Outline

6.1 Cell-Cell and Cell-Matrix Adhesion: An Overview

6.2 Sheetlike Epithelial Tissues: Junctions and Adhesion Molecules

6.3 The Extracellular Matrix of Epithelial Sheets

6.4 The Extracellular Matrix of Nonepithelial Tissues

6.5 Adhesive Interactions and Nonepithelial Cells

6.6 Plant Tissues

6.7 Growth and Use of Cultured Cells the atmosphere and water and nutrients (e.g., minerals) from the soil. The distinct mechanical properties of rigid bones, flexible joints, and contracting muscles permit vertebrates to move efficiently and achieve substantial size. Sheets of tightly attached epithelial cells can act as regulatable, selective permeability barriers, which permit the generation of chemically and functionally distinct compartments in an organism (e.g., stomach, bloodstream). As a result, distinct and sometimes opposite functions (e.g., digestion and synthesis) can efficiently proceed simultaneously within an organism. Such compartmentalization also permits more sophisticated regulation of diverse biological functions. In many ways, the roles of complex tissues and organs in an organism are analogous to those of organelles and membranes in individual cells.

The assembly of distinct tissues and their organization into organs are determined by molecular interactions at the cellular level and would not be possible without the temporally and spatially regulated expression of a wide array of adhesive molecules. Cells in tissues can adhere directly to one another (cell-cell adhesion) through specialized integral membrane proteins called cell-adhesion molecules (CAMs) that often cluster into specialized cell junctions (Figure 6-1). Cells in animal tissues also adhere indirectly (cell-matrix

Tightjunction

Apical surface

Tightjunction

Apical surface

Adherens junction

Desmosome

Hemi-

desmosome

Basal lamina

Extracellular matrix (ECM)

Connexon

Connexon

Your Heart and Nutrition

Your Heart and Nutrition

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