L3- Integrating cells into tissues, organs and systems

Question 1

when do cells first coalesce (come together

Answer 1

during embryogenesis
o Spermatozoa penetrates the eggs and they fuse to make a single cell
o Occurs during the first stages of embryogenesis- blastocysts
 Cells divide into two distinct types
• Inner cell mass- becomes me
• Trophoblast- becomes placenta
 Cells then start to differentiate- becomes embryoblast

Question 2

what is the fate of the embryo blast?

Answer 2

inner cell mass becomes epiblast

cells around the edge become the hypoblast

Question 3

epiblast

Answer 3

all cells fo the body come from here (bilaminar disc will form from this)

Question 4

hypoblast

Answer 4

also forms bilaminar disc- feeds the epiblast

Question 5

definition of an organ

Answer 5

more than one tissue coming together to fulfil the same function

Question 6

what 4 factors hold cells together

Answer 6

• cell-cell adhesion molecules
• ECM proteins
• internal-external scaffolding
• close proximity

Question 7

nerves, lymphatics and blood vessels always found in

Answer 7

connective tissue layer

Question 8

no nerves found in

Answer 8

epithelium

Question 9

Connective tissue and epithelial tissue represent two extremes of organisation
- Main difference between them:

Answer 9

Connective tissue

• cells are sparsely distributed
• ECM is plentiful
• matrix rich in fibre polymer

Epithelial tissue

• Cells are tightly bound together into sheets called epithelia
• Extracellular matrix is scant- consisting mainly of a thin mat called the basal lamina, which underlies the epithelium
• Cell are attached to each other by cell-cell adhesions, which bear mechanical stresses

Question 10

primary cell of connective tissue

Answer 10

mesenchymal stem cells

Question 11

mesenchymal stem cells

Answer 11

• Can interconvert between several cell types

- Produces lots of extracellular fibres that anchor cells into place or make tissue

Question 12

mesenchymal stem cells produce

Answer 12

o Fibronectin
o Laminin
o Collagen

Question 13

epithelia cell sheets line

Answer 13

all cities and surfaces of the body

Question 14

specialised junctions between epithelial cells help to form a tissue barrier, inhibiting:

Answer 14

 Inhibiting movement of water, solutes and cells from one body compartment to another

Question 15

epithelial cells rest on a

Answer 15

supporting bed of connective tissue

- attaches epithelial layer to other tissues such as muscles

Question 16

cell adherence systems found on which surfaces

Answer 16

lateral

basal

Question 17

lateral surface specialisation

Answer 17

• Tight junctions
• Adherens junctions
• Desmosome
• Gap junction
• Cell adhesion molecules (integrin, selectin, CAM)

Question 18

basal surface specialisation

Answer 18

• Hemi-desmosome
• Focal adhesions
• Integrins
• Proteoglycans

Question 19

what’s found on the apical surface of epithelial cells

Answer 19

villi and cilia

Question 20

tight junctions

Answer 20

• near top of the cell

- prevent movement of large molecules into deeper tissue

Question 21

example of where tight junctions are very important

Answer 21

proximal convoluted tubule

Question 22

adheren junctions

Answer 22

Tissue stabilising factor and additional transport barrier

• found 1/3rd distance from apical surface
• found in pairs
• formed from intracellular actin filaments
• linked to E-cadherin proteins that cross the intercellular space

Question 23

desmosomes

Answer 23

provides mechanical strength

• Found half way down the lateral part of the cell
• cbtoketatin fibres intracellularly and E-cadherin inter cellularly

Question 24

where are desmosomes fond

Answer 24

in tissues that experience intense mechanical stress

o Cardiac muscle, bladder tissue, GI mucosa, epithelia and pregnant uterus

Question 25

gap junctions

Answer 25

allow movement of small molecules (sugar, ions and aa)- quickly communicate changes in the intercellular molecules composition

• found close to the base
• virtually all tissues have them except sperm, erythrocyte or developed skeletal muscle

Question 26

why are gap junctions important in smooth muscle

Answer 26

allows wave of electrical impulse

Question 27

gap junctions made of

Answer 27

connexins

- arranged in a hexagonal pattern that open and close (ATP_

Question 28

cell adhesion molecules

Answer 28

integrin
selectin
CAM

Question 29

focal adhesion

Answer 29

anchors action filaments to basal lamina

Question 30

hemi- desmosome

Answer 30

anchors intermediate filaments to basal lamina

- attached to laminin through integrins

Question 31

integrin

Answer 31

anchors actin filament to ECM

- signal transduction from ECM to cell

Question 32

membrane proteoglycans

Answer 32

major component of the ECM

• bid cations and water
• regulate movement of molecules through matrix