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Year 1: Respiratory System > 5. Lung Cell Biology > Flashcards

5. Lung Cell Biology Flashcards

1
Q

How many generations of gas exchange units are there?

A

23

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2
Q

How does the cross sectional area of the lung increase?

A

Peripherally

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3
Q

What is the role of the epithelium?

A

Continuous barrier - isolates external environment from host
Produces secretions for clearance via mucociliary escalator and to protect underlying cells.
Metabolises foreign and host-derived compounds
Releases mediators
Triggers lung repair processess

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4
Q

Where are goblet cells present?

A

Large, central and small airways

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5
Q

What is proportion of epithelial cells are goblet cells?

A

1/5

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6
Q

Function of goblet cells?

A

Secrete and synthesis mucus

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7
Q

What does mucus contain?

A

Mucin proteins, proteoglycan, glycosaminoglycans, serum derived proteins, antiproteases and antioxidants

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8
Q

What does mucin proteins, proteoglycan and glycosaminoglycans give to the mucus?

A

viscoelasticity

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9
Q

What are 2 serum derived proteins?

A

Albumin, alpha 1-antitrypsin (inhibits polymorphonuclear neutrophil proteases)

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10
Q

What are antioxidants?

A

From the blood and synthesised by epithelial cells and phagocytes, they counteract oxidants released by activated phagocytes

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11
Q

In smokers what is the number of goblet cells?

A

This goblet cell number doubles

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12
Q

In smokers how do the secretions of goblet cells change?

A

Secretions increase in quantity and are thicker

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13
Q

Where are ciliated cells present?

A

Large, central and small airways

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14
Q

What is proportion of epithelial cells are ciliated cells?

A

80%

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15
Q

What type of beating do cilia have?

A

metachronous beating

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16
Q

What is the function of the cilia?

A

Tips of the cilia are in the sol phase of mucus and pushes the mucus towards the epiglottis

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17
Q

Describe the structure of mucus in terms of phase?

A

The part of the mucus touching the epithelial cells are in the sol phase. The part in contact with the air is in the gel phase

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18
Q

In smokers the cilia are:

A

1) severely depleted
2) beat asynchronously
3) found in bronchioles
4) unable to transport thickened mucus - reduced clearance

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19
Q

What are the size of small airways?

A

<2mm in diameter

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20
Q

Are small airways cartilagenous?

A

no

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21
Q

How does COPD affect small airways?

A

Mucus becomes trapped, narrowing the airway. The airway is then broken down by enzymes and inflammatory cells reducing peripheral gas exhange

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22
Q

What are clara cells?

A

Non-ciliated secretory epithelial cells found in large, central and small airways and bronchi and bronchioles

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23
Q

What type of airways are Clara cells found?

A

Conducting and transitional airways but increase proportionally distally

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24
Q

What is major role of Clara cells?

A

Xenobiotic metabolism

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25
Q

What is xenobiotic metaboism

A

Metabolism of foreign compounds deposited by inhalation

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26
Q

What enzymes do Clara cells contain?

A

Phase I, phase II, antiproteases and lysozyme

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27
Q

What is the function of phase I enzymes?

A

Metabolise foreign compounds so that phase II enzymes can react to neutralise the toxic agent

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28
Q

Give an example of phase I enzymes

A

Cytochrome p450 oxidases

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29
Q

What is a negative effect of phase I enzymes?

A

They often activate precarcinogen to a carcinogen

30
Q

Give an example of Phase II enzymes

A

glutathionine S-transferase

31
Q

COPD =

A

bronchitis + emphysema + small airways disease

32
Q

In smokers describe the alveoli

A

Holes + large = reduced surface area for gas exhchange

33
Q

Why does smoking cause the loss of in alveoli?

A

Loss of elastic tissue therefore expansion during breathing is reduced

34
Q

What are the types of epithelial cells are in alveolar walls?

A

Type I

Type II

35
Q

Which type of epithelial cell is more susceptible to damage?

A

Type II

36
Q

Which type of epithelial cell is damaged more often?

A

Type I

37
Q

Where are type II epithelial cells found?

A

alveoli

38
Q

What is the function of type II epithelial cells?

A

Secrete surfactant which is phospholipid rich preventing lung collapse on expiration. They also synthesise and secrete antiproteases. Repair cells

39
Q

Where are type II epithelial cells positioned?

A

On the corner of the alveoli and are embedded in the interstitium with the apical membrane facing the air

40
Q

What type of cells are precursors to alveolar epithelial type I cells?

A

Type II cells

41
Q

What is the ratio of epithelial cells in an alveolar unit?

A

TII:TI
2:1

42
Q

What is the function of Type I epithelial cells?

A

Thin - to allow gaseous exchange

Cover 95% of alveolar surface

43
Q

What does an alveolar unit consist of?

A 
Type I cells
Type II cells
Stromal fibroblasts
Alveolar macrophages
Capillary endothelium
44
Q

What is function of stromal fibroblasts?

A

Make extracellular matrix
Make collagen and elastin
Divide to repair

45
Q

Where is the capillary endothelium situated?

A

In close proximity to alveolus to reduce diffusion distance

46
Q

What is the function of alveolar macrophages?

A

1) Signal to inflammatory cells during infection
2) Secrete proteases
3) Generate oxidants during phagocytosis and when activated
4) Generate antioxidants to neutralise oxidative molecules
5) Contain enzyme to metabolise toxicants

47
Q

What percentage of total phagocytic cells in a normal lung are alveolar macrophages?

A

70%

48
Q

What percentage of lower respiratory tract phagocytes are polymophonuclear neutrophils?

A

5%

49
Q

How many fold increase is the number of polymorphonuclear neutrophils and alveolar macrophages in smokers?

A

5-10 fold increase

50
Q

What do polymophonuclear neutrophils store?

A

Proteases in granules

51
Q

What do polymorphonuclear neutrophils release during activation?

A

Oxidative molcules = hydroxyl anions

52
Q

Where are a large proportion of polymorphonuclear neutrophils located?

A

conducting/large airways

53
Q

What occurs during infection - emphysema?

A 
Infection
Chronic damage (T1 cell death)
Alveolar fibrosis (repair)
54
Q

What happens during alveolar fibrosis?

A

Increased type II epithelial cells

Increased fibroblasts

55
Q

What is function of fibroblasts?

A

To produce connective tissue and collagen

56
Q

What determines whether the repair mechanisms in the alveoli occur normally or abnormally?

A

Communication between the type II epithelial cells and the fibroblasts

57
Q

What happens in normal repair?

A

Type I cells die causing growth factor release which increases type II cells

58
Q

What happens in abnormal repair?

A

There is an excess of tissue breakdown resulting in high levels of growth factor. This cause a fibrotic effect causing irreversible damage

59
Q

What happens in a fibrotic effect?

A

Increased type II cells, fibroblasts and connective tissue synthesis in interstitial space

60
Q

How does smoking affect the epithelial cells?

A

It blocks the proliferation of type II cells and type I cells.
Stimulates apoptosis and necrosis between Type I and II cels
Blocks communication between Type II and fibroblasts, blocking repair

61
Q

How does smoking affect macrophages and neutrophils?

A

It increases them by 10 fold

62
Q

What is the macrophage:neutrophil ratio in a non smoker?

A

70:30

63
Q

What is the macrophage:neutrophil ratio in a COPD patient?

A

30:70

64
Q

How do macrophages and neutrophils cause alveolar inflammation?

A

Secrete serine proteases and metalloproteases which activate other proteinases, cytokines, chemokines and overall increasing the number of inflammatory molecules within the alveoli

65
Q

What effects does antimicrobial oxidant have?

A

They generate highly reactive peroxides which fragment connective tissue

66
Q

What do peroxides interact with?

A

Lipids and proteins

67
Q

What does smoking contain which are activated by phase I enzymes?

A

procarcinogens

68
Q

What are procarcinogens activated by?

A

phase I enzymes

69
Q

In normal metabolism what is the function of phase II enzymes?

A

They make active compounds/carcinogen water soluble

70
Q

What is the point of making active compounds soluble?

A

So they can be metabolised and excreted

71
Q

How does smoking affect phase II enzymes?

A

They may inactivate the enzyme

Overload the pathway so that there are not enough enzymes to cope with the amount of carcinogen

Year 1: Respiratory System (19 decks)

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