Lecture 21: Mechanics of Breathing and Respiration Flashcards
(17 cards)
What is Boyle’s Law?
At a constant temperature, the pressure of a gas changes inversely with its volume. (Air will always flow from the region under more pressure to less pressure)
What is atmospheric pressure?
The pressure exerted by the air surrounding our bodies. (760 mmHg)
What is respiratory pressure?
Negative respiratory pressure: Pressure inside the lungs is lower than atmospheric.
Positive Respiratory pressure: Pressure inside the lungs is higher than atmospheric.
What is intrapulmonary pressure?
The pressure in the alveoli in the lungs. During inhalation, thoracic volume cavity increases causing air to flow into the lungs. During expiration, thoracic volume cavity decreases causing air to flow out of lungs.
What is intrapleural pressure?
The pressure in the pleural cavity. It is always about 4mmHg less than intrapulmonary pressure.
Excess fluid in the pleural cavity would make the intrapleural pressure positive and reduce side of lungs.
What are the two underlying reasons behind lung collapse?
- Bronchioles are blocked (alveoli absorb all the air left and collapse; pneumonia)
- Pneumothorax: Air enters the pleural cavity. Breaks the adhesion between the parietal and visceral pleurae.
What happens during inspiration?
- External intercostal muscles and diaphragm contract.
- Thoracic cavity expands.
- Lungs are stretched causing increased pulmonary volume and decreased intrapulmonary pressure.
- Air flows into the lungs.
What happens during expiration?
- External intercostal muscles and diaphragm relax.
- Thoracic cavity size reduces.
- Lungs recoil which decrease pulmonary volume and increase intrapulmonary pressure.
- Air flows out of the lungs.
What is the difference between passive and forced expiration?
Passive expiration relies on recoiling of the lungs to expel air and not any muscle contraction. Whereas forced expiration relies on abdominal and internal intercostal muscles.
What are factors that influence our ability to breathe?
- Airway resistance
- Alveolar surface tension
(water molecules cling to each other causing an inward force within alveoli) - Ability of lungs to stretch
What is asthma and cystic fibrosis?
Asthma: Inflammation of bronchioles due to substances like pollen, dust mites etc.
Cystic Fibrosis: Genetically inherited disease which causes accumulation of mucus in the airways.
What is chronic obstructive pulmonary disease and some causes of it?
COPD: Decreased ability to force air out of the lungs.
1. Emphysema: Alveoli get damaged and lose their stretchiness.
2. Chronic Bronchitis: Bronchi become inflamed and filled with mucus.
Define tidal volume, inspiratory volume, expiratory volume and residual volume?
Tidal Volume: Regular breathing
Inspiratory reserve volume: Deep breath after inhale
Expiratory reserve volume: Big push out after normal exhale
Residual volume: Air that stays inside the lungs.
What is the difference between the partial pressures of CO2 and O2?
Partial pressure of CO2 is higher in alveolar air compared to atmospheric air.
Partial pressure of O2 is lower in alveolar air compared to atmospheric air.
What is Henry’s law?
Greater the gas pressure, greater the amount of gas that dissolves into the liquid.
What are some factors that influence external respiration?
- Partial pressure gradients
- Thickness and surface area of the respiratory membrane.
What are the different partial pressure gradients for external and internal respiration?
External respiration: Blood entering the capillaries has PO2 of 40mmHg while inspired air has a PO2 of 160mmHg.
Internal respiration: Blood entering capillary beds have 100mmHg whereas tissues have 40mmHg. PCO2 is 40mmHg in blood compared to 45mmHg or more in tissues.
