The Male Reproductive System

The Reproductive System Gonads—primary sex organs Testes in males Ovaries in females Gonads produce gametes (sex cells) and secrete hormones Sperm—male gametes (Spermatogenesis) Ova (eggs)—female gametes (Oogenesis)

Functions 1. Produces, nurtures and transports gametes (ova/sperm) 2. Secrets hormones 3. Provide a means for fertilization

Divisions of the Male Reproductive System Testes Duct System Accessory Glands External Genitalia We will discuss each of these in more detail

A. Testes Each testis is surrounded by a membrane. This membrane extends into each testis forming partitions that divide the testis into approximately 250 compartments, or lobules.

Seminiferous tubules 1-4 found in each lobule tightly coiled sperm-forming factories

Rete testis *May or may not be considered an actual part of the duct system depending on the reference being used Network of ducts (channels) Take immature sperm cells from seminiferous tubules to epididymus

2 Types of Cells within the testis Interstitial cells: produce androgens (male hormones) such as testosterone Spermatogenic: sperm-producing cells

B. Duct System Epididymis Ductus (vas) deferens Ejaculatory Duct Urethra

1. Epididymis Comma-shaped, tightly coiled tube (20 ft) Found on the superior part of the testis along the posterior lateral side Functions to mature and store sperm cells (at least 20 days) Muscles in the epididymis walls move sperm to the vas deferens

2. Ductus Deferens (Vas Deferens) Carries sperm from the epididymis to the ejaculatory duct Passes over the bladder Moves sperm by peristalsis

Vasectomy cutting of the ductus deferens at the level of the testes to prevent transportation of sperm

3. Ejaculatory Duct Unites the ductus deferen with the urethra

4. Urethra Extends from the base of the urinary bladder to the tip of the penis Carries both urine and sperm Sperm enters from the ejaculatory duct

Figure 16.2b

C. Accessory Organs 1. Seminal vesicles 2. Prostate 3. Bulbourethral glands (Cowper)

1. Seminal Vesicles Located at the base of the bladder Produces a thick, yellowish secretion (60% of semen) Fructose (sugar) Vitamin C Prostaglandins (hormones) Other substances that nourish and activate sperm

2. Prostate Encircles the upper part of the urethra Secretes a milky fluid Helps to activate sperm Enters the urethra through several small ducts

3. Bulbourethral Glands Pea-sized gland inferior to the prostate Produces a thick, clear mucus Cleanses the urethra of acidic urine Serves as a lubricant during sexual intercourse Secreted into the penile urethra

Figure 16.2a

Semen Mixture of sperm and accessory gland secretions Advantages of accessory gland secretions Fructose provides energy for sperm cells Alkalinity of semen helps neutralize the acidic environment of vagina Semen inhibits bacterial growth Elements of semen enhance sperm motility

D. External Genitalia 1. Scrotum 2. Penis

1. Scrotum Divided sac of skin outside the abdomen Maintains testes at 3°C lower than normal body temperature to protect sperm viability Muscles move testes up toward body or lower away from body

2. Penis Delivers sperm into the female reproductive tract Regions of the penis Shaft Glans penis (enlarged tip) Prepuce (foreskin) Folded cuff of skin around proximal end Often removed by circumcision Internally there are three areas of spongy erectile tissue around the urethra Erections occur when this erectile tissue fills with blood during sexual excitement