There is fetal development week by week. Fetal development week by week is a remarkable phenomenon. Prenatal development is spread over three trimesters. In the first and second months of pregnancy, the fetus is called an embryo. The embryo comprises of three layers, which lead to the development of all body organs. Fetus is a term used during the second trimester. In the third trimester, the term baby is used.
Fertilization takes place. The ovum descends to the uterus. Cell division takes place with the embryonic disc formation. The embryo has three layers: ectoderm, mesoderm, and endoderm. The uterus has a special cell layer that forms the placenta. It is through the placenta that nutritive substances are passed from mother to baby. Cells form amnion which encapsulates the embryo. The nervous system is formed. By the end of the first month, the length of an embryo is one-fourth of an inch. The embryo has a crescent shape.
The size of the embryo increases. There is development of bone and muscles. Face and neck are formed. Features of a human being are developed. The forehead gets prominent. The brain develops at a fast pace. There is elongation of the limp buds. Cartilage and muscles tend to develop. There is formation of the sex organs.
The fetal period begins. There is further differentiation of sex. The sexual organs become prominent. Foundation for teeth is laid down. Vocal cords are developed. There is activity in the digestive system. Cells of the stomach secrete fluid. Liver begins to secrete bile. Kidneys start to function, and the urine begins to seep into the amniotic fluid. There is spontaneous development of arms, legs, fingers, and shoulders.
There is rapid development of the lower part of the body. Straightening of the back takes place. Hands and feet are formed. The skin becomes dark red because of the thin layer of skin. Muscles become mature, and reflexes get more active. There is a lot of movement of arms and legs.
The fetus begins to develop skin. There is development of the sweat and sebaceous glands. Nails, hair, toes and fingers begin to develop. The fetus weighs nearly one pound.
Complete formation of eyes takes place. The eyelids begin to open. Appearance of taste buds on the tongue.
Organism is capable of independent living. The complete brain is covered by cerebral hemispheres. Each fetus is capable of variegated responses. The fetus weighs nearly three pounds.
Month 8 and 9:
Different organs are fully developed. The wrinkled skin is smoothed by the body fat. Reddish pigmentation of the skin disappears. Heart rate increases. Excess waste products are eliminated by the digestive system. On birth, the baby excretes meconium. The uterus experiences violent contractions, leading to the birth of the baby.