1. Tissues
Epithelial Tissue

2. Four Main Types of Tissue:
Tissue: mass of specialized cells that work together to perform a specific function
Four Main Types of Tissue:
Connective
Epithelial
Muscle
Nervous

3. Epithelial Tissue Includes :
Epithelia: layer of cells on the outside of EVERYTHING (not just skin, but lines intestinal and respiratory tracts, stomach lining, etc)
Exocrine Glands: produce fluid secretions
Sweat, oil

4. Characteristics of Epithelium
Attached to underlying connective tissue by a basement membrane
Usually has no vascular tissue, which means there is no blood supply
Epithelial cells reproduce rapidly which allows them to also heal quickly
Cells packed tightly together

5. Epithelial cells = firmly attached to one another
Cell Junctions: attachment sites
Tight Junctions: allows no passage of water or solutes
ex: stomach
2. Gap Junctions: narrow passageways that allow diffusion
ex: muscles
3. Desmosomes: many bands and interconnections
ex: skin

7. Functions of Epithelia
1. Provide Protection
2. Control Permeability (what comes in and goes out)
3. Provide Sensation
4. Produce Specialized Secretions

8. Classifications of Epithelia
Classified by cell shape and number of cells in layers
3 Shapes:
(1) Squamous (thin, flat cells)
(2) Cuboidal (boxy)
(3) Columnar (long,thin rectangular)
Number of Cells in Layer
Simple (1)
Stratified (>1)

9. Types of Epithelia Six Main Types of Epithelial Tissue:
Simple Squamous
Simple Cuboidal
Simple Columnar
Stratified Squamous
Pseudostratified Columnar
Transitional Epithelial

10. Simple Squamous
Single layer (simple) of thin, flattened cells (squamous)
Functions to facilitate diffusion of gases and filtration
Found in air sacs of lungs and capillary walls

11. Simple Cuboidal Single layer (simple) cube-shaped cells (cuboidal)
Functions to secrete and absorb
Found in the lining of kidney tubules, gland ducts, and covers the surface of the ovaries

12. Microvilli used to aid in absorption – increases surface area
Simple Columnar
Single layer (simple) rectangular-shaped cells in about the same position in each cell
Functions to secrete, absorb, and protect
Found in digestive tract and uterus lining
Microvilli used to aid in absorption – increases surface area

13. Stratified Squamous
Multiple layers (stratified) of flattened cells (squamous)
Functions to protect
Found in body cavities like the mouth and outer layer of the skin
Why is this good tissue for outer layer of skin?

14. Stratified Squamous
It takes about 27 days for the outer layer of skin to be shed and replaced; that adds up to about 1.5 pounds of skin cells shed per year!!
Where does all that dead skin go?

15. Tattoos
If skin is constantly being replaced, where does ink need to be injected so tattoo doesn’t “shed” away?
The ink must be injected below the basement membrane

16. Pseudostratified Columnar
“Pseudo” means false, stratified means many layers
Psuedostratified looks like many layers but really a single layer with nuclei at different levels, giving appearance of layered cells
Functions to secrete and has cilia to aid in the movement of materials like mucus or eggs
Found in the lining of trachea and fallopian tubes of the female reproductive system

17. Pseudostratified Columnar
Cilia
Goblet Cells
Basement Membrane
Goblet Cells secrete mucus while the cilia “sweep” the mucus through the respiratory tract

18. Transitional Epithelium
Looks like thick layers of cuboidal cells
It is “stretchable” tissue, and forms a barrier to prevent diffusion from occurring
Found in the lining of the urinary bladder to prevent “leaking”
Notice scalloped edges characteristic of transitional epithelial tissue

19. Transitional Epithelium
Relaxed tissue
Contracted tissue

20. Growing an Ear…

21. Cuboidal Columnar Simple Stratified Epithelial Tissue Squamous
Location:
Lungs and blood vessels
Functions:
Diffusion and filtration
Glands, kidneys, ovaries
Secretion and absorption of fluids
Uterus and digestive organs (stomach and intestines)
Absorption/lubrication
Stratified
Skin, throat, mouth
Protection due to layers
Lining of glands/ducts including mammary and sweat
Protection for glands making fluids
Respiratory tract
Filtration due to cilia

22. What type of epithelial tissue is shown below?

23. What type of epithelial tissue is shown below?

24. What type of epithelial tissue is shown below?

25. What type of epithelial tissue is shown below?

26. What type of epithelial tissue is shown below?