Epithelial Tissue

1. What are the four primary types of tissues found in the human body? What is the distinguishing characteristic of each type of tissue?

Epithelial Tissue
- Covering (covers all surfaces)
- Tissue without intercellular surface
Connective
- Support
- Tissue with intercellular substance
- Cells are spread out
Muscle
- Movement
Nervous
- Control/communication

2. Name and describe the six main characteristics of epithelial tissue.

Cellularity
- MOST CELLS
- Cohesive
Polarity
- Apical and Basal surfaces
Attachment
- To basement membrane
Avascular
- No blood vessels
Layers of cells
- Simple (1) or stratified (2+)
Regeneration
- Stem cells

3. Describe the functions of epithelial tissue in the human body.

Protection
- Provides barrier to outside world
Filtration
- Kidneys filter blood
Absorption
- Intestines
Secretions
- Hormones (internal secretion)
Excretions
- Sweat (outside secretion)
Sensory Reception
- Olfactory mucous- Scents
- Taste buds- Taste
- Rods & Cones- Eye
- Auditory Cells- Hearing

4. What can the shape and number of layers of a particular type of epithelial tissue indicate about the function of that tissue? Give specific examples.

Shapes
- Squamous: Flat Cells
- Cuboidal: Cube/Square Cells
- Columnar: Tall/Column Cell
Layers
- Simple: 1 layer of Cells
- Stratified: 2 or more layers of Cells
Function
- Simple
  - Absorption, excretion, diffusion, filtration, secretion
- Stratified
  - Protection
- Little cytoplasm = Lower Metabolism

5. Draw and describe the various types of simple and stratified epithelium. Give an example of where each of these tissues is found in the body.

Simple Squamous Epithelium
- Single layer of flat cells
- Found in:
  - Alveoli in lungs
  - Lining of blood vessels
    - Endothelium
  - Kidneys
    - Glomeruli
- Function: Alveoli & Capillary
  - Diffusion, Absorption, Secretion, Filtration
  - Gas exchanges to remove CO2 from blood stream and replace with O2 from alveoli
Simple Cuboidal
- Single layer of cube cells
- Found in:
  - Tubules of kidneys
- Function: Kidney Tubules
  - Absorption and Secretion
  - Absorb: H2O, Vitamins, and Glucose
  - Secrete: H2O, Urea, Drugs
Simple Columnar
- Single layer of tall/column cells
- Found in:
  - Lines G.I. tract
  - Fallopian tubes
    - Ciliated to push egg
- Functions: G.I. tract
  - Absorbtion:
    - Absorb nutrients
  - Secretion:
    - Secretes mucous and enzymes
Pseudostratified Ciliated Columnar
- Single layer but columned shaped w/ some irregular shapes and nuclei
- Found in:
  - Respiratory tract
- Functions: Respiratory tract
  - Secretion
    - Secrete mucous to collect debris
    - Ciliation helps sweep debris away from lungs
Stratified Squamous
- Multiple layers of flat cells
- Found in:
  - Skin
  - Mouth
  - Esophagus
  - Anus
  - Vagina
- Functions = Protection
  - Skin:
    - Keratinized- Helps waterproof skin
    - Cells full of tough protein (surface cells are dead)
  - Oral cavity:
    - Non-Keratinized
    - Cells lack keratin protein (cells need to stay wet)
Stratified Cuboidal & Stratified Columnar
- Multiple layers of Cube cells & Column cells (both RARE)
- Found in:
  - Sweat glands
  - Salivary glands
  - Mammary glands
- Functions:
  - Secrete
  - Protection
Transitional
- Multiple layers, apical cells are cuboidal, cells become flattened when bladder fills w/ urine
- Found ONLY in bladder/urinary system
- Functions:
  - Protection
    - From urine
    - Permits expansion and recoil

6. What are the two major categories of epithelial tissues found in the body?

Covering epithelium
Glandular epithelium

7. What are microvilli and cilia? How do they differ from one another?

Microvilli
- Most epithelial cells
- Non-motile
- Increase surface are
- Absorption (by 20x more) and secretion
- Stereocilia are very long
  - Found in inner ear
- Intestinal brush border
Cilia
- Longer
- Motile
  - Microtubules
- Structure and function
  - Cillia in mucous membrane push particles away from lung

8. What is the specific purpose of glandular epithelium? What are the two major categories of glandular epithelium (glands)? How do these two types differ from one another?

Glandular epithelium purpose:
- Glands are made up of epithelial cells that are modified to secrete and synthesize chemical substances
Categories: Exocrine Glands and Endocrine Glands
Endocrine Glands
- DUCT-LESS
- Produce hormones for the body
  - Hormones: Chemical messengers that travel through the bloodstream
- Once hormone in blood stream, it diffuses to bind to cell receptor on target organ (where it was intended)
- Hormone producing Glands:
  - Thyroid
  - Pineal
  - Pituitary
  - Pancreas
Exocrine Glands
- Produce a product that ends up secreted onto epithelial surfaces
- DUCT
  - Duct puts product on epithelial membrane
- Ex: Sweat, saliva, tears, mucous, digestive enzymes, etc.

9. What is a unicellular exocrine gland and where are they often found?

A unicellular exocrine gland = GOBLET CELL
Scattered, single cells
- Found in:
  - Mucous membrane of large intestine

10. What does it mean for a gland to be “simple” or for a gland to be “compound?”

Simple
- They contain ONE unbranched duct
  - Tubular, branched tubular, coiled tubular, alveolar, branched alveolar
- Ex: Intestinal glands, sweat glands, gastric glands, sebaceous glands
Compound
- Contain MULTIPLE branching duct
  - Tubular, alveolar, tubuloalveolar

11. Exocrine glands have three major modes of secretion. Name and describe these modes of secretion. Give an example of a specific gland in the body that uses each secretion mode.

Merocrine (Eccrine)
- Most common form
- Uses exocytosis
- NO loss of cytoplasm
  - Ex: salivary and sweat glands
Apocrine
- Apex of cell will break off to release products
- Small loss cytoplasm
  - Mammary gland
Holocrine
- wHOLe cell breaks down to release
  - Ex: sebaceous