1. Histology: the study of tissues

2. Tissues
A group of interrelated cells that function together and perform specialized activities
4 Types of Tissues in the body
Epithelial
Connective
Muscle
Nervous

3. Epithelial Tissue AKA: Epithelium (epi- upon or above) Functions:
(P) Protection
(S) Secretions
(A) Absorption
(F) Filtration

4. Epithelial Tissue Characteristics Closely packed flat cells
Avascular (a- without vasc- blood supply), needs are met through diffusion from neighboring cells

5. Epithelial Tissue Location Coverings or linings of organs
Always has a surface exposed to open space or the outside of the body (apical surface)
Underside always attached to connective tissue by a basement membrane
Mitosis is frequent to replace damaged cells since they are “exposed”

6. Epithelial Tissue Epithelial tissue is classified two ways
By the cell shape
By the number of cell layers
Some may contain goblet cells….these cells are filled with and release mucus.
(This type lines the digestive tract and are sometimes referred to as mucosae)

7. Epithelial Cell Shapes
Squamous- (squashed) flat, nucleus near surface
Cuboidal- (cube) thicker, square shaped with central nucleus

8. Epithelial Cell Shapes
Columnar- (column) elongated cells, some have microvilli (fingerlike projections that increase surface area), some have cilia (tiny hair-like structures that help move materials along)

9. Epithelial Cell Shapes
Transitional- appearance ranges from flat to columnar, cells can stretch and compress (different shapes in the same layer)

10. Arrangement of Layers
Simple- single layer, thinness allows substances to permeate easily
Stratified- (strat-layers) multiple layers, protection for areas that endure large amounts of stress, cells grow from the bottom layer up
Pseudostratified- (psuedo-false) one layer, but appears to be multilayered. All cells are attached to the basement membrane, but not all the cells reach the surface

11. Types of Epithelium
Simple Squamous- single, flat cell layer, nucleus in middle of the cell

12. Types of Epithelium
Simple Cuboidal- Single layer of cubed shaped cells, nucleus in the middle

13. Types continued
Simple Columnar- single layer of rectangular cells, nucleus at base,
Non-ciliated- contains goblet cells (mucous) and microvilli (increase surface area) in some areas

14. Simple Columnar-
Ciliated- single layer of rectangular cells, nucleus at the base

15. Types- continued
Stratified Squamous- Several layers, larger at the bottom and flattened out at the top, bottom replaces top as the superficial layers shed, can produce keratin

16. Types- Continued
Stratified Cuboidal- two or more layers, cubed shaped cell

17. FYI
Stratified Columnar- several layers on columnar in superficial layers
Found in few places of the body (epiglottis, urethra)
*you will not be responsible for the identification of this type

18. Types
Pseudostratified Columnar- single layer, nucleus at different levels, all cells attached to basement membrane

19. Types
Transitional- range from squamous to cuboidal appearance

20. Practice Looks for at Home Review
Epithelia Page
1. Simple Squamous 2. Simple Squamous 3. Simple Cuboidal 4. Simple Cuboidal 5. Simple Columnar 6. Simple Columnar 7. Pseudostratified Columnnar 8. Pseudostratified Columnnar (Ciliated) 9. Transitional 10. Transitional 11. Stratified Squamous 12. Stratified Squamous 13. Stratified Squamous 14. Stratified Squamous (Keratinized) 15. Stratified Squamous (Keratinized 16. Stratified (High) Cuboidal 17. Stratified Cuboidal