Chapter 4-6 Flashcards
The series of divisions of the early embryo is called
Cleavage
The resulting cells are called
blastomeres and blastoderm
What type of cleavage has animal and vegetal poles?
Meroblastic
contains a little yolk material that undergo the segmentation division first
Animal pole
contains much of the yolk material which is the last to be segmented.
Vegetal pole
Types of yolks Based on the amount of yolk
• Oligolecithal/miolecithal
• Mesolecithal/medialecithal
• Polylecithal/megalecithal
Types of yolks Based on the distribution of yolk
• Isolecithal
• Centrolecithal
• Telolecithal
Commonly called “ball of cells”, after the Latin name for mulberry. Cellular mass of the embryo occupies most of the perivitelline space.
Morula
form tight junctions destined to become trophoblast or trophoectoderm
Outer blastomeres
form gap junctions destined to become inner cell mass
Inner blastomeres
when water osmotically flow inside, fluid accumulates making some of the blastomeres flattened and a cavity is formed called blastocoele.
Early Blastocyst
The outer cells become the trophoblast and the inner cells are destined to be the _____ that becomes the embryonic disc. Still the embryo is confined inside the zona pellucida.
inner cell mass (ICM)
diameter of the embryo dramatically increased with concurrent thinning of the zona pellucida.
Expanded blastocyst
is best done on blastocyst stage (early to expanded blastocyst).
Embryo Transfer (ET)
zona pellucida ruptures, blastocyst leaves the zona pellucida and attaches (adheres) to the uterine mucosa, followed by the implantation/nidation and placentation of the embryo.
Hatching blastocyst
Other term for inner cell sheet
Hypoblast
ICM differentiates into two cell populations:
Hypoblast and epiblast
Blastocyst Elongation- varies among species of animals:
marked round to oval expansion of the blastocyst
Horses, dogs, cats and rabbits
Blastocyst Elongation- varies among species of animals
marked thread-like expansion
Cattle, sheep, pig-
Blastocyst Elongation- varies among species of animals
little expansion occurs because blastocyst invades the endometrium
Primates, rodents, guinea pigs
Consists of a thin layer of cells and overlies the subgerminal cavity and with no yolk material attached
Area pellucida
Consists of a layer of large cells and overlies the unaltered yolk
Area opaca
comes from a greek term “Gaster” which mean “stomach
Gastrulation
It is a developmental stage in placental mammals which begins with the formation of ____?
primitve streak
outer layer gives rise to the epidermis and nervous system, and connective tissue of the head
Ectoderm
inner layer gives rise to the primitive gut or “archenteron” , (gk.
Arche, “origin”, enteron “gut”.
Endoderm
divides into paraxial or dorsal mesoderm, intermediate mesoderm and lateral mesoderm.
Mesoderm
gives rise to the vertebral bones muscles and skeletal connective tissues of the trunk;
paraxial mesoderm
Gives rise to the urogenital system, heart and blood vessels
intermediate mesoderm
subdivides into lateral and splanchnic mesoderm and a cavity in between called coelom.
lateral mesoderm
In avian, development starts in a whitish disc area on the surface of the yolk called ___?
blastodisc/ embryonic disc/ germinal disc.
During gastrulation the central portion of the blastoderm, the area pellucida is separated from the yolk via
subgerminal cavity
A cavity between hypoblast and epiblast?
blastocoele
gives rise to the three germ layers
Epiblast
gives rise to extraembryonic endoderm.
hypoblast
Within the posterior half of the epiblast, cells rearrange by moving first to the caudal midline and then anteriorly forming a fountain like flow and the cells which aggregate into solid median ridge is called the
primitive streak
the epiblast assumes a pear shape. The stage of embryo development then is called
primitive streak stage.
As primitive streak elongates, a furrow called
primitive groove
Terminate anteriorly in a thickening
Primitive ridge/hensen’s node
The node has a funnel shape depression, called
primitive pit
Organ development
organogenesis
Is an example of organogenesis marked by the establishment of the CNS, initial development of the gut and heart and the segmentation of the paraxial mesoderm At this stage the body of the embryo begins to delienate from the three germ layers.
Neurulation
There are two major ways of forming a neural tube
Primary and Secondary neurulation
is first indicated by thickening (columnation of cells ) of the surface ectoderm along the dorsal midline called neural plate. This is then followed by infolding (depressed) at the midline to form the neural groove causing a slight elevation on either side of the neural folds. Subsequently, neural folds converge, meet and fuse towards the dorsal midline to form the neural tube.
Primary nerulation
formation of the neural tube in the posterior portion is without folding
secondary neurulation
The cells which are not incorporated during the closure of the neural tube are called
neural crest cells.