Chapter 42-Development - Chapter 42 Animal Development...

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Unformatted text preview: Chapter 42: Animal Development Steps to Embryonic Development 1 st Step: • Fertilization occurs within the uterine tube (fallopian tube; oviduct). • The zygote or fertilized egg is swept down the tube by beating cilia ( fimbriae ) and released into the uterus. 2 nd Step • The formation of an embryo begins with cleavage • The solid ball of cells is the morula . 3 rd Step • The morula multiplies until the ball of cells becomes hollow . • It is now called a blastocyst ( blastula ), which develops into the embryonic disk. 4 th step • The embryonic disk is the flat, two-layered group of cells that separates the amniotic cavity where the embryo will grow from the yolk sac (not present in most mammals). 5 th step • The embryonic disc develops into the gastrula . • The gastrula looks like a blastula that someone poked their thumb into. • This occurs at the second week of pregnancy. Gastrula Three Embryonic Layers of Gastrulation • Endoderm- “inner skin” - Lining of digestive and respiratory tracts, liver, pancreas. • Ectoderm- “outer skin” - Epidermis of skin , hair, lining of mouth and nose, glands of skin, nervous system. Three Embryonic Layers of Gastrulation • Mesoderm- “middle skin” - Dermis of skin, muscle , skeleton, circulatory system, gonads, kidneys, outer layers of digestive and respiratory tracts. Three Embryonic Layers of Gastrulation If an animal is missing its skin epidermis upon birth, which of the following might cause it?...
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This note was uploaded on 05/27/2011 for the course BIO 112 taught by Professor Kirkpatrick during the Spring '11 term at Moraine Valley Community College.

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Chapter 42-Development - Chapter 42 Animal Development...

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