Because the uterus is getting ready to host a foeatus.
Because if the egg is fertilised, it implants into the thick uterus lining. If it wasn't thick, there would be nothing for it to implant into. Also, once the egg is fertilised and is implanted there, it provides protection around the egg
The lining of the uterus breaking apart is the mucus lining that is usually formed so as to create a conducive environment for a fertilized egg to develop. If the ovum is not fertilized, the thick lining breaks apart which is what causes menstruation.
to prepare the uterus to receive any fertilized eggs
After fertilization, the egg implants in the lining of the uterus. It can implant on any side of the uterus where the endometrial lining is thick enough to support pregnancy.
Premenstrually the lining thickens and is later shed if there is no fertilized egg to implant into the lining. A hormonal imbalance, infection or endometriosis can all cause a thickening of the lining, irregularly during your cycle.
To prepare for any fertilized eggs XD
The uterus produces a lining called the endometrium. The endometrium creates an environment for the fertilized egg to implant to and grow. the lining is thick so when the fertilised egg lands on it, it can have like a sort of perfect house to live in
The lining of the uterus is made up of endometrial tissue. This tissue contains glands, blood vessels, and a thick layer of cells that support and nourish a fertilized egg during pregnancy. Each month, the endometrial lining thickens in preparation for a potential pregnancy, and sheds if pregnancy does not occur during menstruation.
The uterus is adapted for its job of nurturing a developing fetus by having thick muscular walls that can expand during pregnancy to accommodate the growing baby. It also has a lining that thickens and sheds monthly to support implantation of a fertilized egg. The cervix acts as a barrier to protect the uterus from infections.
Progestrone causes the uterine lining to thicken in preparation of a fertilized egg. If no egg is fertilized, the thick lining is shed as a menstrual cycle.
So that it can form a protective environment for the egg to develop into a baby.
You have the proliferative phase before the ovulation. After the ovulation you get the secretary phase. Here the glands becomes tortuous. The uterine lining becomes thick. This happens under the influence of both oestrogen and progesterone hormones.