Organisation of epithelial cells

Question 1

What type of epithelium does the small intestine have?

Answer 1

simple columnar

absorptive epithelium with goblet cells

Question 2

What is a gland?

Answer 2

Tubular structure with secretory role - known as crypts in intestine

Question 3

What are the types of glands?

Answer 3

Simple tubular – e.g. crypts; single closed tube

Compound – branched

Acina/alveolar – secretory cells restricted to regions with a specialised rounded shape at the ends of the
tubus

Question 4

What is the mesentery

Answer 4

tissue attaching intestine to rest of the body - allows intestine to be folded to be contained in the abdominal cavity but still have blood and nerve supply

Question 5

What is the epithelium type of the mesentery?

Answer 5

simple squamous (same as endothelium)

Question 6

oesophagus epithelium

Answer 6

stratified, squamous

Question 7

why is the oesophagus epithelium stratified?

Answer 7

The stratified arrangement means that if the cells adjacent to the lumen become damaged, the cells underneath maintain the function of the epithelium as a barrier and can divide to replace those that are lost.

Question 8

What does trachea epithelium do?

Answer 8

Separates the lumen from the surrounding body tissue, including rings of cartilage which hold the airway open

Question 9

What kind of epithelium does the trachea have?

Answer 9

Pseudo-stratified columnar ciliated epithelium

Question 10

Cell renewal in epithelia

Answer 10

• The cells in a pseudo-stratified epithelium which do not extend all the way to the luminal surface provide a specialised population of dividing cells, known as stem cells.
• In the small intestine stem cells are located within the crypts.
• In stratified epithelia the dividing stem cells are present in the basal layer adjacent to the basal lamina.
• In all three cases the dividing cells are located where they have minimum susceptibility to damage.
• A different strategy is found in some other epithelia, including simple squamous and the simple cuboidal epithelia of many ducts. Here all of the cells are capable of cell division when required.

Question 11

What is the importance of stratified squamous epithelium?

Type of epithelium in skin?

Answer 11

The body uses a stratified squamous epithelium in several locations as a protective strategy, with the skin being a special case. Skin has to be waterproof to prevent the cells below drying out and dying. The surface cells of the epithelium have died leaving only the dense network of their keratin
- The epithelium of the skin is the epidermis. This is a stratified squamous epithelium..

Question 12

Layers of the skin

Answer 12

• The most basal layer is the stratum basale, a single layer of cuboidal cells sitting on the basal lamina. Stem cells in this layer produce new cells that form the upper layers that differentiate and ultimately replace the cells being lost from the surface.
• The melanocytes, which provide pigment granules the keratinocytes, are found in this layer.
• The layer just apical to the stratum basale is the stratum spinosum. In this region, the cells form a few layers of cells which often have a spiky appearance.
• The region apical to this is the stratum granulosum. The cells in these layers contain numerous granules, which may not be visible in the specimen.
• The apical layers, the stratum corneum, are layers of dead cells that have been “cornified” (keratinised) during the differentiation and turnover of the epidermis.
• Nuclei cannot be observed in the cells of the stratum corneum.
• In thin skin (this specimen), hairs and their follicles are present.
• In thick skin hair is not present, and the stratum corneum is typically many times thicker than in thin skin.