Lecture 1 Flashcards
zygote
single cell
development continues ________
throughout life
generate new blood cells, liver cells, etc
metamorphosis
larvae to adult
regeneration
replace amputated or removed organs or limbs
genomic (nuclear) equivalence
each cell has the same complement of DNA
totipotent stem cells
each cell has the ability to form the entire embryo plus fetal placenta
pluripotent stem cells
each cell has the ability to form all the embryonic structure
committed stem cells
can give rise to subsets of cell types
progenitor (precursor)
no longer stem cells
give rise to very specific types of cells yet can still be considered general
pluripotent stem cell form the
embryo
totipotent stem cells form the
embryo and fetal placenta
committed stem cells can give rise to
subsets of cell types
i.e. hemangioblasts- blood vessels blood cells and lymphocytes.
invagination occurs at
the vegetal pole
embryonic movement eventually lead to the formation of all three germs layers
endoderm, mesoderm, ectoderm
egg and sperm are
gametes
most animals have a clear separation of ______ and ______ early in development
germ cells, somatic cells
some animals ______ can become ______ even in adults
somatic cells can become germ cells
accessory cells
contribute to oogonium
primordial cells _________
make their way to the gonads, and are not formed there.
syngamy
sperm is in egg, but nuclei are not fused together yet
after meiosis 1
germinal vesicle
after meiosis 2
pronucleus
holoblastic cleavage
cells cleave completely into 2 cells
meroblastic cleavage
cells do not cleave completely
occurs in both telolecithal and centrolecithal eggs
eggs with yolk
cleave more slowly and unevenly
spermiogenesis
maturation of spermatids to spermatozoon
histones replaced by protamines
head of sperm contains
pronucleus, acrosome
midpiece of sperm contains
2 centrioles which are micro tubular organizing center for microtubules of flagella
also contain mitochondria
blastocoel
hollow section of blastula
blastula
hollow sphere formed by blastomeres surrounding blastocoel
types of cell division
holoplastic, meroblastic, superficial, radial, spiral
holoblastic cleavage
isolecithal and mesolecithal eggs
seen in species with low to moderate yolk content
radial cleavage
echinoderms and amphibians
spiral cleavage
annelids, mulluscs, and flatworms
has no blastocoel
bilateral cleavage
tunicates
rotational cleavage
mammals and nematodes
blastocoel formed by fluid secreted by trophoblasts
entire structure is called blastocyst
cleavage process controlled by
maternal effect factors
cleavage of an egg eventually forms a
blastula
128 cell stage
a blastula is formed
mammals can divide cells __________
assymetrically, (i.e. 2-3-4 cells) only mammals
spiral cleavage occurs in
snails
cleavage planes are at oblique angles to animal-vegetal axis
no blastocoel=
stereoblastula (in spiral cleavage)
blastocyst
mammalian equivalent of a blastula but is different because it has internal cells
discoidal (telolecithal) cleavage
fish reptiles and birds
superficial (centrolecithal) cleavage
most insects
birds cleavage
discoidal cleavage
restricted to small disc of yolk free cytoplasm
discoidal cleavage in egg forms
blastoderm
cells in center of blastoderm
area pellucida
1 cell thick
cells around center of blastoderm
area opaca
5-6 cells thick
new cells produced from the area opaque and pellucida form
lower layer called hypoblast
upper layer is epiblast
in between the two layers is blastocoel
single cell with multiple nuclei
syncytium
nuclei migrate to the cell surface and divide 2 more times producing
syncytial blastoderm
nuclei at the posterior end form membranes creating
pole cells
membranes form around pole cells producing
cellular blastoderm
superficial cleavage
multiple nuclei in a single cell form multiple cells along the membrane
no blastocoel
cellularization
the process by which cell membranes form around the nuclei
pattern of reaggregation
cells of embryo when scattered would realign to for the same layers as would typically be found in the embryo
convergent extension
simultaneous narrowing and lengthening of a sheet of cells. brought about by intercalation of cells
ingression
migration of individual cells from surface layer to the interior of embryo
invagination
movement of a sheet of cells into the interior of the embryo, forming a pocket which has an opening to the surface
involution
folding of a sheet of cells under itself. The sheet then spreads over the internal surface of the cells that remain on the outside.
epiboly
spreading of a sheet of cells to enclose underlying layers. It is brought about by increase in cell numbers (cell division) flattening of cells or intercalation of subsurface cells into the surface layer
delamination
splitting of a layer of cells into 2 layers
condensation
to form an aggregate is often a prelude to the formation of structures, for example the somites, or the skeletal elements of the limbs. Condensation arises partly by increased local cell division, partly by reduction of local matrix secretion, and partly by increased cell to cell adhesion
cavitation
a fluid-filled space can be hollowed out from a solid mass of cells by cell rearrangement, as in secondary neurulation, or by apoptosis of the cells in the interior
epithelial to Mesenchymal transitions
occur whenever cells leave an epithelium and move off as individuals or as a mesenchymal mass
planar cell polarity
acquisition of a polarity by cell in an epithelium in the direction of the plane of the epithelium
