Physiology 1 Flashcards
External Respiration Definition
Sequence of events that leads to the exchange of O2 and CO2 between the external environment and cells of the body
How many steps in external respiration?
4
4 steps of external respiration?
Ventilation
Gas exchange between alveoli
Gas transport in the blood
Gas exchange at tissue level
Internal Respiration Definition?
Intra-cellular mechanism which consumes O2 and produces CO2
Ventilation
Mechanical process of moving air between the atmosphere and the alveolar sacs
Gas exchange between alveoli
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 blood
Gas exchange at tissue level
The exchange of 02 and CO2 between blood in the systematic capillaries and the body cells
4 body systems involved in external respiration
Respiratory
Circulatory
Nervous
Haematology
Boyles Law?
At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas
(As volume of gas increases the pressure exerted by the gas decreases)
What must happen to intra-alveolar pressure for air to flow into the lungs during inspiration?
Must become lower than atmospheric pressure
Intra-alveolar pressure before inspiration?
Equivalent to atmospheric pressure
Why do thorax and lungs expand in Inspiration
Contraction of Inspiratory muscles
2 forces that hold the lungs and thoracic wall in close opposition?
Intrapleural Fluid cohesiveness- water molecules attract each other, pleural membranes stick together
Negative intraplueral pressure- transmural pressure gradient across lung and chest walls
3 pressures important in ventilation?
Atmospheric pressure
Intra-alveolar pressure
Intra-pleural pressure
Normal atmospheric pressure?
760 mm hg at sea level
How is the volume of the thorax increased?
Contraction of the diaphragm, flattening out its dome shape
What lifts the ribs and moves out the sternum?
External intercostal muscle contraction
Physiology during inspiration?
Elevated Rib cage- Increases side to side dimensions of thoracic cavity
Contraction of diaphragm- increases vertical volume of thoracic cavity
Process of Inspiration
Chest walls and lungs are stretched
Increase in size of lungs causes decrease in intra-alveolar pressure
Air then enters the lungs down the concentration gradient, until intra-alveolar pressure becomes equal to atmospheric
Normal expiration?
Passive process brought about by relaxation of the inspiratory muscles
Pneumothorax
Air in the pleural space
What can abolishe the transmeural pressure gradient?
A Pneumothorax
Symptoms of pneumothorax
Shortness of breath, Chest pains
Physical signs of pneumothorax?
Hyperresonant percusssion
Decreased/absent breath sounds
What causes the lungs to recoil during expiration?
Elastic connective tissue
Alveolar surface tension
Alveolar surface tension?
Attraction between water molecules at liquid air interface
What reduces alveolar surface tension?
Surfactant
If alveoli were coated in water alone?
Surface tension too much, aveoli would collapse
LaPlace’s Law?
P=2T/r
P=Inward directed collapsing pressure
T= Surface Tension
r=Radius of the bubble
What does LaPlace’s law say?
Alveoli with smaller radiuses have a higher tendancy to collapse
Pulmonary surfactant?
Complex mixture of lipids and proteins secreted by type 2 alveoli
How does pulmonary Surfactant work?
Lowers alveolar surface tension by interspersing between water molecules lining the alveoli
What are developing fetal lungs unable to do until late in pregnancy?
Synthesize surfactant = premature babies may not have enough= Respiratory distress syndrome of newborn
Factor which helps keep the alveoli open?
The alveolar interdependence
Alveolar Interdependence
If an alveolus starts to collapse, the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to keep it open.
Forces keeping alveoli open?
Transmural pressure gradient
Pulmonary surfactant
Alveolar Interdependence
Forces promoting alveolar collapse?
Elasticity of stretched lung connective tissue
Alveolar surface tension
