Chapter 13.1. Chick Development

Amniote

A group of vertebrates that includes reptiles, birds, and mammals, characterized by having an amniotic egg.

Gallus gallus

The scientific name for the domestic chicken, a model organism in vertebrate development studies.

Hypoblast

The lower layer of the blastoderm in early embryonic development that contributes to the formation of the yolk sac and future endoderm.

Epiblast

The upper layer of the blastoderm from which the embryo and its tissues are formed.

Primitive streak

A structure that forms during the early stages of embryonic development; it is where cells migrate inward and contribute to germ layers.

Hensen's node

The organizer region at the anterior end of the primitive streak, which plays a crucial role in the development of embryonic structures.

Ectoderm

The outermost germ layer that develops into skin and nervous system structures.

Mesoderm

The middle germ layer that forms muscles, bones, and the circulatory system.

Endoderm

The innermost germ layer that develops into the digestive tract and respiratory system.

BMP (Bone Morphogenetic Protein)

A group of proteins that regulate bone and cartilage development; their signaling is inhibited by organizer molecules like Noggin and Chordin.

Retinoic acid

A signaling molecule derived from vitamin A that influences gene expression and development along the anterior-posterior axis.

Chorion

The outermost membrane of the amniotic egg that helps in gas exchange and forms part of the placenta in placental mammals.

Allantois

An extraembryonic membrane that stores waste products and contributes to gas exchange and nutrient transfer in the embryo.

Yolk sac

An extraembryonic membrane that provides nutrients to the developing embryo in birds and reptiles.

Blastodisc

A small disk of cytoplasm in the chick egg that contains the newly fertilized zygote and where cell division occurs.

Fate map

A diagram that shows the future developmental fates of different regions of the embryo.

Neural tube

The embryonic structure that eventually develops into the brain and spinal cord.

Hox genes

A group of related genes that control the body plan of an embryo along the anterior-posterior axis.

Somites

Segmented blocks of mesoderm that give rise to vertebrae, skeletal muscles, and dermis.

Gastrulation

The phase of embryonic development that transforms the blastula into a multilayered structure, establishing the three germ layers.

Amnion

A membrane surrounding the embryo that contains amniotic fluid, providing protection and cushioning.