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Ch. 4 Part 1

Ch. 4 Part 1. Tissues and Junctions. Histology. Science that deals with the study of tissues Tissue – group of similar cells that usually have a common embryonic origin and functions together to carry out specialized activities

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Ch. 4 Part 1

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  1. Ch. 4 Part 1 Tissues and Junctions

  2. Histology • Science that deals with the study of tissues • Tissue – group of similar cells that usually have a common embryonic origin and functions together to carry out specialized activities • Pathology – study of cells and tissues for the purpose of diagnosis

  3. 4 Main Types of Tissues • Epithelial • Cover body surfaces and line hollow organs, body cavities, and ducts; also forms glands • Connective • Protects and supports the body and its organs; bind organs together, store energy reserves, help provide immunity • Muscular • Generates physical force needed to make body structures move • Nervous • Detects changes in body conditions and responds by generating action potentials to help maintain homeostasis

  4. Primary Germ Layers • All 4 body tissues arise during embryonic period from: • Ectoderm – epithelial, nervous • Endoderm – epithelial • Mesoderm – epithelial, connective, muscular

  5. Checkpoint • Define a tissue. • What are the four basic types of human tissues? • What are the 3 primary germ layers and which tissue is derived from each?

  6. Cell Junctions • Cell junctions – contact points between the plasma membrane of tissue cells • 5 types: • Tight junctions • Adherens junctions • Desmosomes • Hemidesmosomes • Gap junctions

  7. Tight Junctions • Consist of weblike strands of transmembrane proteins that fuse the outer surfaces of plasma membranes together • Where in the body? • Epithelial tissue of stomach, intestines, and bladder • Function: • Prevent passage of substances between cells • Prevent leaking of contents into blood

  8. Tight Junction

  9. Adherens Junctions • Contain plaque – dense layer of proteins on the inside of the plasma membrane • Cadherins (proteins) attach to the plaque in each cell and create a belt around the cells • Where in the body? • Epithelial tissue • Function: • Resist separation during contractile activities (ie: moving food through intestines)

  10. Adherens Junctions

  11. Desmosomes • Contain plaque and cadherins that connect cells together • Do not create belt • Where in the body? • Epidermis (skin), cardiac (heart) muscle cells • Function • Prevent separation during tension and contraction

  12. Desmosomes

  13. Hemidesmosomes • Hemi = half • Look like desmosomes, but don’t actually connect cells • Use integrins instead of cadherins • Where in the body? • Epithelial tissue • Function: • Connect cells to basement membrane

  14. Hemidesmosomes

  15. Gap Junctions • Use connexins to form tiny fluid-filled tunnels call connexons that connect cells • Cells have space between them • Where in the body? • Eye tissue, embryos, nerve and muscle cells, heart, intestinal tract, uterus • Function: • Allow communication through passage of ions, chemical and electrical signals

  16. Gap Junctions

  17. Checkpoint • Which type of cell junctions allow cellular communication? • Which types of cell junctions are found in epithelial tissues?

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