0401 - Epithelium - RM Flashcards
Describe the appearance of simple squamous epithelium.
Also known as ‘pavement epithelium’ or ‘endothelium’ – a single layer of flat cells at the free edge, above the basement membrane. Each cell wider than it is tall, providing a large surface area. Cytoplasm may be very difficult to see. Nuclei may look as though they protrude into the lumen.
Describe the appearance of simple cuboidal epithelium.
Single layer of cells as round as tall as they are wide, and usually have a large central nucleus.
Describe the appearance of simple columnar epithelia.
Single layer of cells that are taller than they are wide, with nucleus towards the base. Can be ciliated or non-ciliated.May contain goblet cells (glandular epithelium).
Describe the appearance of pseudostratified ciliated columnar epithelium.
More complex and less regular than simple columnar. Appears to be more than one layer of cells due to nuclei on different levels.Actually a single layer with all cells actually resting on basement membrane.Ciliated.
Describe the appearance of stratified squamous epithelium.
2 or more layers, transitioning from a cuboidal or columnar basal layer to a squamous surface layer. Consists of a distinct basal layer (lowest) and spinous layer (above) that includes desmosomes, which appear as striations between the cells. May be keratinised, in which case there will be a granular layer, with overlying keratin.
Describe the appearance of stratified cuboidal epithelium.
2 or 3 layers of cuboidal or low-columnar cells, other cell types may be present beneath the top layers. Not much absorption or excretion, so unlikely to contain microscopic pores or goblet cells.
Describe the appearance of stratified columnar epithelium.
Several layers of epithelial cells of any type, with a surface layer of columnar cells.
Describe the appearance of transitional (urothelium) epithelium.
4-5 layers. Basal layer is cuboidal, surface layer larger and rounded.Transitional between stratified cuboidal and stratified squamous, so may be hard to identify.
Where would you find simple squamous epithelium? What is its function in each place?
Lungs – Gas exchangeBlood vessels – gas, waste, nutrient exchangeKidney – urine filtrationMesothelium – secretion of lubricating fluid
Where would you find simple cuboidal epithelium? What is its function in each place?
Lining the ducts of the kidney – absorbing substances to give urine its final composition.Lining the ducts of salivary glands and pancreas – secreting fluids.
Where would you find simple columnar epithelium?
GallbladderFallopian tubes (with cilia)Small and large bowel, stomach, and uterus (with microvilli).
Where would you find pseudostratified ciliated columnar epithelium?
Lining of the bronchi.
Where would you find stratified squamous epithelium?
Anywhere where abrasion is a risk – skin (keratinised), mouth, oesophagus, tongue, vagina (all non-keratinised in healthy people).
Where would you find stratified cuboidal epithelium?
Lining the larger ducts of the exocrine glands, such as salivary glands.
Where would you find stratified columnar epithelium?
Very rare – found in parts of male urethra, conjunctiva of eye, and uterus.
