Extracellular matrix

Question 1

Describe the localisation of the ECM:

Answer 1

Found in all tissues, occupying the space outside of cells.
Organised into basement membranes (underlie epithelia) and interstitial matrix (fills spaces in connective tissues).

Question 2

Describe the origin of the ECM:

Answer 2

Secreted by resident cells in tissues:
Fibroblasts: Main producers in connective tissue.
Epithelial cells: Produce basement membrane components.
Chondrocytes and Osteoblasts: Specialized ECM production in cartilage and bone.

Question 3

What are the structural proteins involved in the ECM?

Answer 3

Collagen: Provides tensile strength; types:
Type I: Bone, skin, tendons.
Type II: Cartilage.
Type IV: Basement membranes.
Elastin: Provides elasticity, allowing tissues to stretch and recoil.

Question 4

What are the adhesive proteins involved in the ECM ?

Answer 4

Fibronectin: Binds cells to ECM via integrins, guides cell migration.
Laminin: Found in basement membranes, connects cells to Type IV collagen.

Question 5

Describe the hydrated matrix compounds:

Answer 5

Proteoglycans: Core protein + glycosaminoglycans (GAGs, e.g., hyaluronic acid).
Function: Hydration, resist compression, reservoir for growth factors.

Question 6

What are the functions of the ECM?

Answer 6

Structural support - provides a scaffold for tissue organisation, maintains tissue structure

Cellular regulation - modulates cell behaviour (proliferation, differentiation, migration), stores and presents growth factors

Mechanical properties - contributes to tissue stiffness, elasticity, and resistance to forces

Barrier function - Basement membranes act as selective barriers

Question 7

Describe the importance for tissue integrity:

Answer 7

Mechanical Stability: ECM and CAMs create a cohesive tissue framework.

Signal Transduction: ECM-cell adhesion regulates intracellular signalling.

Wound Healing and Development: Coordinated adhesion supports tissue remodelling and repair.

Question 8

Describe the cell adhesion molecules (CAMs)

Answer 8

Integrins: Mediate cell-ECM adhesion, link ECM to cytoskeleton.

Cadherins: Mediate cell-cell adhesion via adherens junctions.

Question 9

Describe the ECM turnover molecules:

Answer 9

Matrix Metalloproteinases (MMPs): Enzymes that degrade ECM components.

Tissue Inhibitors of Metalloproteinases (TIMPs): Regulate MMP activity.

Question 10

What are the dynamics of the ECM and Tissue Remodelling ?

Answer 10

ECM degradation → Cellular migration → ECM synthesis for tissue repair.