Lecture 24: Gastrulation

Question 1

gastrulation

Answer 1

formation of the endoderm, mesoderm, and ectoderm from epiblast and hypoblast, axes development also occurs at this time

Question 2

ingression

Answer 2

movement of cells from the outside to the inside of the embryo, AKA epithelial to mesenchymal transformation

Question 3

invagination

Answer 3

cells fold inward

Question 4

involution

Answer 4

cells folding over each other

Question 5

spreading/convergent extension

Answer 5

cells move into a narrow line, helps lengthen the tissue, move it forward, or form tubular structures, process occurs via cell surface lampellipodia

Question 6

bilaminar disc

Answer 6

contains an epiblast and hypoblast layer, also has buccopharyngeal membrane and cloacal membrane

Question 7

buccopharyngeal membrane

Answer 7

forms into mouth

Question 8

cloacal membrane

Answer 8

forms into anus

Question 9

gastrulation process

Answer 9

1.) cells from epiderm ingress through primitive streak to form the definitive endoderm 2.) ingresssing cells replace the hypoblast 3.) once suffice definitive endoderm cells have ingressed, the ingressing cells form the mesoderm 4.) mesodermal cells migrate via spreading convergent extension after leaving the primitive streak 5.) cells with different cranial/caudal positions who leave the primitive streaks have different fates

Question 10

hyaluronic acid

Answer 10

prevents mesodermal cells from clumping together

Question 11

morphogenesis

Answer 11

process by which tissue and organs form

Question 12

ectoderm

Answer 12

skin and nervous system

Question 13

mesoderm

Answer 13

muscle, bone, blood

Question 14

endoderm

Answer 14

guts, lungs, liver, pancreas

Question 15

differentiation

Answer 15

occurs at the level of CELLS (process by which cells take on their separate identity)

Question 16

morphogenesis

Answer 16

occurs at the level of TISSUES (process the gives rise to the shape and form of tissue and organs)

Question 17

ingression

Answer 17

involves the movment of single cells away from a surface layer into the interior of the embryo

Question 18

germ disk

Answer 18

embryonic stage around 2 weeks that consists of the epiblast (blue) and hypoblast (yellow); bilaminar aka two layer disk

Question 19

buccopharngyal membrane

Answer 19

form the mouth and oral cavity at the cranial (head) region of the embryo

Question 20

cloacal membrane

Answer 20

region where epiblast and hypoblast fuse to form the anus at the caudal end of the embryo

Question 21

primitive groove

Answer 21

the furrow extending the length of the streak

Question 22

primitive node

Answer 22

raised circle of cells at the cranial end

Question 23

primitive pit

Answer 23

depression in the center of the primitive node

Question 24

extraembryonic mesoderm

Answer 24

forms prior to gastrulation and forms the amnion, chorion, and yolk sac

Question 25

embryonic mesoderm

Answer 25

forms the embryo proper as a result of gastrulation

Question 26

process of gastrulation

Answer 26

The epiblast cells will first ingress form endoderm, with subsequent ingression and spreading to fill in and form mesoderm

Question 27

hyaluronic acid

Answer 27

Epiblast cells will secrete hyaluronic acid into the space between the ectoderm and endoderm, which is important to prevent mesoderm from aggregating

Question 28

fibronectin

Answer 28

on the basal side of the ectoderm help mesoderm to migrate

Question 29

cilia

Answer 29

on ectoderm near the primitive node help the mesoderm cells to migrate

Question 30

Kartagener’s syndrome

Answer 30

cilia on the ectoderm near the primitive node cannot form the proper current necessary for the distribution of intercellular molecules. Dysfunction dynein arms on the cilia will present this syndrome.Leads to situs inverstus of embryonic lethality

Question 31

Cells that move CRANIAL from the primitive node form:

Answer 31

Prechordal plate and notochord

Question 32

prechordal plate

Answer 32

thickening of hypoblast and mostly mesoderm rostral to the notochord, crictical for formation of forebrain

Question 33

notochord process

Answer 33

extends caudally from prechordal plate and primitive streak regresses simultaneously

Question 34

notochordal plate

Answer 34

the notochord process fuses with the | definitive endoderm for about a day

Question 35

neurenteric canal

Answer 35

one side of the notochordal plate is exposed to the fluid of the definitive yolk sack while the other side sees cells

Question 36

notochord

Answer 36

tissue then involutes and lifts off the endoderm to form a column of cells, no cells like notochord process

Question 37

neural plate

Answer 37

prechordal plate and notochord will induce overlying ectoderm on the dorsal side to become neural precursor cells

Question 38

neural tube

Answer 38

prechordal plate and notochord signal overlying ectoderm to invaginate to form neural grooves and neural folds, eventually forms neural tube, which is the basis for the spinal chord *neural groove forms basis for neural tube*

Question 39

extracellular matrix induction

Answer 39

one cell touches another indirectly through extracellular matrix, causing integrins in the affected cell to become active.

Question 40

direct cell induction

Answer 40

the cells are directly touching each other

Question 41

diffusion of a morphogen

Answer 41

secreted morphogen from one cell is picked up by another