Physiology Flashcards
(108 cards)
Define internal respiration
The intracellular mechanisms which consumes O2 and produces CO2
Define external respiration
Refers to the sequence of events that leads to the exchange of O2 and CO2 between external environment and the cells of the body
What are the four steps of external respiration?
- ventilation
- gas exchange between alveoli and the blood
- gas transport in the blood
- gas exchange at the tissue level
Describe the four steps of external respiration?
- Ventilation; the mechanical process of moving gas in and out of the lungs
- gas exchange between alveoli and blood; the exchange of O2 and CO2 between the air in the alveoli and the blood in the pulmonary capillaries
- gas transport in the blood; the binding and transport of O2 and CO2 in the circulating the blood
- gas exchange at the tissue level; the exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells
What are the four body systems involved in external respiration?
- the respiratory system
- the cardiovascular system
- the haematology system
- the nervous system
Define Boyles law
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas. As the volume of a gas increases, the pressure exerted by the gas decreases
What needs to happen to the intra-alveolar pressure for air to flow into the lungs during inspiration?
The intra-alveolar pressure must become less than atmospheric pressure
During inspiration, what expands as a result of contraction of respiratory muscles?
The thorax and lungs
What are the two forces that hold the thoracic wall and the lungs in close apposition?
- intrapleural fluid cohesiveness
- negative intrapleural pressure
Describe the intrapleural fluid cohesiveness
The water molecules in the intrapleural fluid are attached to each other and resist being pulled apart. The pleural membrane tend to stick together
Describe the negative intrapleural pressure
The sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and across the chest wall. So the lungs are forced to expand outwards while the chest is forced to squeeze inwards
What is the atmospheric pressure, the intra-alveolar pressure and the intrapleural pressure?
Atmospheric = 760 mmHg Intra-alveolar = 760 mmHg Intrapleural = 756 mmHg
What three pressure are important in ventilation?
- atmospheric pressure
- intra alveolar pressure
- intrapleural pressure
Inspiration is an active process dependant on what?
Muscle contraction
Which nerve supplies the diaphragm?
The phrenic nerve
What occurs when the external intercostal muscle contracts?
Lifts the ribs and moves out the sternum
Why do the lungs increase in size?
To make the intra-alveolar pressure fall
Why does the intra-alveolar pressure fall when the lungs increase in size?
Air molecules become contained in a larger volume (Boyles law)
Is normal expiration a passive process or an active process?
A passive process
How do the chest wall and stretched lungs recoil to their pre-inspiratory size?
Due to their elastic properties
What does the re-coiling of the lungs do to the intra-alveolar pressure?
The intra-alveolar pressure rises
Describe the movement of the diaphragm during inhalation and exhalation
During inhalation the diaphragm contracts and moves down. During exhalation the diaphragm relaxes and moves up
Describe a pneumothorax
- loss of pressure gradient
- air in the pleural space
- can be spontaneous, traumatic or iatrogenic
- this can abolish transmural pressure gradient leading to lung collapse
- small pneumothorax can be asymptomatic
What are the physical signs and symptoms of pneumothorax?
Symptoms; shortness of breath, chest pain
Physical signs; hyper-resonant, percussion note, decreases / absent breath sounds