Scott.lehbauer@lethbridgecollege.ab
.ca

• Tissues - are groups of similar cells that are specialized to perform specific functions. For example, nervous tissue is specialized to conduct impulses that help control and coordinate body activities.
• The study of tissues is called histology.

• Are tissues that cover all the body surfaces inside and out.
• are tissues that are composed of at least one layer of cells.
• more specifically they make up the outer layer of the skin, form the inner lining of body cavities, cover organs, line the chambers inside hollow organs, and are the major tissue component of glands.

• Epithelial tissues always have one side exposed to the outside or to an open space internally.
• The underside of all epithelial tissues is anchored to connective tissue by a nonliving layer called a basement membrane.
Basement Membrane

• Epithelial tissues are avascular (lack blood vessels)
• Epithelial tissues obtain nutrients from the vessels in the underlying connective tissue.
• Epithelial tissues reproduce rapidly, therefore injuries to epithelial tissues repair quickly.

• Epithelial tissues are tightly packed together.
(little intercellular space)
• Epithelial tissues are classified according to their shape, arrangement and function of their cells.

1. According to arrangement
2. According to shape

• Simple – one layer thick
Simple Squamous Epithelium Simple Cuboidal Epithelium
• Stratified – two or more layers
Stratified Squamous Epithelium Transitional Epithelium

Examples of Shapes of Epithelial Tissues. Wikipedia 2007.

1.G
landular – in skin, intestines, endocrine glands they make and secrete substances.
2.A
bsorption – through microvilli on the top surface of the cells.
3.P
rotection – the densely packed cells provide a protective layer for the underlying tissues.
4.S
ecretion – of fluid, enzymes mucus and other substances.

Simple Squamous Epithelium
Description – one cell layer thick.
• Squamous (thin) – thin cells that look like fried eggs.

Simple Squamous Epithelium
Function – diffusion of gases
• secrete serous fluid to lubricate covering of organs.

Simple Sqamous Epithelium
Location
• Lining of alveoli
• Lining of capillaries
• Lining of lymph vessels
• Covering around organs

Simple Columnar Epithelium
Description
• Elongated column shaped cells
• One cell layer thick
• Nuclei are arranged near the bottom of cells

Simple Columnar Epithelium
Function
• Absorption, secretion of mucus, movement of materials (mucus and reproductive cells)

Simple Columnar Epithelium
• Goblet Cells secrete mucus which protects and lubricates the tissue.
• Brush Border
Brush Border contains microvilli which vastly
Nucleus increase the surface area of the cell for absorption.
Basement
Membrane
Goblet
Cell

Simple Columnar Epithelium
Location
• Lines the digestive tract from stomach through to the rectum.
• Also found in the gall bladder and oviducts.
Wikipedia 2007

Simple Cuboidal Epithelium
Description
• Short cube shaped cells with a large centrally located nuclei

Simple Cuboidal Epithelium
Location
• They are found in small glands, ovaries, kidney tubules and the retina.
X – Section of Kidney Tubule

Simple Cuboidal Epithelium
Function
• In glands cuboidal epithelial cells secrete substances.
• In the kidney tubules they absorb substances
(water and solutes).
Cube Shaped
Cells

Pseudostratified Ciliated
Columnar Epithelium
Description
• Cells vary in height, only the tallest cells reach the free surface. (simple tissue)
• Cell nuclei are at different heights giving the tissue a false (Pseudo) stratified appearance.
• Cells are again columnar in shape

• Location
• Found in the trachea and the upper respiratory tract.
• Also found in spermcarrying ducts

Function
• This type of epithelium secretes and absorbs substances.
• It also protects the respiratory tract by sweeping dirt and bacteria toward the pharynx.
Nuclei
Basement Membrane

Cilia
• Cilia sweep dirt and bacteria back towards the pharynx.
Goblet Cell
• Goblet Cells secrete mucus which collects bacteria and moistens the respiratory tract.

Stratified Squamous
• Description
• Thick membrane composed of several cell layers.
• Cells near the basement membrane are cuboidal or columnar in shape and alive.
• Cells near the surface are squamosal in shape and are full of keratin and dead.

Stratified Squamous
Location
• This epithelium is found in areas of high wear and tear.
Any area in the body exposed to the outside world.
• Examples - Epidermis of the skin, the lining of the mouth, anus and vagina

• Keratin is a tough, insoluble, fibrous structural protein.
• Keratin accumulates in the cells as they approach the outer surface.
• Cells rely on diffusion for nutrients so cells near the basement membrane are viable and cells near the surface are less viable.
Basement
Membrane
Dead Cells full of Keratin
Living Cells
(Cuboidal)

Stratified Squamous
Function
• This epithelium protects against scrapes, cuts and bacteria.
• Also it provides a water proofing layer around the body.

Transitional Epithelium
Description – note:
• outer cells are rounded not flattened as in
Stratified Squamous.
• Layers of cuboidal and elongated cells are held tightly together

Transitional Epithelium
Location –
• Ureters
• Urinary bladder
• Parts of the urethra

Transitional Epithelium
Function –
• Able to distend which allows for expansion and contraction
• Prevent any passage of urine into the surrounding areas.

Where in the body would you find this type of
Epithelial Tissue?

Name this type of Epithelial Tissue.

What is the function of the structure labeled A?
A

Name one main function of this tissue.

Name this type of Epithelial Tissue.

1. Small glands, ovaries, kidney tubules, retina.
2. Pseudostratified Ciliated Columnar
Epithelium
3. Secrete mucus
4. Protection against cuts and scrapes, waterproofing
5. Simple Columnar Epithelium.