Tissues

1. Epithelial – covering & lining2. Connective – support 3. Muscle - movement4. Nervous - control

4 Primary Tissue Types

Epithelial Tissue

1. Protection2. Secretion3. Absorption4. Filtration

Functions

1. Composed of sheets of closely packed cells

cells are often strongly connected via tight junctions and desmosomes

Characteristics

• Tight junctions are common in lining of the stomach & intestines. Why?

• Desmosomes are common in the epidermis. Why?

Look at the cartoon below (it represents the epithelium that lines much of your respiratory tract) . Do you see much space between these cells? Now look at the actual slide and notice the same thing.

2. Has polar sides Apical Surface

– side open to exterior or body cavity

Basal surface – rests on a basement membrane of connective tissue

3. Avascular – no blood vessels Depends on diffusion of

nutrients from underlying tissues

4. Has the capacity to regenerate

1. number of cell layers Simple – 1 layer Stratified – more than 1

layer

2. shape of cells in the apical layer

Squamous – flat, scale-like

Cuboidal – cube-like Columnar – column-like

Classification

Locations Alveoli – air sacs of

lungs Kidney Endothelium – lining of

heart and blood vessels

1. Simple Squamous Epithelium

Functions Rapid diffusion FiltrationIn peneumonia, a build-up of

mucous can increase the distance that the gases move. Why does this make it “harder to breathe?”

Locations Liver Pancreas Most glands Kidney tubules

2. Simple Cuboidal Epithelium

Functions Absorption Secretion

Locations Inner linings of:

GI TractGallbladderUterus & uterine

tubes

3. Simple Columnar Epithelium

Functions Absorption & Secretion

Intestines; Microvilli increase S.A. Movement of egg & embryo

Cilia Secretion of mucous

by Goblet cells

Locations Epidermis of skin

Keratinized – filled with keratin

Lining ofOral cavityTongue surfaceEsophagusVagina & anal canal

4. Stratified Squamous Epithelium

Functions Protection

Which is & is not keratinized?

Locations Sweat gland ducts Ovarian follicle – cells

surrounding egg

5. Stratified Cuboidal Epithelium

Functions Secretion

Sweat Ovarian hormones

To the left, we have an oocyte (egg cell) surrounded by stratified cuboidal epithelium. The oocyte is circled in blue

Locations Rare Large ducts of sweat

and salivary glands

6. Stratified Columnar Epithelium

Functions Structure

Locations Respiratory tract from

nasal cavity to bronchiCiliatedGoblet cells

7. Pseudostratified Ciliated Columnar Epithelium

Functions Mucous traps dust &

bacteria Cilia sweep debris

away from lungs

Here, we have pathogens traveling down the pharynx trying to attack the surface cells. How can they be repelled???

The mucosal cells lining the trachea have released a flood of mucus, trapping the pathogens! Now what???

The cilia successfully sweep the pathogens up and away!

Smoking paralyzes the cilia so they have to cough violently to expel mucous

..Then they die!

Why do smokers cough?

Locations Urinary tract

8. Transitional Epithelium

Functions Stretches to allow

filling of urinary organs

Locations Pancreas Stomach Sweat glands Salivary glands Mammary glands Oil glands Goblet cells

9. Exocrine GlandsFunctions Secrete material into

ducts that lead to a tract or body surface

Locations Thyroid Thymus Pituitary Adrenal Testes Ovaries

10. Endocrine GlandsFunctions Secrete hormones into

the bloodstream where they travel to other cells

Easy Epithelium Review