Epithelia Flashcards Preview

Histology > Epithelia > Flashcards

Flashcards in Epithelia Deck (63):
0

5 characteristics of epithelia

Form a BM
Lay on CT
Formed by cells
Avascular therefore
...gain nutrients from connective tissue

1

What are cells and ECM defined as?

Tissues

2

4 types of tissue

Epithelia, muscular, neural, connective

3

4 functions of epithelia

Secretion, absorption, lining pathways, protect connective tissue below

4

2 characteristics of 2 adjacent epithelia?

Continuous with each other
Space between small - 15-30nm

5

Epithelia formation in lining and glandular tissue?

Lining - form tight sheets
Glandular - form aggregates

6

3 distinct characteristics of a epithelial cell?

Cytoskeleton different roles
Morpho-functional polarity
Apical, lateral, basal parts have different specialisations at PM

7

Epithelia cytoskeleton and functions?

Microfilaments - microvilli and terminal web
Int filaments - tonofilaments - keratin - add stability
Microtubules - MTOC - movement of vesicles.

8

Microtubules MTOC arrangement?

Centrosomal MT - radial arrangement
Non centrisomal MT - non radial, apical and basal axis, linear. (-) apical (+) basal
Polymerisation at. + end. What req?

9

Morpho-functional polarity?

Eg intestine and secreting cells - columnar epithelium
Apical - ER, vesicles
Basal - Golgi, mitochondria. Basal infoldings - increase sa...

10

3 apical specialisations?

Microvilli, cilia, stereocilia

11

Microvilli

Covered by glycocalx ( glycoproteins and gags )
Form brush border (small intestine)
Only seen at EM not LM

12

Cilia?

Movement of material on apical surface. Eg mucus, dust, bacteria.
Found in higher respiratory tract. Fallopian tubes.

13

Cilia structure

9 pairs of MT around 1 central pair (axonem)
Attached to basal body via 9 triplets of MT

14

Stereocilia?

Up to 100um therefore seen at LM and EM.
No basal body.
Actin filaments (parallel array).
Involved in absorption, function similar to microvilli
Epididymis - release specific factors - maturation of sperm

15

Baso-lateral specialisations (basal)

Basal infolding.
High no of mitochondria and Golgi.
Seen in kidneys, exocrine glands, salivary glands.

16

3 types of lateral junctions

Occluding, anchoring, communication

17

5 types of junctions and their type

Tight occluding - zonula occludens occluding therefore prevent transmembrane movement of molecule.
Adhesion - zonula adherens anchoring
Desmosomes - macula adherens anchoring
Gap junction - communication.
Hemidesmosomes - anchor cell to BM

18

Gap junctions / nexuses

Allow ions, small molecules, metabolites
Variable no. pores
12 sub units of connexon - phosphorylation = closed.
Each connexon contain 6 subunits of connexin (Integral membrane proteins)

19

Tight junctions, functions and characteristics?

Occluding.
Point to point fusion, prevent transmembrane movement.
TEM - seen as series of loops between cells.
Proteins - occludin and claudin connected to ZO proteins - actin filaments

20

What is jam?

Junction adhesion complex.
Found in tight junctions.
Glycoproteins
Cross at the widest point in between tight junctions ( the loops )

21

What is a paracrine gland?

Epithelia secrete substance not reach bloodstream
Effect cells in close vicinity

22

Loss of E - Cadherin (tmp) in zonula adherens?

Methylation, mutation, transcriptional repression, post-transcriptional down reg.
Lead to loss of adhesion. B-catenin released into cytoplasm. Translocated into nucleus. Effect gene expression.

23

Desmosomes proteins involved? Tmp imp

Tmp - desmocollin(basal), desmoglein (apical)
Imp - plakoglobin, plakophillin

24

Desmosomes function?

Strong adhesion. Linked to int filaments - tonofilaments - keratin.

25

Importance of desmosomes in structures?

Resist high mechanical stress.
Eg oral mucosa, gingiva, tongue, epidermis (polarised imp)

26

What us pemohigus foliacus?

Autoimmune response. To tmp. Antibodies against Desmoglein 1. Loss of adhesion.

27

Gjic - gap junction intercellular complex loss?

Loss of cell communication. May lead to cancer. Tumour spead. Loss of bm therefore to CT then blood stream.
Reverse by adding connexin - gap junction - reverse tumour - tumour suppressor gene .

28

Where are gap junctions important?

Cardiac smooth muscle
Neurons - synapse

29

Hemidesmosomes?

Link to BM
Integrins family proteins - link to keratin int filaments
Associated with plaque.

30

BM detect at LM?

Add PAS stain.
Seen single black line.
Contain proteoglycans, proteins, glycoproteins.

31

3 layers in BM and composition of each?

Lamina lucida - entactin, glycoproteins, laminin, integrin
Lamina densa - collagen 4, fibronectin, proteoglycans
Lamina reticularis - collagen 1 3 6

32

Functions of BM - CMR LSM

C cell polarity
M metabolism
R regulate cell repair mech and regulation
L link to CT
S selective barrier. Allow certain mat thru
M prevent metastasis of cancerous cells

33

Example of simple squamous epithelia? 5

Nucleus elongated. Thin cytoplasm
Lungs, lining of heart, bowmans capsule, endothelium, mesothelium

34

Simple cuboidal

Retina, terminal bronchioles, pancreas, liver, kidney ducts, ovaries

35

Simple columnar

Absorption and secretion.
Microvilli - small intestine
Portion of kidney, colon, gallblader, excretory ducts, stomach, small bronchioles

36

Pseudo-stratified epithelium? Microscope points

Need TEM to detect.
Presence of cilia and goblet cells therefore seen at LM.

37

Pseudostratified, more info?

All cells lie on basal membrane
Nuclei of varying heights
Not all cells reach free edge
Stratified appearance,

38

Examples of pseudo stratified?

Mucosa of airways, ear canal, urethra, epididymis, large excretion duct of exocrine glands

39

Stratified squamous epithelia non keratinised. Where found?

Buccal mucosa, vagina, anal canal, esophageous, parts of larynx and pharynx.

40

Function and structure of SSE non keratinised?

Kept moist
Stand mechanical stress
Structure: superficial layer - 5 layers of squamous cells
Spinosum layer - proliferating
Basal layer

41

Stratified squamous epithelia, keratinised?

Epidermis. 5 layers. Avascular. Nutrients from CT.
Stratum, corneum, granulosum, spinosum, basal.

42

Function of dermal papillae and epidermal ridges?

Fingerlike connective projections. Indent deepest layers.
Maintain anchoring
Exchange of nutrients

43

Length of differentiation, from basale to straum?

28 days

44

Basale layer function?

Proliferation of cells
Move to upper layers
Lost to environment

45

Spinosum layer?

Spinous projections.
Large no of desmosomes - adhesion

46

Granulosum proteins

Loricrin and filaggrin

47

Lucidum layer

Contain cells with advanced keratinisation.

48

Corneum

Cornified cell envelop

49

Keratin protein in basale?

Keratin 5 and 14.
1 layer
Proliferation
Differentiation

50

Lipid production in skin and importance?

Stratum lucidum and corneum produce lipid mixed with sweat
Lubricates skin
Prevent dehydration

51

Why oral keratinocytes faster transition from basale to corneum than skin?

Missing desmocollin protein ( TMP ) desmosomes
Weakened adhesion.

52

4 examples of cells in squamous stratified epithelia keratinised skin?

Keratinocytes
Melanocytes - RER syn tyrosine. Melanin and tyrosine stores in lysosomes (melanosomes)
Merkel cells - tactile receptors
Langerhans - immune response - present antigen vis lymph nodes to lymphocytes.

53

Difference between pemphigus vulgarus and foliacus?

Foliacus - superficial skin blistering
Vulgarus - suprabasal skin blistering

54

Psoriasis mechanism?

BM destroyed.
Factors released
Underlying keratinocytes hyperproliferation
Modification of epidermis

55

Stratified cuboidal epithelium examples?

Karge exocrine ducts, sweat glands, sebacous glands

56

Example of stratified columnar epithelia?

Male urethra, big gland ducts, larynx mucosa, conjuntiva

57

Transitional epithelium and examples?

Urethra, pelvis, urinary bladder
Dome shaped cells may be binucleated

Stretching - vesicles insert new pieces into PM

58

EMT - Epithelial cells to mesenchymal transition

Epithelium cell - layers connected, junctions, not concave, polarity(and of cytoskeleton arrangement), connected to bm, no syn of collagen, little extracellular space, not motile.
Mesenchymal cell - no polarity, concave, syn collagen and extracellular space, extracellular space exceeds total vol of cells, motile, no laminins

59

EMT - down regulation of...?

E-cadherin
Occludin (zo proteins)
Desmocollin/glein
Plakoglobin
Cytokeratin 8,9,18

60

EMT - Mesenchymal cell upregulation

aSMA isoform of actin
FSP1
Fibronectin
Vimentin
Collagen 1
MMP 2&9 - hydrolyse BM

61

EMT Physiological and pathological?

Physiological - embryogenesis, healing damaged tissue
Pathological - cancer, fibrosis

62

Primary cilia microtubule arrangement?
Where found?
Function?

9 + 0 MT. arrangement
Kidneys, liver, pancreas (when developing organs)
Fluid flow sensor, passively bend, non-motile.