PRENATAL DEVELOPMENT
...yer of cell formation is called the amnion also known as the water-sac, the water-sac surrounds the embryo fully except at the ambilical cord. After this process takes place, the heart tube forms and begins to pulsate and force blood to corculate through the blood vessels in the embryonic disk. Then the nervous system begins to arise. Finally the development of intestinal tract, lungs, liver and kidneys begins. By the end of the first month the embro is about one-fourth inches long, curled into a cresent, with small nibbings on sides of body indicating incipient arms and legs. By the second month the embryo increases in size about 11/2 inches, the bones and muscles begin to round out the contours of the body. The face and neck develop and begin to give a human appearance. The forehead is very prominent, reflecting precocious development of the brain in comparison to the rest of the body. By the end of the second month the sex organs begin to form. The third month is known as the fetal period. The sexual differentiation of the embryo continues, buds for all 20 temporary teeth begin to lay down. Vocal cords appear; and digestive systems begin to show activity. the stomach cells begin to secrete fluid; liver begins to pour bile into the intestine. Kidney's begin functioning with urine gradually seeping into amniotic fluid. Other waste products passes through the placenta into the mother's blood. Bones and muscles continue development, and by the end of the third month spontaneous movement of arms, legs, shoulders and fingers are possible. Second Trimester Then begins the start of the socond trimester, also known as the start of the first month, at this time lower body parts start to show at a relatively accelerated rate, and the head size also decreases form one-half to one-fourth of the body size. The back straightens, and the hands and are well-formed. At the end of this process the 'embryo' is now known a 'fetus'. The skin of the fetus now appears dark red, because of the flowing blood showing through the thin skin of the fetus. Reflexes also become more active as muscles start to mature. In this stage the fetus makes alot of rapid movements. In the fifth month skin structures begin to reach their final formation. ...