AP Biology: Animal Reproduction and Development, Chapter 14 - Embryonic Development
Blastodisc
A blastula having the form of a disk of cells on top of the yolk in the eggs of reptiles and birds.
Blastocoel
A cavity in the blastocyst containing inner cell mass cells destined to develop into the embryo.
Inner Cell Mass
A cell mass an internal cluster of cells at the embryonic pole of the blastocyst which develops into the body of the embryo.
Blastocyst
A cell produced by division (cleavage) in a fertilised egg.
Homeotic Gene
A class of regulatory genes that determine the identity of body parts and regions in an animal embryo; mutations in these genes can transform one body part into another.
Inner Cell Mass
A cluster of cells localized at the animal pole of the blastocyst of placental mammals from which the embryo develops.
Blastocyst
A cluster of cells representing multiple cell divisions that have occurred in the fallopian tube after successful fertilization of an ovum by a sperm.
Umbilical Cord
A cordlike structure connecting the fetus with the placenta during pregnancy, conveying nourishment from the mother and removing wastes.
Gray Crescent
A cortical region of the newly fertilised egg of frogs and some salamanders that forms just after fertilization on the side opposite sperm penetration.
Blastoderm
A disk of cells lying betwen the yolk sac and the amniotic cavity, from which the embryo develops.
Amnion
A fluid filled membrane that protects the embryo from shock and desiccation.
Blastocoel
A fluid-filled cavity in the blastocyst; clustered at one end of this cavity are inner cell mass cells, which will develop into the embryo.
Blastocoel
A fluid-filled cavity in the blastocyst; contains inner cell mass cells which will develop into the embryo.
Primitive Streak
A groove on the surface of an early avian embryo along the future long axis of the body; forms instead of a grey crescent.
Primitive Streak
A groove with raised edges that establishes the longitudinal axis on the embryo during gastrulation; forms instead of a gray crescent.
Blastula
A hollow sphere formed during the early embryonic development of higher animals; dividing cells line up on the outside and are bathed by fluid within the adjacent cavity (blastocoele).
Gray Crescent
A light-gray region of cytoplasm located near the equator of the egg on the side opposite the sperm entry; the marker of the future dorsal side.
Homeotic Gene
A master control gene that determines the identity of a body structure of a developing organism, presumably by controlling the developmental fate of groups of cells.
Extraembryonic Membrane
A membrane that is not a part of the embryo but it necessary to the continued existence and health of the embryo
Yolk Sac
A membranous sac attached to the embryo and enclosing the yolk in egg-laying vertebrates.
Allantois
A membranous sac growing out of the ventral surface of the hind gut of embryonic reptiles, birds, and mammals; combines with the chorion to form the mammalian placenta.
Allantois
A membranous sac that develops from the posterior part of the digestive tract in the embryos of mammals, birds, and reptiles; important in the formation of the umbilical cord and placenta in mammals.
Allantois
A membranous sac that grows out of the lower end of the alimentary canal in embryos of reptiles, birds, and mammals; in mammals, the blood vessels of the allantois develop into the blood vessels of the umbilical cord.
Yolk Sac
A membranous structure that functions as the circulatory system in placental mammalian embryos until the heart becomes functional.
Placenta
A membranous vascular organ that develops in female eutherian mammals during pregnancy, lining the uterine wall and partially enveloping the fetus, to which it is attached by the umbilical cord.
Embryo
A new organism in the earliest stage of development; in humans, defined as the developing organism from the fourth day after fertilization to the end of the eighth week.
Mesoglea
A noncellular layer that develops in place of the mesoderm in some primitive animals such as sponges.
Allantois
A nourishing membrane surrounding the embryo, between the amnion and chorion, in birds and reptiles developing as a sac from the hindgut and in mammals as an inner layer of the placenta.
Organogenesis
A process by which cells continue to differentiate, producing organs from the three embryonic germ layers.
Induction
A process by which the presence of one tissue influences the development of others; certain tissues, especially in very young embryos, have the potential to direct the differentiation of adjacent cell.
Cleavage
A process during which the embryo remains uniform in size as its cells, or blastomeres, become smaller with each division.
Organogenesis
A process evidenced by morphogenetic changes- folds, splits and dense clustering referred to as condensation; once the process ends, the embryo simply increases in size.
Gastrularion
A process that involves rearrangement of the blastula or blastocyst and begins with the formation of the blastopore.
Dorsal Lip
A region of the blastopore which initiates a chain of inductions that result in the formation of a neural tube.
Amnion
A sac of thin, tough membrane containing a watery liquid in which the embryo of a reptile, bird, or mammal is suspended.
Blastodisc
A small region at the animal pole of the telolecithal eggs containing the yolk-free cytoplasm where cleavage can occur and that gives rise to the embryo.
Blastodisc
A small-circular patch of relatively yolk-free cytoplasm at the animal pole of the oocyte that undergoes cleavage to form blastoderm.
Gastrula
A stage in embryonic development in which the BLASTULA has invaginated, so giving rise to a two-layered embryo by a process of gastrulation.
Blastoderm
A superficial layer of a fertilised egg which, in birds, is a flat disc of cells at one pole, and in insects, an outer layer of cells surrounding the yolk mass.
Amnion
A tough, thin membrane that forms a sac enclosing the embryo or fetus of a mammal, bird, or reptile; filled with a serous fluid in which the embryo or fetus is suspended.
Blastula
An early embryonic form produced by cleavage of a fertilized ovum and consisting of a spherical layer of cells surrounding a fluid-filled cavity.
Blastula
An early stage of an embryo formed by the rearrangement of the blastomeres of the morula to form a hollow sphere.
Blastula
An early stage of the process through which a zygote develops into an embryo, characterized by a fluid-filled sphere formed by a single layer of cells.
Gastrula
An embryo at the stage following the blastula, after the movement of cells results in the formation of the three germ layers, ectoderm, mesoderm, and endoderm.
Gastrula
An embryo in the stage following the blastula stage; the simplest type consists of two layers of cells, the ectoderm and entoderm, which have invaginated to form the archenteron and an opening, the blastopore.
Blastodisc
An embryonic cap of dividing cells resting on a large undivided yolk.
Fetus
An unborn or unhatched vertebrate especially after attaining the basic structural plan of its kind.
Mesoglea
Analogous to the mesoderm in some primitive animals, such as the sponge and cnidarians.
Homeotic Gene
Any of a group of homeobox genes that exist as clusters in animals, especially in vertebrates, and determine the identity and locations of body parts along the anterior-posterior body axis in a developing fetus or larva.
Blastocyst
Any of the cells resulting from the cleavage of a fertilized ovum during early embryonic development.
Extraembryonic Membrane
Any of the membranes derived from embryonic tissue that lie outside the embryo, as the allantois, amnion, chorion, and yolk sac.
Homeotic Gene
Any of various genes that determine the type or location of a body part during an organism's development, especially in the early embryonic development of vertebrates.
Pluripotent
Cells having the capacity to affect more than one organ; characteristic of the early blastocoel stage.
Pluripotent
Cells of the inner cell mass are able to give rise to any of the three germ layers and therefore to any cell of the body.
Cytoplasmic Determinant
Cytoplasmic molecules surrounding the nucleus which have profound effects of embryonic development.
Gray Crescent
Embryologically, what establishes body axis and is located close to an eggs equator on opposite side of sperm entry; the marker of the future dorsal side.
Extraembryonic Membrane
Four membranes (yolk sac, amnion, chorion, allantois) that support the developing embryo in reptiles, birds, and mammals.
Dorsal Lip
In an amphibian embryo, the margin or lip of the fold of blastula wall marking the dorsal limit of the blastopore during gastrulation and constituting the primary organizer.
Embryo
In animals, those derivatives of the zygote that eventually become the offspring, during their period of most rapid growth
Gray Crescent
In frog development, a band of diffusely pigmented cytoplasm on the side of the egg opposite the site of sperm entry; establish the anterior-posterior axis of the zygote.
Yolk Sac
In humans and other placental mammals, functions as the circulatory system for the embryo before internal circulation begins.
Embryo
In humans, the developing organism from conception until the end of the eighth month; developmental stages from this time to birth are commonly designated as fetal.
Fetus
In humans, the unborn young from the end of the eighth week after conception to the moment of birth, as distinguished from the earlier embryo.
Blastomere
Individual cells of the blastocyst.
Endoderm
Inner layer of the three primary germ layers forming an embryo; gives rise to gut and associated structures.
Cleavage
Limited to a small, nonyolky disc at the top of the egg in eggs with a great deal of yolk.
Cytoplasmic Determinant
Maternal substances in the egg that influence early development; zygote divides by mitosis, cells contain different maternal substances, which lead to different gene expression.
Trophoblast
Mesectodermal cell layer covering the blastocyst that erodes uterine mucosa and through which embryo receives nourishment from mother.
Mesoderm
Middle of the three embryonic primary germ layers; gives origin to all connective tissues.
Dorsal Lip
Necessary to the development of neural tissue, and forms the originating point of chordamesoderm.
Extraembryonic Membrane
Not part of the body of the embryo itself, develop from tissue layers that grow out from the embryo; allow reproduction away from water.
Blastomere
One of the cells into which the oocyte divides after its fertilization.
Blastocyst
One of the cells produced by cleavage of a fertilized ovum.
Endoderm
One of the three primary (embryonic) germ layers formed during gastrulation; ultimately forms internal structures, such as the inner lining of the GI tract and glandular organs.
Chorion
Outermost layer of the two membranes surrounding the embryo; it forms the fetal part of the placenta.
Ectoderm
Primary germ layer of embryonic cells, forming epidermal structures and nerve tissue.
Organogenesis
Process by which cells continue to differentiate and form the organs in the three layers; once all organs are formed, the embryo grows in size to become a fetus
Organogenesis
Process by which cells continue to differentiate and form the organs in the three layers; once all organs are formed, the embryo grows in size to become a fetus.
Pluripotent
Relating to or being a cell that is capable of differentiating into cells of any type of tissue except placental tissue; evident in the blastocoel stage.
Dorsal Lip
Responsible for neural induction; has the ability to direct the development of host tissue to form a second neural tube.
Cytoplasmic Determinant
Special molecules which play a very important role during oocyte maturation, in the female's ovary; during this time, some regions of the cytoplasm accumulate some of these molecules, whose distribution is thus very heterogenic.
Induction
The action of one group of cells on another that leads to the establishment of the developmental pathway in the responding tissue.
Gastrulation
The blastula or blastocyst into the gastrula; the development and invagination of the embryonic germ layers.
Inner Cell Mass
The cells at the embryonic pole of the blastocyst concerned with formation of the embryo.
Archenteron
The central cavity of the gastrula, which ultimately becomes the intestinal or digestive cavity.
Archenteron
The central cavity that is the provisional gut in the gastrula; the primitive digestive cavity of the embryo.
Archenteron
The central cavity that is the provisional gut in the gastrula; the primordial digestive cavity of the embryo.
Embryo
The collection of cells that has developed from the fertilized egg of a vertebrate animal, before all the major organs have developed.
Gastrulation
The development of the gastrula in lower animals and the formation of the three germ layers in the embryo of humans and higher animals.
Cleavage
The division of the cytoplasm during nuclear division following FERTILIZATION of the egg to form the ZYGOTE.
Cleavage
The early successive splitting of a fertilized ovum (zygote) into smaller cells (blastomeres) by mitosis.
Gastrula
The embryo in the stage following the blastula or blastocyst; the simplest type consists of two layers of cells, the ectoderm and endoderm, which have invaginated to form the archenteron and an opening, the blastopore.
Gastrula
The embryo in the stage of development following the blastula or blastocyst formation; in the human embryo, the absence of yolk allows for a rapid, direct "putting in place" of the germ layers (ectoderm and endoderm), which are derived from the pluripotential embryonic disc.
Fetus
The embryo of a mammal in the later stages of development, when it shows all the main recognizable features of the mature animal, esp a human embryo from the end of the second month of pregnancy until birth.
Chorion
The embryo's outer membrane, which helps to form the placenta.
Blastocyst
The embryonic form that follows the morula in human development;(consists of an outer layer (trophoblast) which is attached to the inner cell mast.
Archenteron
The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.
Umbilical Cord
The flexible cord-like structure connecting a fetus at the abdomen to the placenta; contains blood vessels that supply nourishment to the fetus and remove its wastes.
Umbilical Cord
The flexible cordlike structure connecting a fetus at the abdomen with the placenta and containing two umbilical arteries and one vein that transport nourishment to the fetus and remove its wastes.
Ectoderm
The germ layer lying on the outside of the developing embryo that eventually gives rise largely to the EPIDERMIS, but also to nervous tissue.
Induction
The influence of one cell group over a neighboring cell group during embryogenesis; considered to play an important role in the development of tissues and organs in most animal embryos, from the lower chordates to the higher vertebrates.
Endoderm
The innermost of the three primary germ layers of an animal embryo, developing into the gastrointestinal tract, the lungs, and associated structures
Endoderm
The innermost of the three primary germ layers of the embryo; from it are derived the epithelium of the pharynx, respiratory tract, digestive tract, bladder, and urethra.
Endoderm
The innermost of the three primary germ layers of the embryo; from it is derived the epithelial lining of the primordial gut and the epithelial component of the glands and other structures that develop as outgrowths from the gut.
Amnion
The innermost of two membranes enclosing an embryonic reptile, bird, or mammal.
Mesoderm
The intermediate of the three primary germ layers of the developing embryo, lying between the outer ECTODERM and the inner ENDODERM.
Blastoderm
The layer of cells formed by the cleavage of a fertilized mammalian egg. It later divides into the three germ layers from which the embryo develops.
Blastoderm
The layer of cells forming the wall of the blastocyst in mammals and the blastula in lower animals during the early stages of embryonic development.
Blastoderm
The layer of cells forming the wall of the blastula.
Blastoderm
The layer of cells that develops on the surface of the yolk in an avian or reptilian egg and gives rise to the germinal disk from which the embryo develops.
Umbilical Cord
The long flexible tubelike structure connecting a fetus with the placenta: it provides a means of metabolic interchange with the mother.
Blastocyst
The mammalian conceptus in the post-morula stage, consisting of the trophoblast and an inner cell mass.
Blastocyst
The mammalian conceptus in the post-morula stage, consisting of the trophoblast, an inner cell mass, and a central, fluid-filled cavity.
Blastocyst
The mammalian conceptus in the postmorula stage, consisting of an embryoblast (inner cell mass) and a thin trophoblast layer enclosing a blastocyst cavity.
Inner Cell Mass
The mass of cells at the embryonic pole of the blastocyst that forms the embryo and some extraembryonic or adnexal tissues.
Cytoplasmic Determinant
The maternal substances in the egg that influences the course of early development by regulating the expression of genes that affect the developmental fate of cells.
Yolk Sac
The membranous sac that is attached to the ventral surface of the embryos of birds, reptiles, and some fishes and contains yolk.
Mesoderm
The middle embryonic germ layer, lying between the ectoderm and the endoderm, from which connective tissue, muscle, bone, and the urogenital and circulatory systems develop.
Mesoglea
The middle later of a two layered animal, like sponges or hydra, which holds the two layers together; develops instead of the mesoderm.
Mesoderm
The middle of the three primary germ layers of the embryo, lying between the ectoderm and entoderm; from it are derived the muscle, blood, and bones.
Mesoderm
The middle of the three primary germ layers of the embryo; the origin of connective tissues, myoblasts, blood, the cardiovascular and lymphatic systems, most of the urogenital system, and the lining of the pericardial, pleural, and peritoneal cavities.
Blostocyst
The modified blastula stage of mammalian embryos, consisting of the embryoblast or inner cell mass and a thin trophoblast layer enclosing the blastocystic cavity or blastocele.
Blastocyst
The modified blastula that is characteristic of placental mammals.
Blastocoel
The name given to the fluid-filled cavity of the blastula (blastocyst) that results from cleavage of the oocyte (ovum) after fertilization.
Mesoglea
The noncellular, gelatinous material between the inner and outer body walls of cnidarians and ctenophores; develops instead of the mesoderm.
Blastopore
The opening into the archenteron formed by invagination of the blastula (e.g., amphibians) to form a gastrula.
Blastopore
The opening into the blastula; becomes the mouth in some animals, and the anus in others.
Blastopore
The opening of the archenteron to the exterior of the embryo at the gastrula stage
Blastopore
The opening of the archenteron to the exterior of the embryo at the gastrula stage.
Blastopore
The opening of the archenteron, the primitive gut, to the outside, formed by invagination of cells on the embryo's surface which form the mesoderm and endoderm during during gastrulation.
Placenta
The organ in most mammals, formed in the lining of the uterus by the union of the uterine mucous membrane with the membranes of the fetus, that provides for the nourishment of the fetus and the elimination of its waste products.
Ectoderm
The outer layer of cells in the embryo, after establishment of the three primary germ layers (ectoderm, mesoderm, endoderm), the germ layer in contact with the amnionic cavity.
Chorion
The outer membrane enclosing the embryo in reptiles, birds, and mammals; in placental mammals contributes to the development of the placenta.
Chorion
The outer of two membranes that form a sac around the embryonic reptile, bird, or mammal: contributes to the placenta in mammals.
Trophoblast
The outermost layer of cells of the mammalian blastocyst that attaches the fertilized ovum to the uterine wall and serves as a nutritive pathway for the embryo.
Trophoblast
The outermost layer of cells surrounding the BLASTOCYST, consisting of embryonic epithelium, which subsequently encloses all the embryonic structures of the developing mammal and forms the outer layer of the CHORION and the embryonic side of the placenta.
Trophoblast
The outermost layer of tissue that forms the wall of the blastocyst of placental mammals in the early stages of embryonic development; functions in the implantation of the blastocyst in the uterine wall and in supplying nutrients to the embryo.
Chorion
The outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals).
Ectoderm
The outermost of the three primary cell layers of an embryo; gives rise to the nervous system, the organs of special sense, the epidermis, and epidermal tissues such as fingernails, hair, and skin glands.
Ectoderm
The outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue, and, in vertebrates, sense organs develop.
Ectoderm
The outermost of the three primary germ layers of an embryo, the others being the MESODERM and the ENDODERM; develops into the skin, the nervous system, and the sense organs.
Ectoderm
The outermost of the three primary germ layers of the embryo; from it are derived the epidermis and epidermic tissues and the nervous system.
Trophoblast
The peripheral cells of the blastocyst, which attach the blastocyst to the uterine wall and become the placenta and the membranes that nourish and protect the developing organism.
Trophoblast
The peripheral cells of the blastocyst, which attach the fertilized ovum to the uterine wall and contribute to the placenta and the membranes that nourish and protect the developing organism.
Trophoblast
The peripheral cells of the blastocyst, which attach the zygote (fertilized ovum) to the uterine wall and become the placenta and the membranes that nourish and protect the developing organism.
Vegetal Pole
The point at the end of an egg in the hemisphere where most yolk is concentrated; opposite of animal pole.
Animal Pole
The point at the end of an egg in the hemisphere where the least yolk is concentrated; opposite of vegetal pole.
Vegetal Pole
The portion of an egg that is opposite the animal pole and that contains most of the yolk.
Animal Pole
The portion of an egg that is opposite the vegetal pole, that contains the nucleus and most of the cytoplasm, and from which polar bodies are extruded during maturation.
Vegetal Pole
The portion of the egg where most yolk is concentrated; opposite of animal pole.
Animal Pole
The portion of the egg where the least yolk is concentrated; opposite of vegetal pole.
Archenteron
The primitive digestive cavity formed by invagination into the gastrula, which is lined with entoderm during the embryonic development of many animals.
Archenteron
The primordial digestive cavity of those embryonic forms whose blastula becomes a gastrula by invagination.
Gastrulation
The process by which a blastula becomes a gastrula or, in forms without a true blastula, the process by which three germ cell layers are acquired.
Gastrulation
The process by which a blastula becomes a gastrula or, in forms without a true blastula, the process by which three germ cell layers are acquired:
Induction
The process by which one part of an embryo causes adjacent tissues or parts to change form or shape, as by the diffusion of hormones or other chemicals.
Organogenesis
The process by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism.
Cleavage
The process of splitting, especially the repeated stages of cell division that produce a BLASTULA from an ovum that has been fertilized by a spermatozoon.
Dorsal Lip
The region in which gastrulation starts, where the cells will ultimately form the mesoderm and notochord.
Vegetal Pole
The relatively inactive part of an ovum opposite the animal pole, containing much yolk and little cytoplasm.
Placenta
The sac-shaped organ that attaches the embryo or fetus to the uterus during pregnancy in most mammals; supplies the fetus with oxygen and nutrients and is expelled after birth.
Cleavage
The series of mitotic cell divisions that produces a blastula from a fertilized ovum. It is the basis of the multicellularity of complex organisms.
Cleavage
The series of repeated mitotic cell divisions that occur in an ovum immediately after fertilization; transforms the single-celled zygote into a multicellular embryo capable of growth and differentiation.
Pluripotent
The source of embryonic stem cell lines; evident in the very early blastocoel.
Blastula
The spherical body produced by cleavage of a fertilized ovum; consists of a single layer of cells (blastoderm) surrounding a fluid-filled cavity (blastocoele).
Gastrula
The stage in the development of an EMBRYO following the BLASTULA stage when the ECTODERM, ENDODERM and primitive GUT have developed.
Organogenesis
The stage of human development during which the organs are formed; begins after gastrulation and is completed by the eight week of gestation.
Blastocyst
The state of the development of the embryo consisting of a double-layered sphere full of fluid.
Primitive Streak
The strip of cells in the early chick embryo through which mesodermal and endodermal cells invaginate during gastrulation; forms instead of the grey crescent.
Blastoderm
The thin, disc-shaped cell mass of a young embryo and its extraembryonic extensions over the surface of the yolk; when fully formed, all three primary germ layers (ectoderm, endoderm, and mesoderm) are present.
Fetus
The unborn young of a mammal at the later stages of its development, especially a human embryo from its eighth week of development to its birth.
Dorsal Lip
The upper edge of the blastopore produced by invagination during gastrula formation in amphibian embryos; the site toward which surface cells of the gastrula converge and migrate inward along the roof of the blastocoel in the process of involution.
Placenta
The vascular organ formed in the uterus during pregnancy, consisting of both maternal and embryonic tissues and providing oxygen and nutrients for the fetus and transfer of waste products from the fetal to the maternal blood circulation.
Placenta
The vascular structure in the uterus of most mammals providing oxygen and nutrients for and transferring wastes from the developing fetus.
Fetus
The young of an animal in the womb or egg, esp. in the later stages of development, in humans being after the end of the second month of gestation.
Primitive Streak
Thickened region from which endoderm and mesoderm are formed; forms instead of a gray crescent.
Cleavage
Unequal in eggs with more yolk, with very little cell division in the yolky region.
Gray Crescent
Were invagination will occur to begin gastrulation, forming the dorsal lip of the blastopore; this determines the dorsal-ventral axis of the embryo.
Gastrula
n embryo in the stage following the blastula stage; the simplest type consists of two layers of cells, the ectoderm and entoderm, which have invaginated to form the archenteron and an opening, the blastopore.