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Human Reproduction

Multiple Choice Questions

121.

Which one of the following statements with regard to embryonic development in humans is correct?

Cleavage divisions bring about considerable increase in the mass of protoplasm
In the second cleavage division, one of the two blastomeres usually divides a little sooner than the second
With more cleavage divisions, the resultant blastomeres become larger and large
Cleavage division results in a hollow ball of cells called morula

122.
Endometrium is the lining of

bladder

vagina

uterus

oviduct

uterus

The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer; the functional layer thickens and then is shed during mensuration in humans. In most other mammals, the endometrium is reabsorbed in the estrous cycle.

The endometrium changes throughout the menstrual cycle in response to hormones. During the first part of the cycle, the hormone estrogen is made by the ovaries. Estrogen causes the lining to grow and thicken to prepare the uterus for pregnancy. In the middle of the cycle, an egg is released from one of the ovaries (ovulation). Following ovulation, levels of another hormone called progesterone begin to increase. Progesterone prepares the endometrium to receive and nourish a fertilized egg. If pregnancy does not occur, estrogen and progesterone levels decrease. The decrease in progesterone triggers menstruation, or shedding of the lining. Once the lining is completely shed, a new menstrual cycle begins.