The epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation between the embryo and the mother are:

1.	chorionic villi cells	2.	cytotrophoblast cells
3.	inner cell mass	4.	syncytiotrophoblast cells

The fluid-filled cavities near the embryonic ectoderm and the embryonic endoderm are respectively:
1. amniotic cavity, blastocele
2. amniotic cavity, yolk sac
3. blastocele, amniotic cavity
4. yolk sac, amniotic cavity

The epidermis and the dermis of the skin develops respectively from embryonic:
1. ectoderm, endoderm
2. ectoderm, mesoderm
3. endoderm, mesoderm
4. endoderm, ectoderm

Identify the organ system in humans that is derived from all the three embryonic germ layers:
1. cardiovascular system.
2. digestive system.
3. endocrine system.
4. muscular system.

Parturition involves a positive feedback between:
1. uterine contraction, estrogen
2. estrogen, progesterone
3. estrogen, oxytocin
4. uterine contraction, oxytocin

Lactation after child birth is possible due to decrease in the secretion of:
1. HCG
2. oxytocin
3. FSH and LH
4. estrogen and progesterone

The initial phase of the cortical reaction leads to:
1. slow block to polyspermy
2. fast block to polyspermy
3. formation of pronuclei
4. completion of acrosome reaction

Prolactin is secreted by:
1. hypothalamus
2. anterior pituitary
3. posterior pituitary
4. mammary glands

The first form of milk produced by the mammary glands of mammals immediately following delivery of the newborn is called:

The most common age for the onset of puberty in females is:
1. 8-9 years
2. 9-10 years
3. 11-13 years
4. 14-15 years