In the Beginning was Information

few days later another wonderful event takes place: Within the tinybreast of the 1.7 mm long embryo two blood vessels join to formthe heart, which begins to pump blood through the miniscule bodybefore the end of the third week. The tiny new heart provides thedeveloping brain with blood and oxygen. In the fourth month theheart of the fetus 1 already pumps 30 litres of blood per day, and atbirth this volume will be 350 litres.In the embryonic stage lungs, eyes and ears develop, although theyare not used yet. After two months the embryo is only three to fourcentimetres long. It is so small that it could literally fit inside awalnutshell, but even at this stage all organs are already present.During the following months the organs increase in size andassume their eventual shape.Various stages of human embryonic and fetal development areshown in Figure 4 [B3]:Part A: A four weeks old embryo which is 4.2 mm long: 1 boundarybetween back and abdomen, 2 incipient shoulder groove, 3 liverbulge, 4 heart bulge, 5 eye, 6 thin and thick part of the navelfunnel, 7 Anulis umbilicalis, 8, Anulis umbilicalis impar, 9 coccyx.Part B: The embryo at four weeks when it is 4.2 mm longPart C: The nervous system of a two months old embryo which is17.7 mm long: 1 Telencephalon (= the front part of the first brainbubble), 2 optical nerve, 3 Cerebellum, 4 Medulla oblongata,5 Lobus olfactorius (sense of smell), 6 Nervus ulnaris (elbow),7 Nervus obturatorius (hip region), 8 Nervus plantaris lateralis(outer foot-sole) and Nervus suralis (calf).Part D: Fetus of 75 mm, shown inside the uterus: 1 Placenta,2 Myometrium (= muscular wall of the womb), 3 amniotic membrane.The amniotic fluid has been removed.1 Fetus: After 12 weeks no new organs are formed. When organo-genesis(= embryo-genesis = the growth and differentiation of cells at the sites of neworgans during the first 12 weeks) is concluded, the embryo is referred to as afetus, and its further growth is known as fetal development.17