The Female Reproductive System

Chapter 28: The Female Reproductive System

This chapter covers the anatomy and physiology of the female reproductive system, detailing its structure, functions, hormonal regulation, and related health issues.

28.1 Female Reproductive Anatomy

Expected Learning Outcomes

Describe the structure of the ovary.
Trace the female reproductive tract and describe the gross anatomy and histology of each organ.
Identify the ligaments that support the female reproductive organs.
Describe the blood supply to the female reproductive tract.
Identify the external genitalia of the female.
Describe the structure of the breast.

Sexual Differentiation

The two sexes are indistinguishable during the first 8 to 10 weeks of development.
The female reproductive tract develops from paramesonephric ducts due to the absence of testosterone and Müllerian-inhibiting factor (MIF): - Without testosterone: - Mesonephric ducts degenerate. - Genital tubercle becomes the glans clitoris. - Urogenital folds develop into labia minora. - Labioscrotal folds develop into labia majora. - Without MIF: - Paramesonephric ducts develop into the uterine tubes, uterus, and vagina.

Overview of Female Genitalia

Internal Genitalia: - Ovaries: Produce egg cells (ova) and sex hormones. - Uterine tubes: Also called oviducts or fallopian tubes; - Uterus: Thick muscular chamber. - Vagina: Muscular tube.
External Genitalia: - Clitoris: Erect and sensory organ. - Labia minora: Thin, hairless folds of skin. - Labia majora: Thick folds of skin that enclose the labia minora. - Associated glands and erectile tissues. - These organs occupy the perineum.

Structure of the Ovary

The ovaries are the female gonads producing egg cells and sex hormones.
Shape and Location: Almond-shaped, nestled in the ovarian fossa of the posterior pelvic wall.
Layers: - Tunica albuginea: A capsule similar to that of testes. - Outer Cortex: Contains developing germ cells. - Inner Medulla: Contains major arteries and veins.
Each egg develops in a fluid-filled follicle.
Ovulation: The follicle bursts and releases the egg.

Ligaments of the Ovary

Ovarian ligament: Attaches the ovary to the uterus.
Suspensory ligament: Attaches to pelvic wall, contains the ovarian artery, vein, and nerves.
Mesovarium: Anchors the ovary to the broad ligament.

Blood Supply to the Ovary

Blood Supply: - Ovarian artery and ovarian branch of uterine artery anastomose along the margin of the artery, supplying the ovary.
Ovarian veins, lymphatics, and nerves travel through the suspensory ligaments.

Uterine Tubes (Oviducts)

Canals about 10 cm long, leading from ovaries to the uterus.
Regions: - Infundibulum: Flared distal end with fimbriae. - Ampulla: Middle and longest part. - Isthmus: Narrowed portion near the uterus.
The wall of the tube is muscular, lined with ciliated and secretory cells. Cilia beat toward the uterus to facilitate the movement of the egg.

Uterus

A thick muscular chamber opening into the roof of the vagina.
Usually tilts forward over the urinary bladder.
Functions: - Harbors fetus. - Provides nutrition source. - Expels the fetus at the end of development.
Shape: Pear-shaped with various regions: - Fundus: Broad superior curvature. - Body: Middle portion. - Cervix: Cylindrical inferior end.

Cervical Canal

Passage connecting the lumen of the uterus to the vagina.
Internal os: Superior opening into the body of the uterus.
External os: Inferior opening into the vagina.
Cervical glands: Secrete mucus to prevent the spread of microorganisms from the vagina to the uterus.
Mucus becomes thinner near ovulation, allowing easier sperm passage.

Uterine Wall

Consists of three layers: - Perimetrium: Outermost layer with simple squamous epithelium and loose connective tissue. - Myometrium: Middle layer made mainly of smooth muscle. - Endometrium: Inner mucosa comprised of simple columnar epithelium, tubular glands, and a stroma populated with leukocytes and macrophages. - Functional Layer (Stratum Functionalis): Shed during each menstrual period. - Basal Layer (Stratum Basalis): Remains to regenerate a new functional layer with each cycle.

Uterine Ligaments and Peritoneum

The uterus is supported by the muscular pelvic floor and peritoneum that forms various ligaments: - Broad ligament: Two parts; the mesosalpinx connects to the ovary, mesometrium flanking the uterus. - Cardinal ligaments: Support cervix and superior vagina to the pelvic wall. - Uterosacral ligaments: Attach posterior uterus to sacrum. - Round ligaments: Arise from the anterior surface of the uterus and terminate in labia majora.

Uterine Blood Supply

Uterine artery: Arises from the internal iliac artery, penetrates the myometrium to form arcuate arteries.
Arcuate arteries form spiral arteries that supply the endometrial layer, rhythmically constricting and dilating to fluctuate blood flow.

Vagina

A distensible muscular tube about 8 to 10 cm long.
Functions: - Discharges menstrual fluid. - Receives penis and semen. - Allows for childbirth.
Structure: - Wall contains outer adventitia, middle muscularis, and inner mucosal layers. - Tilted posteriorly between rectum and urethra.
Vaginal rugae: Transverse friction ridges at the lower end, and hymen: mucosal folds covering the vaginal opening.

Vaginal Epithelium and Health Considerations

Vaginal epithelium transitions from simple cuboidal in childhood to stratified squamous at puberty.
Bacteria ferment glycogen to lactic acid, creating an acidic environment that inhibits pathogens.

External Genitalia (Vulva)

Mons Pubis: Fat deposit over the pubic symphysis.
Labia Majora: Thick folds of skin.
Labia Minora: Thin, hairless folds located medially.
Vestibule: The space formed between labia minora containing urethral and vaginal openings.
Clitoris: Erectile organ serving as the center of sexual stimulation with glans, body, and crura.
Glands: Greater vestibular (Bartholin) glands provide lubrication.

Breasts and Mammary Glands

The breast consists of tissue overlying the pectoralis major muscle and enlarges during puberty and pregnancy.
Mammary glands develop within the breast during pregnancy and remain active during lactation, atrophying once nursing ceases.
Breasts are predominantly adipose and connective tissue; they contain ducts that converge to the nipple.

Breast Cancer

Leading cancer among women worldwide, often initiated from mammary ducts.
Symptoms: lumps, skin changes, drainage from the nipple.
Risk factors: Aging, genetics, environment, lifestyle.
Detection: Self-exams, mammograms.
Treatment: Ranges from lumpectomy to mastectomy and may include chemotherapy.

28.2 Puberty and Menopause

Expected Learning Outcomes

Name hormones regulating female reproductive function and their roles.
Describe signs of puberty and hormonal changes during the climacteric.
Define menopause and differentiate it from climacteric.

Puberty

Begins at ages 8 to 10 in well-nourished girls.
Triggered by gonadotropin-releasing hormone (GnRH), which stimulates the anterior pituitary to secrete FSH and LH.
FSH stimulates ovarian follicles to produce: - Estrogen: Includes estradiol, estriol, and estrone; promotes female characteristics. - Other hormones include progesterone and inhibin.

Pubertal Development Timeline

Thelarche: Development of breasts, triggered by estrogen and progesterone.
Pubarche: Appearance of pubic and axillary hair; begins shortly after breast development.
Menarche: First menstrual period; average age is now about 12.5 years.
Initial menstrual cycles often anovulatory. Regular ovulation typically starts one year after menarche.

Climacteric and Menopause

Climacteric marks a midlife change in hormone secretion, often culminating in menopause—the cessation of menstruation.
Women are born with approximately 2 million eggs; climacteric begins with about 1,000 follicles left.
Consequences of climacteric: - Atrophy of the uterus, vagina, and breast. - Heightened risk of vaginal infections.