UTERUS

Location: pear-shaped, hollow organ located in the pelvis between the bladder and rectum.

Function: the site of embryonic and fetal development. Its lumen continues with the oviducts and the vagina.

Anatomic features

• The body is the large upper portion of the uterus.
• The cervix is the lower, barrel-shaped part separated from the body by isthmus. The cervical canal has a constricted opening or os at each end. The internal os communicates with the cavity of the uterus; the external os, with the vagina.
• The straight arteries and proximal part of the spiral arteries do not change during menstrual cycle. The distal portion of the spiral arteries undergoes degeneration and regeneration with each menstrual cycle.

ENDOMETRIUM

Function: cyclic changes each month that prepare it for the implantation of the embryo: proliferative, secretory, and menstrual phases. The end of each cycle is characterized by the partial destruction and bleeding is referred to as the menstruation or menstrual flow.

• Stratum functionale or function layer, the thick part, which is sloughed off at menstruation.
• Stratum basale (basal layer) is retained during menstruation and serves as the source for the regeneration of the stratum functionale.

Composition:

• simple columnar epithelium on the basal lamina.
• Ciliated cells

• Nonciliated cells

• lamina propria, the layer of loose connective tissue with abundant intercellular ground substance

• uterine glands, simple tubular glands.

SUBMUCOSA

Composition: loose connective tissue.

MYOMETRIUM

Function: enormous enlargement during pregnancy.

Composition: smooth muscle tissue

• The inner layer predominantly oriented parallel to the long axis of the uterus.
• The middle layer, the thickest circular or spiral layer contains numerous large blood vessels (venous plexuses) and lymphatics.
• The outer layer predominantly oriented parallel to the long axis of the uterus.

PERIMETRIUM

Composition: the thin layer of connective tissue covered by mesothelium.

CERVIX

Composition:

• An abrupt change from simple columnar epithelium to stratified squamous epithelium occurs at external os.
• The endometrial glands branch extensively and secrete a mucous substance which amount and character vary at different times of menstrual cycle.
• The extensive network of fibrous connective tissue is situated in the myometrium.