Lab2 Flashcards
Fertilization
Process that initiates development; ovum and spermatozoon fuse to form an embryo.
Gray crescent
Crescent-shaped area located between the pigmented animal hemisphere and unpigmented vegetal hemisphere.
Zygote
Single cell embryo.
Cleavage
Phase of development in which embryo’s cells rapidly undergo mitosis with little or no cell growth.
Holoblastic cleavage
Type of cleavage in which two seperate daughter cells form.
Radial cleavage
Cleavage plane is perpendicular or parallel to the previous one.
Rotational cleavage
During second cleavage, one blastomere divides meridionally, and the other equatorially.
Morula
a solid ball of cells resulting from division of a fertilized ovum, and from which a blastula is formed.
Blastula
an embryo at the end of the cleavage stage when it is a sphere of cells surrounding a cavity, the blastocoel.
Blastomere
An embryonic cell of an early embryo formed during the cleavage stage.
Micromere
Small cells; in sea urchins they are located in the vegetal pole; in amphibians they are the cells of the animal hemisphere.
Macromere
4 large blastomeres of the vegetal hemispheres.
Blastocoel
A cavity within the embryo at the blastula or blastocyst stage.
Gastrulation(gastrula)
Phase of development during which the 3 embryonic germ layers form. An embryo undergoing this phase is called a gastrula.
Primary germ layers
ectoderm(outermost layer), mesoderm(middle layer), endoderm(innermost layer)
Invagination
Infolding or a buckling inward of a sheet of cells during gastrulation.
Involution
Inward migration of an expanding outer sheet of cells during gastrulation so that it spreads over the basal surface of the remaining external cells.
Epiboly
Expansion of an outer sheet of cells during gastrulation to cover the embryo’s surface.
Blastopore
The opening of the archenteron which in deuterostomes becomes the anus.
Dorsal blastopore lip
A lip-like structure over which the cells involute during gastrulation. It is the amphibian organizer. (Spemann organizer)
Bottle cells
The first cells to migrate inwards at the blastopre during amphibian gastrulation.
Marginal zone
Area surrounding the equator of the amphibian embryo where the micromeres and macromeres meet.
Archenteron
The embryonic gut. Also called gasrocoel.
Yolk plug
24.A small patch of endoderm cells that protrudes from the amphibian blastopore.
Chordamesoderm
Mesoderm that generates the notochord.
Neurulation
Process by which the neural tube forms. Embryo undergoing this is neurula.
Neural plate
Thickened ectoderm which is the earliest rudiment of the central nervous system.
Neural fold
The paired, raised lateral edges of the neural plate to form the neural tube during neurulation.
Neural groove
The depression in the neural plate located between the raised neural folds.
Neural tube
A dorsal tube of neural ectoderm cells that run along anterior-posterier axis and give rises to the central nervous system.
Neurocoel
The lumen of the neural tube.
Neural ectoderm
Embryonic ectoderm that becomes the neral plate, neural folds, and neural tube.
Skin ectoderm
Ectoderm that differentiates into the epidermis of the skin.
Neural crest cells
Group of ectoderm cells that migrate to various areas of the embryo to become several structures.
Forebrain
The rostral region of the embryonic brain.
Prosencephalon
The most rostral primary region of the neural tube that gives rise to the forebrain.
Telecephalon
Rostralmost brain vesicle located cranial to the diencephalon.
Diencephalon
Second brain vesicle located between the telencephalon and mesencephalon.
Midbrain(mesencephalon)
Middle region of the embryonic brain.
Hindbrain(rhombencephalon)
The caudal region of the embryonic brain that gives rise to the metencephalon and mylencephalon.
Notochord
A longitudinal, rod-like structure that runs the length of the dorsal embryonic axis between the digestive and neural tube.
Paraxial(segmental plate) mesoderm
Mesoderm that lies to the left and right sides of the neural tube that gives rise to the somites.
Somites
Paired blocks of paraxial mesoderm located ventrolateral to the neural tube.
Mesenchyme
Loosely scattered cells mostly of mesoderm origin.
Foregut
Cranial region of the embryonic gut.
Midgut
Middle region of the embryonic gut.
Hindgut
The caudal region of the embryonic brain.
