Chapter 3

Epithelial tissues

Overview

4 main types of tissues in the human body What is a tissue?

4 TYPES

Epithelial tissue

Connective tissue

Muscular tissue

Nervous tissue

Structure and Function

Epithelial tissue provides coverings and linings

provide protection Allow for diffusion, filtration and osmosis Secretion, transport, absorption

Basic structure

Epithelial cells are packed close together Little intercellular material between them Form continuous sheets with no blood

vessels

That is why epithelial tissues provide good coverings

Shape and Arrangement

Epithelial cells are classified according to the shape of the shell and how they are arranged

Shape of Cells

Squamous: flat and scale-like

Cuboidal: cube shaped

Columnar: higher than wide

Transitional: varying shapes that can stretch

Arrangement of Cells

Simple: single layer of cells of the same shape

Stratified: many layers of cells, named for the shape of the cells in the outer layer

Pseudostratified: appears to be layered, but is not

Attachment

Epithelial tissues attach to other tissues

A basement membrane forms at the bottom of the tissue

Generally this then attaches to a connective tissue

Simple Squamous Epithelium

Single layer, very thin

Substances can easily pass through

Diffusion of gases occurs easily

Example: alveoli (tiny air sacs in lungs) and the linings of blood vessels and lymphatic tissue

Stratified Squamous Epithelium

Several layers of closely packed cells

Protection

Examples; epidermis, lining of mouth

Simple Columnar

Single layers Higher than wide (columns) specialize in absorption Open spaces; goblet cells Goblet cells make mucus

Simple Cuboidal

Does not form coverings

Forms clusters of tubules Tubules secrete

Example; gland tissue and the secretion of hormones

Transitional epithelium

Several layers and has the ability to stretch Bladder tissue When cells stretch, they flatten out

Psuedostratified

Appears to be two layers thick, but is not

Cilia extend from from cells

Allow rapid movement of substances

Line the trachea (rapid removal of dust)

Make a chart to study

List category of tissues List each type Describe it’s structure List it’s function Give one or two examples of where it is

located in the human body Use the chart to make a matching quiz for

yourself