1. Epithelial Tissue
Thursday, November 22, 2018

2. Characteristics Polarity
Apical surface – faces the lumen or outside environment
Have microvilli
Absorb or secret substances
Ex: lining of kidney tubules & intestines
Basal surface – attaches to basement membrane
Basal lamina – thin sheet of connective tissue

3. Characteristics Specialized contacts
Fit tightly together to form sheets
Tight junctions – Keep cells close together, and proteins on the apical side of the membranes
Desmosomes – attach the cells

4. Characteristics Supported by connective tissue
Basement membrane: - reinforces epithelial membrane and helps prevent stretching and tearing
Avascular and innervated
No blood vessels
Has nerve endings
Regeneration
High regenerative capacity
Can divide very quickly and very often

5. Classification of Epithelial Cells
1. By the number of cell layers
simple – one layer
stratified – more than one layer
2. By the shape of the cells
squamous
cuboidal
columnar

7. Simple Squamous Epithelium
A single layer of flat cells
Lines the body cavities
Lines the lungs and capillaries

8. Simple Squamous Epithelium
Endothelium
Friction-reducing lining
Lymphatic vessels & blood vessels
Mesothelium
In serous membranes
Membranes that line ventral cavity & cover the organs

9. The green arrow points directly at the nucleus of an endothelial cell
The green arrow points directly at the nucleus of an endothelial cell. What type of cell does the purple arrow indicate?
11/22/2018

10. Simple Cuboidal Epithelium
A single layer of cube-like cells
Seen in many types of smaller glands and their ducts
Also seen in the walls of kidney tubules

11. Cross-Section of a kidney tubule
Lumen
Cross-Section of a kidney tubule
Above, we have a longitudinal section of a kidney tubule. Notice the almost square-shaped cells . One cell is highlighted for you in red.
11/22/2018

12. Simple Columnar Epithelium
A single layer of tall cells
Common modifications:
1 goblet cells – cells that produce mucus that
coats the epithelial membrane
2. cilia
3. microvilli
Associated with stomach, intestine, uterine, and respiratory tract

13. Simple columnar epithelium lining the lumen of the gallbladder.
11/22/2018

14. Pseudostratified Columnar Epithelium
A single layer of irregularly shaped columnar cells that appear to be stratified due to the cells having varying heights and the nuclei being at various locations.
Often have cilia
Found in the lining of the respiratory tract and the male urethra

15. Pseudostratified Columnar Epithelium
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16. Stratified Squamous Epithelium
Cells at the free edge are squamous and cells closer to the basement membrane are cuboidal or columnar
May be keratinized
Found in places where friction is common:
Outer layer of skin
Bottom of feet
Throat

17. Non-keratinized stratified squamous epithelium
This is keratinized stratified squamous epithelium from the sole of the foot. It extends the length of the orange line on the left. Notice the multiple layers of clear, dead, enucleated cells.

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19. Stratified Cuboidal and Columnar Epithelium
Rare in the human body
Found mainly in ducts of large glands
Stratified cuboidal cells from a sweat gland.

20. Transitional Epithelium
Modified, simple squamous epithelium
The shape of the cells depends on the amount of stretching
Found in urinary bladder

21. Transitional Epithelium

23. Identify the following Epithelial tissues.
Simple cuboidal
Stratified squamous
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24. Identify the following Epithelial tissue.
Transitional Epithelium
Distended
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25. Identify the following Epithelial tissues.
Simple columnar
Pseudo-stratified columnar
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