KINS 1224 Chapter Notes - Chapter 29: Amniotic Sac, Umbilical Cord, Paratyphoid Fever
27 Apr 2016
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Document Summary
Sixteen das after conception the germ layers are present and the embryonic stage of development begins. Over the 6 weeks a placenta forms on the uterine wall and becomes the embryo"s primary means of nutrition. The germ layers will differentiate into organs and organ systems through a process called organogenesis. The lateral fold from the yolk sac forms the primitive gut which later becomes the digestive tract. One of them adheres to the ectoderm and the other endoderm creating a cavity called the coelom. The coelom divides into the thoracic cavity and peritoneal cavity separated by the diaphragm. The neural tube will become the brain and spinal cord. The mesoderm will be segmented creating tissue called somites which give rise to the vertebral column, trunk muscles, and dermis of the skin. By now it is 8 weeks in and the cells are considered a fetus. The bones have begun to calcify and skeletal muscles exhibit contraction.
