MMED1005 Lecture Notes - Lecture 18: Interstitial Lung Disease, Salbutamol, Chronic Obstructive Pulmonary Disease
7 Jun 2018
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Respiratory lectures:
Main points:
- Why do we need to breathe?
- Basic lung structure
o Conducting region
o Gas exchange region
- What specific features does a gas exchange organ require
- Structure of the conducting region
- Structure of the alveolus
- Diffusion equation
- Surface tension and pulmonary surfactant
Main points:
- The lung consists of a conducting zone (trachea, bronchi, bronchioles) and a
respiratory zone (alveolar sacs and alveolus)
- There is a huge increase in surface area in the alveolar regions
- The lung is optimised for gas exchange. There is large surface area in contact with
the air and a large area in contact with the blood with a thin barrier between the
two regions
- The volume of gas transferred is proportional to the surface area, the gas pressure
and the diffusion capacity of the gas but inversely proportional to the thickness of
the barrier
- The alveolus is a small fluid-lined sack and surface tension is a serious problem
- The lung overcomes this structural problem by secreting pulmonary surfactant from
alveolar type II cells
- Pulmonary surfactant reduces surface tension in proportion to the radius: the
smaller the radius (when you breathe out) the lower the surface tension
- Pulmonary surfactant allows the lung to inflate easily when you breathe in
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Apgar score:
- Nearly all babies score between 8 and 10, with 1 or 2 points taken off for blue hands
and feet because of immature circulation
- If a baby has a difficult time during delivery, this can lower the oxygen levels in the
blood, which can lower the Apgar score
- Apgar scores of 3 or less often mean a baby needs immediate attention and care
- e.g. blue, having trouble breathing (using abdominal muscle for breathing), having
grunting sound (trying to keep airways open)
Why do we need to breathe?
- To oxygenate our blood
o Oxygen is needed to make energy (ATP)
- To remove carbon dioxide
o Carbon dioxide is the by-product of using oxygen to make energy
How does the body get oxygen and remove carbon dioxide?
- We use the lungs
- The lung is used to get oxygen from the air and oxygenate the blood and remove
carbon dioxide from the blood (there are partial pressure gradients for O2 and CO2
between the air and the blood)
- The lung needs to have these properties:
o Large surface area open to the air
o Large surface area for the blood
o The air and the blood would need to be in close contact
Organisation of the lung and alveoli:
- The respiratory system is composed of two parts:
o Conducting portion
â–Ş Consists of a series of cavities and tubes conducting air to the lungs
â–Ş It is composed of:
• Nose
• Pharynx
• Larynx
• Trachea
• Bronchi
• Bronchioles
• Terminal bronchioles (no alveoli)
o Respiratory portion
â–Ş Composed of:
• Respiratory bronchioles (have alveoli)
• Alveoli (tiny air-containing sacs)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Basic lung structure: conducting region, gas exchange region. What specific features does a gas exchange organ require. The lung consists of a conducting zone (trachea, bronchi, bronchioles) and a respiratory zone (alveolar sacs and alveolus) There is a huge increase in surface area in the alveolar regions. The lung is optimised for gas exchange. There is large surface area in contact with the air and a large area in contact with the blood with a thin barrier between the two regions. The volume of gas transferred is proportional to the surface area, the gas pressure and the diffusion capacity of the gas but inversely proportional to the thickness of the barrier. The alveolus is a small fluid-lined sack and surface tension is a serious problem. The lung overcomes this structural problem by secreting pulmonary surfactant from alveolar type ii cells.
