Female Reproductive System: Uterine Tubes and Uterus

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.
• Function:
  • Pathway for sperm to swim to meet the oocyte.
  • Collects the oocyte from the ovary and transports it towards the uterus.

Segments of the Uterine Tube

• Infundibulum:
  • The end of the uterine tube close to the ovary.
  • Funnel-shaped with finger-like extensions called fimbriae.
  • Fimbriae are open-ended to pick up the oocyte released from the ovary during ovulation.
• Ampulla:
  • The central region, widest and longest part of the uterine tube.
  • The typical site of fertilization where sperm and oocyte meet.
• Isthmus:
  • The narrowest part of the uterine tube, connects to the uterus.
  • Site of sperm maturation (capacitation).
    • Sperm become hyperactive (tails beat faster).
    • Acrosome readies to rupture.

Histology of the Uterine Tube

• Lined with simple columnar epithelium.
  • Secretory cells:
    • Produce mucus rich in glycogen (sugars).
    • The mucus is the energy source for sperm, oocyte, and/or fertilized oocyte (zygote).
  • Ciliated cells:
    • Cilia beat towards the uterus.
    • Help to roll the oocyte/zygote towards the uterus for implantation.
• Smooth muscle in the wall of the uterine tubes:
  • Contractions (peristalsis) help move the oocyte/zygote towards the uterus.

Uterus

• Site of menstruation (shedding of the endometrium).
• Site of implantation and development of the fetus/embryo.

Regions of the Uterus

• Fundus: The superior region where the uterine tubes connect.
• Body: The main part with a thick wall, site of implantation.
• Isthmus: Constricted portion of the body at the base.
• Cervix: Inferior narrow region connecting the vagina and the body of the uterus.

Histology of the Uterus

• Perimetrium: Outer layer, thin, with connective tissue covered by serosa (serous membrane making slippery fluid).
• Myometrium: Middle and thickest layer, composed of smooth muscle. Contracts during childbirth to expel the child; the contraction of this muscle layer occurs in response to the hormone oxytocin.
• Endometrium: Inner layer, connective tissue that is very vascular, lined with epithelium. The structure will be discussed further.

Myometrium Details

• Three layers of smooth muscle running in different directions.
• Contraction of these layers generates force to expel a child during childbirth.
• Muscle contracts in response to oxytocin.

Endometrium Details

• Lined by simple columnar epithelium.
• Epithelium forms endometrial glands.
• Underneath the epithelium, loose connective tissue with many blood vessels.
• Blood vessels at the base have a spiral shape.
• Two layers:
  • Stratum functionalis (functional layer):
    • Grows during the female reproductive cycle and is shed during menstruation.
  • Stratum basalis (basal layer):
    • Dense connective tissue, permanent and does not die during menstruation.
    • Stem cells in this layer divide to regenerate the stratum functionalis.

Cervix

• Connects the body of the uterus and the vagina.
• Histologically similar to the uterus (endometrial glands, blood vessels, connective tissue).
• Specialized mucus-producing glands.
  • The cervical mucus changes consistency during the female reproductive cycle.
    • Around ovulation: mucus is watery, allowing sperm to swim through easily.
    • At other times: mucus is thick and viscous, blocking sperm from entering the uterus.

Vagina

• Passageway for childbirth and menstrual flow.
• Muscular canal, about 10 cm long.
• Epithelium: stratified squamous non-keratinized (moist).
• Glands produce mucus rich in glycogen.
  • Glycogen is consumed by healthy bacteria in the vagina, producing organic acids.
  • Organic acids create an acidic environment that prevents the growth of harmful bacteria.
  • The acidic environment is damaging to sperm, so semen is alkaline to neutralize some of the acid.