Lab3 Flashcards
Cleavage
Phase of development in which an embryo’s cells rapidly undergo mitosis with little or no cell growth.
Meroblastic cleavage
cleavage in which the daughter cells seperate incompletely.
Discoidal cleavage
Cleavage occurs only in the blastodisc.
Blastoderm
In fish and birds, the multicellular structure that forms when the blastodisc undergoes cleavage.
Area opaca
Dark-staining region of the avian blastoderm that lies directly over the yolk, and surrounds the area pellucida.
Area opaca Vasculosa
Inner region of area opaca.
Area opaca Vitellina
Outer region of area opaca.
Epiblast
In birds and mammals, the upper or surface layer of the blastoderm.
Hypoblast
In birds and mammals, the lower or inner layer of the blastoderm.
Subgerminal cavity
A space that lies between the yolk and blastoderm of early chick embryos.
Koller’s sickle
In avian gastrulation, Koller’s sickle is a local thickening of cells at the posterior edge of the upper layer of the epiblast.
Primitive streak
A longitudinal thickening of the epiblast through which cells ingress.
Primitive groove
Longitudinal depression in the primitive streak through which cells ingress.
Primitive folds(ridge)
Paired raised edges of primitive streak.
Primitive pit
Depression in primitive knot that is continuous with the primitive groove.
Henson’s node(primitive knot)
Cranial thickening of primitive streak.
Proamnion
A lightly staining, crescent-shaped region of the area pellcida cranial to the developing head of early chick embryo.
Head fold
A ventrally-directed body fold of an early embryo that outlines the head region.
Head process
A longitudinal band of mesoderm cells.
Notochord
A longitudinal, rod-like structure that runs the length of the dorsal embryonic axis between digestive and neural tube.
Neural plate
Thickened ectoderm that is the earliest rudiment of the central nervous system.
Head mesenchyme
Loosely arranged cells found between brain and skin ectoderm of head.
Subcephalic pocket
A space under the head of the chick embryo.
Cranial intestinal portal
Opening of foregut into midgut in amniotes.
Foregut
Cranial region of the embryonic gut that extends from the head to midgut.
Prechordal plate
Thickening in the endodermal layer.
Oral membrane(plate)
A double-layered sheet of ectoderm and endoderm that seperates the foregut and stomodeum.
Mesoderm
Middle embryonic germ layer between ectoderm and endoderm.
Axial mesoderm
Lies central axis under neural tube, gives rise to notochord.
Paraxial mesoderm or Segmental plate or Somitic mesoderm
Lies to the left and right sides of neural tube that gives rise to somites.
Somitomere or somite
Paired blocks of paraxial mesoderm.
Coelom
Cavity of the embryo.
Somatopleure
A layer made of surface ectoderm and somatic mesoderm.
Ectoderm
Outermost embryonic germ layer that forms during gastrulation.
Splanchnopleure
A layer made of splanchnic mesoderm and endoderm.
Endoderm
Innermost embryonci germ layer that forms during gastrulation.
Splanchnic mesoderm
The ventral layer of lateral plate mesoderm.
Heart rudiment
Cone like structure that is formed when myocardial progenitor cells of heart fuse at midline.
Cardiac primordium
Aggregation of angioblastic cells in cardiogenic region.
Pericardial cavity rudiment
Portion of coelom that houses the heart.
Vitelline vein
Paired veins that drain blood and nurients from yolk sac into ductus venosus.
