Why are arteries thick walled while veins are thick walled

Arteries are thick walled because they need much pressure to pump the blood throughout the body and thick walls provide that pressure. The pressure in our arteries is more than in veins as the blood has to reach throughout our body.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.