PHYSIO

Question 1

Cell Junctions I covers which main types?

Answer 1

(Communicating/Gap/Nexus) and Anchoring (Spot/Macula & Zonula)

These types categorize junctions based on their functions and structures.

Question 2

Cell Junctions II covers which main type?

Answer 2

Occluding/Tight

This type is crucial for sealing spaces between cells.

Question 3

List the 5 key junction terms from the title slide.

Answer 3

• Tight
• Adherens
• Desmosomes
• Gap/Nexus
• Hemidesmosomes

These terms represent the main types of cell junctions.

Question 4

Main learning outcome 1?

Answer 4

Relate the structure of communicating and anchoring cell junctions with their functions.

Question 5

Main learning outcome 2?

Answer 5

Relate the structure of gap and occluding junctions with their functions.

Question 6

Each cell is surrounded by?

Answer 6

extracellular space

Question 7

In epithelium & other closely packed tissues, intercellular gap is only?

Answer 7

20 nm

Question 8

Two forces holding cells together?

Answer 8

• Mutual force of cohesion
• Cell junctions (specialized structural arrangements)

These forces are essential for maintaining tissue integrity.

Question 9

Cell junctions are classified based on two main factors?

Answer 9

• Shape & extent of contact area
• Relative closeness & nature of cell contact

These classifications help in understanding the functional roles of junctions.

Question 10

Shape & extent of contact area - limited extent example?

Answer 10

MACULA (spot / punctate area)

Question 11

Shape & extent of contact area - around entire cell example?

Answer 11

ZONULA (belt / girdle like)

Question 12

No intercellular space, membranes fused?

Answer 12

OCCLUDENS (Tight junction / Zonula occludens)

Question 13

Intercellular space 20-25 nm wide with dense granular material in space & on cytoplasmic surfaces?

Answer 13

ADHERENS

Question 14

Very narrow intercellular space = 3 nm?

Answer 14

GAP junctions

Question 15

4 Types of Cell Junctions (list them)?

Answer 15

• Macula Adherens (Desmosome or Spot Desmosome)
• Zonula Adherens (Belt Desmosome)
• Zonula Occludens (Tight Junction)
• Gap Junction (Nexus)

These types reflect the diversity of junctional structures and functions.

Question 16

In zonula occludens, what happens to outer laminae of opposed membranes?

Answer 16

They fuse

Question 17

Zonula occludens and zonula adherens form what around cell apex?

Answer 17

continuous ribbon

Question 18

Desmosomes and gap junctions are?

Answer 18

spot-like plaques

Question 19

Infoldings of membrane and microvilli do what?

Answer 19

amplify membrane area, increase exchanges across membrane and adhesion between cells

Question 20

Macula Adherens (Desmosome) location?

Answer 20

Between epithelial cells, lateral interfaces, long axes perpendicular to basement membrane

Question 21

Macula Adherens shape?

Answer 21

Small discoid structures

Question 22

Macula Adherens intercellular gap?

Answer 22

25 nm

Question 23

Macula Adherens adhesive glycoprotein?

Answer 23

Desmocollin

Question 24

Macula Adherens intra-cytoplasmic densities?

Answer 24

Attachment plaques beneath plasma membranes of adjacent cells

Question 25

Macula Adherens intermediate filaments?

Answer 25

Inserted into attachment plaque or make hairpin loops & turn back into cytoplasm

Question 26

Hemidesmosomes location?

Answer 26

Between certain epithelial cells & basal lamina

Question 27

Hemidesmosomes shape?

Answer 27

Like half a desmosome on epithelial plasma membrane only (sometimes basal lamina thickened)

Question 28

Hemidesmosomes function?

Answer 28

Bind epithelial cells to basal lamina

Question 29

Zonula Adherens arrangement?

Answer 29

Girdle / belt around each joined cell

Question 30

Zonula Adherens intercellular gap?

Answer 30

Normal width (20 nm)

Question 31

Zonula Adherens bridging of gap?

Answer 31

No bridge of filaments, but hooks; filaments & sub-membrane cytoplasmic densities present

Question 32

Zonula Adherens location?

Answer 32

Among epithelial cells, fibroblasts & smooth muscle cells

Question 33

Zonula Occludens arrangement?

Answer 33

Like a girdle

Question 34

Zonula Occludens intercellular gap?

Answer 34

No gap (apparent fusion of plasma membranes)

Question 35

Zonula Occludens main locations?

Answer 35

Intestinal mucosa, urinary bladder mucosa, kidney

Question 36

Zonula Occludens function?

Answer 36

Important sealing effect (prevents change in urine composition or urine leakage into ECF)

Question 37

Gap Junction (Nexus) intercellular gap?

Answer 37

2-3 nm only, traversed by hollow tube-like structures (connexons)

Question 38

Gap Junction main function?

Answer 38

Provide communication channels between adjacent cells; permeable to colloidal substances without entering ECF

Question 39

Gap Junction allows?

Answer 39

Bidirectional spread of electric impulse from cell to cell (smooth / cardiac muscle)

Question 40

Desmosomes vs Nexus attachment?

Answer 40

Nexus usually limited plaques like desmosomes, but sometimes more extensive

Question 41

Gap junction protein units?

Answer 41

Connexons – hexagonal arrays of 6 subunits surrounding a channel

Question 42

Regulators of gap junction channel diameter?

Answer 42

* Increase in Ca²⁺ concentration (subunits slide together, reduce diameter) * pH * Voltage ## Footnote These factors influence the permeability of gap junctions.

Question 43

Gap junctions found in (examples)?

Answer 43

* Cardiac myocytes * Neurons * Cardiac & smooth muscle * Liver * Kidney * Thyroid * Pancreas * Adrenals * Urinary bladder * Nervous system (neurons & glia) * Skin ## Footnote These locations highlight the importance of gap junctions in various tissues.

Question 44

Junctional Complex comprises?

Answer 44

Zonula occludens + Zonula adherens + Macula adherens

Question 45

Junctional Complex typical location?

Answer 45

Small intestinal mucosa (between adjacent epithelial cells)