HISTOLOGY REVIEWHISTOLOGY REVIEWEpitheliaEpithelia

Dr. Tim BallardDr. Tim Ballard

Department of Biology and Marine BiologyDepartment of Biology and Marine Biology

Simple squamous epitheliumSimple squamous epithelium

Arrowheads indicate the locations of Bowman’s capsules within the cortex of the kidney. This is one place to locate simple squamous epithelium.

Kidney – median sagittal section – H&E – 10x objective

Single layer of flattened cells with prominent flattened nucleus, very thin, lining the capsular space of Bowman’s capsule

Simple squamous epitheliumSimple squamous epithelium

Kidney – median sagittal section – H&E – 40x objective

Bowman’s capsule

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Flattened cells, one cell layer thick, lining the lumen of an artery

Simple squamous epitheliumSimple squamous epithelium

Artery – cross section – H&E – 40x objective

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Simple cuboidal epitheliumSimple cuboidal epithelium

Kidney – median sagittal section – H&E – 10x objective

Arrowheads indicate renal tubules in the kidney cortex. “Tubule” is a key word, telling you this is one place to locate simple cuboidal epithelium.

Kidney – median sagittal section – H&E – 40x objective

Renal tubules (arrowheads) – note that the cells appear about as tall as they are wide and that there is a single layer of cells.

Simple cuboidal epitheliumSimple cuboidal epithelium

lumen

lumenApproximate size of one

cell

Approximate location of basement membrane

In the renal medulla you find collecting ducts, lined with a single layer of simple cuboidal cells.

Simple cuboidal epitheliumSimple cuboidal epithelium

Kidney – median sagittal section – H&E – 40x objective

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Simple cuboidal epithelium (arrowheads) forms follicles in the thyroid gland.

Simple cuboidal epitheliumSimple cuboidal epithelium

Thyroid gland – cross section – H&E – 40x objective

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Duct (arrowhead indicates location of the basement membrane) within the pancreas. Note the single layer of simple cuboidal cells.

Simple cuboidal epitheliumSimple cuboidal epithelium

Pancreas – section – H&E – 40x objective

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Villi (arrowheads) – finger-like processes inside the gallbladder. This organ of the digestive system is line with simple columnar epithelium.

Simple columnar epitheliumSimple columnar epithelium

Gallbladder – section – H&E – 10x objectivelumen

Note that the simple cuboidal cells are taller than they are wide.

Simple columnar epitheliumSimple columnar epithelium

Gallbladder – section – H&E – 40x objective

Basement membrane would be located along this line.

Approximate size of one cell

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Although this looks different from the gallbladder, this is still simple columnar epithelium.

Simple columnar epitheliumSimple columnar epithelium

Duodenum – section – H&E – 40x objective

Basement membrane would be located along this line.

Approximate size of one cell

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This is the signature epithelium of the respiratory system. Note the difference between epithelium above and connective tissue below the line.

Ciliated pseudostratified columnar Ciliated pseudostratified columnar epitheliumepithelium

Trachea – cross section – H&E – 10x objective

Basement membrane would be located along this line.

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Underlying connective tissue

epithelium

All cells contact the basement membrane, but not all cells reach the surface. It only appears stratified, hence the name.

Ciliated pseudostratified columnar Ciliated pseudostratified columnar epitheliumepithelium

Trachea – section – H&E – 40x objective lumencilia

Basement membrane

You can tell this isn’t stratified columnar epithelium because no can’t discern individual layers. Stratified columnar would have clear rows of nuclei.

Ciliated pseudostratified columnar Ciliated pseudostratified columnar epitheliumepithelium

Intrapulmonary bronchus – section – H&E – 40x objective

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cilia

Basement membrane

It is easy to see why this is called a stratified epithelium. I counted about 35 layers of cells stretching from the basement membrane to the apical surface.

Stratified squamous epitheliumStratified squamous epithelium

Esophagus – section – H&E – 10x objective lumen

Basement membrane

How many layers of cells do you see here?

Underlying connective

tissue

Cells at the basal surface are cuboidal and mitotic. As new cells are pushed to the top, they become increasingly squamous in shape.

(nonkeratinized) Stratified squamous (nonkeratinized) Stratified squamous epitheliumepithelium

Esophagus – section – H&E – 20x objective lumen

Basement membrane

Again, look at the layers of cells between the basement membrane and the apical surface.

Human skin – section – H&E – 10x objective

Keratinized stratified squamous epitheliumKeratinized stratified squamous epithelium

Basement membrane

free surface

Keratinized layers of cells

Cuboidal cells at the basal surface give way to increasingly flattened cells (squamous) in the upper layers. The cells are filled with water-proof keratin.

Human skin – section – H&E – 40x objective

Keratinized stratified squamous epitheliumKeratinized stratified squamous epithelium

Free surface

Keratinized layers of cells – very long, thin and flattened (scale-like)

Basal surface

Epitheliu

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Larger ducts of the body may have a stratified cuboidal epithelium, where the top layer of cells is cuboidal. There are usually only two layers of cells.

Stratified cuboidal epitheliumStratified cuboidal epithelium

Submandibular (salivary) gland – section – H&E – 40x objective

Apical layer of cells

Approximate size of one apical celllume

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Basal layer of cells

Very large ducts of the body may have a stratified columnar epithelium, where the top layer of cells is columnar. There are usually only two layers of cells.

Stratified columnar epitheliumStratified columnar epithelium

Submandibular (salivary) gland – section – H&E – 40x objective

Apical layer of cells

Approximate size of one apical cell

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Basal layer of cells

What is the epithelial type?

Transitional epithelium is the signature epithelium of the urinary tract. It is found in the ureters and urinary bladder.

Transitional epitheliumTransitional epithelium

Ureter – cross section – H&E – 10x objective

Epithelial layer

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Basal layer of cells

Underlying connective tissue

layer

This is called transitional epithelium because the number of cell layers changes as the organ walls increase and decrease in tension.

Transitional epitheliumTransitional epithelium

Ureter – cross section – H&E – 40x objective

Apical layer of cells

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Basal layer of cells

When the organ walls are under low tension, the epithelium has 6 – 8 layers of cells.

The urinary bladder looks different from the ureter because it is a different organ with different function, but the epithelium is still transitional.

Transitional epitheliumTransitional epithelium

Urinary bladder – section – H&E – 10x objective

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Basement membrane

The distinguishing features of this epithelium are multiple layers and the very large “sofa pillow-like” cells at the apical surface.

Transitional epitheliumTransitional epithelium

Urinary bladder – section – H&E – 40x objective

Apical layer of cells

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Basal layer of cells

Basement membrane

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