Endometrium

Endometrium is the innermost lining layer of the uterus. It has a crucial role in the menstrual cycle and pregnancy. The endometrium changes throughout the menstrual cycle in response to hormones. The endometrium is the tissue that is shed during menstruation.

Structure

The endometrium consists of a single layer of columnar epithelium plus the stroma on which it rests. The stroma is a layer of connective tissue that varies in thickness according to hormonal influences. In the uterus, simple tubular glands reach from the endometrial surface through to the base of the stroma, which also carries a rich blood supply of spiral arteries.

Function

The endometrium plays a vital role in the process of reproduction. It is where the fertilized egg implants and the fetus develops. The endometrium undergoes cyclic regeneration. Humans, apes, and some other species display the menstrual cycle, whereas most other mammals are subject to an Estrous cycle. In both cases, the endometrium initially proliferates under the influence of estrogen. However, once ovulation occurs, in addition to estrogen, the ovary will also start to produce progesterone. This changes the proliferative pattern of the endometrium to a secretory lining. Eventually, the secretory lining provides a hospitable environment for one or more blastocysts.

Clinical significance

The endometrium is the site of implantation of the blastocyst, and it is where the fetus develops during pregnancy. If implantation does not occur, the secretory lining will be shed during the menstrual phase. Endometrial diseases can be classified into four categories: variations of normal function, benign endometrial pathologies, endometrial hyperplasia, and endometrial cancer.

See also

• Endometriosis
• Endometrial cancer
• Endometrial hyperplasia
• Endometrial polyp
• Menstrual cycle
• Uterus

References

Endometrium Resources
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