Avian ectoderm has enamel genes, but are not expressed unless the proper inductive stimulus is present. Growth stops at this point. Basic plan features symmetric system of 6 aortic arches. Compare the following as they relate to oogenesis and spermatogenesis. Sperm must penetrate it in order to reach egg.
Follicles are spheres of cells that house oocytes in ovary.
Tubules are channels of cells that house spermatocytes in testes. Describe the layers in each. HC placenta provides a more intimate maternal-fetal interface. The syntrophoblasts bore through the endometrial all the way into the interior of the maternal blood vessels. Thus, the fetal portion is bathed in maternal blood.