1. Epithelial Tissue Histology: the study of tissues. Tissues:
Simply groups of similar cells that work together performing the same task
Greatest form of teamwork in the body

2. Where are epithelial tissues found?
With few exceptions, organs are composed of four basic tissue types:
– Epithelial Tissue
– Connective Tissue
– Muscular Tissue
– Nervous Tissue

3. Why Study Histology?
Knowing the difference between normal and abnormal tissue is the first step in diagnosis and treatment of patients.

4. Skin, our largest and heaviest organ
Epithelial Tissue
Muscular Tissue
Nervous Tissue
Connective Tissue
made of all four tissue types

5. Epithelial Tissue Makes up 3% of your body weight Cells don’t move
They don’t send messages
Their cells are all touching one another
Of all tissues, they are the most widely varied in structure and function

6. Locations of Epithelial Tissues
Covers the body
Found on the inside of hollow organs and the outside of all organs
Found above a connective tissue layer
Lines the cavities, tubes, ducts, and blood vessels inside the body

7. Epithelial Anatomy
Apical surface – upper surface that is free or exposed to the “exterior”
Basal surface – attached surface (below)
Microvilli – small fingerlike extensions that increase the surface area allowing for more work to be done

8. Functions of Epithelial Tissue
Protects from physical & chemical injury
Protects against microbial infection
Contains nerve endings which respond to stimuli
Filters, secretes & reabsorbs materials
Secretes fluids to lubricate joints

9. Three Basic Shapes
Squamous – like scales, or pancakes (“being squashed like a pancake”)
Cuboidal – looks like cubes
Columnar – longer and look like columns

10. Cell Organization
Simple – single layer of cells; typically found where absorption and filtration occur
simple squamous
simple cuboidal
simple columnar
Stratified – layers of cells; common in areas where protection is needed like the skin
stratified squamous

11. Two Types of Stratified Columnar
Ciliated
Unciliated
cilia
No cilia

12. Squamous Epithelium Simple Squamous Stratified Squamous
Forms solid, single layer of cells
lines blood vessels, body cavities and covers organs
Stratified Squamous
Forms epidermis and is mostly for protection
Found in areas of high friction

13. Cuboidal Epithelium Simple Cuboidal Roughly cube shaped
Line ducts in kidneys where absorption and secretion activities take place.
Very, very rare to have stratified cuboidal

14. Columnar Epithelium Simple columnar– one cell thick
rectangular shaped (long and narrow)
Lines digestive tract where absorption & secretion occurs.
White spots are goblet cells which secrete mucous
No stratified columnar

15. Confusing Epithelial Tissue
Transitional Epithelium – Numerous layers of cells of varying and often irregular shape
Shape of cells depends upon the amount of stretching (ex: bladder)

16. Confusing Epithelial Tissue Continued…
“Pseudostratified Columnar Epithelium”
Tall rectangular cells, with multiple irregular rows of nuclei. Nuclei are positioned at differing levels
Cells narrow in the area without the nucleus
Located in the trachea; secrete & move mucous
Goblet cells secret mucous to aid cilia in moving substances across the cells’ surface

17. Epithelial Tissue in Review…
Epithelial tissues can be found in three types of membranes: Cutaneous, Serous, and mucous membranes.

18. Mucosa Membranes
Mucus-secreting membranes line tubes; moistens and protects from enzymes and acid (i.e., stomach, trachea, mouth, and vagina)
Membranes are involved in absorption and secretion.

19. Serous Membranes
Serous membranes line body cavities that do not open directly to the outside
They cover the organs located in those cavities.
Fluid lubricates the membrane and reduces friction and abrasion when organs move against each other.

20. Cutaneous Membranes Cutaneous membranes cover the surface of the body.
Consists of stratified squamous epithelium
Cutaneous membranes are thick, relatively waterproof, and dry.
Function = protection