HISTOLOGY REVIEW HISTOLOGY REVIEW Epithelia Epithelia Dr. Tim Ballard Dr. Tim Ballard Department of Biology and Marine Department of Biology and Marine Biology Biology
Jan 07, 2016
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
lumen
Flattened cells, one cell layer thick, lining the lumen of an artery
Simple squamous epitheliumSimple squamous epithelium
Artery – cross section – H&E – 40x objective
lumen
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
lumen
Simple cuboidal epithelium (arrowheads) forms follicles in the thyroid gland.
Simple cuboidal epitheliumSimple cuboidal epithelium
Thyroid gland – cross section – H&E – 40x objective
lumen
lumen
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
lumen
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
lumen
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
lumen
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.
lumen
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
lumen
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
m
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
n
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
lumen
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
lumen
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
lumen
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
lumen
Basement membrane