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What are the four tissue types?
- Epithelial Tissue
- - Forms coverings protecting the body from the outside world.
- -Remember that the lumen (opening) of the gut tube is "outside".
- Connective Tissue-Holds structure of body
- Muscular Tissue-Moves body parts
- Nervous Tissue
- -Sensation, information processing, and control of body parts
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Epithelium cells have two surfaces:
an apical surface that faces the outside world; and
a basal surface that rests on, and is attached to, the basement membrane.
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The basement membrane, in turn, has two thin layers, each called a
lamina.
The basal lamina is the nearest the epithelial cells
The reticular lamina is a bit deeper.
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Features of an Epithelium
One free surface (apical surface)
- One surface attached to basement membrane
- -basal lamina
- -reticular lamina
- Underlying connective tissue:
- Locations:
- 1.Barriers to keep outside out and inside in.
- 2.Barriers that secrete substances.
- 3.Barriers for protection.
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Epithelia are usually classified by two adjectives follwed by the word "epithelium". The first word describes the ________________. The second one describes the __________________________.
arrangement of cells in the epithelium;
shape of the individual cells at the apical surface of the epithelium.
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What are the arrangement of cells?
Simple- the cells are a single layer, and all are in contact with the basement membrane.
Pseudostratified- even though the cells appear to have layers, every one is in contact with the basement membrane.
Stratified- cells have layers, so only the lowest layer is in contact with the basement membrane.
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What are the shapes of the cells?
Squamous- cells, as the name suggests, are flat and shaped like fish scales. They are wider than they are tall.
Cuboidal- cells are as wide as they are tall, like little ice cubes.
Columnar- cells, like a column, are taller than they are wide.
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Transitional epithelia contain
cells that change shape, depending on whether the organ is enlarged or shrunken.
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Naming Epithelia:
Arrangement + Shape
Three arrangements x three shapes = nine combinations.
Two of these not used, but add transitional: cells that change shape = eight combinations.
If different shapes present, always by shape of cells in apical (outermost) layer.
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Simple Squamous Epithelia
Single layer of flat cells.
- Locations:-Lining of heart
- -Lining of blood & lymph vessels
- -Air sacs of lungs
- -Kidney filtration
- -Eardrum
- -One layer of serous membranes
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A simple cuboidal epithelium is
often found where secretion or absorption is taking place, as in glandular tissue.
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Simple Cuboidal Epithelia
Single layer of cube-shaped cells.
- Locations:
- -Surface of ovaries
- -Eye
- - Anterior surface of lens
- -Pigmented epithelium
- -Kidney tubules
- -Many glands
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Simple Columnar Epithelia
- Single layer of column-like cells
- -with or without cilia
- -with or without microvilli
- -with or without mucus (goblet cells)
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Simple Columnar Epithelia
-Ciliated simple columnar locations
Respiratory tract
Uterine tubes/uterus
Efferent ducts testes
Some paranasal sinuses
Canal of spinal cord & ventricles of brain
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Simple Columnar Epithelia
-Nonciliated simple columnar locations
GI tract
Glandular ducts
Gallbladder
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