TissueTissue 

 

Definition of tissue: A mass of similar cells that, together, perform a specific function.

There are four basic types of tissue in the human body:

1.Epithelial tissue2.Connective tissue3.Muscular tissue4.Neural tissue

 

Each of these types of tissue has specific forms and functions.

Epithelial TissueEpithelial Tissue

Epithelial tissues form all of the Epithelial tissues form all of the coverings coverings and and liningslinings of the of the

body.body.

Singular (one tissue) = Singular (one tissue) = epitheliumepithelium

Plural (two+ tissues) = Plural (two+ tissues) = epitheliaepithelia

Epithelia: Epithelia: FormForm

1. Cells are closely bound together

2. A free, or apical, surface is exposed to open space (either the environment or a cavity or passageway)

Free surface = apical surface

Example A:

The top layer of our skin is epithelial tissue.

The part of your skin that you can touch is its apical surface.

Example B:

This is a cross-section of an artery (and surrounding tissue).

Arteries and other blood vessels are lined with epithelial tissue.

The inner surface of the artery is the apical surface.

3. Epithelia are attached to underlying connective tissue by a basement membrane.

4. Epithelia are avascular. There are no blood vessels.

without blood vessels = avascular

5. Cells at the apical surface are continually replaced or regenerated.

There is a very fast cell turnover on these surfaces.

Epithelia: Epithelia: FunctionFunction

1. Provide physical protection.

Epithelia protect underlying tissues from pathogens, abrasion, dehydration, and UV rays.

2. Control permeability.

Permeable = having openings that let things through.

3. Provide sensation.

Sensation = physical feelings like hot, cold, pain, etc.

4.Produce specialized secretions.

Secretions = substances such as tears, sweat, saliva, hormones, etc. These secretions an be inside or outside the body.

Why are apical epithelia being continually replaced?

Think of of an epithelial apical surface in the human body and describe why you think it would need to be constantly replaced.

Leave your original answer as a comment onthis post to receive credit.

Finish your notes with this Finish your notes with this “think it through” question:“think it through” question: