Animal Development II: Gastrulation and Organogenesis PDF

FOR GROUP 2 =========== UNIT 6 ====== Learning Outcomes ----------------- In this unit, the student should be able to: 1. explain the features of gastrulation and organogenesis, 2. describe the different types of animal tissues, 3. discuss the roles and relationships of the four extra embry...

FOR GROUP 2 =========== UNIT 6 ====== Learning Outcomes ----------------- In this unit, the student should be able to: 1. explain the features of gastrulation and organogenesis, 2. describe the different types of animal tissues, 3. discuss the roles and relationships of the four extra embryonic membranes in amniotes, 4. describe the roles of induction and regulation of gene expression in cell specialization and morphogenesis using the notochord, neural tube, and somites, 5. document the chick egg development at 33 hours, 72 hours, and 96 hours, and 6. describe the structure of the chick egg embryo. **Time Frame:** 6 hours Lec; 9 hours Lab/3 weeks Content ------- Gastrulation ------------ 1. Embryonic tissues called germ layers are formed; the germ layers include the endoderm, mesoderm, and ectoderm. Each germ layer will later differentiate into tissues and organ systems. 2. Formation of archenteron (embryonic gut) 3. The appearance of the significant body axes; body axes was already present during cleavage as a result of cytoplasmic determinants or yolk polarity, but this becomes more visible during gastrulation. Tissues in Adult Animals ------------------------  - Smooth muscle is found in the walls of blood vessels, as well as in the walls of the digestive tract, the uterus, the urinary bladder, and various other internal structures. Smooth muscle is involuntary, not under conscious control. That means you don't have to think about moving food through your digestive tract. - Skeletal muscle is what we refer to as muscle in everyday life. Skeletal muscle is attached to bones by tendons, and it allows you to control your movements consciously. - Cardiac muscle is found only in the walls of the heart. It's not under voluntary control, so (thankfully!) you don't need to think about making your heart beat. The Four Extra-Embryonic Tissues in Amniotes -------------------------------------------- - The **amnion**, or inner amniotic membrane, surrounds the embryo itself, enclosing the aqueous environment that the embryo develops in to protect the embryo from mechanical shock and support hydration - The **chorion.** which surrounds the embryo and yolk sac, facilitates exchange of oxygen and carbon dioxide between the embryo and the egg's external environment. - The **allantois** stores nitrogenous wastes produced by the embryo and also facilitates respiration in combination with the chorion**.** - The **yolk sac** encloses the nutrient-rich yolk and transports nutrients from the yolk to the embryo (note the yolk sac is not the yolk itself, but is the membrane that surrounds the yolk) - the **chorion** regulates gas exchange - the **amnion** encloses the fluid-filled cavity to provide an aqueous environment for the developing fetus - together, the **yolk sac**, consisting of blood vessels that transport nutrients to the embryo, and - the **allantois**, which functions in waste disposal, both function as part of the mammalian umbilical cord (not labeled above) Organogenesis -------------  Hox Genes, Differential Gene Expression, and Segment Identity -------------------------------------------------------------