Female Reproductive System: Uterine Tubes, Uterus Structure and Function

Female Reproductive System

Overview

• The female reproductive system includes the uterus, cervix, vagina, oviducts (uterine tubes/fallopian tubes), and ovaries.
• Ligaments anchor these structures within the pelvis.

Uterine Tubes (Oviducts/Fallopian Tubes)

• Connect the ovary to the uterus, serving as a route for sperm to meet the oocyte and for the oocyte to travel to the uterus.
• Three segments:
  • Infundibulum:
    • The end of the uterine tube near the ovary, resembling a funnel.
    • Fimbrae: Finger-like extensions at the end of the infundibulum open to the pelvic cavity.
    • Function: To pick up the oocyte released from the ovary during ovulation.
  • Ampulla:
    • The central, widest, and longest part of the uterine tube (yellow).
    • Function: The site of fertilization, where sperm and oocyte meet.
  • Isthmus:
    • The narrowest part of the uterine tube, connecting to the uterus (green).
    • Function: Site of sperm maturation (capacitation).
      • Capacitation: Sperm become hyperactive and the acrosome readies to rupture.

Uterine Tube Histology

• Lined with simple columnar epithelium.
  • Secretory cells:
    • Produce mucus rich in glycogen (sugars).
    • The sugars provide an energy source for sperm, oocytes, and fertilized oocytes.
  • Ciliated cells:
    • Cilia beat towards the uterus.
    • Function: To roll the oocyte and zygote toward the uterus.
• Smooth muscle in the wall of the uterine tubes contracts (peristalsis) to further aid movement of the oocyte or zygote.

Uterus

• Site of menstruation (shedding of the uterine lining).
• Site of implantation and development of a fetus/embryo/child.
• Regions:
  • Fundus: The superior region where uterine tubes connect.
  • Body: The main part of the uterus with a thick wall.
    • Site of implantation.
  • Isthmus: A constricted portion at the base of the body.
  • Cervix: Inferior narrow region connecting the vagina and the body of the uterus.

Uterus Histology

• Three layers:
  • Perimetrium: The outer layer lined with a serosa (serous membrane).
    • Connective tissue covered in serosa producing slippery fluid to reduce friction.
  • Myometrium: The thickest, middle layer composed of smooth muscle.
    • Three layers of smooth muscle running in different directions.
    • Contracts during childbirth to expel the child; contracts in response to oxytocin hormone.
  • Endometrium: The inner layer composed of connective tissue, blood vessels, and epithelium.

Endometrium

• Lined by simple columnar epithelium that forms endometrial glands.
• Two layers:
  • Stratum functionalis (functional layer):
    • Grows and is shed during the female reproductive cycle (menstruation).
    • Undergoes changes during the proliferative, secretory, and menstrual phases.
  • Stratum basalis (basal layer):
    • Dense connective tissue that remains constant during the reproductive cycle.
    • Contains stem cells that regenerate the stratum functionalis after menstruation.

Cervix

• Connects the body of the uterus and the vagina.
• Contains many mucus-producing glands.
• Cervical mucus changes consistency during the female reproductive cycle.
  • Around ovulation: Mucus becomes watery, allowing sperm to swim through easily.
  • At other times: Mucus is thick and dense, blocking sperm from entering the uterus.

Vagina

• Passageway for childbirth and menstrual flow.
• Muscular canal, approximately 10 cm long.
• Epithelium: Stratified squamous non-keratinized (moist).
• Glands produce glycogen-rich mucus.
  • Glycogen is ingested by normal, healthy bacteria, producing organic acids.
  • Acids create an acidic environment in the vagina, retarding the growth of harmful bacteria and microbes.
  • The acidic environment is damaging to sperm; semen (produced by males) is alkaline to neutralize the vaginal acid.