BIOL 1203 Week 10: Reproductive System and Fetal Development

Main function of the male reproductive tract

To produce and introduce sperm into the female reproductive tract, where fertilization occurs

What do testes produce?

Testosterone and sperm (65-75 days, 300 million sperm cells produced daily)

Why is the scrotum outside of the body cavity?

Because a lower temperature is needed for sperm survival

Pathway of sperm

Epididymis → vas deferens → ejaculatory duct → urethra

Epididymis

Organ located posteriorly to the testes, where sperm matures and is stored for up to 4 weeks

Vas deferens

Transports sperm to the ejaculatory duct. May also store sperm for several months

Ejaculatory duct

Site where contents from the seminal vesicles and vas deferens merge

Urethra

Final duct that carries semen (and urine) out of the penis. Contains three regions: Prostatic, intermediate, spongy

Seminal vesicles

Secretes an alkaline and viscous fluid that neutralizes the acidic female environment. High in fructose, to supply sperm with ATP

Prostate gland

Chestnut-sized gland that produces a milky, acidic substance. Contains citric acid (for ATP), and enzymes and prostaglandins that help sperm mobility and viability

Bulbourethral (Cowper’s) gland

Secretes alkaline (neutralizes acidic urine in urethra and vagina) mucous for lubrication

What does the parasympathetic reflex in the penis cause?

Erection through dilation of arterioles in erectile tissue

What does the sympathetic reflex in the penis cause?

Ejaculation, through propulsion of semen by peristalsis and contraction of urethral and penile muscles

What do the ovaries produce?

Ova (eggs), estrogen, and progesterone

Uterine/fallopian tubes

Site of fertilization and transport of ovum/zygote to uterus

What happens when a fertilized egg implants outside the uterus?

An ectopic (non-viable) pregnancy occurs

Three layers of the uterine wall (innermost to outermost)

Endometrium → myometrium → perimetrium

Endometrium

Mucosal lining of the uterine cavity, sheds during menstruation

Layers of endometrium

Stratum functionalis (sheds at menstruation) and stratum basalis (always stays)

Myometrium

Middle layer of uterine wall, contains layers of smooth muscle

Perimetrium

Outermost serous layer of visceral peritoneum (uterine wall)

Function of Bartholin’s (side of vaginal orfice) and Skene’s (side of urethral orfice) glands

Has a mucous secretion that acts as lubricant

Approximately how long does each female reproductive cycle last?

About 28 days

How many primary follicles in each ovary?

About 200k promary follicles

How often and how many eggs mature and are released in the ovarian cycle?

One mature egg is released approximately every 28 days

What hormones regulate the ovarian cycle?

GnRH, FSH, LH, estrogen, and progesterone

Ovarian cycle (day 1-13) hormonal action

Hypothalamus secretes GnRH, a. pituitary secretes FSH and LH. Then, estrogen produced by a follicle acts on hypothalamus to stop FSH and LH secretion.

Ovarian cycle (day 1-13) follicle action

4-5 primary follicles begin development → all primary follicles except for one degenerate → the remaining follicle becomes a secondary follicle

What occurs at around day 6 of ovulation to the secondary follicle?

A single tertiary follicle grows and the fluid inside increases

Graafian follicle

Mature follicle found in the ovaries

When does ovulation occur (approximately)?

Day 14

Ovarian cycle: day 14 ovulation hormonal events

Estrogen levels peak → positive feedback on hypothalamus → increased LH → LH peaks → ovulation occurs

How is the egg released during ovulation?

The follicle bursts, and the ovum is released into the fallopian tube

What does LH transform the ruptured follicle into?

LH transforms the ruptured follicle into a corpus luteum. It produces progesterone and estrogen

What hormone is measured with pregnancy tests?

hCG (human chorionic gonadotropin) is measured, produced by developing placenta

When does the corpus luteum degenerate and the placenta takes over estrogen and progesterone production?

At around 4 months, when the placenta becomes well-developed

Which hormone maintains the corpus luteum?

hCG, produced by developing placenta