1. TISSUES

2. Body Tissues Cells are specialized for particular functions
Tissues - groups of cells with similar structure and function
Histology - study of the organization of cells and extracellular material into tissues and organs
Four primary tissue types
1) Epithelium 2) Connective tissue )Nervous tissue ) Muscle

3. Epithelial Tissues Found in different areas 1) Body coverings
2 ) Body linings
3) Glandular tissue
Functions
1) Protection
2) Absorption
3) Filtration
4) Secretion

4. Epithelium Characteristics
1) Cells fit close together – Desmosomes and Tight junctions
2) Apical Surface - Tissue layer always has one free surface (unattached) exposed to the body’s surface or the cavity of an internal organ
3) The lower surface is bound by a basement membrane
4) Avascular (have no blood supply) so they depend on diffusion for food and oxygen
5) Regenerate easily if well nourished

5. Classification of Epithelium
Each Epithelium is given 2 names:
First name indicates the Number of cell layers
Simple – one layer
Stratified – more than one layer
Figure 3.17a

6. Classification of Epithelium
Second name indicates the Shape of cells
Squamous – flattened
Cuboidal – cube-shaped
Columnar – column-like
Figure 3.17b

7. Simple Epithelium Simple squamous
Single layer of flat cells resting on a basement membrane
Cells fit closely together.
Forms membranes where filtration or exchange of substances through rapid diffusion occurs
Ex: Serous membranes that line organs and air sacs in lungs
Figure 3.18a

8. Simple Epithelium Simple cuboidal
Single layer of cube-like cells on basement membrane
Common in glands and their ducts
Forms walls of kidney tubules and covers the ovaries
Figure 3.18b

9. Simple Epithelium Simple columnar
Single layer of tall cells that fit closely together
Often includes goblet cells, which produce mucus
Lines entire digestive tract
Functions in absorption and secretion
Figure 3.18c

10. Simple Epithelium Pseudostratified Columnar
Single layer, but some cells are shorter than others ALL cells touch basement membrane
Often looks like a double cell layer
Sometimes ciliated, such as in the respiratory tract
May function in absorption or secretion
Also has goblet cells to produce mucous
Figure 3.18d

11. Stratified Epithelium
Stratified squamous
Cells at the free edge are flattened; cells near the basement membrane are cube or column shaped
Found as a protective covering where friction is common
Figure 3.18e

12. Stratified Epithelium
Stratified squamous (continued)
Two types:
1) SS Keratinized – all extenal skin
Keratin is a protein that makes skin dry and rough and keeps water out and things like bacteria and viruses.
Keratin doesn’t allow you to see the nucleus and it will be flaky
2) SS Non-Keratinized – all internal skin Mouth, tongue, vagina
No keratin so the nucleus can be seen to surface layer; still able to resist penetration of organisms but skin is moist & slippery (resists wear & tear)
Figure 3.18e

13. Stratified Epithelium
Stratified cuboidal and columnar
1) Rare in human body
2) Found mainly in ducts of large glands

14. Stratified Epithelium
Transitional epithelium - Highly modified, stratified squamous epithelium
Shape of cells depends upon the amount of stretching
1) Basal layer cells (bottom) are cuboidal or columnar
2) Free (apical) surface cells are rounded and dome like if not stretched but squamous like (flat) when full of urine
Lines organs of the urinary system (Ureters and Bladder)
Figure 3.18f

15. Glandular Epithelium
Gland – one or more cells that secretes a particular product
Two major gland types
Endocrine gland – Ductless and the secretions are hormones
Exocrine gland - Empty through ducts to the epithelial surface.
Include sweat and oil glands

16. Connective Tissue Found everywhere in the body
Includes the most abundant and widely distributed tissues
Functions: 1) Binds body tissues together
2) Supports the body ) Provides protection

17. Connective Tissue Characteristics
Variations in blood supply
Some tissue types are well vascularized (much blood supply) Ex: bone
Some have poor blood supply (tendons or ligaments) or are avascular (no blood) (cartilage)
Extracellular matrix – main difference between other tissue types
Non-living material that surrounds living cells