Chapter 26: The Female Reproductive System – Anatomy & Physiology Study Notes

Introduction

Overview of the Female Reproductive System

The female reproductive system is more complex than the male system due to its multiple functions in reproduction and nurturing offspring. It is characterized by cyclic hormonal changes and serves several essential roles in human development.

• Produces and delivers gametes (egg cells)

• Provides nutrition and safe harbor for fetal development

• Gives birth

• Nourishes infant after birth

• Hormone secretion is cyclic and more complex than in males

Reproductive Anatomy

Expected Learning Outcomes

• Describe the structure of the ovary

• Trace the female reproductive tract and describe the gross anatomy of each organ

• Identify the external genitalia of the female

The Genitalia

Classification and Location

• Internal genitalia: Ovaries, uterine tubes, uterus, and vagina

• External genitalia: Clitoris, labia minora, and labia majora

• All genitalia occupy the perineum

• Primary sex organs: Ovaries

• Secondary sex organs: Other internal and external genitalia

The Ovaries

Structure and Function

• Ovaries are female gonads that produce egg cells (ova) and sex hormones

• Almond-shaped, located in the ovarian fossa (depression in the posterior pelvic wall)

• Covered by a tunica albuginea capsule (similar to testes)

• Outer cortex: Site of germ cell development

• Inner medulla: Contains major arteries and veins

• Lacks ducts: Each egg develops in its own fluid-filled follicle

• Ovulation: Bursting of the follicle and release of the egg

Structure of the Ovary (Diagram Description)

• Primordial, primary, secondary, and mature follicles are present in the cortex

• Ovulated oocyte is released from the mature follicle

• Suspensory ligament and blood vessels supply the ovary

The Uterine Tubes

Anatomy and Histology

• Uterine tube (oviduct or fallopian tube): Muscular canal about 10 cm long from ovary to uterus

• Lined with ciliated cells that help move the egg toward the uterus

• Highly folded into longitudinal ridges for increased surface area

Epithelial Lining

• Ciliated cells (microscopic view) facilitate movement of the ovum

The Uterus

Gross Anatomy

• Uterus: Thick muscular chamber opening into the roof of the vagina

• Usually tilts forward over the urinary bladder

• Functions: Harbors fetus, provides nutrition, expels fetus at end of development

• Pear-shaped organ with three regions:

  • Fundus: Broad superior curvature

  • Body (corpus): Middle portion

  • Cervix: Cylindrical inferior end

Histological Layers

• Perimetrium: External serosa layer

• Myometrium: Middle muscular layer, mainly smooth muscle

  • Produces labor contractions and expels fetus

  • Less muscular and more fibrous near cervix

• Endometrium: Inner mucosa

  • Simple columnar epithelium, compound tubular glands, stroma with immune cells

  • Stratum functionalis: Superficial half, shed each menstrual period

  • Stratum basalis: Deep layer, regenerates new stratum functionalis

  • Site of embryo attachment and maternal part of placenta during pregnancy

The Vagina

Structure and Function

• Vagina (birth canal): 8 to 10 cm distensible muscular tube

• Allows for discharge of menstrual fluid, receipt of penis and semen, and birth of baby

• No glands; transudation lubricates vagina (serous fluid and cervical mucus)

• Transverse friction ridges (vaginal rugae) at lower end

• Mucosal folds form hymen across vaginal opening

Vaginal Epithelium

• Childhood: simple cuboidal epithelium

• Puberty: Estrogens induce transformation to stratified squamous epithelium

• Bacteria ferment glycogen-rich cells, producing acidic pH (protective)

• Metaplasia: Transformation of one tissue type to another

• Dendritic cells: Antigen-presenting cells, route for HIV invasion

Puberty and Menopause

Hormonal Regulation and Life Stages

• Key hormones: GnRH, FSH, LH, estrogen, progesterone, inhibin

• Puberty begins at age 8–10, triggered by rising GnRH

• FSH stimulates ovarian follicles to secrete estrogen, progesterone, inhibin, and androgens

• Estrogens (estradiol, estriol, estrone) have widespread feminizing effects

Principal Signs of Puberty

• Thelarche: Onset of breast development (estrogen, progesterone, prolactin)

• Pubarche: Appearance of pubic/axillary hair, sebaceous and axillary glands (androgens)

• Menarche: First menstrual period (requires minimum body fat, regulated by leptin)

• First cycles are often anovulatory; regular ovulation begins about a year later

Hormonal Effects

• Estradiol: Stimulates vaginal metaplasia, growth of ovaries/sex organs, growth hormone secretion, fat deposition, and skin thickening

• Progesterone: Prepares uterus for possible pregnancy in second half of cycle

• Negative feedback: Estrogens and progesterone suppress FSH/LH; inhibin selectively suppresses FSH

• Hormone secretion is cyclic and sequential

Climacteric and Menopause

• Climacteric: Midlife change in hormone secretion, accompanied by menopause (cessation of menstruation)

• Follicles become less responsive to gonadotropins; estrogen/progesterone secretion declines

• Atrophy of uterus, vagina, and breasts; increased risk of vaginal infections and discomfort

• Cholesterol rises (cardiovascular risk), bone mass declines (osteoporosis risk), blood vessel instability (hot flashes)

• Hormone replacement therapy (HRT): Low doses of estrogen/progesterone may relieve symptoms; risks/benefits debated

Oogenesis and the Sexual Cycle

Overview

• Reproductive cycle: Sequence from fertilization to birth

• Sexual cycle: Monthly events when pregnancy does not occur; includes ovarian cycle (in ovaries) and menstrual cycle (in uterus)

Oogenesis

• Oogenesis: Production of haploid egg cells by meiosis

• Normally releases one egg per month; accompanied by cyclic hormone changes

• Histological changes in ovaries and uterus result in menstrual flow

Embryonic Development of Ovary

• Germ cells arise from yolk sac, colonize gonadal ridges (weeks 5–6)

• Differentiation into oogonia (mitosis to 5–6 million)

• Transform into primary oocytes (meiosis I); most degenerate (atresia) before birth

• By puberty, ~400,000 oocytes remain (lifetime supply: ~480 ovulations)

Egg Development in Adolescence

• FSH stimulates monthly cohorts of oocytes to complete meiosis I

• Each oocyte divides into two haploid cells: large secondary oocyte and small first polar body

• Secondary oocyte arrests at metaphase II until ovulation

• If fertilized, completes meiosis II and casts off second polar body

• Egg chromosomes unite with sperm chromosomes

Folliculogenesis

Development of Ovarian Follicles

• Folliculogenesis: Development of follicles around the egg during oogenesis

• Primordial follicles: Primary oocyte in early meiosis, single layer of squamous follicular cells, concentrated in cortex (90–95% of adult ovary)

• Primary follicles: Larger oocytes, single layer of follicular cells

• Secondary follicles: Larger oocytes, stratified granulosa cells, zona pellucida (glycoprotein layer), theca folliculi (fibrous husk)

• Tertiary follicles: Granulosa cells secrete fluid, forming antrum; cumulus oophorus covers oocyte

• Mature (graafian) follicles: One follicle per cohort matures and ovulates; others degenerate

Oogenesis and Follicle Development (Table)

Stage	Oogenesis	Folliculogenesis
Before Birth	Oogonium undergoes mitosis, becomes primary oocyte (meiosis I begins)	Primordial follicle forms around primary oocyte
Childhood to Puberty	Primary oocyte arrested in prophase I	Primary follicle develops
Puberty to Menopause	Primary oocyte completes meiosis I (secondary oocyte + first polar body); secondary oocyte arrested in metaphase II	Secondary follicle → vesicular (tertiary) follicle → ovulation → corpus luteum
Fertilization	Secondary oocyte completes meiosis II (second polar body + ovum)	Corpus luteum supports early pregnancy