Third set of review questions for the third exam You should be able to describe and draw diagrams of the following: Endoderm and the organs that develop from it (including 2 of the 4 extraembryonic membranes) Including the stomodeum, teeth, palatal shelves, palate, nasal cavity, proctodeum, cloaca, bladder rectum, allantois, yolk sac, amnion, chorion, amniotic cavity, bag of waters, extraembryonic membrane Mesodermal subdivisions, and the organs that develop from them, especially kidneys and heart. You ought to be able to draw the notochord, somites, subdivisions of the somites, intermediate mesoderm, lateral plate mesoderm, coelomic cavity, location of the heart. Pronephros, pronephric duct (also called the Wolffian Duct), mesonephros, metanephros (the duct of which is the "ureter") The path of blood flow through the heart of mammals (including human), and how this path changes at the time of birth. (Including the functional reasons for this change, the names and descriptions of the two openings through which blood flows before birth, descriptions of the processes of closure of these two openings.) What tissues are the testis and the ovary derived from? What about the male sex duct? What about the female sex duct? What is the Müllerian duct? What is the Wolffian duct? What happens to them in embryonic development? Where do the testes originate in development of mammals, and what happens to them during development? What is another example of organ migration in mammals (in addition to the testes)? kidney Contrast the internal histology of the testes and the ovaries. How can you cause a vertebrate embryo to develop two hearts? Why do bird and mammal embryos develop three pairs of kidneys? In the development of the heart, do we first form a one-chambered embryonic heart, then replace it with a two chambered fetal heart, which we use to pump blood while we construct the 4-chambered heart that we will use after birth and for the rest of our life? (Hint: no) But what do we do instead? In what way is the imaginary sequence of hearts analogous to what actually happens in the embryonic development of kidneys? The sperm ducts of male mammals, reptiles and birds was used for what purpose during embryonic development, when no sperm were being produced? Does the future oviduct ever serve as a urine duct? Hint: no The lateral plate mesoderm splits into two layers, with what between them? the coelom A serious birth defect that sometimes occurs is that a hole connects the right and left ventricles of the heart. To what other birth defects is this analogous? Hint: It isn't called "cardia bifida" but that might have been chosen as a name. (Does it result from something having cut or cleaved a hole through the septum between the ventricles?) Hint: no.) Until birth, blood flow and oxygenation of blood is not abnormal in babies with holes connecting their two ventricles: why not? Please explain why oxygenation of blood then suddenly become very abnormal in these babies, at the time of birth (but worked OK before birth)? Do mammal embryos ever develop a hole connecting their right and left atria? (Trick question!) Yes, always - and what shape is this window-like hole? In what sequence do somites become separated from each other? First on one side, then on the other? First near the front, then one pair after another toward the rear? First at the rear and gradually toward the anterior? First in the middle, and then sequentially toward both ends? Or what? If you had a drug or treatment that could cause more somites to form on one side of the body than on the other side, then list all the anatomical abnormalities this would be expected to produce. In embryos of mammals and birds, the diameter of the notochord is much smaller than the diameter of the neural tube; but in embryos of salamanders and /frogs, the notochord is almost as big as the neural tube, and sometimes bigger. What sense does this make in relation to the function of the notochord in swimming? (Hint: As compared with its inductive function.) What are three embryonic organs whose medio-lateral, anterior-posterior and dorso-vental axes become irreversibly decided during early development? Limb buds, inner ears, retinas Are all three axes decided simultaneously, or one at a time, or sometimes one at a time, but other times simultaneously? first mediolateral, second anterior-posterior, third dorso-ventral. Does the answer to the preceding question differ between organs? no What are two mesodermal organs that start development as two separate organs (right and left), but then their tissues fuse? heart, uterus

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