivery of Sperm to the Egg

• The duct system stores and transports sperm

– Delivery through reproductive tubules: epididymis

vas deferens urethra penis

Delivery of Sperm to the Egg

• The seminal vesicles and prostate gland (accessory glands) produce most of the volume of semen

• The penis transfers

sperm to the female

The organ where sperm are

produced is

A. Testes

B. Prostate gland

C. Seminal vesicle

D. Penis

• Sperm development involves reduction in the

number of chromosomes and in the structure

of sperm cells

• Several cell divisions of mitosis and meiosis

–Purpose: produce a large number (> 100

million/day) of sperm with half the number of

chromosomes of somatic cells (haploid)

Sperm Production

(Leydig cells)

The organ where sperm are

produced is

A. Prostate gland

B. Testes

C. Seminal vesicle

D. Ovary

Mature sperm contain:

A. 46 chromosomes

B. The same number of chromosomes

as the father

C. 23 chromosomes

D. Half the number of chromosomes as

the father

• Hormones:– Testosterone• Source: Interstitial (Leydig) cells in testes

– LH: stimulates production of testosterone in interstitial (Leydig) cells

– FSH: enhances sperm formation by Sertoli cells

Male Reproductive Hormones

Testosterone secretion is regulated by a negative

feedback loop (see in class worksheet)

The Male Reproductive System

• The hypothalamus (neurosecretory cells)

releases gonadotropin-releasing hormone

(GnRH)

• GnRH stimulates the anterior pituitary

gland to secrete luteinizing hormone

(LH)

• LH stimulates the production of

testosterone by the testes

The rising testosterone level inhibits the

release of GnRH to complete the loop

Actions of Testosterone on Target

Tissues

• Actions of Testosterone

– Controls growth and function of male

reproductive tissues (e.g., prostate &

seminal vesicles)

– Secondary sexual characteristics: muscle,

auxiliary hair, larynx, balding pattern

– Stimulates aggression and sexual behavior

Testosterone has effects on:

A. Male secondary sexual

characteristics, e.g., muscle, beard

growth

B. Prostate gland

C. Sex drive

The function of the prostate gland is to:

A. Produce sperm

B. Produce testosterone

C. Produce secretions (semen) that

make sperm mobile

D. Store sperm