Question

The layer of uterus, which becomes much eroded due to placental villi is known as
A. Endothelium
B. Endometrium
C. Endoderm
D. Trophoblast

Answer 1

Hint: The female reproductive system consists of both external and internal sex organs that are associated with the process of reproduction through fertilization of the ovum by the sperm or male gamete and birth of the offspring. Ovary, fallopian tubes and the uterus are the internal reproductive or sex organs.

Complete answer:
The uterus is an important internal sex organ of the female reproductive system. It is a vital hormone responsive organ or secondary sex organ. The uterus connects with the fallopian tubes through a structure known as the fundus. Its lower end is known as the cervix and it opens into the vagina.
The uterus is the womb and it is the place where the developing fetus remains and grows during the gestation period. The fetus derives nutrition, oxygen and nourishment through the uterus of the mother.
The uterus is known to comprise three distinct layers which are together known as the uterine walls. The different layers are the endometrium, myometrium and the perimetrium. The endometrium is the innermost layer. It forms the inner epithelial layer. The endometrium functions to maintain the pregnancy by preventing the adhesion between the opposed walls of the myometrium.
During the period of pregnancy or implantation of the fetus, the endometrium increases in numbers as well as size of blood vessels and glands. The fetus now forms the placenta and it fuses with the vascular spaces of the walls of the endometrium. The placenta gives rise to certain types of projections known as the villi of placenta villi. These villi arise from the chorion and move deep inside the endometrium layer of the uterus. This establishes maximum contact area of the fetus with the maternal blood and the fetus gets the nourishment and oxygen from the mother.
Endothelium is a single layer of cells that lines the inner surfaces of blood vessels and lymphatic vessels. It is made up of squamous endothelial cells.
Endoderm is the inner most primary germ layer in an early embryo. Trophoblast are outer layers of cells of the blastocyst and provide nutrients to the embryo.

Therefore, the correct option is option B.

Note: The uterus is the site of the implantation of the fertilized embryo and it grows for the entire period up to childbirth. The fetus develops into a placenta and gives off fine projections like structures. These projections or the placental villi erode or move inside the innermost layer of the uterus or the endometrium.