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October, 2006
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Extraembryonic Membranes: The thin layers of tissue that surround the developing embryo. There are four extra-embryonic membranes commonly found in Vertebrates, such as Reptiles; Birds; and Mammals. They are the Yolk sac, the Allantois, the Amnion, and the Chorion. These membranes provide protection and means to transport nutrients and wastes.

Development of the Chick

JoVE 5155

The chicken embryo (Gallus gallus domesticus) provides an economical and accessible model for developmental biology research. Chicks develop rapidly and are amenable to genetic and physiological manipulations, allowing researchers to investigate developmental pathways down to the cell and molecular levels.

This video review of chick development begins by describing the process of egg fertilization and formation within the chicken reproductive tract. Next, the most commonly used chick staging nomenclature, the Hamburger Hamilton staging series, is introduced. Major events in chick development are then outlined, including the dramatic cellular movements known as gastrulation that form the three major cell layers: The ectoderm, mesoderm, and endoderm. Cells from these layers go on to generate all the tissues within the organism, as well as extraembryonic membranes, which are necessary for the transport of gases, nutrients, and wastes within the eggshell. To conclude the discussion, some exciting techniques will be presented as strategies for studying chick development in greater detail.

 Biology II

An Introduction to the Chick: Gallus gallus domesticus

JoVE 5153

The chicken embryo (Gallus gallus domesticus) is an extremely valuable model organism for research in developmental biology, in part because most of their development takes place within an egg that is incubated outside of the mother. As a result, early developmental stages can be accessed, visualized and manipulated by simply creating a small hole in the eggshell. Since billions of chickens are raised worldwide for meat and egg production, scientists can easily and economically acquire large numbers of fertilized eggs throughout the year. Furthermore, chickens share significant genetic conservation with humans, so the genetic mechanisms that have been found to regulate chicken development are also relevant to our own biology. This video focuses on introducing the domesticated chicken as a scientific model. The discussion begins with a review of chicken phylogeny, revealing the features that make them amniotes, like other birds, reptiles, and mammals. Highlights from the millennia of chicken research will be presented, ranging from Aristotle’s postulates about the function of extra-embryonic membranes to more recent, Nobel-prize winning discoveries in neuroscience. Additionally, some current examples of studies performed in chicken embryos will be provided, such as in vivo tracking of cell movements during development and the recruitment of

 Biology II

Basic Chick Care and Maintenance

JoVE 5154

Chicks (Gallus gallus domesticus) are a valuable research tool, not only for studying important concepts in vertebrate development, neuroscience, and tumor biology, but also as an efficient system in which to propagate viruses. Although eggs can be purchased from external suppliers and working with chicks requires very little specialized equipment, an understanding of proper handling procedures is required for normal embryo development. This video will provide an overview of egg handling principles, including an explanation of the incubation parameters that can profoundly impact development: temperature, humidity, and egg rotation. Most experiments that use chicken eggs require access to the embryo within the shell, which is achieved by cutting a small, resealable hole, or “window.” This process is described in step-by-step detail, along with several other techniques essential for working with chicks, such as candling and India ink injection. Finally, the video will review some practical applications of these basic techniques in advanced scientific research.

 Biology II

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