Female Reproductive

Chapter 27: The Reproductive System

Anatomy of the Female Reproductive System

  • Structures Identified:

    • Perimetrium

    • Uterosacral ligament

    • Rectouterine pouch

    • Fornix

    • Cervix

    • Vagina

    • Suspensory ligament of ovary

    • Uterine tube

    • Ovary

    • Fimbriae

    • Uterus

    • Round ligament

    • Vesicouterine pouch

    • Mons pubis

    • Clitoris

    • Hymen

    • Labium minus

    • Labium majus

    • Peritoneum

    • Rectum

    • Anus

    • Pelvic floor

    • Bartholin’s gland

    • Urinary bladder

    • Pubic symphysis

    • Urethra

    • Urethral meatus

    • Clitoral hood (prepuce)

  • Key Functions:

    • Production of gametes (ova)

    • Secretion of sex hormones: estrogens (estradiol, estrone, estriol) and progesterone

    • Gestation (supporting development of fetus)

Ovarian Anatomy

  • Blood Supply: Ovarian blood vessels

  • Ovary Description: Each ovary is surrounded by a fibrous layer called the tunica albuginea, which is covered by germinal cuboidal epithelium (continuation of peritoneum).

    • Regions of the Ovary:

    • Outer Cortex: Houses developing gametes

    • Inner Medulla: Contains large blood vessels and nerves

Ovarian Follicles

  • Definition: Tiny saclike structures in the ovarian cortex containing immature eggs (oocytes).

  • Cell Types:

    • Follicle cells (if a single layer is present)

    • Granulosa cells (if multiple layers are present)

  • Developmental Stages:

    1. Primordial Follicle: Comprises a single layer of follicle cells plus an oocyte.

    2. Primary and Secondary Follicles: Multiple layers of granulosa cells plus an oocyte.

    3. Vesicular Follicle: Fully mature follicle with a fluid-filled antrum that bulges from the ovary surface.

  • Ovulation Process: The ejection of the oocyte from a ripening follicle.

  • Corpus Luteum Formation: Develops from the ruptured follicle after ovulation.

Female Duct System

  • Definition: The female duct system includes structures that do not have direct contact with the ovaries. The ovulated oocyte is cast into the peritoneal cavity; hence, some may never reach the duct system.

  • Components:

    • Fallopian tubes

    • Uterus

    • Vagina

Fallopian Tubes

  • Alternative Names: Also called uterine tubes or oviducts.

  • Functionality: Receives ovulated oocyte; usual site for fertilization.

  • Dimensions: Approximately 10 cm (4 inches) long, extending from the ovary to the uterus.

  • Mechanisms:

    • Ciliated fimbriae create currents to move the oocyte into the tube.

    • Smooth muscle peristalsis and the action of ciliated cells assist in carrying the oocyte toward the uterus.

    • Nourishing functions are performed by nonciliated cells in the tube.

  • Supportive Structures: Externally covered by peritoneum and supported by the broad ligament.

Uterus

  • Description: Hollow, thick-walled, muscular organ.

  • Major Functions: To receive, retain, and nourish a fertilized ovum.

  • Positions:

    • Anteverted or antegrade

    • Retroverted or retrograde

  • Regions:

    • Body: The major portion of the uterus.

    • Fundus: The rounded superior region.

    • Isthmus: The narrowed inferior region.

    • Cervix: The narrow neck, which projects into the vagina.

    • Cervical Canal:

    • External os (opening at the vaginal end)

    • Cervical glands that secrete mucus (blocks sperm except during midcycle).

    • Peritoneal Sacs: Surrounding sacs of the peritoneum around the uterus include the vesicouterine pouch and rectouterine pouch.

Layers of Uterine Wall

  • Perimetrium: The outermost serous layer (visceral peritoneum).

  • Myometrium: The bulky middle layer consisting of interlacing smooth muscle, which contracts rhythmically during childbirth.

  • Endometrium: The mucosal lining consisting of:

    • Simple columnar epithelium on top of a thick lamina propria, serving as the implantation site for embryos.

    • Stratum Functionalis:

    • Changes in response to ovarian hormone cycles.

    • Stratum Basalis:

    • Forms a new stratum functionalis after menstruation, unresponsive to ovarian hormones.

Vagina

  • Description: Thin-walled tube measuring 8–10 cm (3–4 inches) in length.

  • Functions:

    • Serves as a birth canal.

    • Passageway for menstrual flow.

    • Organ of copulation.

  • Anatomy: Extends between the bladder and rectum from the cervix to the exterior.

  • Urethra Relation: Runs parallel to the vagina anteriorly.

  • Layers of Vagina:

    • Outer adventitia (outer layer)

    • Smooth muscle (interior layer)

    • Nonkeratinized stratified squamous mucosa with rugae (folds).

  • Vaginal Secretions: Typically acidic in adult females; alkaline in adolescents, increasing susceptibility to STDs.

  • Distal Vaginal Orifice: Mucosa forms a hymen near the external opening.

  • Vaginal Fornix: The upper end surrounding the cervix.

Vulva

  • Mons Pubis: Fatty area overlying the pubic symphysis.

  • Labia Majora: Hair-covered, fatty skin folds homologous to male scrotum.

  • Labia Minora: Skin folds inside the labia majora.

  • Vestibule: Recess within the labia minora.

  • Fourchette: Ridge where the posterior vestibule and labia minora meet.

  • Bartholin’s Glands: Often referred to as greater vestibular glands, flank the vaginal opening, homologous to bulbo-urethral glands, and release mucus into the vestibule for lubrication.

  • Perineum: Diamond-shaped region bordered by the pubic arch anteriorly and the coccyx posteriorly, with ischial tuberosities on the lateral sides.

Clitoris

  • Homologous Function: Clitoris is homologous to the penis and contains erectile tissue that engorges with blood, resulting in engorgement.

  • Components:

    • Glans Clitoris: The external portion.

    • Clitoral Hood (Prepuce): Continuous with labia minora.

    • Corpora Spongiosum: Proximal ends of erectile tissue; unlike male structures, this does not surround the urethra or contribute to the glans or body.

    • Corpora Cavernosa: Found at the crura, which anchor the clitoris to the pubic arch.

Mammary Glands

  • Presence: Mammary glands are present in both males and females but are normally functional only in females.

  • Main Function: Milk production for nourishment of newborns.

  • Structure: Modified sweat glands comprising 15-25 lobes, with lobules containing glandular alveoli that produce milk, which is passed into lactiferous ducts leading to lactiferous sinuses that open at the nipple.

  • Development: Undeveloped glandular structure in non-nursing women.

  • Areola: Pigmented skin surrounding the nipple.

  • Suspensory Ligaments: Connect the breast to the underlying muscle.

Female Reproductive Physiology

  • Egg Reserve: Females are born with all the eggs they will ever have.

  • Oogenesis: The production of female gametes takes years to complete, beginning in the fetal period.

    • Process:

    • Oogonia (2n ovarian stem cells) multiply through mitosis, storing nutrients.

    • Primary oocytes develop in primordial follicles, surrounded by follicle cells.

    • Primary oocytes begin meiosis but stall in prophase I, resulting in approximately 1 million primary oocytes at birth.

  • Activation: By puberty, around 100,000 oocytes are present. Each month a few primary oocytes are activated, with one maturing into a dominant follicle.

  • Meiosis in Oogenesis:

    • The selected primary oocyte resumes meiosis I, producing a secondary oocyte, which is large and contains most of the cytoplasm and organelles.

    • The second oocyte arrests at metaphase II and is ovulated. If fertilized, it completes meiosis II.

  • Polar Bodies: First polar body is small, containing minimal cytoplasm and eventually degenerates.

Follicular Development

  • Follicle Stages: The movement from primordial to primary to secondary to vesicular follicles.

  • Hormonal Influence: FSH rising levels stimulate growth in multiple vesicular follicles before one becomes dominant. The follicular phase can vary in length.

Ovulation

  • Overview: Triggered by rising LH levels, resulting in ovary wall rupture, releasing the secondary oocyte into the peritoneal cavity.

  • Mittelschmerz: A twinge of pain some women feel during ovulation.

  • Multiple Oocytes: Rarely (1-2%), more than one secondary oocyte is released, leading to fraternal twins. Identical twins originate from a single fertilized oocyte that subsequently separates into cells.

Luteal Phase of the Ovarian Cycle

  • Formation of Corpus Luteum: After ovulation, granulosa and internal thecal cells enlarge to form the corpus luteum that secretes progesterone and some estrogen.

  • Without Pregnancy: The corpus luteum will degenerate after 10-14 days if fertilization does not occur, leading to the onset of menses. If fertilization does occur, hormones from the corpus luteum sustain the pregnancy until the placenta takes over around 3 months.

Regulation of Female Reproductive System

  • Hormonal Regulation:

    • Before puberty, low estrogen levels inhibit the hypothalamic release of gonadotropin-releasing hormone (GnRH).

    • Puberty results in increased GnRH release, promoting FSH and LH release from the anterior pituitary, which stimulates ovarian functions.

  • Mensuration Cycle Stages:

    • Menstrual Phase (Days 1–5): Ovarian hormones are at their lowest.

    • Proliferative Phase (Days 6–14): New stratum functionalis formation; ovulation occurs at the end.

    • Secretory Phase (Days 15–28): Endometrium responds to progesterone, preparing for potential implantation.

Sexual Response

  • Physiology:

    • Parasympathetic Innervation: Leads to lubrication and engorgement of clitoris, vaginal mucosa, and breasts.

    • Sympathetic Response: Results in muscle contractions and orgasm.

    • No Refractory Period: Females do not experience a refractory period after orgasm, allowing for multiple orgasms.

References

  • Campbell, N. A., Reece, J. B. (2005). Biology.

  • Ovulation Calculator. (2017). How cervical mucus helps you get pregnant.

  • Readtiger.com. (2017). Sexual arousal.

  • Ross, C. (2012). Examples of unbroken hymens.

  • Vagina Owner's Manual. (2013). Anatomy: the clitoris.