Memory tricks for male and female anatomy

Sperm are produced in the seminiferous tubules of the testes → tubuli recti (straight tubules) → rete testis → efferent ductules → epididymis (maturation and storage, 20 days) → vas deferens (ductus deferens) → ejaculatory duct → urethra → external. The epididymis is where sperm gain motility. Vasectomy cuts the vas deferens. Accessory glands add fluid: seminal vesicles (60% of semen volume, fructose), prostate (alkaline, PSA), bulbourethral glands (pre-ejaculatory fluid).

Ovaries produce eggs (oocytes) and hormones (estrogen, progesterone). Uterine tubes (fallopian tubes) — 4 parts: infundibulum, ampulla (fertilization occurs here), isthmus, intramural. Uterus: fundus (top), body, cervix (bottom). Three layers: perimetrium, myometrium (muscle — contracts during labor), endometrium (shed during menstruation). Vagina: birth canal, receives penis during intercourse. The cervix dilates to 10 cm during labor — fully effaced and dilated = ready to push.

Day 1-5 Menstrual phase: endometrium shed, FSH rises. Day 6-13 Proliferative/Follicular phase: estrogen rises, endometrium rebuilds, follicle matures. Day 14 Ovulation: LH surge triggers egg release. Day 15-28 Luteal/Secretory phase: corpus luteum produces progesterone, endometrium thickens for implantation. If no pregnancy: corpus luteum degenerates, progesterone drops, menstruation begins again. Progesterone maintains pregnancy in early weeks — before placenta takes over.

GnRH (hypothalamus) → FSH and LH (anterior pituitary) → gonadal hormones. FSH stimulates follicle development in females and spermatogenesis in males. LH triggers ovulation in females and testosterone production in males (Leydig cells). Estrogen: female secondary sex characteristics, endometrial growth, LH surge feedback. Progesterone: maintains pregnancy, thickens endometrium, suppresses ovulation. Testosterone: male secondary sex characteristics, spermatogenesis, libido.

Spermatogenesis begins at puberty and continues throughout life. Spermatogonia (diploid stem cells) → Primary spermatocyte (meiosis I begins) → Secondary spermatocyte (after meiosis I, haploid) → Spermatids (after meiosis II) → Spermatozoa (mature sperm after spermiogenesis — when the tail develops). Takes approximately 64-72 days. Sertoli cells provide nutrients and form the blood-testis barrier. Sperm production requires temperature 2-3°C below body temperature — hence external testes.

Oogenesis begins before birth — primary oocytes are formed in the fetal ovary and arrested in meiosis I prophase. At puberty, one follicle matures each cycle. At ovulation, meiosis I completes → secondary oocyte released. Meiosis II only completes if fertilization occurs. Females are born with ~2 million oocytes — only ~400 will ever be ovulated. Oogenesis produces one egg and three polar bodies (non-functional). This is why advanced maternal age increases chromosomal abnormality risk — eggs have been paused in meiosis for decades.

Ovulation (day 14) → sperm must reach ampulla within 24-48 hours (egg viable) → fertilization in ampulla of uterine tube → zygote → cleavage (cell division without growth) → morula (solid ball) → blastocyst (hollow, ~day 5) → travels to uterus → implantation in endometrium (days 6-10 after fertilization). hCG is produced by the trophoblast immediately after implantation — this is what pregnancy tests detect. hCG maintains the corpus luteum to keep producing progesterone.

hCG: first hormone of pregnancy, maintains corpus luteum. Peaks at week 10, then declines as placenta takes over. Morning sickness correlates with hCG levels. Progesterone: prevents uterine contractions, maintains endometrium, suppresses immune rejection of fetus. Estrogen: uterine growth, breast development. Oxytocin: labor contractions, milk letdown — positive feedback loop during labor. Prolactin: milk production. Relaxin: softens ligaments and cervix for delivery.

All tissues and organs derive from three primary germ layers formed during gastrulation. Ectoderm (outer): skin, hair, nails, nervous system, sense organs, lens of eye, enamel of teeth. Mesoderm (middle): muscle, bone, cartilage, blood, kidneys, gonads, connective tissue, cardiovascular system. Endoderm (inner): lining of GI tract, respiratory tract, urinary bladder, liver, pancreas, thyroid. Memory: Ecto = outside (skin and nervous), Meso = middle (muscles and bones), Endo = inside (organ linings).