The Endometrium of Uterus
The endometrium of uterus is the innermost of three layers of uterus and consists of epithelial cells.
Cervical Endometrium:
The cervix is spindle shaped and measure about 2.5 cm and bounded by external os below and internal os above. The mucosal lining of cervical endometrium is different from that of the body of the uterus and the sub mucosa is absent in cervix. The cervix is lined by high columnar ciliated epithelium. The nuclei of the epithelium are spindle shaped and near the basement membrane. The direction of cilia is downwards and toward external os. The cervical endometrial glands are racemose type and secrete mucus which is rich in fructose. The secretion is alkaline and its high pH and fructose content make it attractive to ascending spermatozoa (male sperms). The secretions rich in sucrose and high pH collects in the cervical canal as a plug and probably stops the ascending infection. In gonorrhea the gonococcus are present in the crypts of the glands.
The external os is circular in nulliparous (woman who has not born a child) woman, but after vaginal delivery there is transverse slit of the external os, which is characteristic of parous (woman who has given birth) women.
The body of the uterus differs from that of cervix both structurally and functionally. Unlike epithelium of the body of the uterus the cervical epithelium does not show changes during menstrual cycle and also during pregnancy the cervical epithelium rarely changes, unlike the epithelium of the body of the uterus which undergo dramatic change in shape and size. The cancer of the body of the uterus is adenocarcinoma od the endometrium but that of the cervix is squamous cell carcinoma (cancer) type which is highly malignant.
There is an intermediate zone between endometrium of body and the mucous membrane of the cervix, known as the isthumus which is about 6 mm in length. The endometrium of the isthumus is anatomically and functionally similar to the body of the uterus. This isthmic portion forms the lower uterine segment in late pregnancy.
The relationship between the length of cervix and the body of the uterus varies according to age. The ratio of cervix to the body is 2:1 before puberty. At puberty the ratio reverses and become 1:2. During reproductive age the ratio is between, 1:3 to 1:4. After menopause the whole of the organ (uterus) atrophy.