Describe an embryo at the 3 week stage of development. What is the major process that occurs at this stage?
Name the germ layers and describe what types of tissue/organs they form in the developing embryo.
- The most characteristic event occurring during the third week of gestation is gastrulation, the process that establishes all three germ layers (ectoderm, mesoderm, and endoderm) in the embryo
- 1. Endoderm: Lining of internal organs gastrointestinal (trachea, pancreas, liver), respiratory, and endocrine systems
- 2. Mesoderm: Muscles (including myocytes/heart muscle), gonads, kidneys, connective tissue, and the notochord
- 3. Ectoderm: CNS (brain and spinal cord), skin