Tissues
Epithelial tissue (Epithelium)
- Closely packed flattened cells to make the inside/outside lining of the body
Little intercellular material
- Avascular tissue (no blood vessels)
- Upper surface is exposed to the outside of the body/ to an internal body cavity
Basal surface rests on connective tissue
- Basement membrane (thin extracellular layer) forms between epithelial and connective
tissue
Two kinds:
- Covering and lining
Covers outside surfaces of body, lines internal organs
- Glandular epithelium
Hormone secretion
Covering and lining:
Classified by cell shape and number of cell layers
- Squamous cells
Flat, nucleus locates near upper surface (fried egg like)
- Cuboidal cells
Cube/hexagon shaped with central round nucleus
Produce secretions/ absorb substances
- Columnar cells
Tall with an oval nucleus near the basement membrane.
Protect underlying tissues/absorb substances
May have microvilli or cilia
- Transitional cells
Range of shapes (flat to tall)
Extend/compress in response to body movement
Number of cell layers:
- Simple = single layer
- Stratified = multiple layers
- Pseudostratified = single layer of different sizes (looks multilayered but isn’t)
Simple squamous = single layer of flat cells
Pseudostratified columnar ciliated = single layer of tall ciliated cells of more than one size.
Stratified epithelium – named after the shape of the outermost cell layer
Epithelial tissue (Epithelium)
- Closely packed flattened cells to make the inside/outside lining of the body
Little intercellular material
- Avascular tissue (no blood vessels)
- Upper surface is exposed to the outside of the body/ to an internal body cavity
Basal surface rests on connective tissue
- Basement membrane (thin extracellular layer) forms between epithelial and connective
tissue
Two kinds:
- Covering and lining
Covers outside surfaces of body, lines internal organs
- Glandular epithelium
Hormone secretion
Covering and lining:
Classified by cell shape and number of cell layers
- Squamous cells
Flat, nucleus locates near upper surface (fried egg like)
- Cuboidal cells
Cube/hexagon shaped with central round nucleus
Produce secretions/ absorb substances
- Columnar cells
Tall with an oval nucleus near the basement membrane.
Protect underlying tissues/absorb substances
May have microvilli or cilia
- Transitional cells
Range of shapes (flat to tall)
Extend/compress in response to body movement
Number of cell layers:
- Simple = single layer
- Stratified = multiple layers
- Pseudostratified = single layer of different sizes (looks multilayered but isn’t)
Simple squamous = single layer of flat cells
Pseudostratified columnar ciliated = single layer of tall ciliated cells of more than one size.
Stratified epithelium – named after the shape of the outermost cell layer
