PHYSIO 3200 - Exam 5 (Dr. Ai)

Why are the testes located in the scrotum instead of the abdominal cavity?

Spermatogenesis requires a temperature ~1–2°C below core body temperature; higher temperatures impair sperm production.

Trace the path of sperm from production to ejaculation.

Seminiferous tubules → epididymis (maturation/storage) → vas deferens → ejaculatory duct → urethra → penis.

What part of the epididymis promotes maturation?

the head

What part of the epididymis stores sperm?

the tail

Why does a vasectomy not significantly reduce semen volume?

~90% of semen is glandular fluid (seminal vesicles, prostate, bulbourethral glands), not sperm.

What are the three main functions of secretory gland fluids in semen?

Provide nutrients, enhance sperm motility, and neutralize acidic vaginal pH.

Where are immature sperm found in the seminiferous tubules?

Found near tubule wall

Where are mature sperm found?

Found seminiferous lumen

Why don’t spermatogonia all differentiate into sperm?

A subset remains as stem cells to maintain the germ cell population and sustain lifelong sperm production.

List the stages of sperm development in order.

Spermatogonia → primary spermatocytes → secondary spermatocytes → spermatids → spermatozoa.

What is the function of the blood-testis (Sertoli cell) barrier?

Protects developing sperm from toxins and immune attack by isolating them from the bloodstream.

List four functions of Sertoli cells.

Form barrier, nourish sperm, phagocytose defective sperm, secrete inhibin

What is the role of inhibin?

Negative feedback inhibition of FSH secretion

Where are Leydig cells located?

between seminiferous tubules

What do Leydig cells do?

produce testosterone

Outline the hypothalamic-pituitary-gonadal (HPG) axis in males

Hypothalamus (GnRH) → anterior pituitary (FSH, LH) → testes (spermatogenesis + testosterone)

Why must GnRH be released in pulses?

prevents desensitization

What stimulates GnRH release?

Action potentials in hypothalamic neurons

What are the specific roles of FSH in males?

Acts on Sertoli cells → spermatogenesis + inhibin

What are the specific roles of LH in males?

Acts on Leydig cells → testosterone production

Describe the negative feedback loop in male reproduction

Testosterone inhibits GnRH and LH; inhibin inhibits FSH

What enzyme converts testosterone to dihydrotestosterone (DHT)?

5-α-reductase

Why is DHT clinically important?

It is more potent than testosterone and drives prostate growth (e.g., BPH

What is the function of the acrosome of the head of sperm?

Contains enzymes that allow sperm to penetrate the egg during fertilization

What triggers penile erection at the molecular level?

Nitric oxide release → vasodilation of penile arteries → increased blood flow

How is erection maintained once initiated?

Venous compression prevents blood outflow, sustaining high pressure

Why does cryptorchidism lead to infertility?

Elevated temperature impairs spermatogenesis

What is hypogonadism?

Reduced testosterone production, leading to impaired reproductive and secondary sex functions

How do effects of hypogonadism differ before vs after puberty?

Before: lack of secondary sex characteristics
After: decreased libido, muscle mass, etc.

Why do 5-α-reductase inhibitors treat benign prostatic hyperplasia BPH?

They reduce DHT production, decreasing prostate growth

What are the main functions of the ovaries?

Produce ova (eggs) and secrete estrogen + progesterone

What is the function of the uterus?

Site of fetal development

What is ovulation?

Release of a mature egg from the ovary

What happens to the egg after ovulation?

Travels through fallopian tube; may be fertilized

How many eggs are ovulated in a lifetime?

~400 / 2-4 million

What is meiotic arrest?

Prolonged pause of meiosis in primary oocytes until puberty

When is meiosis I completed?

Just before ovulation

When is meiosis II completed?

Only after fertilization

What does one primary oocyte produce?

One ovum/egg + polar bodies

What is a follicle?

Structure that contains and supports an oocyte

What cells produce estrogen?

Granulosa cells

What is the order of follicle maturation?

Primordial → Primary → Secondary → Mature

What is the antrum?

Fluid-filled cavity in developing follicle

What is atresia?

Apoptosis of follicles

What is the dominant follicle?

The follicle that reaches ovulation

What forms after ovulation?

Corpus luteum

What does corpus luteum secrete?

Progesterone, estrogen, inhibin

What are the 3 phases. of menstruation?

Follicular, ovulation, luteal

What do FSH and LH do?

Stimulate ovaries → gametes + hormones

What hormone rises to start the Early Follicular Phase cycle?

FSH

What do granulosa cells produce in the early follicular phase?

Estrogen + inhibin

What type of feedback does estrogen exert early (early phase)?

Negative feedback

What does inhibin do?

Suppresses FSH

What happens to estrogen levels in the Late Follicular Phase?

Increase dramatically

What type of feedback occurs during the Late Follicular Phase?

Positive feedback

What causes the LH surge?

High estrogen

What does the LH surge trigger?

Ovulation

What structure dominates the Luteal Phase?

Corpus luteum

What hormone is dominant in the Luteal Phase?

Progesterone

What happens if no pregnancy occurs?

Corpus luteum degenerates

What happens to hormone levels at the end of cycle?

Estrogen & progesterone drop

What happens when hormones drop?

FSH rises → new cycle begins

How does hormonal birth control work?

Mimics luteal phase → prevents LH surge

What are the two main layers of the uterus?

Myometrium (muscle) and endometrium (inner lining)

Which layer changes during the menstrual cycle?

Endometrium

What are the 3 uterine phases?

Menstrual, proliferative, secretory

What happens during the menstrual phase?

Endometrium sheds

What occurs during the proliferative phase?

endometrium starts to regrow

Which uterine phases correspond to the follicular phase?

Menstrual + proliferative

What hormone drives the proliferative phase?

Estrogen

Which uterine phase corresponds to the luteal phase?

Secretory phase

What hormone dominates this the secretory/luteal?

Progesterone

What does progesterone do to the endometrium?

Prepares it for implantation

What causes menstrual cramps?

Prostaglandins

What is PMS?

Mild physical + mood symptoms before menstruati

What is PMDD?

Severe form of PMS

What is endometriosis?

Endometrium forms outside of the uterus

Common symptoms of Endometriosis?

Pelvic pain, painful sex, infertility

Why does endometriosis cause pain?

Tissue still bleeds → inflammation

What triggers puberty?

Increased GnRH

What is menarche?

First menstrual period

What is primary amenorrhea?

No menstruation by puberty

What is secondary amenorrhea?

Loss of normal cycles

What causes menopause?

Loss of follicles/eggs

What happens to FSH and LH in menopause?

Increase

Why does FSH and LH increase during menopause?

Loss of negative feedback from estrogen

What is perimenopause?

Transition period before menopause

When is menopause officially defined?

12 months without menstruation

How long does an egg survive?

1–2 days

How long do sperm survive in female reproductive tract?

4–6 days

When is fertilization most likely?

~5 days before to 1 day after ovulation

Of the several hundred million sperm ejaculated, how many make it to the fallopian tubes?

100-200

What is capacitation?

Activation of sperm in female tract

Why is capacitation necessary?

Enables sperm to fertilize egg

What surrounds the egg after ovulation?

Zona pellucida + corona radiata

Can multiple sperm bind the egg?

Yes, BUT only one fertilizes it

What happens in the acrosome reaction?

Enzymes released to breakdown zona pellucida (preventing more than one sperm fertilization)

What is the purpose of the cortical reaction?

Prevent polyspermy by hardening the zona pellucida

What is a zygote?

Fertilized egg before implantation

What is cleavage?

Cell division without growth