2.4: Tissue Morphogenesis

Question 1

define development

Answer 1

organism growth and change

Question 2

t/f is multicellular development an ongoing process (even in adults)

Answer 2

true, it still occurs in adults from stem cells + even completely new developmental processes can also be initiated in adults aka pregnancy

Question 3

which layer of the skin can be dubbed the stem cells on the skin and which are the connective tissue and epithelial of the skin

Answer 3

basal-cell layer is the stem cells. dermis is connective tissue and epithelial is epidermis

Question 4

describe the steps on how to get from egg to blastula, to gastrula in multicellular development during embryogenesis

Answer 4

fertilized egg –cleavage–> blastula –gastrulation–> gastrula
*gastrulation if the formation of the gut tube

Question 5

state the 3 key steps in the outline of multicellular development and morphogenesis

Answer 5

1. cell proliferation
2. cell differentiation
3. morphogenesis

Question 6

define morphogenesis and the 3 steps (+ their components)

Answer 6

morphogenesis = generation of shape
1. cell internationalization: ingression/delamination, invagination/involution
2. elongation: convergent extension, cell growth/cell division/and cell matrix deposition
3. fine repositioning of cells: migration of whole cells and migration of a cell extension

Question 7

which 3 key tissue layers are formed during gastrulation (morphogenesis)

Answer 7

ectoderm (epidermis and nervous system), mesoderm (muscles, connective tissue, bones, blood, kidneys, etc), endoderm (gut, lungs, pancreas, liver, etc)

Question 8

define gastrulation

Answer 8

change from ball of cells to embryo with a gut and 3 germ layers (ectoderm, mesoderm, endoderm)

Question 9

how is the mesoderm formed from the blastomeres in gastrulation

Answer 9

cell internalization by ingression (moving inwards)/delamination (forming into layers)

Question 10

the ectoderm, mesoderm, and endoderm are made from which types of cells

Answer 10

blastomeres (ecto are the cells that stay put, meso are the ones crawling around the inner surface, endo is the indented lining)

Question 11

explain the ingression and delamination processes in gastrulation

Answer 11

ingression: individual cells detach from the outer cell layer and migrate in (this is an epithelial to mesenchymal transition)
*mesenchymal is the loose, undifferentiated, connective tissue
delamination: these cells form a new layer = mesoderm

Question 12

t/f do epithelial to mesenchymal transition need to be carefully controlled

Answer 12

true - they might become cancer

Question 13

describe the process of how the endoderm arises from blastomeres through gastrulation

Answer 13

cell internalization by invagination (making cavity/pouch)/involution (curling inward) form the endoderm. attached cells in an epithelial cell sheet are pulled into the middle of the embryo while remaining attached (invagination) and these cells curl in and grow (involution) to form the endoderm.

Question 14

invagination of epithelial sheet is caused by what

Answer 14

caused by a organized tightening along adhesion belts in selected regions of cell sheets

Question 15

the vertebrate neural tube forms via which processes

Answer 15

invagination/involution

Question 16

explain the formation of the vertebrate neural tube

Answer 16

• the vertebrate neural tube forms via invagination/involution.
• upstream developmental signals instruct specific cells to differentiate from ectoderm to neural plate cells
• neural crest plate invaginate to form the neural tube
• instructions include differential gene expression (eg different cadherins)

Question 17

regarding vertebrate neural tube, the neural tube becomes what ? and the neural crest tails becomes ?

Answer 17

the neural tube becomes brain or spinal cord and the neural crest tails becomes peripheral nervous system

Question 18

Which of the following statements made by (imaginary) BIO230 students is
not true?
a) “Formation of the neural tube uses invagination, but formation of the gut
tube does not.”
b) “Tissues with high cellular turnover typically also have molecular
turnover.”
c) “Some cells do differentiate in adults.”
d) “Development occurs throughout all phases of life, including during
adulthood.”

Answer 18

A.
It does, the part where it says “does not” is wrong

Question 19

state the 2 steps of convergent extension

Answer 19

1. cell converge (pile up in the middle), or crawl together
2. cells extend of form a line (from the pile)

Question 20

list how elongation can occur

Answer 20

convergent extension, mass cell migration, cell growth, division, matrix deposition, directional expansion
*cell growth, division, matrix deposition must be asymmetric

Question 21

describe how mass cell migration can lead to elongation

Answer 21

cells can move as individuals or as a group to form different shapes, called collective cell migration.
chain type migration involves cell adherent cells (not stuck together)
sheet type migration involved more adherent cells
cluster cells are the in between form

Question 22

what are the 3 forms of mass cell migration and what process does it lead to

Answer 22

1. chain
2. cluster
3. sheet
   they lead to elongation

Question 23

what condition must be met for cell elongation to occur from cell growth, division, matrix deposition

Answer 23

the processes must be asymmetric

Question 24

state the process of how plant cells often grow

Answer 24

directional expansion

Question 25

describe how plant cells grow

Answer 25

they grow through directional expansion. the cell wall is an ecm made of polysaccharides - cellulose (a polysacc( can be asymmetrically distributed in the plane cell wall. cellulose constricts plan cell expansion forcing expansion in one direction = elongation. the plant cell wall seposition is guided by microtubules (uses udp gluc as energy_

Question 26

depending on _________, it affects the alignment of cellulose synthase complex which makes many cellulose molecules and assembles them into a micrfibril

Answer 26

microtubules

Question 27

disorganized _________ will disrupt plan cell elongation

Answer 27

microtubules

Question 28

describe disorganized vs organized microtubules in plant cell organization

Answer 28

disorganized microtubules (=disorganized cellulose) will disrupt plan cell elongation by having no directional elongation and just lead to cell swelling. organized microtubles (organized cellulose) leads to turgor pressure and directional elongation

Question 29

cerebral cortex cells (outer layer of brain made of many layers) are repositioned by ___________________

Answer 29

whole cell migrations - the first born neurons (older) are deeper in and newer ones at the surface)

Question 30

describe the repoisitioning of cerebral cortex cells

Answer 30

cerebral cortex cells are repositioned by whole cell migrations. whole cells migrate to the tip of the radial glial cells; the neurons from the dividing progenitor cell run up the radial glial cell to the top layer. first born neurons are in the deeper layer and last born are in eh outer layer.

Question 31

______ are positioned by migration of cell extension - attractants direct the extensions of the growth cone in a particular direction

Answer 31

axons

Question 32

what directs the extensions of the growth cone in a particular direction in regards to neural growth

Answer 32

attractants (similar to rac rho signalling for neutrophils but with diff specifics)

Question 33

Which morphogenesis process is correctly matched with the example
developmental process?
a) Cell division & cell shape change – neural tube formation
b) Convergent extension – plant cell elongation
c) Ingression/delamination – cerebral cortex development
d) Invagination/involution – gastrulation

Answer 33

D.
A is wrong bc its invagination/involution. B is wrong bc it’s directional expansion (like slinky). C is wrong bc it’s whole cell migrations.