Module #2 Histology

Histology – the study of

tissues

Four tissue types:

Epithelial

Connective

Muscle

Nerve

Epithelial

Tissuehttp://lima.osu.edu/biology/images/anatomy/Stratified%20squamous%20epithelium%20400X.jpg

General Features of Epithelial Tissue

•Cells are closely packed with little extracellular material (between cells)

•Are in continuous sheets

•Single or multiple layered

General Features of Epithelial Tissue

•Epithelia is avascular meaning “without blood vessels”.

•Nutrients and wastes are exchanged by diffusion with the adjacent connective tissue.

General Features of Epithelial Tissue

•have a free surface which is exposed to a body cavity, lining of an internal organ, or the exterior of the body, and

• a basal surface which is attached to the basement

membrane.

basal surface

General Features of Epithelial Tissue

•Subject to wear, tear and injury, so has a high capacity for renewal (high mitotic rate).

•Functions include protection, filtration, lubrication, secretion, digestion, absorption, transportation, excretion, sensory reception, and reproduction.

General Features of Epithelial Tissue

•Epithelial tissue sits on a basement membrane located between it and the tissue underneath.

http://www.ouhsc.edu/histology/Glass%20slides/13_04.jpg

Epithelial tissue

Connective tissue

There are two kinds epithelial tissue based on function:

(1) lining or covering epithelium –covers the skin and outside of some internal organs, forms the inner lining of body cavities, blood vessels, and internal organs.

Epithelial Tissue con’t

There are two kinds epithelial tissue (function):

(2) glandular epithelium -consists of cells that secrete substances. (ex. Thyroid/sweat/oil glands)

Epithelial Tissue con’t

Epithelial tissue can be divided into categories based on……

>the shape of the cells and

> the number of layers of cells.

SHAPES of epithelium:

1. Squamous

-flat cells-thin which allows substances to pass through (diffuse) them. -have limited cell structures due to size

2. Cuboidalcube shapedImportant in secretion and absorptionHave more cell structures than squamousUses active transport to secrete and absorb substances

3. Columnar

cells are tall and cylindrical Have the most cell structures Most complex Most secretion ability

4. Transitional

•cells can readily change shape from squamous to columnar•change shape due to stretching, of body parts. (ex. Found in bladder)

Arrangement of Layers

1. Simple epithelium a single layer of cellsfound in areas where diffusion, osmosis, filtration, secretion and absorption occur.Can be squamous, columnar, or cuboidalEx. lungs

Arrangement of Layers

2. Stratified epithelium contains two or more layers of cells protects underlying tissues found where there is wear and tearEx. Skin Named by the free surface.

http://photos1.blogger.com/blogger/7703/2162/1600/stratified epi.jpg

Arrangement of Layers

3. Pseudostratified epithelium contains a single layer of a mixture of cell typeshas a stratified appearancebut is a single layerAll cells touch basementmembrane

Glandular Epithelium

Columnar epithelium that contains special cells capable of synthesizing and secreting certain substances such as enzymes, hormones, milk, mucus, sweat, wax and saliva

Glandular Epithelium

Goblet cells :

Special columnar cells that their function is to secret mucin which mixes with water to form mucous -intestines

Goblet cell