Chapter 17: Cell Communties: Tissues

Name the four major types of tissues in veterbrates

1. Epithelial tissue

2. Connective tissue

3. Muscular tissue

4. Nervous tissue

Describe cell-cell adhesion and cell matrix adhesion and their roles in tissue formation.

Cell-cell adhesion: Cells attach to each other through cell junctions using CAMs, helping form cohesive tissue layers and allowing communication between neighboring cells.
Cell-matrix adhesion: Cells attach to the extracellular matrix (ECM) using integrins, anchoring cells to the basal lamina and allowing them to sense/respond to the ECM.
Together, these adhesions integrate cells into tissues, provide mechanical support, and regulate communication and organization in tissues.

Describe the structural features and functions of five different types of cell junctions.

Tight junctions: Seal cells together; prevent leakage of molecules. CAMs: claudins & occludins.
• Adherens junctions: Connect actin cytoskeletons between cells via cadherins; form belt-like support for tissues.
• Desmosomes: Button-like junctions connecting intermediate filaments (keratin) via desmosomal cadherins; provide strength.
• Hemidesmosomes: Anchor cells to basal lamina using integrins; connect to intermediate filaments.
• Gap junctions: Channels made of connexins allowing small molecules and ions to pass for cell communication.

Describe the features of cell adhesion molecules (CAMs) and name the specific CAMs in different cell junctions.

CAM features: Transmembrane proteins; bind extracellularly to other CAMs or ECM; bind intracellularly to adaptor proteins and cytoskeleton; mediate adhesion and signaling.
• Tight junctions: claudins, occludins
• Adherens junctions: cadherins
• Desmosomes: desmosomal cadherins
• Hemidesmosomes: integrins
• Gap junctions: connexins

Describe the structure and function of the ECM.

Structure: Insoluble network of fibrous proteins (collagen, elastin), proteoglycans/GAGs, and adhesive proteins (fibronectin) surrounding cells.
Function: Provides mechanical support, organizes tissues, anchors cells, and regulates cell behavior including proliferation, differentiation, and survival.

Describe the structure of integrin, collagen, and their roles in tissue formation.

Integrins: Transmembrane α/β proteins that bind ECM outside the cell and connect to actin inside; anchor cells to ECM and transmit mechanical/chemical signals.
Collagen: Fibrous protein providing tensile strength; secreted by fibroblasts and assembled into extracellular fibrils; most abundant protein in the body.
Both contribute to tissue strength, structure, and stability.

Cell Junction

Specialized regions on the cell membrane where cell-cell or cell matrix are joined together.

Cell Adhesion molecules

Trans membrane proteins that help join together cell junctions.

The extracellular matrix ( ECM)

A network of proteins and other molecules that surround cells providing structure that surrounds a plant cell/ ECM is the equivalent of structure.

Collagen

The most abundant protein in human body

Proteoglycan

Glycoproteins in which the polysaccharides units contain amino sugars.

Integrin

The major cell adhesion molecules that interact with ECM, sensing and transducing signals

Cadherins

A family of transmembrane proteins that play a crucial role in cell-cell adhesion

Glycosaminoglycans

The major polysaccharide units in proteoglycans

Basal lamina

The cell are sitting on a thin layer of extracellular matrix

Fibroblasts

Responsible for synthesis of collegans