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Unformatted text preview: Chapter 3: Vertebrate Embryology Purpose Understand the development of the vertebrate body plan using the embryonic chick as a model system. Identify the characteristics that classify the chick as a chordate/craniate/vertebrate. Identify the required anatomy on both the chicken embryos and slides. Introduction (Ch. 3 supplement-Figs 3-1 to 3-14) In chapter 3, you will explore embryonic development using the chicken as a model vertebrate system. The morphological complexity and general course of development is similar in both avian and mammalian embryos. However, avian embryos are easier to obtain and observe, and therefore are often used to perform embryonic experiments and manipulations. Many observations and experimental manipulations can be executed by simply windowing, or opening the eggshell. Additionally, the avian embryo can be cultured outside of the egg. In this lab, you will observe chicken embryos at three stages of development (stages 12, 18, 25 approximately). Provided below is the Hamburger and Hamilton chicken staging guide, detailing features of the chicken that can be observed at specific times after fertilization. Observe the progression of development through the various stages. What features should be seen at stages 12, 18, and 25? Keep in mind that the Hamburger and Hamilton staging guide is not inclusive, and that many additional features can be observed on the embryo. Hamburger Hamilton Stage Age Identification of Stages (Before Laying) Early cleavage 3.5-4.5 hr Shell membrane of egg formed in isthmus of oviduct During cleavage Germ wall formed from marginal periblast Late cleavage 4.5-24.0 hr Shell of egg formed in uterus (After Laying) 1 Preprimitive streak (embryonic shield) 2 6-7 hr Initial primitive streak, 0.3-0.5 mm long 3 12-13 hr Intermediate primitive streak 4 18-19 hr Definitive primitive streak, 1.88 mm long 5 19-22 hr Head process (notochord) 6 23-25 hr Head fold 7 23-26 hr 1 somite; neural folds 7 to 8- ca. 23-26 hr 1-3 somites; coelom 8 26-29 hr 4 somites; blood islands 9 29-33 hr 7 somites; primary optic vesicles 9+ to 10- ca. 33 hr 8-9 somites; anterior amniotic fold 10 33-38 hr 10 somites; 3 primary brain vesicles 11 40-45 hr 13 somites; 5 neuromeres of hindbrain 12 45-49 hr 16 somites; telencephalon 13 48-52 hr 19 somites; atrioventricular canal 13+ to 14- ca. 50-52 hr 20-21 somites; tail bud 14 50-53 hr 22 somites; trunk flexure; visceral arches I and II, clefts 1 and 2 14+ to 15- ca. 50-54 hr 23 somites; premandibular head cavities 15 50-55 hr 24-27 somites; visceral arch III, cleft 3 16 51-56 hr 26-28 somites; wing bud; posterior amniotic fold 17 52-64 hr 29-32 somites; leg bud; epiphysis 18 3 da 30-36 somites extending beyond level of leg bud; allantois 19 3.0-3.5 da 37- 40 somites extending into tail; maxillary process 20 3.0-3.5 da 40-43 somites; rotation completed; eye pigment 21 3.5 da 43-44 somites; visceral arch IV, cleft 4 22 3.5-4.0 da Somites extend to tip of tail...
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- Spring '09