Epithelial Cells

Question 1

What are tissues

Answer 1

A group or groups of cells whose type, organisation and architecture are integral to its function. Madeup of cells, extracellular matrix and fluid.

Question 2

Large number of cells can be grouped into 5 major categories

Answer 2

Haemopoietic, Epithelial, Contractile, Connective tissues and neural cells

Question 3

Epithelial cancers

Answer 3

Carcinomas

Question 4

Mesenchymal cancers( connective tissue and muscle)

Answer 4

Sarcomas

Question 5

Haemopoietic cancers

Answer 5

Leukaemias ( from bone marrow cells) or lymphomas (from lymphocytes)

Question 6

Neural cell cancers

Answer 6

Neuroblastomas or gliomas

Question 7

Functions of epithelial cells

Answer 7

Transport, absorption, secretion and protection

Question 8

Squamous

Answer 8

Flattened, plate shapes

Question 9

Columnar

Answer 9

Arranged in colums

Question 10

Cuboidal

Answer 10

Cube-like

Question 11

Single layer

Answer 11

Simple epithelium

Question 12

Multi layer

Answer 12

Stratified epithelium

Question 13

simple squamous epithelium

Answer 13

Lung alveolar epithelium, mesothelium (lining major body cavities) , endothelium lining blood vessels and other blood spaces). Forms thin epithelium allowing exchange to occur

Question 14

Simple Cuboidal epithelium

Answer 14

Linings of ducts e.g. kidney collecting ducts

Question 15

Simple Columnar epithelium

Answer 15

Absorption and secretion of molecules ( enterocytes lining the gut, involved n the take up of the breakdown products)

Question 16

Stratified squamous epithelium

Answer 16

Two types:
Keratanizing: produce keratin and die in doing so and become much thicker and stronger structures (e.g. skin epithelium). Such cells lose their celullar organelles and nuclei which are not visible under light microscopy

Non-keratanizing: retain nuclei and organelles. (e.g. epithelium lining the mouth, oesophagus, anus, cervix and vagina)

Question 17

Pseudo-stratified epithelium

Answer 17

Appears to be multi-layered but on close examination, the surface cells have contact with basal lamina, e.g. airway(trachea and bronchi) epithelium, various ducts in the urinary and reproductive tractd

Question 18

Read the notes on epithelial cell polarity on onenote

Answer 18

read the notes on epithelil cell polarity on onenote

Question 19

Different types of cell-cell junctions in epithelia

Answer 19

Tight junction, cell-cell anchoring junction , channel-forming junction and cell-matrix anchoring junction

Question 20

Examples of cell-cell anchoring junctions

Answer 20

Adherens and desosomes

Question 21

example of channel-forming junction

Answer 21

gap junction

Question 22

example of cell-matrix anchoring junctions

Answer 22

actin-linked cell-matrix junction (anchors actin filaments in a cell to extracellular matrix) and hemidesomosome (anchors intermediate filaments in a cell to extracellular matrix)

Question 23

function of tight junctions

Answer 23

usually form a belt usually arounf the apical lateral membrane. Involved in sealing the gapd beteween cells.

Question 24

adherens junctions

Answer 24

Just below tight junction- basically master junction which controls the formation of all the other junctions

Question 25

desmosomes

Answer 25

scattered through the lateral membrane . These are spot junctions that form mechanically tough junctions between cells and are important in tissues that require to resist mechanical stresses.

Question 26

gap junction

Answer 26

channel forming juncion. Usually forms pores between cells and allows cells to exchange and share materials- help cells in synchronizing activities.

Question 27

features in transporting epithelial cells

Answer 27

Plasma membrane contains high concs of ion transporters. Normally, mitochondria are closely associated with extensive basal membrane infoldings , providing energy for AT . Infoldings increase the amount of basal membrane that can pump ions and water.
Apical plasma membrane has many ion and water channels for passive transport of water and ions

Question 28

Absorptive epithelium

Answer 28

Carriers transporting nutrients are found on brushborder membrane (columnar or cuboidal membrane), e.g. absorptive intestinal cells (enterocytes) and kidney proximal tubule cells.

Secretory cells (goblet cells secreting mucus)

Active transporters and channels for the uptake of nutrients

Question 29

where is the secretory epithelium found

Answer 29

epithelium is arranged into tubules and glands.

2 main types of secretion: exocrine(into duct/lumen) and endocrine (into the bloodstream)

Question 30

where are the secretory granules positioned in the exocrine and the endocrine cells

Answer 30

Exocrine: positioned towards apical cytoplasm as they are arranged for secretion from the apical plasma membrane

Question 31

where are the secretory granules positioned in the endocrine cells

Answer 31

towards the basal aspects so that when their contents are released, they have close access to blood circulation

Question 32

2 ways to classify endothelial cells on the way they secrete

Answer 32

constitutive : secretory vesicles as they are formed move directly to the plasma membrane and release their contents, e.g. production of plasma proteins by hepatocytes

stimulated: secretory vesicles are stored in the cytoplasm and only fuse with the plasma membrane to release their contents, e.g. the release of adrenaline from cells of adrenal medulla after a fight-or-flight stimulus (stimulated endocrine secretion)

Question 33

inhibition of epithelial turnover in the small intestine (intestinal crypt cells)

Answer 33

Cancer chemotherapy - reults in loss of finger like villi and flattening of intestinal muscosa. Responsible for many of gastro-intestinal disturbances that are side -effects of chemotherapy. 5-FU example of drug

Question 34

Epithelial turnover in the epidermis (keratinising squamous epithelium of body)

Answer 34

Cells are constantly being lost but are replaced by new cells being formed in the basal layer which migrate up while undergoing a programme of differentiation that eventually leads to them flattening out and keratanising. Each layer replaces the one above as the layers are lost from the surface

Question 35

Hyperproliferation of epithelial cells

Answer 35

Results in increased cell numbers and a thickening of cell layers. Can be in esponse to repeated or constant pressure. If increase in cell production is greater than cell loss , cells will accumulate creating a thick, hard layer/corn.

Papilloma virus can induce hyperproliferation - do this by hijacking the cellular machinery of stratified squamous epithelia and inducing increased cell proliferation