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Epithelial Functions
- Protecting underlying structures.
- Acting as barriers.
- Permitting passage of certain substances.
- Secreting substances.
- Absorbing substances.
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Keratinized
or
Non-Keratinized: that is the question!
- •During the process of
- epithelial differentiation, cells become cornified as keratin protein is incorporated into longer keratin
- intermediate filaments.
- • In many other cell
- types, (dermis) keratin filaments and other intermediate filaments function as
- part of the cytoskeleton to mechanically
- stabilize the cell against physical stress.
- •Cells
- in the epidermis contain a structural matrix of keratin, which makes this
- outermost layer of the skin almost waterproof, and along with collagen and elastin, gives skin its
- strength.
•calluses
•dandruff
-
connective tissue and functions
- Enclosing and separating as capsules around organs.
- Connecting tissues to one another as tendons and ligaments.
- Supporting and moving as bones.
- Storing as fat.
- Cushioning and insulating as fat.
- Transporting as blood.
- Protecting as cells of the immune system.
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Muscle and functions
- Movement of body – voluntary/striated.
- Pumping of blood – involuntary/striated (myocardium).
- Involuntary control – peristalsis, eye movement, blood vessels, etc.
- associated w/ viscera (Viscera: The internal organs of the body, specifically those
- within the chest (as the heart or lungs) or abdomen )
-
Nervous and functions
- Communicate to/from CNS to/from PNS.
- Conduct chemical-electrical impulses within the CNS and PNS.
- Support of neurons (neuroglia)
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Key Facts of Epithelial Cells
- All cells with Little Extra-cellular Material between.
- Will Cover Body Surfaces and Form Glands.
- Has free and basal surfaces, shares lateral surfaces.
- Specialized cell – cell contacts including Desmosomes,
- Tight Junctions And Gap Junctions.
- Is Avascular – nutrients and gasses from blood must Diffuse across basement membrane.
- Very active Mitosis
- – have stem cells.
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Cell Types (epithelial)
- Squamous: Fried Egg, Flat
- Cuboidal: Cubes w/ Large Nucleus
- Columnar: Tall & Thin
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Epithelial Classifications
- Simple
- Stratified
- Pseudo
- Stratified
- Transitional
-
Simple Epithelial Tissue
Subtypes: Squamous, Cuboidal, Columnar
- consists of a single (1) layer of cells, with each cell
- extending from the basement membrane to the free surface.
-
Stratified Epithelial Tissue
Subtypes: Squamous, Cuboidal, Columnar
- consists of multiple layers of cells, only one of which is
- Stratified attached to the basement membrane.
-
Pseudo-stratified
No subtypes
- consists of a single (1) layer of cells; some tall and thin; some reach the free surface while others do not.
- Cells are always ciliated.
- Nuclei at different levels.
-
Transitional Epithelium
- Subtypes: Cuboidal, Squamous (when stretched)
- consists of stratified cells that appear cuboidal when the organ or tube (ex: urinary bladder) is not stretched, and squamous when stretched by fluids.
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