Histology

What is an Epithelial tissue?

An avascular tissue that cover that exterior surfaces, line internal closed cavities and line body tubes.

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What is the epithelial tissues main function? (6)

1. Protection
2. Secretion
3. Transport
4. Absorption
5. Selective permeability
6. Detection of sensations

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What are the 3 main features of an epithelial tissue?

1. Adhesion to each other via cell junctions
2. Functional and morphological polarity; the apical surface faces lumen, the basal surface faces basement membrane, lateral surface is in-between.
3. Connection to the basement membrane

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What are cell junctions and what are the different types?

Are connections that hold cells together.
1. Tight junction: complete fluid barrier, impermeable
2. Desmosomes: connected to cytoskeleton, allows H2O/ions to flow. Function to anchor cells.
3. Gap junctions: tunnel-like, exchange of charged ions which tra

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What is the basement membrane and what does it do?

A protein-polysaccharide rich layer made by epithelial cells and connective cells underneath the epithelial membrane.
Its function is to provide the epithelial cells with oxygen and nourishment.

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How can epithelial cells be classified?

Through the amount of layers and shape of the epithelial cell.

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What are the terms given to classify the amount of layers?
Give the functions of these different layers.

1. Simple, one layer of epithelial cells, each cell is connected to the basement membrane. This type allows regulated transport between cells.
2. Stratified, more than one layer. Protection from injury + a barrier to H2O and disease.

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What are the terms given to classify the shape?

1. Cuboidal, this looks cube-shaped
2. Columnar, this looks tall and thin
3. Squamous, this looks flattened.

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What does Pseudostratified epithelium mean?

Gives the appearance of being stratified, but is not.
Is actually simple as all cells touch the basement membrane.

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What does transitional epithelium (urothelium) mean and where is it found?

Is a stratified epithelium with morphological characteristics.
Found in urinal system and it relaxed when the bladder is empty and distended when bladder is full.

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Give specialisation of the apical surface.

Microvilli, increase absorptive surface of the cell. Present in many epithelial. Contain actin filaments cross-linked with actin-bundling proteins. Have a bundle of actin filaments anchored in the terminal web which allows for passive movement.

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P2: Specialisation of the apical surface.

Stereocillia, have absorptive functions and are in sensory hair cells in the inner ear (mechanoreceptors). longer than Microvilli. Contain actin filaments (same as MV), allow passive movement.

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P3: Specialisation of the apical surface

Cilia, 3 types:
1. Motile-most common, function in transport, present on sperm cells as flagella. Active movement.
2. Primary-in almost all body cells, function as sensory antennae, generate+transmit signals from extracellular space-cell. Passive
3. Noda

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Histology

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