M2 L6

Question 1

what is a tissue?

Answer 1

• specialised cells embedded in ECM
• form organs

Question 2

what is ECM made of and by?

Answer 2

of: filaments
by: cells then excreted

Question 3

what are the functions of the ECM?

Answer 3

• support
• structure
• regulation of cell communication and behaviour
• maintains normal development
• maintains cell differentiation

Question 4

what are some features of epithelia?

Answer 4

• lines organs, cavities, and external body
• protective, absorptive, secretory specialisations
• has polarity
• avascular
• regenerative via stem cells

Question 5

what are the different types of epithelia with examples?

Answer 5

• simple: squamous = capillaries, columnar = small intestine, cuboidal = pancreas ducts
• strat: squamous = skin, columnar = anus, cuboidal = mammary glands

-pseudostrat: columnar = resp. tract

Question 6

what are the two types of glandular epithelium?

Answer 6

• single : goblet cells
• multiple : glands

Question 7

what are the 4 types of cell surface specialisations? with examples for apical

Answer 7

• cilia
  eg. sperm flagellum
  eg. resp tract
• microvilli
  eg. small intestines
• basement membrane
• basal folding

Question 8

what are the features of cilia?

Answer 8

• non motile: sensory info
• motile: rhythmic beating to move things
• up to 10 micrometers long (length of 1/2 cell)
• core of microtubules

Question 9

what are the features of microvilli?

Answer 9

• fingerlike projections
• very short (0.5-1 micrometers)
• core of parallel actin fibres
• increase SA for absorption

Question 10

what are features of the basement membrane?

Answer 10

• binds epi to connective tissue
• formed and maintained by epi and conn tissue
• sheet-like arrangement of ECM fibres
• selective permeability
• controls growth and differentiation
• 3 layers (lucida, densa, fibroreticularis)

Question 11

what does basal folding do?

Answer 11

increases SA

Question 12

what are the 3 cell junction types, and the 5 junction subtypes?

Answer 12

occluding
- tight junctions (zonula occludens)

anchoring
- zonula adherens
- desmosomes
- hemidesmosomes

communication
- gap junctions

Question 13

describe tight junctions inc. important proteins

Answer 13

• control paracellular pathway
• important proteins: occludins, claudins

Question 14

explain the importance of Claudin proteins inc. two examples

Answer 14

• affect permeability
• claudin-16: controls Mg2+ perm. in kidney cells
• claudin-16 mutation: impermeable to Mg2+, kidney failure, Mg2+ deficiency
• claudin-1: waterproofs skin

Question 15

describe zonula adherens

Answer 15

• link adjacent cells cytoskeletons
• connect actin myofilaments
• main prot: E-cadherins

Question 16

Explain the importance of E-cadherens

Answer 16

• loss linked to cancer metastasis
• less expressed in malignant cells
• screened for and treated with preventative surgery

Question 17

describe desmosomes

Answer 17

• link cytoskeleton of adjacent cells
• connect cytokeratin intermediate filaments
• main protein: cadherins eg. desmoglein

Question 18

describe pemphigus vulgaris

Answer 18

• autoimmune attacking desmoglein 3 ( resp. for holding skin together)
• cells fall apart
• skin sloughs off

Question 19

describe hemidesmosomes

Answer 19

• attach epi cells to basement membrane
• modified desmosomes
• main prot: integrins

Question 20

describe gap junctions

Answer 20

• main prot: connexins
• connexins form pores called connexons that can open and close
• allow small ions and molecules through for fast communication

Question 21

where is each junction type located from apical to basal?

Answer 21

• tight (apical)
• zonula adherens (apical)
• gap junctions
• desmosomes
• hemidesmosomes (basement membrane)

Question 22

what is the significance of epithelial polarity?

Answer 22

• allows for sheet formation
• allows for diff specialisations at diff surfaces