Histology Guide virtual histology laboratory

Chapter 2 - Epithelium

Epithelium forms continuous sheets of cells that line internal surfaces and cover the external surface of the body. It is a selective barrier that protects tissues and is often involved in absorption or secretion. A basement membrane separates an epithelium from the underlying connective tissue.

Epithelia are classified based on three criteria:

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Fig 008 Epithelium

Epithelial cells are highly polarized:

An epithelium does not contain blood vessels and receives nourishment via diffission from the underlying connective tissue.

Glands are formed by the down growth of an epithelium into the underlying connective tissue (discussed in Chapter 12 - Exocrine Glands).

It is not necessary to learn the names of specific tissues for this chapter, but rather learn to recognize variations in epithelia.

Simple Squamous Epithelium

Simple squamous epithelium consists of a single layer of flattened cells. The thinness of these cells facilitates the transfer of materials (e.g., gases, fluids or nutrients) across the epithelium.

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MH 016 Simple Epithelia

(H&E)

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MHS 261 Common Bile Duct

(H&E)

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MHS 227a Eye

(H&E)

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MHS 224 Ovary and Oviduct

(H&E)

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MHS 281 Pavement Epithelium

(H&E)

Simple Cuboidal Epithelium

Simple cuboidal epithelium consists of a single layer of cuboidal cells. This epithelium is often associated with absorption, secretion, or excretion of waste matter.

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MH 016 Simple Epithelia

(H&E)

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MHS 211 Pancreas

(H&E)

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MHS 224 Ovary and Oviduct

(H&E)

Simple Columnar Epithelium

Single columnar epithelium consists of a single layer of cells that are taller than they are wide. This epithelium is often associated with absorption or secretion.

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MH 016 Simple Epithelia

(H&E)

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MH 119 Ileum

(H&E)

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MH 120 Ileum

(H&E)

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MHS 219 Jejunum

(H&E)

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MHS 261 Common Bile Duct

(H&E)

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MHS 224 Ovary and Oviduct

(H&E)

Pseudostratified Columnar Epithelium

Pseudostratified epithelium appears to be stratified because the nuclei of the epithelial cells are at different levels. However, every cell is in contact with the basement membrane, but not all cells reach the lumen.

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MH 016 Simple Epithelia

(H&E)

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MH 135 Larynx

(H&E)

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MH 136 Trachea

(H&E)

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MHS 222 Trachea

(H&E)

Stratified Squamous Epithelium

Stratified squamous epithelium has multiple layers of cells becoming flattened as they move from the basal layer to the apical layers. It provides protection from abrasion and is keratinized on the external surface of the body.

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MH 017 Stratified Epithelia

(H&E)

(keratinized and non-keratinized)

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MH 109 Esophagus

(H&E)

(non-keratinized)

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MH 038 Epiglottis

(H&E)

(non-keratinized)

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MH 090 Thin Skin

(H&E)

(keratinized)

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MH 091 Thick Skin

(H&E)

(keratinized)

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MHS 235 Thick Skin

(H&E)

(keratinized)

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MHS 227a Eye

(H&E)

(non-keratinized)

Stratified Cuboidal Epithelium

Stratified cuboidal epithelium has multiple layers of cells with an outermost layer of cuboidal cells. Limited distribution - found in the lining of larger ducts.

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MH 109 Esophagus

(H&E)

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MHS 234 Esophagus

(H&E)

Transitional Epithelium

Transitional epithelium (urothelium) is adapted for extensibility and is restricted to the urinary tract. It has multiple layers of cells with an outermost layer of much larger, dome-shaped cells (umbrella cells) that change shape during contraction and distention.

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MH 018 Transitional Epithelia

(H&E)

(relaxed and stretched bladder)

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MHS 214 Bladder

(H&E)