Histology

1. Histology

2. Histology- The Study of Tissues • Groups of tissues that are similar in structure and function

3. Epithelial tissue 1. Epithelial Tissue: cover outside surfaces and surfaces exposed to outside. Ex. Inside of mouth, nose intestines, rectum, skin.

4. Muscle tissue 2. Muscle tissue: Causes movement of bones, movement of heart, movement of blood vessels, intestines, esophagus.

5. Connective tissue 3. Connective tissue: most common in the body. Supports organs, covers muscle, connects bones and organs.

6. Nervous Tissue 4. Nervous tissue: controls the body. Important in homeostasis.

7. General Characteristics of Epithelial Tissue • 1. Fits tightly to form continuous sheets. Neighboring cells are tightly bound together by cell junctions. (to keep fluid from going between cells)

8. General Characteristics of Epithelial Tissue • 2. Epithelial membranes have a free edge unattached to other tissues or organs – called apical surface. The apical surface is exposed to the body’s exterior or the cavity of an internal organ, like the urinary bladder.

9. Characteristics of apical surface • Some apical surfaces are slick and smooth, some have cilia (long hairs), or microvilli (short infoldings of membrane).

10. General Characteristics of Epithelial Tissue • 3. The lower surface of the epithelial cell rests on a basement membrane – a structureless glue secreted by the cell. Attaches to the layers below it.

11. General Characteristics of Epithelial Tissue • 4. Epithelial tissue is avascular- they have no blood supply of their own. They depend on diffusion of nutrients and oxygen from capillaries in the underlying tissue.

12. General Characteristics of Epithelial Tissue • 5. Regenerates easily!

13. Classification of Epithelial Tissue Cells • Simple Squamous Epithelium: • Looks like fish scales • Rests on basement membrane • Thin membrane, good for diffusion and exchange of nutrients • Found in alveoli (lungs) and capillaries (blood vessels)

14. Classification of Epithelial Tissue Cells • Simple Cuboidal Epithelium: • Shaped like dice • Rest on basement membrane • They are common in ducts and glands (like salivary glands) and kidney tubules

15. Classification of Epithelial Tissue Cells • Simple Columnar Epithelium: • Found in entire digestive tract, from stomach to anus • Found in mucous membranes that line body cavities open to outside • May have cilia to trap dust and particles

16. Classification of Epithelial Tissue Cells • Simple Pseudo Stratified Epithelium: • Really one layer- looks like multiple layers but all are attached to basement membrane • Not all reach surface, cells have different heights • May have cilia • Function in absorption and secretion • Line most of the respiratory tract

17. Classification of Epithelial Tissue Cells • Stratified Squamous Epithelium: • Apical layer squamous cells • Most common stratified epithelium in body • Near basement membrane, cells are more cuboidal or columnar • Found on surfaces that have a lot of abuse or friction

18. Classification of Epithelial Tissue Cells • Stratified Cuboidal Epithelium: • Usually only two layers • Rare in body, but can be found in large glands and ducts

19. Classification of Epithelial Tissue Cells • Stratified Columnar Epithelium: • Apical cells columnar, inner cells vary in size and shape • Rare in body, but can be found in large glands and ducts

20. Classification of Epithelial Tissue Cells • Stratified Transitional Epithelium: • Apical layer is squamous when stretched • Highly specialized and modified for stretching • Found in places that need to stretch like the urinary bladder • Bottom layer is usually cuboidal or columnar