What are the five characteristics of epithelia?
- Continuous
- Avascular
- Rest on a basal lamina
- Little extracellular matrix
- Polarized (apical and basolateral surfaces differ)
What does continuous mean?
On all body surfaces; there is no break
What does avascular mean?
No blood vessels out on epithelium
Where is the apical (free) surface located?
On the outside/closer to the outside world
Where is the basal surface located?
On the inside
What is the basal lamina?
- Where communication between the epithelium and
connective tissue occur - Acts as a selective barrier
Do all epithelia serve the same functions?
No, different types of epithelia serve different functions
How is epithelia named?
- The number of layers of cell
- The shape of the cells in the outermost layer
What are the seven classifications of epithelia?
- Simple squamous
- Simple cuboidal
- Simple columnar
- Stratified squamous
- Stratified columnar
- Pseudostratified columnar
- Transitional
What are the four characteristics of simple squamous epithelium?
- Single fine layer of flat, delicate cells
- Lines body cavities (mesothelium - pleural and pericardial cavities)
- Lines heart chambers and blood vessels (endothelium)
- Lines site of gas exchange in the lungs
What are the three functions of simple squamous epithelium?
- Reduces friction
- Controls vessel permeability
- Performs absorption and secretion
Where are the five locations that simple squamous epithelium is found?
- Mesothelia lining ventral body cavities
- Endothelia lining heart and blood vessels
- Portions of kidney tubules (thin sections of loop of Henle)
- Inner lining of cornea
- Alveoli of lungs
What do you call a single layer of cells?
Simple
What do you call more than a single layer of cells?
Stratified epithelium
What are the two characteristics of simple cuboidal epithelium?
- Single layer of cells
- Cell heigh equal width
Where are the two places simple cuboidal epithelium found?
- In areas where secretion or absorption occur
- Found in glands and their ducts
Why is simple cuboidal epithelium found in area where secretion or absorption occur?
Because there is more room inside the cell for machines to function
What does the simple cuboidal epithelium line?
Line portions of the kidney tubule system
What are the two functions of simple cuboidal epithelium?
- Limited protection
- Secretion and/or absorption
Where are the four locations where simple cuboidal epithelium is found?
- Glands
- Ducts
- Portions of kidney tubules
- Thyroid gland
What are the two characteristics of simple columnar epithelium?
- Simple layer of cells
- Cells taller than they are wide - provide protection
What three things does the simple columnar epithelium line?
Lines:
1. Digestive tract
2. Fallopian tubes
3. Excretory ducts (gall bladder)
What are the three functions of simple columnar epithelium?
- Protection
- Secretion
- Absorption
What does the microvilli help in simple columnar epithelium?
Increase surface area (absorption/secretion)
