Key Concepts in Male and Female Reproductive Biology

a dense, fibrous connective tissue layer surrounding the testes. It provides structural support, forms septa that divide the testis into lobules, and helps maintain the shape of the testes.

tunica albuginea

the process of sperm production in the seminiferous tubules. It includes mitosis of spermatogonia, meiosis to form spermatids, and spermiogenesis to mature spermatozoa. The process takes ~64 days.

spermatogenesis

What are the consequences of cryptorchidism if left untreated?

infertility, increased risk of testicular cancer, testicular torsion, and psychological effects. Early surgical correction is recommended.

Receives sperm, starts maturation.

head

Further sperm maturation, gaining motility.

body

Stores mature sperm until ejaculation.

tail

What is the role of the bulbourethral glands in male reproduction

secrete alkaline mucus that lubricates the urethra and neutralizes acidic urine, preparing the urethra for sperm during ejaculation.

Describe the mechanism of vasocongestion and its role in penile erection.

occurs when blood vessels dilate, increasing blood flow to erectile tissues in the penis. This engorges the tissue, causing an erection.

What is the anatomical significance of the hymen?

a thin membrane that partially covers the vaginal opening. It has no specific function and can vary in thickness and shape.

List the components that contribute to semen production and their specific functions.

Seminal vesicles: Fructose and prostaglandins; Prostate: Citrate and enzymes; Bulbourethral glands: Mucus for lubrication; Testes: Sperm.

Fructose and prostaglandins;

Seminal vesicles

Citrate and enzymes;

Prostate

mucus for lubrication

Bulbourethral glands:

semen

testes

ovarian cycle phases

Follicular phase (day 1-14): Follicle grows

; Ovulation (~day 14):Egg released;

Luteal phase (day 15-28): Corpus luteum forms and secretes hormones.

Q: When and how are oogonia formed in female development?

during fetal development (~5-6 weeks gestation) through mitotic divisions of primordial germ cells

. They differentiate into primary oocytes by birth.

Define atresia and explain its significance in ovarian function.

degeneration and resorption of immature ovarian follicles that don't reach maturity. It ensures only one (or a few) follicles mature during each cycle.

Describe the progression of follicular development from primordial to tertiary stages.

Primordial follicle → Primary follicle (oocyte growth + granulosa cells) → Secondary follicle (antrum forms) → Tertiary (Graafian) follicle (large antrum + ready for ovulation).

Explain the formation and function of the corpus luteum.

After ovulation, the follicle collapses and forms___ which secretes progesterone and estrogen to maintain the endometrium for potential implantation.

: Compare the different sections of the uterine tube and their roles.

Infundibulum: Catches oocyte; Ampulla: Fertilization site; Isthmus: Connects to uterus; Interstitial (intramural) part: Passes through uterine wall.

Catches oocyte

infundibulum

Fertilization site;

Ampulla:

Connects to uterus;

isthumus

Passes through uterine wall.

Interstitial (intramural) part:

is shed during menstruation and rebuilt each cycle;

Stratum functionalis

remains and regenerates the functionalis layer.

stratum basale

classify mammary glands and explain their function.

Modified apocrine glands that produce milk (lactation) under hormonal control after childbirth.

How do birth control pills affect hormone production

Contain synthetic estrogen and/or progesterone, inhibiting FSH and LH release, preventing ovulation and follicle development.

describe the embryological origin of female reproductive structures

Develop from the paramesonephric (Müllerian) ducts in the absence of male hormones.

Factors affecting sperm survival

Include vaginal pH (acidic), cervical mucus (thick or thin depending on cycle phase), immune responses, and sperm motility.

Explain the biological mechanism behind identical twin formation.n

Occurs when a single fertilized egg (zygote) splits into two embryos during early cleavage stages, leading to genetically identical offspring.

Immediate cellular responses to fertilization

Include block of polyspermy (fast & slow block), completion of meiosis II by the oocyte, and formation of the male and female pronuclei.

Define cellular potency and its significance in early development.

A cell's ability to differentiate into other cell types; totipotent cells can become any cell type, while pluripotent cells have more limited potential.

hCG function in early pregnancy detection

secreted by the syncytiotrophoblast; it maintains the corpus luteum, which continues producing progesterone.

Explain the role of the yolk sac in early fetal development.

Forms blood cells, gives rise to germ cells, and contributes to the gut and early circulation before the placenta fully forms.

Describe the structure and function of the umbilical vessels

The umbilical cord contains 2 arteries (carry deoxygenated blood from fetus to placenta) and 1 vein (carries oxygenated blood to the fetus).

(carries oxygenated blood to the fetus).

1 vein in umbilical cord

(carry deoxygenated blood from fetus to placenta)

2 arteries in umbilical cord

What is embryonic folding and why is it important

Transforms the flat trilaminar disc into a 3D body shape, forming the gut tube, body cavities, and axial structures.

explain the timing and significance of testosterone in male development.

Produced by fetal Leydig cells by week 7; it drives development of male reproductive organs and secondary sexual characteristics.

Q: How does the hypothalamic-pituitary axis regulate testosterone levels?

GnRH from the hypothalamus stimulates LH release from the pituitary, which acts on Leydig cells in the testes to produce testosterone; negative feedback inhibits GnRH and LH when levels are high.

What causes the onset of labor contractions?

Begins due to increased oxytocin and prostaglandin levels, uterine stretch, and positive feedback from fetal signals, leading to coordinated uterine contractions.

Pregnancy effects on the gastrointestinal system

Increases progesterone, which relaxes smooth muscle, causing slowed digestion, constipation, heartburn, and potential nausea (morning sickness).

Describes the structure and function of the tunica albuginea surrounding the testes.

a dense fibrous connective tissue that surrounds the testes, forming septa that divide it into lobules containing seminiferous tubules.

Functionalis is shed during menstruation; basale regenerates the functionalis layer.

Stratum functionalis vs. stratum basale

Paramesonephric (Müllerian) ducts form uterus, fallopian tubes, and upper vagina.

Embryological origin of female reproductive structures

Completion of meiosis II, and pronuclei formation.

Block of polyspermy

Forms blood cells, germ cells, and contributes to the gut.

Role of the yolk sac in early fetal development

2 arteries (deoxygenated), 1 vein (oxygenated).

Structure and function of the umbilical vessels

Produced from ~7 weeks gestation; develops male organs and traits.

Timing and significance of testosterone in male development

GnRH → LH → Leydig cells → Testosterone; negative feedback controls GnRH/LH.

Hypothalamic-pituitary axis regulation of testosterone levels

Stimulates uterine contractions and milk ejection during labor and breastfeeding.

Role of oxytocin in labor and delivery

First milk, rich in antibodies, proteins, and nutrients for newborn immunity.

Colostrum

Genotype = genetic makeup; phenotype = observable traits.

Genotype vs. phenotype

Having two identical alleles; e.g., AA or aa.

Homozygosity

Age, family history, race (higher in African American men), and diet.

Risk factors for prostate cancer

Stimulates follicle growth and estrogen production.

Role of FSH in follicular development

Ampulla of uterine tube; optimal environment for sperm-egg interaction.

Fertilization location

Example: Bb (brown) x Bb → 75% brown, 25% blue (simplified model).

Punnett square for eye color inheritance

XX = female, XY = male; Y chromosome carries SRY gene for testes formation.

Sex determination in human chromosomes

Two different alleles (e.g., Bb); increases genetic diversity.

Heterozygosity

Corona radiata (granulosa cells) and zona pellucida (glycoprotein shell).

Layers surrounding a mature oocyte

46 total (23 pairs).

Normal number of human chromosomes

Vas deferens is cut and sealed, preventing sperm transport.

Anatomical changes in a vasectomy

2 corpora cavernosa (main erectile bodies) and 1 corpus spongiosum (surrounds urethra).

Three erectile chambers in the penis

Relaxes smooth muscle in penile arteries, increasing blood flow for erection.

Primary function of nitric oxide in erectile function

hCG, progesterone, and estrogen rise; maintain uterine lining, suppress FSH/LH.

Hormonal changes during pregnancy

Fraternal = 2 eggs, 2 sperm; identical = 1 zygote splits into two.

Difference between fraternal and identical twins

Nutrient/waste exchange, hormone production, and barrier protection.

Role of the placenta in fetal development

Dilation (cervix opens), Expulsion (baby delivery), Placental (placenta delivery).

Stages of labor and delivery

Withdrawal bleeding is hormone-induced (from stopping birth control); true menstruation is natural shedding of the endometrium.

Withdrawal bleeding vs. true menstruation