Chapter 16, Reproductive System, Part A

Chapter 16: Reproductive System
Part A: Male System
1. Gonads
a. Primary sex organs
i. Males = testes
ii. Females = ovaries
b. Produce gametes (sex cells) and secrete hormones
i. Males = sperm (male gametes)
ii. Females = ova/eggs (female gametes)
2. Male reproductive system overview
a. Testes (2)
b. Duct system—transport sperm:
i. Epididymis (2)
ii. Ductus deferens = vas deferens (2)
iii. Urethra (1)
c. Accessory organs
i. Seminal vesicles (2)
ii. Prostate (1)
iii. Bulbourethral glands (2)
d. External genitalia
i. Penis
ii. Scrotum
3. Specialized structures
a. Testes
i. Coverings
1. Tunica albuginea—capsule that surrounds each testis
2. Septa (singular = septum)—extensions of the capsule; divide testes into lobules
ii. Internal structure
1. Lobules contain one to four seminiferous tubules
a. Tightly coiled structures
b. Function as sperm-forming factories
2. Sperm travels through the rete teswtis to the epididymis
3. Interstitial cells in the s.t.’s produce androgens (testosterone)
a. Castration—removal of testes
b. Duct system
i. Epididymis
1. Comma shaped, tightly coiled tube
2. Functions to mature and store sperm cells (at least 20 days)
3. Expels sperm with the contraction of muscles in walls to the vas deferens
ii. Vas deferens
1. Carries sperm from the epididymis to the ejaculatory duct
2. Passes through the inguinal canal and over the bladder
3. Moves sperm by peristalsis
4. Spermatic cord—ductus deferns, blood vessels, and nerves in a connective tissue sheath
5. Ends in the ejaculatory duct which unites with the urethra
6. Ejaculation—smooth muscle in the walls of the vas create peristaltic waves to squeeze sperm foward
7. Vasectomy—cutting of the ductus deferens at the level of the testes to prevent transportation of sperm
iii. Urethra
1. Extends from the base of the urinary bladder to the tip of the penis
2. Carries both urine and sperm
3. Sperm enters from the ejaculatory duct
c. Semen
i. Mixture of and accessory gland secretions
ii. Advantages of accessory gland secretions:
1. Fructose provides energy for sperm cells
2. Alkalinity of semen helps neutralize the acidic envioronment of vagina
3. Semen inhibits bacteria
4. Elements of semen enhance sperm motility
d. Accessory organs
i. Seminal vesicle
1. Located at the base of the bladder
2. Produces thick, yellowish secretion (60% of semen)
3. Contains:
a. Fructose (sugar)
b. Vitamin C
c. Other substances that nourish and activate sperm
ii. Prostate
1. Encircles the upper part of the urethra
2. Secretes milky fluid that helps to activate sperm, enters the urethra through several small ducts
3. Enlarged prostate constricts flow through urethra
iii. Bulbourethral gland
1. Pea-sized gland inferior to the prostate
2. Produces thick, clear mucus that
a. Cleanses the urethra of acidic urine
b. Serves as a lubricant during sexual intercourse
c. Secreted into the penile urethra
e. External genitalia
i. Scrotum
1. Divided sac of skin outside the abdomen
2. Maintains testes at 3oC (5oF) lower than normal body temperature to protect sperm viability
ii. Penis
1. Delivers sperm into the female reproductive tract
2. Regions of the penis
a. Shaft—with erectile tissue
b. Glans penis (enlarged tip)--sensitivity
c. Prepuce = foreskin
i. Folded cuff of skin around proximal end
ii. Often removed
3. Internal
a. Three areas of spongy tissue
b. Erections occur
4. Spermatogenesis
a. Overview
i. Production of sperm
ii. Begins at puberty and continues throughout life
iii. Occurs in the seminiferous tubules
b. Spermatogonia = stem cells undergo rapid mitosis to produce more stem cells before puberty
i. Follicle-stimulating hormone (FSH) modifies cell division
1. One cell produced is a stem cell, called a type A daughter cell
2. The other cell produced becomes a primary spermatocyte, called a type B daughter cell
ii. Primary spermatocytes undergo meiosis
1. One primary spermatocyte  produces four haploid spermatids
2. Spermatids—23 chromosomes (half as much material as other body cells)
c. Human life cycle
i. Union of a sperm (n or 23 chromosomes) with an egg (23 chromosomes) creates a zygote (2n or 46 chromosomes)
1. N + N =
d. Spermiogenesis
i. Late spermatids develop distinct regions:
ii. Sperm cells result
iii. Entire spermatogenesis process
e. Sperm cell anatomy
i. The only
ii. Three parts
1. Head
a. Contains
b. Acrosome
c. Breaks down and releases
2. Midpiece
3. Tail
f. Testosterone production
i. The most important
ii. Produced in
iii. Luteinizing hormone (LH)
1. This causes
iv. Functions of testosterone
1. Stimulates
2. Underlies
3. Causes
a. Deepening
b. Increased
c. Enlargement
d. Thickening