1. Three Types of Junctions Occluding junctions – Zonula occludens Occluding junctions – Zonula occludens restrict and direct movement of fluids in intercellular space restrict and direct movement of fluids in intercellular space Focal adhesions in a band around cell; composed of Focal adhesions in a band around cell; composed of Transmembrane = occludin, Transmembrane = occludin, cytoplasmic proteins = ZO 1-3 (1 is tumor supressor, 2 is part of EGF signaling, 3 is linker) Breach ZO – leaky epithelia Breach ZO – leaky epithelia Most apical attachment, restricting movements of PM proteins and maintaining integrity of apical vs. basal/lateral surfaces Most apical attachment, restricting movements of PM proteins and maintaining integrity of apical vs. basal/lateral surfaces Tightness of anastomosing network differs b/w tissues Tightness of anastomosing network differs b/w tissues

2. Three Types of Junctions, cont’d Anchoring Junctions (lateral face) Anchoring Junctions (lateral face) Zonula Adherens Zonula Adherens Lateral adhesion Lateral adhesion Continuous band of transmembrane cadherins bound to catenin/vinculin/actin on cytoplasmic side Continuous band of transmembrane cadherins bound to catenin/vinculin/actin on cytoplasmic side Adhesion is Ca+ dependent Adhesion is Ca+ dependent Macula Adherens (Desmosomes) Macula Adherens (Desmosomes) High tensile strength High tensile strength Desmoplakin/plakoglobin attach to intermediate filaments Desmoplakin/plakoglobin attach to intermediate filaments Not a continuous structure around cell Not a continuous structure around cell Attachment plaque – shock absorber Attachment plaque – shock absorber Attach to other cells by desmogleins (cadherin zipper) Attach to other cells by desmogleins (cadherin zipper)

3. Three Types of Junctions, cont’d Communicating Junctions Communicating Junctions Gap junctions Gap junctions Lateral pores composed of connexins Lateral pores composed of connexins Pore size alters, but still restricts cell-cell communication physically Pore size alters, but still restricts cell-cell communication physically Lowers electrical resistance in cells (permits ion passage) Lowers electrical resistance in cells (permits ion passage) Protein = Connexin Protein = Connexin

4. Basal Face Basement Membrane Basement Membrane Basal lamina Basal lamina Collagen Collagen Proteoglycans Proteoglycans Laminin Laminin Entactin and Fibronectin Entactin and Fibronectin H & E stains poorly; use PAS H & E stains poorly; use PAS Beneath Basal Lamina is Reticular lamin (connective tissue) Beneath Basal Lamina is Reticular lamin (connective tissue) Attachment, Compartmentalization, Filtration, Polarity induction, Tissue scaffolding Attachment, Compartmentalization, Filtration, Polarity induction, Tissue scaffolding Cell-ECM junctions Cell-ECM junctions Focal Adhesions (via actin) Focal Adhesions (via actin) Hemidesmosomes (present in mechanically abraded tissues) Hemidesmosomes (present in mechanically abraded tissues) PM foldings PM foldings

5. Exocrine Glands Merocrine Merocrine Vesicle bound products; exocytosis Vesicle bound products; exocytosis Apocrine Apocrine Released in apical portion of cell Released in apical portion of cell Holocrine Holocrine Apoptosis related release (eg., sebaceous glands) Apoptosis related release (eg., sebaceous glands)