Ch 47 Ap Bio

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acrosomal reaction

Back 1

acrosomal enzyme from sperm digesting egg gel coating

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allantois

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A membranous sac that develops from the posterior part of the alimentary canal in the embryos of mammals, birds, and reptiles. It is important in the formation of the umbilical cord and placenta in mammals

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amnion

Back 3

A thin, tough, membranous sac that encloses the embryo or fetus of a mammal, bird, or reptile. It is filled with a serous fluid in which the embryo is suspended

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amniotes

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Any of a group of vertebrates that have an amnion during embryonic development, including reptiles, birds, and mammals

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animal pole

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the point on the surface of an egg that is diametrically opposite to the vegetal pole and usually marks the most active part of the protoplasm or the part containing least yolk

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archenteron

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The central cavity of the gastrula, which ultimately becomes the intestinal or digestive cavity

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blastocoel

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The fluid-filled, central cavity of a blastula

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blastocyst

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The modified blastula that is characteristic of placental mammals

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blastodisc

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the embryo-forming portion of an egg with discoidal cleavage usually appearing as a small disc on the upper surface of the yolk mass

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blastomeres

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Any of the cells resulting from the cleavage of a fertilized ovum during early embryonic development

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blastopore

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The opening of the archenteron

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blastula

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An early embryonic form produced by cleavage of a fertilized ovum and consisting of a spherical layer of cells surrounding a fluid-filled cavity

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cadherins

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A group of functionally related glycoproteins responsible for the calcium-dependent cell-to-cell adhesion mechanism

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chorion

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The outer membrane enclosing the embryo in reptiles, birds, and mammals. In placental mammals it contributes to the development of the placenta

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cleavage

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The series of mitotic cell divisions that produces a blastula from a fertilized ovum. It is the basis of the multicellularity of complex organisms

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cortical reaction

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realease of Ca upon sperm fusion, cause cortical granules to realease compounds and harden gell coat

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dorsal lip

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the margin of the fold of blastula wall that delineates the dorsal limit of the blastopore

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ectoderm

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The outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue, and, in vertebrates, sense organs develop

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endoderm

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The innermost of the three primary germ layers of an animal embryo, developing into the gastrointestinal tract, the lungs, and associated structures

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epigenesis

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The theory that an individual is developed by successive differentiation of an unstructured egg rather than by a simple enlarging of a preformed entity

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fast block to polyspermy

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Change in membrane potential caused by sperm binding

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gastrula

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An embryo at the stage following the blastula, consisting of a hollow, two-layered sac of ectoderm and endoderm surrounding an archenteron that communicates with the exterior through the blastopore

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gastrulation

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The process of forming a gastrula

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holoblastic cleavage

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characterized by cleavage planes that divide the whole egg into distinct and separate though coherent blastomeres

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inner cell mass

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The mass at the embryonic pole of the blastocyst concerned with the formation of the body of the embryo

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invagination

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The infolding of a portion of the outer layer of a blastula in the formation of a gastrula

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involution

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The ingrowth and curling inward of a group of cells, as in the formation of a gastrula from a blastula

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meroblastic cleavage

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characterized by or being incomplete cleavage as a result of the presence of an impeding mass of yolk material

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mesoderm

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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

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morula

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The spherical embryonic mass of blastomeres formed before the blastula and resulting from cleavage of the fertilized ovum

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neural tube

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A dorsal tubular structure in the vertebrate embryo formed by longitudinal folding of the neural plate and differentiating into the brain and spinal cord

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notochord

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a flexible rodlike structure that forms the supporting axis of the body (spinal cord) in the lowest chordates and lowest vertebrates and in embryos of higher vertebrates

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organogenesis

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The formation and development of the organs of living things

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preformation

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A theory popular in the 18th century that all parts of an organism exist completely formed in the germ cell and develop only by increasing in size.

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primitive streak

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an elongated band of cells that forms along the axis of an embryo early in gastrulation by the movement of lateral cells toward the axis and that develops a groove along its midline through which cells move to the interior of the embryo to form the mesoderm

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slow block to polyspermy

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harden gell coat, called fertilization membrane, preventing polyspermy

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somites

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A segmental mass of mesoderm in the vertebrate embryo, occurring in pairs along the notochord and developing into muscles and vertebrae

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trophoblast

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The outermost layer of cells of the blastocyst that attaches the fertilized ovum to the uterine wall and serves as a nutritive pathway for the embryo

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vegetal pole

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The portion of an egg that is opposite the animal pole and that contains most of the yolk

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yolk

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nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)

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yolk plug

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a mass of yolk cells found in the blastopore of the embryos of some vertebrates

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yolk sac

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A membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals and functioning as the circulatory system of the human embryo before internal circulation begins

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zona pellucida

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The thick, solid, transparent outer membrane of a developed mammalian ovum