1) Cleavage is the process of cell by which a zygote becomes an and an embryo develops into a ball of cells. is the attachment of the embryo to the uterus wall. Differentiation is the process by which cells become altered to perform specific functions.
2) twins are "identical": twins are non-identical.
3) During useful transfer of materials occurs continuously between maternal and circulations. Harmful substances and can also be transferred from the mother and affect the foetus adversely.
4) During gestation, and oestrogen secreted by the corpus luteum, and later by the placenta, maintain the endometrium, inhibit release of new and stimulate milk-secreting tissues in the glands. The hormone from the anterior pituitary stimulates milk production.
5) A Rhesus positive foetus developing inside a negative mother is regarded as foreign by the mother's system. The mother makes antibodies which destroy the foetal cells.
6) The hormone oxytocin brings about the contractions of the uterus, which lead to the of the baby. Synthetic oxytocin can be used to birth artificially.
7) brings about release of milk from the mother's breasts. , the first milk, is watery and rich in . Normal breast milk contains fewer antibodies but is richer in lactose and .
8) Two in overall growth occur in humans: the first during the two years following birth: the second at . Changes in the body also occur during growth.
9) The anterior pituitary secretes the hormone somatotrophin which promotes . Over or under-production in adolescence leads to giantism or respectively.
10) At puberty male and female organs mature and begin to function. This process is accompanied by changes in the body, which lead to the development of sexual characteristics. These are controlled by hormones.