Embryo Development

fertilization

Begins with contact between egg and sperm, ends with transfer of paternal chromosomes into the egg to form a zygote

cleavage

the process ofd vision, single-cell zygote begins a series of organized, successive mitosis to produce a multicellular, hollow structured called the blastula; no growth of embryo

gastrulation

the period of cell movement; starts with the formation of a curved groove (blastopore) in the region formally occupied by the gray crescent

unfertilized egg

stage 1; appears as a large cell with a clear nucleus and nucleolus

gray crescent

stage 2; a region located opposite the site of sperm penetration, becomes the dorsal side, where gastrulation will begin

2 cell stage

stage 3; The result of the first cleavage event after fertilization

4-cell stage

stage 4; The result of a second cleavage event

16-cell stage

stage 6

mid cleavage

stage 8; characterized by continued irregular cleavage and intrusion of pigmented area over pale area

late cleavage

stage 9; cells in animal hemisphere are small and pigmented and extend and well down toward the vegetal pole

dorsal lip

stage 10; The region above the blastopore on the dorsal side of the amphibian embryo.

mid gastrula

stage 11; the groove of the blastopore and the dorsal lip have spread to form a circle around the small area of the remaining yolk

late gastrula

stage 12; Blastoporeformed, surrounding yolk plug, blastopore elevated to point of posterior axis of embryo.

zygote

fertilized egg

yolk

made of proteins and lipids

vegetable pole

yolky side

animal pole

dark colored

blastula

a multicellular, hollow structure produced after a series of organized successive mitoses

blastomere

each cell of the blastula

blastocoel

the central cavity of the blastula

blastopore

the opening though which the cells on the surface of the embryo begin migrating to the Indies (into the blastocoel)

dorsal lip

The region above the blastopore on the dorsal side of the amphibian embryo

yolk plug

the remaining yolk in which the dorsal lips forms a circle around

ectoderm

outer germ layer, the brain and spinal cord

mesoderm

middle germ layer, muscles, skeleton, urogenital organs, muscle layer, and outer walls of digestive and respiratory tracts

endoderm

outer germ layer; inner lining of digestive and respiratory tracts

archenteron

the cavity formed by the endoderm; primitive gut; replaces the blastocoel and will eventually form the lumen of the digestive tract

dueterostomes

blastopore will form anus opening first

organogenesis

processes by which the cells of the three primary germ layers form actual organ systems in the embryo

differentiation

cells express their different morphological and functional specializations

neural plate

the flattening of the neural ectoderm

neural folds

forms when the neural plate rolls up at the edges

neural groove

area between the neural folds

neural tube

formed when the neural folds eventually fuse together to form an enclosed, hollow structure, ultimately forms the brain and spinal cord

notochord

A flexible rod that supports a chordate's back

yolk plug

A group of large, nutrient-laden endodermal cells surrounded by the completed blastopore in an amphibian gastrula. These cells will be covered by ectoderm and end up inside the embryo.

stage 22

tail fin circulation

stage 21

mouth open, cornea transparent

stage 20

gill circulation

stage 19

heart beat

stage 18

muscular response

stage 17

tail bud

stage 16

neural tube

stage 15

rotation

stage 14

neural folds

stage 13

neural plate, dorsal flattening