Bio Ch 42 Flashcards
Fertilization
union of a sperm and an egg to form a zygote
Development
includes all the changes that occur during the life cycle of an organism
Embryo
during the early stages of development, an organism is called this
Cleavage
cell division without growth
Morula
solid ball of cells
Blastula
hollow ball of cells having a fluid-filled cavity (blastocoel)
Blastocoel
fluid-filled cavity in the blastula
Yolk
dense nutrient material in a hard-shelled egg
Gastrulation
tissue stages of development involve the formation of a gastrula
Gastrula
forms from the blastula; 2 stages - early and late
Ectoderm
outer layer of cells
Endoderm
inner layer of cells
Blastopore
pore/hole created by invagination
Mesoderm
in addition to ectoderm and endoderm, the late gastrula has a middle layer of cells called this
Germ layers
ectoderm, mesoderm, and endoderm are called the embryonic ____ ______
Notochord
newly formed mesoderm cells lie along the main longitudinal axis of the animal and coalesce to form this dorsal supporting rod
Neural plate
thickening of cells first seen along the dorsal surface of the embryo
Neural tube
neural folds develop on either side of the neural groove, which becomes this when these folds fuse
Cellular differentiation
occurs when cells become specialized in structure and function
Morphogenesis
produces the shape and form of the body; one of the earliest indicators is cell movement
Pattern formation
how tissues and organs are arranged in the body
Apoptosis
programmed cell death
Totipotent
having the ability to generate the entire organism, and therefore must contain all the instructions needed by any other specialized cell in the body
Maternal determinants
egg is known to contain these substances in the cytoplasm which influence the course of development
Cytoplasmic segregation
parceling out of maternal determinants as mitosis occurs
Induction
ability of one embryonic tissue to influence the development of another tissue
Homeotic genes
selector genes that select for segmental identity (dictate which body parts arise from the segments)
Homeobox
homeotic genes have all been found to share a structural feature called this; a sequence of nucleotides that encodes a 60-amino acid sequence (homeodomain)
Homeodomain
a 60-amino acid sequence encoded by a homeobox
Embryonic development
1st part of human development when major organs are formed
Extraembryonic membranes
membrane that is not a part of the embryo but is necessary to the continued existence and health of the embryo
Chorion
egg membrane lying next to the shell; carries on gas exchange
Amnion
egg membrane containing the protective amniotic fluid, which bathes the developing embryo
Allantois
part of the egg that collects nitrogenous wastes
Yolk sac
part of the egg that surrounds the remaining yolk, which provides nourishment
Blastocyst
fluid-filled cavity with a single layer of outer cells (trophoblast), and an inner cell mass
Trophoblast
single layer of outer cells of a blastocyst that provides nourishment for the embryo
Implantation
at the end of the 1st week, the embryo begins this process in the wall of the uterus
Human Chorionic Gonadotropin (HCG)
trophoblast secretes this hormone that is the basis for the pregnancy test and that serves the maintain the corpus luteum past the time it normally disintegrates
Embryonic disk
inner cell mass has flattened into this during the 2nd week of pregnancy; composed of 2 layers of cells (ectoderm and endoderm); elongates to form the primitive streak
Chorionic villi
treelike projections of the chorion
Umbilical cord
connects the developing embryo to the placenta
Placenta
mammalian structure that functions in gas, nutrient, and waste exchange between embryonic and maternal cardiovascular systems
Menopause
period in a woman’s life during which the ovarian and uterine cycles cease; usually occurs between ages 45 & 55
