Reproductive System Overview and Key Concepts

Forms septa dividing testes into lobules; supports and protects seminiferous tubules.

Dense connective tissue capsule

Occurs in seminiferous tubules; lasts 64-72 days; involves mitosis of spermatogonia, meiosis of spermatocytes, and spermiogenesis to spermatozoa.

Spermatogenesis

Testicular atrophy, increased cancer risk, impaired spermatogenesis.

Infertility

Head stores immature sperm; body supports maturation; tail stores mature sperm for ejaculation.

Epididymis

Secretes pre-ejaculate fluid to lubricate urethra and neutralize acidity, protecting sperm.

Bulbourethral gland

Increased blood flow fills erectile tissues; veins compressed, trapping blood; causes penile erection.

Penile erection

Thin membrane partially covering vaginal opening; no essential reproductive function.

Hymen

Sperm, seminal vesicle fluid (fructose, prostaglandins), prostate fluid (enzymes, alkaline pH), bulbourethral fluid (mucus).

Semen composition

Follicular phase, ovulation, luteal phase.

Menstrual cycle phases

Formed in fetal life via mitosis; peak number around 20 weeks gestation.

Oocyte development

Degeneration of non-dominant follicles; ensures single dominant follicle for ovulation.

Atresia

Primordial → primary → secondary → tertiary; follicles grow, granulosa cells proliferate, antrum forms.

Follicular development stages

Formed from ruptured follicle post-ovulation; secretes progesterone to support uterine lining.

Corpus luteum

Infundibulum captures oocyte; ampulla site of fertilization; isthmus connects to uterus; intramural part within uterine wall.

Fallopian tube anatomy

Stratum functionalis is superficial, sheds during menstruation; stratum basale regenerates functionalis layer.

Endometrial layers

Modified sweat glands; produce and secrete milk.

Mammary glands

Suppress ovulation by inhibiting FSH and LH; stabilize hormone levels to prevent follicle development.

Hormonal contraception

Derived from paramesonephric (Müllerian) ducts; form uterus, fallopian tubes, and part of vagina.

Müllerian ducts

Cervical mucus pH, immune responses, and female tract environment.

Fertilization factors

Single fertilized egg splits into two genetically identical embryos.

Identical twins

Sperm and oocyte membranes fuse; oocyte completes meiosis II; zygote forms.

Zygote formation

A cell's ability to differentiate into specific cell types; highest in zygote and stem cells.

Cellular differentiation

Produced by syncytiotrophoblast; maintains corpus luteum; detectable in early pregnancy tests.

Human chorionic gonadotropin (hCG)

Provides early nutrient transfer and hematopoiesis; forms part of gut.

Yolk sac

Carry deoxygenated blood from fetus to placenta.

Arteries

Carries oxygenated blood to fetus.

Vein

Folds along longitudinal and transverse axes; essential for body shaping and internal organ placement.

Embryo folding

Hypothalamus releases GnRH → stimulates anterior pituitary to release LH → stimulates Leydig cells to produce testosterone.

Testosterone production

Increased fetal cortisol, placental CRH, oxytocin, and prostaglandins stimulate uterine contractions.

Uterine contractions

Relaxes smooth muscle; slower motility leads to reflux, constipation, nausea.

Progesterone

Stimulates uterine contractions; promotes cervical dilation; positive feedback loop enhances contractions.

Uterine contractions (positive feedback)

First breast secretion; rich in antibodies, proteins, and nutrients; supports newborn immunity.

Colostrum

Genotype: genetic makeup; phenotype: observable traits from gene expression.

Genotype vs Phenotype

Having identical alleles at a gene locus; e.g., AA or aa for a gene.

Homozygous

Age, family history, African ancestry, high-fat diet, obesity, smoking.

Risk factors for diseases

Stimulates granulosa cell proliferation and estrogen production; supports follicle maturation.

Follicle maturation

In the ampulla of the uterine tube; optimal environment for sperm-oocyte meeting.

Sperm-oocyte meeting

Brown (B) is dominant; blue (b) is recessive; cross Bb x Bb: 25% BB, 50% Bb, 25% bb.

Punnett Square

XX = female; XY = male; Y chromosome carries SRY gene initiating testes development.

Sex chromosomes

Two different alleles at a locus; increases genetic variation.

Heterozygous

Corona radiata (granulosa cells), zona pellucida (glycoprotein layer), oocyte plasma membrane.

Oocyte structure

46 total; 23 pairs.

Chromosome count

Vas deferens is cut and sealed; prevents sperm from reaching ejaculate.

Vasectomy

Two corpora cavernosa (erectile rigidity); one corpus spongiosum (urethra protection, glans expansion).

Erectile tissue

Dilates penile arteries; increases blood flow for erection.

Erection mechanism

hCG, estrogen, and progesterone levels rise; hCG maintains corpus luteum; later, placenta produces hormones.

Hormonal changes during pregnancy

Fraternal: two eggs fertilized by two sperm; genetically unique. Identical: one zygote splits; genetically identical.

Fraternal vs Identical twins

Nutrient and gas exchange, waste removal, hormone production, immune barrier.

Placental functions

Dilation stage (cervix dilates), expulsion stage (delivery of baby), placental stage (delivery of placenta).

Stages of labor

Withdrawal bleeding occurs from stopping hormones (e.g., birth control); true menstruation from natural endometrial shedding due to lack of implantation.

Withdrawal bleeding vs Menstruation