4-2: Organisation Of Epithelial Tissues

Question 1

Q: What is meant by simple epithelium?

Answer 1

A: cells are lined up in a single row, with their nuclei alongside each other

Question 2

Q: What is meant by the basal lamina/basement membrane? Can it be viewed under a light microscope

Answer 2

A: the fibrous layer to which the base of each cell is attached

only just detectable in the light microscope

Question 3

Q: What is meant by columnar epithelium? Colour staining of cytoplasm? Function? Also known as?

Answer 3

A: pink staining cytoplasm, function: absorption of the products of food digestion. Also known as intestinal absorptive cells/enterocytes

Question 4

Q: What are goblet cells? Cytoplasm? Shape?

Answer 4

A: mucus secreting cells interspersed between epithelium with very pale cytoplasm and bulbous shape

Question 5

Q: What is the brush border? Function?

Answer 5

A: close packed row of small finger-like projections of the apical membrane (ONLY) which serve to increase the surface area; known as microvilli – required for cell polarisation

Question 6

Q: What do junctions refer to?

Answer 6

A: between adjacent cells

Question 7

Q: Describe the organisation of the intestinal epithelium tissue?

Answer 7

A: “simple columnar absorptive epithelium with goblet cells”

Question 8

Q: What does the lining epithelium of the intestines separate? Small lumen?

Answer 8

A: Lining epithelium separating the lumen and the rest of the body. If the lumen is small, the epithelium forms a gland or duct

Question 9

Q: What are glands?

Answer 9

A: tubular structure with secretory role

Question 10

Q: What are glands in the intestine called?

Answer 10

A: crypts (simple tube with closed end).

Question 11

Q: What are the secretory cells of the small intestine called? How are they recognised?

Answer 11

A: Paneth cells, recognised by the brightly pink stained granules positioned assymetrically at the apical surface

Question 12

Q: What are the 3 types of glands?

Answer 12

A: 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 13

Q: What is the mesentery?

Answer 13

A: The mesentery is a thin layer of tissue that attaches parts of the intestines to the rest of the body.

Question 14

Q: What does the mesentery allow?

Answer 14

A: It allows the whole length of the intestines to be folded up to fit within the abdominal cavity but still have a connection carrying its blood and nerve supply, and it means that the intestines can be somewhat mobile during peristalsis

Question 15

Q: Describe the organisation of the epithelium tissue of the mesentery. What shape are cells? What reflects the shape of cells?

Answer 15

A: one cell deep = simple

The cells are flat and wide, something that is also reflected in the shape of the nuclei.

Cells which are wider than they are tall are known as squamous

Question 16

Q: What is the epithelium lining blood vessels referred to as?

Answer 16

A: simple squamous epithelium (endothelium)

Question 17

Q: Describe the organisation of the epithelium tissue of the oesophagus.

Answer 17

A: lining the central lumen = stratified = many cells thick and squamous

Question 18

Q: How do cells of the oesophagus epithelium stain?

Answer 18

A: The cells stain differently according to their level with those nearest the basal lamina being almost purple, those higher up having a deep pink cytoplasm, and those nearest the lumen having a very pale cytoplasm

Question 19

Q: How do cells of the oesophagus epithelium differ in shape?

Answer 19

A: The individual cells have a range of different shapes with basal cells being almost rounded but those closer to the lumen

Question 20

Q: Why is the oesophagus epithelium tissues arranged in such a way?

Answer 20

A: The arrangement is designed to line the lumen of the oesophagus in a way which is resistant to damage. 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 21

Q: What type of epithelium is used in skin tissue?

Answer 21

A: stratified squamous epithelium

Question 22

Q: Describe the tissue organisation of the skin. How is the waterproof surface created?

Answer 22

A: Skin has to be waterproof to prevent the cells below drying out and dying. The surface cells of the epithelium have died (“cornified”) leaving only the dense network of their keratin-containing intermediate filaments to form a non-cellular protective layer that absorbs oily secretions to become waterproof

Question 23

Q: What does the epithelium tissue of the trachea separate?

Answer 23

A: The epithelium separates the lumen from the surrounding body tissue, including rings of cartilage which hold the airway open

Question 24

Q: Describe the organisation of the epithelium tissue of the trachea.

Answer 24

A: “pseudo-stratified columnar ciliated epithelium” =

Although you can identify individual columnar cells you will find that their nuclei are not lined up neatly. Some cells don’t stretch all the way to the luminal surface of the epithelium. This type of epithelium is referred to as pseudo-stratified because the nuclei look as if they are arranged in layers. It is not actually stratified because all of the epithelial cells have their base attached at the basal lamina.

Question 25

Q: Describe the roles of cilia and goblet cells (trachea). Placement? Goblet staining?

Answer 25

A: On their apical surface are fibrous projections = cilia. Interspersed among the ciliated cells are goblet cells (with this stain they are purplish). Goblet cells produce mucus which lines the airway and protects it from drying out. The cilia beat to move the mucus up towards the back of the mouth so that the mucus doesn’t accumulate.

Question 26

Q: What are 2 more examples of epithelium types?

Answer 26

A: Cuboidal – cells of approx. equal height and width, which are often present in ducts but are functionally unimportant

Urinary – certain features of both stratified and pseudo-stratifies (sometimes called transitional); specialised to be highly impermeable to urine and to be able to stretch as the bladder fills

Question 27

Q: Explain cell renewal in epithelia.

Answer 27

A: The cells in a pseudo-stratified epithelium which do not extend all the way to the luminal surface = specialised population of dividing cells = stem cells.

dividing cells are located where they have minimum susceptibility to damage

Question 28

Q: Where are stem cells in the small intestine? What happens to daughter cells?

Answer 28

A: within the crypts

daughter cells can form enterocytes which become specialised for absorption and move out of the crypt to cover the villi

Question 29

Q: Where are stem cells in stratified epithelia?

Answer 29

A: dividing stem cells are present in the basal layer adjacent to the basal lamina

Question 30

Q: What’s the strategy for cell division for simple squamous and simple cuboidal epithelia?

Answer 30

A: all of the cells are capable of cell division when required