Endometrium

The endometrium is the layer of mucosal tissue that lines the uterus, it is where the egg is implanted when fertilization has occured. This lining changes during the menstrual cycle in response to changes in hormone levels^[1].

Structure and function

The endometrium consists of three different layers: stratum compactum, stratum spongialis and stratum basalis.

The stratum basalis is a stable layer that doesn't change much, it is close to the myometrium. The stratum compactum and the stratum spongialis are however subject to greater change during the cycle. Together, the stratum compactum and stratum spongialis form the stratum functionalis. The stratum functionalis is the layer that will host the fertilized egg^[2].

Cycle

The menstrual cycle consists of a proliferative phase, a secretative phase and menstruation.

During the proliferative phase, rising levels of FSH and oestrogen cause the stratum functionalis to become highly vascularized and to thicken. Levels of LH cause the start of ovulation and the endometrium glands responds by secreting glycogen. This phase is calle the secretative phase, it allows for a the uterus to provide an optimal enviroment for the fertilized egg^[3].

If fertilization of the egg isnt successful, drops in levels of progesterone and LH cause the uterine wall to be shed. The stratum functionalis degenerates resulting in rupture of arteries and veins. This is the menstrual phase.

The end of menstruation is marked by fluctuating levels of hormones and the cycle is repeated until a woman reaches menopause^[4].

References:

1. ↑ Cornforth, Tracee. “The Role the Endometrium Plays in Your Reproductive Health.” Verywell, 3 Dec. 2017, www.verywell.com/what-is-the-endometrium-2721857.
2. ↑ Paxton, Steve, et al. “The Leeds Histology Guide.” Histology Guide, 1 Jan. 1970, www.histology.leeds.ac.uk/female/uterus.php.
3. ↑ Paxton, Steve, et al. “The Leeds Histology Guide.” Histology Guide, 1 Jan. 1970, www.histology.leeds.ac.uk/female/uterus.php.
4. ↑ Boundless. “Physiology of the Female Reproductive System.” Physiology of the Female Reproductive System | Boundless Anatomy and Physiology, courses.lumenlearning.com/boundless-ap/chapter/physiology-of-the-female-reproductive-system/.