Cell Adhesion I - Keeping cells together

Question 1

What is the main stress bearing component of epithelial tissue?

Answer 1

Cell cytoskeletons

Cell-cell and cell-matrix junctions

Question 2

What is the main stress bearing component of connective tissue?

Answer 2

Extracellular matrix

Question 3

What is epithelial tissue?

Answer 3

Tissue that lines body surfaces, cavities and tubes

Supported by an underlying basement membrane

Question 4

What type of junctions are contained within epithelial tissue?

Answer 4

Desomsomes

Hemidesomosomes

Question 5

How is epithelial tissue classified?

Answer 5

1. Number of cell layers - Simple, Pseudostratefied, stratified
2. Cell shape - Squamous, Cuboidal, columnar
3. Presence of surface specialisations - Keratinisation, microvilli

Question 6

What are the distinguishing features of epithelial cells?

Answer 6

Apical surface is free
Basal surface is attached to BM
Lateral surfaces adhere to neighbouring cells
Polarised morphology
Presence of specialised cell-cell junctions

Question 7

What are the various cell-cell and cell-matrix junctions?

Answer 7

Tight junctions - Boundary between apical and basal domain

Cell-cell:
Adherens junctions
Desmosomes

Cell-matrix:
Hemidesmosomes
Focal adhesions

Question 8

What do cell-cell junctions do?

Answer 8

Rivet cells together

Question 9

What do cell-matrix junctions do?

Answer 9

Rivet the cells to the basement membrane

Question 10

What is the cell-cell and cell-matrix junctions important for?

Answer 10

Maintaining tissue integrity

Question 11

What are the components of the cytoskeleton?

Answer 11

Actin microfilaments - cell migration

Microtubules - Cell division

Intermediate filaments - maintaining tissue integrity

Question 12

What are the 3 major types of intermediate proteins and what cell types are they found on?

Answer 12

Keratin - Epithelial cells

Vimentin - Mesenchymal cells

Desmin - Myocardial cells

Question 13

What are keratin intermediate filaments?

Answer 13

Assemble into heterodimers of type 1 (acidic) and type 2 (basic) keratins

Keratin IFs associate with desmosomes in epithelial cells

Question 14

What is the structure of the skin?

Answer 14

Epidermis - stratified keratinised epithelium

Dermis - dense fibroelastic connective tissue

Hypodermis - Loose fibro-fatty connective tissue

Question 15

What are some epidermal appendages?

Answer 15

Hair follicles
Sebaceous glands
Sweat glands

Question 16

What are the layers of the epidermis?

Answer 16

4 layers:
Stratum corneum
Granular
Spinus
Basal

Question 17

What are the cell types found in the epidermis?

Answer 17

Keratinocytes (>90%)
Mealnocytes
Langerhans cells

Question 18

What is the purpose of the epidermis?

Answer 18

Prevents microbial invasion and loss of water (barrier function)

Essential for survival

Question 19

What are desmosomes?

Answer 19

Mediate cell-cell adhesion

Anchor keratin intermediate filaments into the membrane

Question 20

What are desmosomes made up of?

Answer 20

Desmocollins & Desmogleins - Membrane spanning proteins

Plakoglobin & Plakophilin - Cytoplasmic proteins

Desmophakin - links structure to cytoskeleton

Question 21

What are the desmosomal cadherin families?

Answer 21

Desmocollins - DSC1, DSC2, DSC3

Desmogleins - DSG1, DSG2, DSG3, DSG4

(all 7 act in the epidermis)

Question 22

What desmosomal cadherin family act in the upper layers of the epidermis?

Answer 22

DSC1 and DSG1

Question 23

What desmosomal cadherin family act in the lower layers of the epidermis?

Answer 23

DSG3 and DSC3

Question 24

What is pemphigus?

Answer 24

An autoimmune (acquired) blistering disease caused by defective cell-cell adhesion

Question 25

What are the 2 types of pemphigus?

Answer 25

Pemphigus foliaceus | Pemphigus Vulgaris

Question 26

What is Pemphigus foliaceus?

Answer 26

Autoantibodies targeting DSG1 (upper epidermis) causing blistering in the upper epidermis. Good prognosis

Question 27

What is Pemphigus Vulgaris?

Answer 27

Autoantibodies target DSG3 (lower epidermis) Blistering in lower epidermis epidermis is severely compromised poor prognosis Almost always fatal if untreated due to fluid loss and infection

Question 28

Where are hemisdesmosomes found?

Answer 28

Mediate cell-matrix adhesion | found at the basal surface of the basal layer cells

Question 29

What do hemidesmosomes do?

Answer 29

Interact with keratin IFs anchoring them to the basement membrane in the cell Also interact with laminin-5 out of the cell

Question 30

What is the basement membrane?

Answer 30

Underlies all epithelial tissue | Not vascularised

Question 31

What are the components of the basement membrane?

Answer 31

Laminin | Collagen IV

Question 32

What is laminin?

Answer 32

Consist of 3 chains (alpha, beta, gamma) arranged in an asymmetric cross Contain collagen and cell binding domains

Question 33

What does laminin do?

Answer 33

Contributes to organising the matrix and helping cells attach to it

Question 34

What is collagen?

Answer 34

Most abundant protein in mammals | Found in the BM and connective tissue

Question 35

What is the structure of collagen?

Answer 35

3 alpha chains forming a triple helical structure Helices form fibrils Fibrils form collagen fibres

Question 36

What is the hemidesmosome composition?

Answer 36

Alpha 6 beta 4 integrin BPAG1/2 (bullous pemphigoid antigen 1/2) Plectin

Question 37

What is epidermolysis bullosa?

Answer 37

A family of genetic (inherited) blistering diseases of the skin caused by defective cell-ECM adhesion

Question 38

What are the 3 types of EB?

Answer 38

EB simplex Junctional EB Dystrophic EB

Question 39

What is EB simplex?

Answer 39

Tissue separation of the epidermis (basal) Generally localised to hands and feet Mutation in keratin 5, BPAG1, a6b4 integrin

Question 40

What is Junctional EB?

Answer 40

Tissue separation of the basement membrane Patients have large areas of body devoid of skin due to blistering Mutation in Laminin5, BPAG2, a6b4

Question 41

What is Dystrophic EB?

Answer 41

Tissue separation in upper epidermis Repeated blistering and scarring throughout life. Join contractures and fusion of digits Mutation in Collagen VII