Glossary of Words used when describing the development of a duckling in the egg.

al•lan•to•is a vascular fetal membrane of reptiles, birds, or mammals that is formed as a pouch from the hindgut and that in placental mammals is intimately associated with the chorion in formation of the placenta

A thin membrane surrounding the embryo during incubation. The amnion is the inner of the two fetal membranes (the chorion is the outer one). It contains the amniotic fluid.

(front/head) open end of the neural tube (becomes the spinal cord)

area pel•lu•ci•da the pellucid (transparent) central area that immediately surrounds a vertebrate embryo (as of a bird) formed by discoidal cleavage

an embryo at the stage of development in which it consists of usually one layer of cells around a central cavity, forming a hollow sphere [WNW]

a ventral bend in the neural tube of the vertebrate embryo marking the point of transition from brain to spinal cord .

the middle of the three anterior flexures of an embryo in which the front part of the brain bends downward in an angle of 90 degrees - called also cephalic flexure

meroblastic cleavage in which a disk of cells is produced at the animal pole of the zygote (as in bird eggs)

what will become the beak

a triangular embryonic process that grows out from the dorsal end of the mandibular arch on each side and forms the lateral part of the upper lip, the cheek, and the upper jaw except the premaxilla

the middle layer of cells of an embryo, from which the skeletal, reproductive, muscular, vascular, connective, etc. tissues develop [WNW]

future muscle cells

these will become the eyes

a platelike thickening of embryonic ectoderm from which a definitive structure develops

organ or tissue in its earliest recognizable stage of development.

a projection from a structure (something that sticks out)

a blocklike segment of mesodermal (midlayer) tissue in the vertebrate embryo, giving rise to muscle, bone, etc. [WNW]

primitive streak: an elongated band of cells that forms along the axis of an embryo early in gastrulation by the movement of lateral cells toward the axis and that develops a groove along its midline through which cells move to the interior of the embryo to form the mesoderm .

active at the surface

the anterior subdivision of the embryonic forebrain or the corresponding part of the adult forebrain that includes the cerebral hemispheres and associated structures .

A hollow sphere with the shell made up of a surfactant bilayer. Cells are examples of vesicles. www.cem.msu.edu/~cem181h/glossary.html

one of a series of bony or cartilaginous arches that develop in the walls of the mouth cavity and pharynx of a vertebrate embryo, consist typically of a curved segmented bar or rod on each side meeting the contralateral bar or rod at the ventral end, and correspond to the gill arches of fishes and amphibians - called also pharyngeal arch , bronchial arch

circulation around the yolk - there is a network of blood vessels that starts on the surface of the yolk and ands up being the one that lines the inside of the shell