The uterus is divided into three main parts:

1. Fundus

• • The upper rounded portion above the openings of the uterine tubes.
  • It is the site where the uterine tubes enter the uterus.

2. Body

• • The central portion between the fundus and cervix.
  • It contains the uterine cavity, which is triangular in shape.
  • The body forms the bulk of the uterus and is the site of implantation during pregnancy.

3. Cervix

• • The lower narrow portion that projects into the vagina.
  • It connects the uterine cavity to the vaginal canal via the cervical canal.
  • The cervix is discussed in detail in Section 2.8.

Microscopic Structure

The uterine wall consists of three layers:

1. Endometrium (Inner lining)

• Composed of columnar epithelium and glandular tissue.
• Undergoes cyclical changes during the menstrual cycle:
  • Proliferative phase: Thickens under the influence of estrogen.
  • Secretory phase: Becomes glandular under progesterone.
  • Menstrual phase: Sheds if fertilization does not occur.
• Provides the site for implantation of the fertilized ovum.

2. Myometrium (Middle muscular layer)

• Thick layer of smooth muscle fibers arranged in longitudinal, circular, and oblique directions.
• Responsible for uterine contractions during menstruation and labor.
• The muscle fibers increase in size and number during pregnancy.

3. Perimetrium (Outer serous layer)

• A thin layer of peritoneum covering the fundus and body.
• It is continuous with the broad ligament.
• It provides a smooth surface and reduces friction with surrounding organs.

Blood Supply

Diagram Showing Blood Supply To The  Uterus