ANAT241 Lecture 8 - Epithelial Tissue and Cell Membrane Specialisations

Question 1

what are tissues?

Answer 1

tissues are specialised, similar cells embedded in an extracellular matrix (ECM)

Question 2

what are the 4 tissue types?

Answer 2

epithelial tissue
connective (support) tissue
muscle tissue
nervous tissue

Question 3

what are cells composed of?

Answer 3

an internal cytoskeleton network

Question 4

what is the function of the internal cytoskeleton network?

Answer 4

for shape, support and movement

Question 5

what do cells secrete?

Answer 5

extracellular matrix (ECM)

Question 6

why do cells secrete extracellular matrix?

Answer 6

for support, structure, regulation of cell communication and behaviour

Question 7

where does epithelial tissue line?

Answer 7

lines organs and cavities within the body and covers the external body as the epidermis

Question 8

what is epithelial tissue?

Answer 8

a protective barrier with absorptive and secretory adaptations that has polarity with an apical and basal surface and a basement membrane that acts as a scaffold to underlying connective (support) tissue

Question 9

how does epithelial tissue acquire nutrients?

Answer 9

epithelial tissue is avascular and therefore acquires nutrients via diffusion

Question 10

what allows the regeneration of epithelial tissue layers?

Answer 10

stem cells

Question 11

what 3 criteria is epithelia classified based on?

Answer 11

classified based on cell shape
the number of cell layers
cell surface specialisations

Question 12

what are the 3 types of epithelial cell shape?

Answer 12

squamous
cuboidal
columnar

Question 13

what are the 4 types of epithelial cell layers?

Answer 13

simple
stratified
pseudo-stratified
transitional

Question 14

what are the 2 epithelial cell surface specialisations?

Answer 14

microvilli and cilia

Question 15

what are microvilli?

Answer 15

finger-like projections of the plasma membrane

Question 16

what is the size of microvilli?

Answer 16

they are short between 0.5um and 1um

Question 17

what is the function of microvilli?

Answer 17

increase the surface area for absorption in the intestine and kidney

Question 18

what are microvilli composed of?

Answer 18

composed of a core of parallel actin bundles

Question 19

what do microvilli appear as under light microscopy?

Answer 19

appear as a brush border

Question 20

what do microvilli appear as electron microscopy?

Answer 20

appear as individual microvilli

Question 21

what is the shape of microvilli maintained by?

Answer 21

maintained by actin filaments

Question 22

what are cilia composed of?

Answer 22

a cytoskeleton with a core of microtubules

Question 23

what is the size of cilia?

Answer 23

they are half of the cell length as they are upto 10um long

Question 24

what is the function of non-motile cilia?

Answer 24

to provide sensory information

Question 25

what is the function of motile cilia?

Answer 25

to beat in rhythm to move substances across the surface of epithelium

Question 26

what is an example of motile cilia?

Answer 26

cilia in the respiratory tract or sperm flagellum

Question 27

what are modified cillium?

Answer 27

sperm flagellum

Question 28

what are epithelial cells connected together by?

Answer 28

connected via cellular junctions

Question 29

what are the 3 types of cell junctions?

Answer 29

occluding junctions anchoring junctions communication junctions

Question 30

what are the 2 types of occluding junctions

Answer 30

tight junctions | zonula occludens

Question 31

what are tight junctions?

Answer 31

tightly bound junctions at the apical region of a cell

Question 32

what do tight junctions control?

Answer 32

control the paracellular pathway through the transmembrane proteins of occludens and claudins

Question 33

what is the function of claudins?

Answer 33

different provide different permeabilities in different tissues

Question 34

what is the function of claudin-1?

Answer 34

claudin-1 is responsible for the waterproof qualities of the skin

Question 35

what is claudin-16 responsible for?

Answer 35

responsible for permeability to Mg2+ ions in specific regions of the kidney

Question 36

what does a mutation in the claudin-16 gene result in?

Answer 36

results in an abnormal claudin-16 causing the tight junction to be impermeable to the Mg2+ ion

Question 37

what is the effect of low Mg2+ reabsorption?

Answer 37

low Mg2+ reabsorption back into the blood results in a deficiency causing kidney damage/renal failure

Question 38

what are the 3 types of anchoring junctions?

Answer 38

zonula adherens desmosomes hemidesmosomes

Question 39

what is the function of zonula adherens?

Answer 39

to strengthen the attachment to neighbouring cells at the apical region by linking the cytoskeleton of adjacent cells through the main transmembrane protein of E-cadherins attached to actin microfilaments via anchoring proteins

Question 40

why are cadherins important?

Answer 40

the loss of E-cadherins has been linked to the metastasis of cancer cells

Question 41

what is the relationship between malignant cancer cells and E-cadherins?

Answer 41

cancer cells have lower levels of E-cadherin expression

Question 42

what is another name for desmosomes?

Answer 42

macula adherens

Question 43

what is the function of desmosomes?

Answer 43

to firmly anchor neighbouring cells together by linking the cytoskeletons of adjacent cells by connecting to the intermediate filaments of cytokeratin

Question 44

what is the main transmembrane protein in desmosomes?

Answer 44

cadherins such as desmoglien

Question 45

what are hemidesmosomes?

Answer 45

modified desmosomes on the basal surface of cells

Question 46

what is the function of hemidesmosomes?

Answer 46

to anchor cells to the basement membrane by binding to cytokeratin

Question 47

what is the main transmembrane protein of hemidesmosomes?

Answer 47

integrins

Question 48

what is a type of communication junction?

Answer 48

gap junctions

Question 49

what is the function of gap junctions?

Answer 49

communication between neighbouring cells

Question 50

what is the main transmembrane protein of gap junctions?

Answer 50

connexins

Question 51

what is the function of connexins?

Answer 51

connexins form channels called connexons that can open/close to allow the passage of ions and small molecules

Question 52

what are connexons?

Answer 52

connexin channels that open/close to allow the passage of ions and small molecules

Question 53

how is epithelial tissue linked?

Answer 53

linked as sheets through lateral junctions and linked to the basement membrane via junctions

Question 54

what is the function of the basement membrane?

Answer 54

the basement membrane binds epithelial cells to connective tissue and form a barrier that allows nutrients to pass to epithelia to regulate permeability controlling growth and differentiation

Question 55

what is the basement membrane?

Answer 55

sheet-like arrangement of ECM proteins that if formed and maintained by both epithelia and connective tissue

Question 56

what is the relationship between the basement membrane and the light microscope?

Answer 56

under light microscope the basement membrane is not easily distinguished with H&E staining but immunocytochemistry can be used to stain specific components e.g collagen

Question 57

what are the 3 layers of the basement membrane?

Answer 57

lamina lucida lamina densa (basal lamina) lamina fibroreticularis

Question 58

what can be seen under the electron microscope in terms of basement membrane?

Answer 58

the 3 layers of lamina lucida, lamina densa (basal lamina) and the lamina fibroreticularis

Question 59

where are basal foldings present?

Answer 59

present on the basal surface

Question 60

what is the function of basal foldings?

Answer 60

to increase the surface area on the basal surface of a cell

Question 61

what are the structures that act as a protective barrier in epithelium?

Answer 61

the basement membrane and junctional complexes that hold epithelium as a sheet

Question 62

what is the dual function of microvilli, basal foldings and the basement membrane?

Answer 62

structures that absorb substances from the apical surface and pass it onto to the underlying tissues