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HISTOLOGY REVIEW Epithelia. Dr. Tim Ballard Department of Biology and Marine Biology. Simple squamous epithelium. Kidney – median sagittal section – H&E – 10x objective.

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HISTOLOGY REVIEW Epithelia

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HISTOLOGY REVIEWEpithelia

Dr. Tim Ballard

Department of Biology and Marine Biology


Simple squamous epithelium

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

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


Simple squamous epithelium

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

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Bowman’s capsule

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


Simple squamous epithelium

Artery – cross section – H&E – 40xobjective

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


Simple cuboidal epithelium

Kidney – median sagittal section – H&E – 10xobjective

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


Simple cuboidal epithelium

Kidney – median sagittal section – H&E – 40xobjective

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Approximate location of basement membrane

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Approximate size of one cell

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 epithelium

Kidney – median sagittal section – H&E – 40xobjective

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


Simple cuboidal epithelium

Thyroid gland – cross section – H&E – 40xobjective

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


Simple cuboidal epithelium

Pancreas – section – H&E – 40xobjective

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


Simple columnar epithelium

Gallbladder – section – H&E – 10xobjective

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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 epithelium

Gallbladder – section – H&E – 40xobjective

Basement membrane would be located along this line.

Approximate size of one cell

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


Simple columnar epithelium

Duodenum – section – H&E – 40xobjective

Approximate size of one cell

Basement membrane would be located along this line.

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


Ciliated pseudostratified columnar epithelium

Trachea – cross section – H&E – 10xobjective

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epithelium

Basement membrane would be located along this line.

Underlying connective tissue

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


Ciliated pseudostratified columnar epithelium

Trachea – section – H&E – 40xobjective

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cilia

Basement membrane

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


Ciliated pseudostratified columnar epithelium

Intrapulmonary bronchus – section – H&E – 40xobjective

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cilia

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.


Stratified squamous epithelium

Esophagus – section – H&E – 10xobjective

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How many layers of cells do you see here?

Basement membrane

Underlying connective tissue

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.


(nonkeratinized) Stratified squamous epithelium

Esophagus – section – H&E – 20xobjective

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Basement membrane

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


Keratinized stratified squamous epithelium

Human skin – section – H&E – 10xobjective

Keratinized layers of cells

free surface

Basement membrane

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


Keratinized stratified squamous epithelium

Human skin – section – H&E – 40xobjective

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

Free surface

Epithelium

Basal surface

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.


Stratified cuboidal epithelium

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

Basal layer of cells

Approximate size of one apical cell

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Apical layer of cells

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 columnar epithelium

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

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Apical layer of cells

Approximate size of one apical cell

What is the epithelial type?

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.


Transitional epithelium

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

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Epithelial layer

Underlying connective tissue layer

Basal layer of cells

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


Transitional epithelium

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

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Apical layer of cells

Basal layer of cells

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

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


Transitional epithelium

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

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Basement membrane

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


Transitional epithelium

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

Apical layer of cells

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Basal layer of cells

Basement membrane

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

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