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Respiratory > Lung cell biology > Flashcards

Lung cell biology Flashcards

1
Q

What are the gas exchange units lined with?

A

surfactant

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2
Q

How many generations of gas exchange units are there?

A

23

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3
Q

What are the roles of the epithelium in the lung?

A
  • protects from the internal cavity
  • produces secretions important in clearing of unwanted substances, reduce surface tension and protect cells underneath
  • metabolise compounds inc. foreign
  • release mediators to control inflammatory ones
  • trigger lung repair
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4
Q

Compared to a healthy airway, what would an airway in a COPD patient have different?

A
  • more goblet cells

- more mucus

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5
Q

What are goblet cells?

A
  • Found in airways
  • 1/5 of epithelial cells
  • produce mucus
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6
Q

Describe the composition of mucus

A
  • complex
  • thin sol phase and thick gel phase at air interface
  • mucin proteins, proteoglycans, glycosaminoglycans
  • serum derived proteins like albumin and alpha-1-trypsin (inhibits neutrophil proteases)
  • antiproteases combating microorganism and phagocyte proteases
  • antioxdiants from blood such as uric acid to combat inhaled oxidants or excess from phagocytes
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7
Q

What happens to goblet cells in smokers?

A
  • doubles
  • more secretion
  • thicker secretions
  • modified gel traps smoke particles and foreign things more
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8
Q

Where are ciliated cell found, how do they beat and where is the mucus moved?

A
  • Present in large, central and small airways
  • Metachronous beating
  • Tips of the cilia are in the sol phase of mucus and pushes the mucus towards the epiglottis
  • The mucus is usually swallowed or expectorated
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9
Q

What happens to the ciliated cells in smokers?

A
  • depleted
  • beat is not synchronised
  • ciliated cells found in bronchioles
  • Cannot transport mucus
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10
Q

What happens in COPD to the airways and alveoli?

A
  • mucus is trapped
  • airway narrows
  • broken down alveoli by enzymes and inflammatory cells
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11
Q

What are clara cells and where are they found?

A
  • non ciliated secretory epithelial cells
  • found in large, central and small airways, bronchioles and bronchi
  • they increase proportionally distally
  • ## abundant in bronchi and bronchioles
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12
Q

What are the roles of clara cells?

A
  • xenobiotic metabolism (metabolise foreign inhaled things)
  • They have phase 1 and phase 2 enzymes
  • They make and release anitporteases
  • They make and secrete lysozymes
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13
Q

Give an example of a phase 1 clara enzyme and what are their roles?

A
  • Cytochrome p450 oxidases included

- They are meant to metabolise foreign compounds to enable phase II enzymes to react and neutralise the toxic agent

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14
Q

Give an example of a phase 2 enzyme and what it does

A
  • Glutathione S-transferase, which enables conjugation of BPDE to a small molecule that neutralises its activity
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15
Q

What is a problem that occurs with phase 1 enzymes?

A

They often activate a precarcinogen to a carcinogen
e.g: Benzopyrene (precarcinogen in cigarette smoke). One cytochrome P450, oxidases BP to benzopyrene diol epoxide which is a potent carcinogen.

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16
Q

What happens to those people who don’t have glutathione S -transferase ?

A

They cannot neutralise BDPE. If an individual who smokes has CYPIRA1 extensive metaboliser gene and the null glutathione gene they are 40 times more likely to get lung cancer

17
Q

What are the three disease under the umbrella term COPD?

A
  • bronchitis
  • emphysema
  • small airways disease
18
Q

What happens to the alevoli in suscepible smokers?

A
  • they develop holes which may become larger over time
  • reduces surface area so elastic tissue loss
  • dead space increases
19
Q

What are the two types of epithelial cells that make up the alveolar wall?

A
  • Type 1: thin but strong to allow gas exchange

- Type 2: a.k.a type 2 pneumocytes, more susceptible to damage, only found in alveoli

20
Q

What do type 2 epithelial cells do, what do they contain, and where are they found in the alveolus?

A
  • Contain lamellar bodies that store surfactant prior to release onto the air-liquid interface
  • Synthesise and secrete antiproteases
  • Positioned in the corners of the alveoli and are embedded in the interstitium with the apical membranes facing the air
  • Very close to capillaries
  • Precursors for alveolar epithelial type I cells
21
Q

What is surfactant?

A

Phospholipid rich surface active material that prevents lung collapse on expiration and has immunological functions

22
Q

What is the ratio of type 1 to type 2 cells?

A

1:2

23
Q

What does the alveolus consist of?

A

type 1 cells, type 2 cells, stomal fibroblasts (make ECM, collagen and elastin), alveolar macrophages, capillary endothelium

24
Q

Where are alveolar macrophages found and how do their numbers change in smokers?

A
  • in lower respiratory tract but found throughout

- increase 5-10 fold

25
Q

Where are neutrophils found in airwyas and how do their numbers change in smokers?

A
  • throughout airways
  • increase 5-10 fold in smokers and during infection
  • higher proportion in conducting/large airways
26
Q

What do neutrophils store and how does this change in smokers?

A
  • Potent proteases in granules - released on activation
  • Smokers lungs contain high levels of these proteases
  • Release potent oxidative molecules such as hydroxyl anions during activation
27
Q

What are some of the effects of smoking?

A
  • blocks proliferation of type 2 into type 1 cells
  • stimulates type 1/2 cell death
  • blocks communication between t2 cells and fibroblasts so no repair
  • increases number of macrophages and neutrophils
  • procarcinogens activates by phase 1 enzymes. Normally made water soluble by phase 2 enzymes but smoking affects pathway and so carcinogen can bind to DNA and cause mutation and no repair
28
Q

How does normal and abnormal repair occur?

A
  • In normal repair, type I cell death causes growth factor release to increase type II cell proliferation and differentiation
  • In ABNORMAL repair, there is excess tissue breakdown and elevated GF release which leads to a fibrotic effect (increased type II cells, increased stromal/fibroblast and connective tissue synthesis in interstitial space = irreversible)
29
Q

What percentage of the alveolar surface is covered by type 2 and type 1 cells?

A
  • Type 1: 95% (they are very large but in fact fewer number of them)
  • Type 2: 5%
30
Q

What is chronic bronchitis?

A

Chronic bronchitis – large/central airways

Airways obstructed by mucus and thickened mucosal cell layer.

31
Q

What is small airways disease?

A

The small airways become obstructed due to mucus secretion and stenosis/narrowing of airway wall due to fibrosis.

32
Q

What is emphysema?

A

Damage by enzymes, results in the loss of connective tissue, basement membrane and normal cell organisation. Loss of surface area, elastic recoil and vascular tissue.

Respiratory (23 decks)

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