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Tissues part a
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Body Tissues Tissues Groups of cells with similar structure and function Four primary types Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue
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Epithelial Tissues Locations Functions Body coverings Body linings
Glandular tissue Functions Protection Absorption Filtration Secretion
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Epithelium Characteristics
Cells fit closely together and often form sheets The apical surface is the free surface of the tissue The lower surface of the epithelium rests on a basement membrane Avascular (no blood supply) Regenerate easily if well nourished
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Epithelium Characteristics
Figure 3.17a
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Classification of Epithelia
Number of cell layers Simple—one layer Stratified—more than one layer Figure 3.17a
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Classification of Epithelia
Shape of cells Squamous flattened Cuboidal cube-shaped Columnar column-like Figure 3.17b
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Simple squamous Epithelia
Single layer of flat cells Usually forms membranes Lines body cavities Lines lungs and capillaries
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Simple squamous Epithelia
Figure 3.18a
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Simple cuboidal Epithelia
Single layer of cube-like cells Common in glands and their ducts Forms walls of kidney tubules Covers the ovaries
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Simple cuboidal Epithelia
Figure 3.18b
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Simple columnar Epithelia
Single layer of tall cells Often includes mucus-producing goblet cells Lines digestive tract
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Simple columnar Epithelia
Figure 3.18c
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Simple Pseudostratified columnar Epithelia
Single layer, but some cells are shorter than others Often looks like a double layer of cells Sometimes ciliated, such as in the respiratory tract May function in absorption or secretion
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Simple Pseudostratified columnar Epithelia
Figure 3.18d
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Stratified squamous Epithelia
Cells at the apical surface are flattened Found as a protective covering where friction is common Locations Skin Mouth Esophagus
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Stratified squamous Epithelia
Figure 3.18e
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Stratified Epithelia Stratified cuboidal—two layers of cuboidal cells
Stratified columnar—surface cells are columnar, cells underneath vary in size and shape Stratified cuboidal and columnar Rare in human body Found mainly in ducts of large glands
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Stratified TransitionaL Epithelia
Shape of cells depends upon the amount of stretching Lines organs of the urinary system
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Stratified TransitionaL Epithelia
Figure 3.18f
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Glandular Epithelium Gland
One or more cells responsible for secreting a particular product
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Glandular Epithelium Two major gland types Endocrine gland
Ductless since secretions diffuse into blood vessels All secretions are hormones Exocrine gland Secretions empty through ducts to the epithelial surface Include sweat and oil glands
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