1. Histology
the study of
TISSUE A groups of cells with similar structure that function together as a unit

2. Types of Cell to Cell Junctions
Tight junctions provide seals to prevent leaking across the free epithelial surface.
Ex. epithelia in the digestive tract that prevents attack of the wall by acids and enzymes.
Adhesion junctions (AKA Desmosomes) are like "spot welds" that cement cells together and prevents them from pulling apart so that they function as a unit. Ex. Skin
Gap junctions contain hollow cylinders (connexons) that allow chemical cell to cell communication
Ex. heart cells and embryonic cells

3. Interstitial fluid (ISF):
Before we start:
Interstitial fluid (ISF):
The fluid found in the spaces between cells
Composed of water, amino acids, sugars, fatty acids, coenzymes, hormones, salts and cellular products.
It bathes and surrounds the cells of the body, and provides a means of delivering materials

4. 1. Epithelial Tissue AKA: Epithelium (epi- upon) Functions
Protection (skin)
Secretion (glands)
Absorption (intestines)
Filtration (kidneys)
Undergo frequent wear and tear
Mitosis is frequent to replace damaged cells

5. Epithelial Tissue Characteristics Closely packed cells
(little intercellular material)
Avascular (lacking blood vessels)
needs are meet through diffusion from neighboring connective tissue
Always have one “free” surface not attached to any other tissue
Form basement membranes (secretions below)

6. Other terms to know:
Apical surface: surface of epithelial tissue that is exposed to open space or the outside of the body
Basal surface: surface of the epithelial tissue that is the furthest from the apical surface
Basement membrane: extracellular substance secreted by epithelial cells, found on the inferior surface of tissue

7. Epithelial Location Coverings or linings of organs
Upper surface of the epithelium is exposed to the outside of the body OR to an internal cavity

8. 1. Classifying Epithelium
A. Cell shape
Squamous (squashed): cells are flat, nucleus near surface of cell, looks like “fried egg”

9. 1. Classifying Epithelium
cell shape
Cuboidal (cube): cells square shaped with a central nucleus

10. 1. Classifying Epithelium
cell shape
Columnar (column): enlongated cell, nucleus near the bottom, some have microvilli (finger-like projections that increase surface area), some have cilia (tiny “hair-like” structures that help move materials along)

11. 1. Classifying Epithelium
cell shape
Transitional: flat and/or tall, can extend and compress

12. 1. Classifying Epithelium
B. Number of cell layers
Simple: single layer
Statified: (strat- layer) multiple layers
Psuedostratified: (pseudo- false) seems to appear as if it is layered, however, it is one layer of cells that are differing in size

13. Practice Looks 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