Test: Pregnancy and Embryonic Development (November 5) - NEET MCQ

Placenta acts as an endocrine gland during pregnancy and produces several hormones including human chorionic gonadotropin (hCG), estrogen, progesterone, etc. hCG stimulates the corpus luteum to secrete progesterone.

Prolactin is secreted by the anterior lobe of pituitary gland. After parturition, secretion and storage of milk in mammary glands is under the influence of this hormone.

• A. The developmental stage of an animal passed in the mother's womb is called (i)-embryo.


• B. The outer layer of blastula is called (ii)-trophoblast. It does not take part in the formation of (iii)-embryo proper.


• C. (iv)-Endoderm is the first germ layer formed from the inner cell mass by differentiation.

Placenta is an intimate connection between the fetus and uterine wall of the mother to exchange the materials. Food materials and oxygen pass from the mother's blood into the fetal blood and fetal excretory products diffuse into maternal blood through placenta.

During embryonic development, the blastocyst formed consists of an outer envelope of cells called the trophoblast and the inner cell mass. The cells of trophoblast form chorion and amnion and hence part of placenta.

During pregnancy, human chorionic gonadotropin hormone is released by trophoblastic cells which passes out in urine. Thus, if this hormone appears in urine test, it means the woman is pregnant. This hormone maintains the corpus luteum and stimulates it to secrete progesterone which is required for the maintenance of the uterus.

Early human embryo possesses a dorsal hollow nerve cord, a well developed notochord and a series of gill slits, which represent the fundamental chordate characters.

Umbilical cord is a narrow. Tube like structure that connects the fetus to the placenta. Through this tube, nutrients and oxygen are supplied from the mother to the baby and waste products are removed from the baby,.

• (i) - heart: After one month of pregnancy, the embryo's heart is formed.


• (ii) - second: By the end of the second month of pregnancy, the fetus develops limbs and digits.


• (iii) - first trimester: By the end of the first trimester, most major organ systems are formed, such as well-developed limbs and external genital organs.


• (iv) - second trimester: By the end of the second trimester, the body is covered with fine hair, eyelids separate, and eyelashes are formed.