Desmosomes & hemidesmosomes

cell biology

1. DESMOSOMES & HEMIDESMOSOMES Submitted by, AJAY DOMINIC.V ROLL NO:251

2. The plasma membranes of adjacent cells are usually separated by a uniform intercellular space of about 100-200 A. But at certain places the plasma membranes of adjacent cells may come too close to each other the term CELL JUNCTION. It refers to specialisations in the plasma membrane formed at sites where two cells make contact. Cell junctions are different types : desmosomes, gap-junctions, tight junctions & plasmodesmata….

3. DESMOSOMES(Adherent junctions) Desmosomes are essential adhesion structures in most epithelia that link the intermediate filament network of one cell to its neighbour , thereby forming a strong bond. They are particularly numerous in tissues that are subjected to mechanical stress, such as the skin & uterine cervix.

4. Structure of Desmosomes

5. Desmosome consists of three component The Transmembrane molecules The plaque molecules or cytoplasmic adaptor protein Intermediate filament E xtracellularly , desmosomes are separated by a 25-30 nm space .

6. The interaction of the transmembrane proteins with those from the adjacent cell results in a dense line in the middle of the intercellular space.

7. Function of Desmosomes Desmosomes create a transcellular network throughout a tissue that resist forces of mechanical stress. Hence found in stratified squamous epithelia and myocardium subjected to constant stress.

8. ASSOCIATED PATHOLOGY Desmosomes are adhesive intercellular junctions prominent in the oral epithelium, skin & heart. Loss of desmosome function is associated with severe congenital & acquired disorders characterized by tissue fragility. Diseases associated are- Pemphigus Drug-induced pemphigus

9. PEMPHIGUS Mutations in genes encoding desmosomal components & autoantibodies directed against the desmosomal cadherins lead to severe epidermal blistering disorders termed pemphigus .

10. HEMIDESMOSOMES Hemidesmosomes are specialized junctional complexes that contribute to the attachment of epithelial cell to the underlying basement membrane in stratified & other complex epithelia .

11. Hemidesmosomes are very small stud or rivet like structures on the inner basal surface of keratinocytes in the epidermis of skin. While desmosomes link two cells together, hemidesmosomes attach one cell to the extracellular matrix. Hemidesmosomes use integrin cell adhesion proteins. Hemidesmosomes are asymmetrical & are found in epithelial cells connecting the basal face to other cells. Function : maintenance of tissue structure.

12. DISORDERS AUTOIMMUNE DISEASES PEMPHIGOID Term used to indicate a blistering disease in which epithelial separation takes place at the level of the basement membrane.

13. Thank you