1. Epithelial Tissues
BIO 1110

2. Tissues
Tissues: A group of similar cells, having a similar origin, and functioning together to carry out specialized activities.
Tissues can be solid, semi-solid or liquid.
From conception until approximately day 14, all cells look and function the same (undifferentiated=stem cells).
Around day 15 post conception, cells start to differentiate or take on new characteristics.
This is the start of tissue formation.

4. Tissues Histology is the study of tissues.
There are 4 main types of tissues in the human body:
Epithelial
Connective
Muscular
Nervous

5. Epithelial Tissue (Epithelium)
Tightly packed cells arranged in continuous single or multi-layered sheets.
Characteristics:
Avascular- without blood vessels. Epithelium gets nutrients from the adjacent connective tissue.
Bottom surface of epithelium is attached to the basement membrane (fibers that act like glue)
Has a nerve supply.

7. Covering/Lining Epithelium
This type of tissue is found on the outer covering of the skin and some internal organs as well as lining body cavities and some internal hollow organs.
There are 9 different types of lining/covering epithelium.
Epithelial tissue is classified based on the number of cell layers present and the shape of the cells of the tissue.

8. Number of Layers Simple- Stratified-
Single layer of tightly packed cells
Stratified-
2 or more layers of tightly packed cells

9. Number of Layers Continued..
Pseudostratified
Looks like many layers because not all cells reach the surface and the nuclei lie at different levels

10. Cell Shape Squamous Thin, flat and irregularly shaped Cuboidal
Square/cube shaped
Columnar
taller than wide
Transitional
change shape due to stretching or movement of body parts

11. Simple Squamous
A single layer of tightly packed thin, flat, irregularly shaped cells
Location:
Lines the blood vessels
Forms the peritoneum, pericardium and pleural linings
Found in the air sacs of lungs (alveoli)
Function:
Allows for easy diffusion of gases and blood components

12. Simple Squamous – Top View – found in the walls of capillaries and alveoli of lungs

13. Simple Cuboidal A single layer of tightly packed cube shaped cells.
Location:
Lines kidney tubules, ducts of glands, and secreting parts of glands
Function:
Secretion (force materials out of the cells) and absorption (pull materials into the cells)

14. Simple Cuboidal Epithelial Tissue – this is of ducts of the kidney

17. Simple Columnar A single layer of tightly packed rectangular cells
Can be non-ciliated or ciliated (tiny hairs)
Non-ciliated have microvilli (finger-like projections) on the free surface of the cells
Non-ciliated Location:
Lines the gastrointestinal tract (from stomach to anus)
Non-ciliated Function:
Secretion and absorption
Microvilli (folds in the cell membrane) increase surface area times for absorption

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19. Simple Columnar Continued…
Ciliated Location:
Lines tubes of the respiratory tract, fallopian tubes, and ventricles of the brain
Ciliated Function:
The cilia beat in unison to move substances outside the cell like mucus and egg cells.

20. Simple Columnar Non-Ciliated Epithelial Tissue - This is a cross section through the small intestine – for absorption – microvilli on surface of cells

23. Pseudostratified Columnar
A single layer of tightly packed columnar cells that appear to be multi-layered
Location:
Ciliated- Lines respiratory tract
Non-ciliated- Male urethra
Function:
Ciliated- moves materials across the apical surface of a tissue.
Non-ciliated- Absorb and protect

25. Stratified Squamous
Multiple layers of tightly packed squamous epithelial cells.
Location:
Areas that are subject to much “wear and tear”.
Skin and vagina
Function:
Protection

27. Stratified Cuboidal Two layers of cube shaped epithelial cells Rare
Location:
Lining the ducts of glands found in the esophagus
Function:
Moderate protection from the stomach acid that refluxes

29. Stratified Columnar Multiple layers of columnar epithelial cells Rare
Only the layer closest to the lumen (opening in a duct) is columnar in shape. The outer layers are somewhat squashed.
Location:
Lining the ducts of glands lining the esophagus
Function:
Moderate protection from stomach acid that refluxes

31. Transitional Epithelial tissue that has a variable shape
Can stretch and relax multiple times without being damaged
Location:
Lines the urinary bladder
Function:
Protection

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