AP Bio Chapter 47 Key Terms Flashcards
acrosomal reaction
The discharge of a sperm’s acrosome when the sperm approaches an egg.
acrosome
A vesicle at the tip of a sperm cell that helps the sperm penetrate the egg.
allantois
One of four extraembryonic membranes; serves as a repository for the embryo’s nitrogenous waste.
amnion
The innermost of four extraembryonic membranes; encloses a fluid-filled sac in which the embryo is suspended.
amniote
Member of a clade of tetrapods that have an amniotic egg containing specialized membranes that protect the embryo, including mammals and birds and other reptiles.
animal pole
The portion of the egg where the least yolk is concentrated; opposite of vegetal pole.
apical ectodermal ridge
A limb-bud organizer region consisting of a thickened area of ectoderm at the tip of a limb bud.
archenteron
The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.
blastocoel
The fluid-filled cavity that forms in the center of the blastula embryo.
blastocyst
An embryonic stage in mammals; a hollow ball of cells produced one week after fertilization in humans.
blastoderm
An embryonic cap of dividing cells resting on a large undivided yolk.
blastomere
A small cell of an early embryo.
blastopore
The opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterostomes.
blastula
The hollow ball of cells marking the end stage of cleavage during early embryonic development.
cadherins
An important class of cell-to-cell adhesion molecules.
cell adhesion molecules (CAMs)
Glycoproteins that contribute to cell migration and stable tissue structure.
cell differentiation
The structural and functional divergence of cells as they become specialized during a multicellular organism’s development; dependent on the control of gene expression.
chorion
The outermost of four extraembryonic membranes; contributes to the formation of the mammalian placenta.
cleavage
The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane; specifically, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.
convergent extension
A mechanism of cell crawling in which the cells of a tissue layer rearrange themselves in such a way that the sheet of cells becomes narrower while it becomes longer.
cortical granules
Vesicles located just under the plasma membrane of an egg cell that undergo exocytosis during the cortical reaction.
cortical reaction
Exocytosis of enzymes from cortical granules in the egg cytoplasm during fertilization.
cytoplasmic determinants
The maternal substances in the egg that influence the course of early development by regulating the expression of genes that affect the developmental fate of cells.
dorsal lip
The dorsal side of the blastopore.
ectoderm
The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye.
endoderm
The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract.
extraembryonic membranes
Four membranes (yolk sac, amnion, chorion, allantois) that support the developing embryo in mammals and birds and other reptiles.
fast block to polyspermy
The depolarization of the egg membrane within 1–3 seconds after sperm binding to the vitelline layer. The reaction prevents additional sperm from fusing with the egg’s plasma membrane.
fate map
Territorial diagram of embryonic development that reveals the future development of individual cells and tissues.
fertilization envelope
The swelling of the vitelline layer away from the plasma membrane.
gastrulation
The formation of a gastrula from a blastula.
germ layers
Three main layers that form the various tissues and organs of an animal body.
gray crescent
A light-gray region of cytoplasm located near the equator of the egg on the side opposite the sperm entry.
holoblastic cleavage
A type of cleavage in which there is complete division of the egg, as in eggs having little yolk (sea urchin) or a moderate amount of yolk (frog).
induction
The ability of one group of embryonic cells to influence the development of another.
inner cell mass
A cluster of cells in a mammalian blastocyst that protrudes into one end of the cavity and subsequently develops into the embryo proper and some of the extraembryonic membranes.
invagination
The infolding of cells.
involution
Cells rolling over the edge of the lip of the blastopore into the interior of the embryo during gastrulation.
meroblastic cleavage
A type of cleavage in which there is incomplete division of yolk-rich egg, characteristic of avian development.
mesoderm
The middle primary germ layer of an early embryo that develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system.
morphogenesis
The development of body shape and organization.
morula
A solid ball of blastomeres formed by early cleavage.
neural crest
A band of cells along the border where the neural tube pinches off from the ectoderm. The cells migrate to various parts of the embryo and form the pigment cells in the skin, bones of the skull, the teeth, the adrenal glands, and parts of the peripheral nervous system.
neural tube
A tube of cells running along the dorsal axis of the body, just dorsal to the notochord. It will give rise to the central nervous system.
notochord
A long flexible rod that runs along the dorsal axis of the body in the future position of the vertebral column.
organogenesis
The development of organ rudiments from the three germ layers.
pattern formation
The ordering of cells into specific three-dimensional structures, an essential part of shaping an organism and its individual parts during development.
positional information
Signals to which genes regulating development respond, indicating a cell’s location relative to other cells in an embryonic structure.
primitive streak
A groove on the surface of an early avian embryo along the future long axis of the body.
slow block to polyspermy
The formation of the fertilization envelope and other changes in the egg’s surface that prevent fusion of the egg with more than one sperm.
somites
Paired blocks of mesoderm just lateral to the notochord of a vertebrate embryo.
totipotent
Describing a cell that can give rise to all parts of an organism.
trophoblast
The outer epithelium of the blastocyst, which forms the fetal part of the placenta.
vegetal pole
The portion of the egg where most yolk is concentrated; opposite of animal pole.
yolk
Nutrients stored in an egg.
yolk plug
Large food-laden endodermal cells surrounded by the blastopore of an amphibian gastrula.
yolk sac
One of four extraembryonic membranes that support embryonic development; the first site of blood cells and circulatory system function.
zona pellucida
The extracellular matrix of a mammalian egg.
zone of polarizing activity (ZPA)
A limb-bud organizer region consisting of a block of mesoderm located where the posterior side of the bud is attached to the body.
