Epithelial Tissue

Body Building Blocks

Standards/Objectives:

• Students will be able to identify the four major tissues of the body and each tissue’s over-all function.

• Students apply the principle of ‘structure determines function’ to each tissue type and how the tissue’s structure determines its function and location within the body.

• Students discuss the effects of skin cancer and burns and incorporate the importance of preventative practices for both disorders.

Tissues

• We are made of four types of tissues:• 1. Epithelial tissue• 2. Connective tissue• 3. Muscle tissue• 4. Nervous tissue• Combinations of two or more of these tissues

make up organs.

Remember: Structure Determines FunctionAND Function Determines Location!

Epithelial Tissue

• Epi=sit on top of something

• Epithelial tissues form the outer layer or cover and sit on top of other tissues.

Epithelial Tissue

• This tissue can also line the inside of hollow organs, where again it sits on top of other tissues.

• Epithelial tissue makes up glands.• Remember: covering and glands!

Epithelial Tissue Characteristics

• CELLULARITY=more cells than matrix• (When you look at this tissue all you see are

cells!)

Epithelial Tissue Characteristics

• Cells are anchored together with cell junctions, called desmosomes and tight junctions, to form SHEETS of cells.

Cell Junctions

• These structures allow cells to anchor to one another or communicate better.

Desmosomes• Cell membranes are NOT touching!• Longer desmosomes are known as belt desmosomes. • Short desmosomes are known as spot desmosomes.

Tight Junctions

• Cell membranes are touching each other.

• They are actually bound together to prevent anything from passing in between. (I.e. cell that line the digestive tract do not allow digestive enzymes, acid, or bacteria to pass between them)

Epithelial Tissue Characteristics

• Epithelial tissue ALWAYS has a free top or apex.• Nothing sits or is attached to the top of this tissue.

(#1 on the diagram)

Epithelial Tissue Characteristics

• Cilia and Microvilli!• Epithelial cells can have

special structures attached to the apex of their cells to help them do their job.

Epithelial Tissue Characteristics

• Epithelial tissue ALWAYS sits on a BASEMENT MEMBRANE.

(#2 on diagram)• This basement membrane

(lamina) is a connective tissue.

Epithelial Tissue Characteristics

• AVASCULAR (no blood vessels) WITH NERVE ENDINGS (INNERVATION)

• Epithelial tissue is fed by diffusion from blood vessels in the tissues underneath.

• There are no blood vessels in the skin!

(#3 on diagram)

Epithelial Tissue Characteristics

• Epithelial Tissue can REGENERATE. It does all the time! New cells are always being made and pushed up where the old cells fall off. Also, damaged cells can be replaced quite quickly.

Epithelial Tissue Characteristics

• Cilia are Sweepers and Cleaners and they can also be used in the ear to stimulate nerves:

• (I.E. bronchi of the lungs)

Epithelial Tissue Characteristics

• Microvilli are for absorption. Anytime you see them, you know that this cell or tissue is taking something into the cell.

• (I.E. small intestines)