Difference between gestational sac and endometrium

After becoming pregnant, women may find the word "gestational sac" during B-ultrasound examination. At this time, many women will confuse the gestational sac with the endometrium, thinking that the two are the same thing. In fact, they are not. There is a certain difference between the gestational sac and the endometrium. They are completely different. What is the difference between the gestational sac and the endometrium? Let’s do a detailed analysis below so that pregnant mothers can understand some knowledge.

The gestational sac is the primitive placental tissue, a small embryo wrapped by the amniotic membrane and vascular network. The gestational sac is the initial form of pregnancy. At that time, the fetus has not yet formed, and the fetal heartbeat is already there when the embryonic bud appears.

The gestational sac is also a product of ectopic pregnancy. The fertilized egg fails to enter the uterus at 7 days due to certain factors such as inflammation and adhesion. Ectopic pregnancy usually causes heavy bleeding, and generally the fetus cannot survive. The mother of the little baby was experiencing an intrauterine pregnancy, but due to poor development of the uterus, the gestational sac broke through the weak top of the uterus and entered the abdominal cavity. The villi around the gestational sac sought nutrients everywhere in the abdominal cavity and then supplied them to the fetus through the placenta. Usually, such a fetus will die within two months because it has no protection from the uterine environment and lives in an extremely harsh environment with poor nutrition.

The endometrium (uterine endometrium) refers to the layer that makes up the inner wall of the mammalian uterus. It responds to both estrogen and progesterone and can therefore change significantly with the sexual cycle (estrus cycle, menstrual cycle).

The endometrium is divided into three layers: the compact layer, the spongy layer, and the basal layer. The dense layer and spongy layer of the 2/3 endometrial surface are collectively called the functional layer, which are shed periodically under the influence of ovarian sex hormones. The basal layer is the 1/3 of the endometrium close to the myometrium. It is not affected by ovarian hormones and does not undergo cyclical changes.

Estrogen can cause uterine hypertrophy, and progesterone can promote special changes in the endometrium in early pregnancy, or change the properties of the endometrium so that it has the ability to produce decidua. The endometrium is covered with mucosa, which is composed of the mucosal epithelium and the underlying lamina propria. The mucosal epithelium is columnar epithelium, cuboidal epithelium or stratified columnar epithelium. When estrogen is secreted, each epithelial cell will grow and divide, increasing in number. The portion of the lamina propria below the mucosal epithelium is called the functional layer, into which epithelial cells enter to form uterine glands and respond to estrogen. The lower layer of the functional layer is called the basal layer, which is rich in blood vessels.