Presentation on theme: "The mechanics of breathing and Respiratory Volumes"— Presentation transcript:
1 The mechanics of breathing and Respiratory Volumes Pass andMerit
2 Overview Breathing is regulated by: Breathing in = Inspiration the respiratory centre, located in the brain.Receptors in the air passages and lungsBreathing in = InspirationBreathing out = ExpirationTo breathe the thorax must increase and then decrease in size
3 InspirationIn order to breathe in the volume of the chest cavity needs to increase.This increase in size of the chest cavity, causes a decrease in pressure within the lungsBoyle’s Law states that a volume of gas is inversely proportional to its pressure.This means that the increase in volume in the lungs causes a decrease in pressure.Gases flow from a high pressure area to a low pressure areaIn this situation the ambient air is the high pressure area and the lungs are the low pressure area, so the air flows into the lungs
4 Inspiration Inspiration – Breathing in Diaphragm contracts It flattens and pulls downThis is an active processExternal intercostal muscles contractThe sternum moves up and out, with the lungs followingThe lungs are attached to the pleural sac (containing pleural fluid), which in turn is attached to the thoracic cageAs the chest expands, the surface tension, created by the film of pleural fluid causes the lungs to be pulled outwards, with the chestThese two actions cause the volume of the thoracic cavity to increaseAccording to Boyles Law this increase in volume causes a decrease in pressureAir flows into the lungsAs gas flows from high pressure to low pressure.
5 Expiration To breathe out – Expiration: Diaphragm relaxes It moves back up and into the thoracic cavityThis is a passive processThe external intercostal muscles relaxThe ribs/sternum moves down.The lungs, sternum and rib cage are elastic structures that naturally 'spring' back to their resting positions once the forces of the inspiratory muscles are removed. So expiration is a passive process.The volume of the thoracic cavity decreases causing the air to move out of the lungs.This is because air pressure in the lungs is now higher than atmospheric pressure, according to Boyles Law, so the air is forced out of the lungs to equate the pressure in and out of the body.
8 Lung VolumesLung volumes: refers to physical differences in lung volume, while lung capacities represent different combinations of lung volumes, usually in relation to inhalation and exhalation.The average pair of human lungs can hold about 6 litres of air, but only a small amount of this capacity is used during normal breathing.
10 Respiratory volumes Tidal Volume The volume of air inspired or expired per breath (Approx 500ml at rest)Inspiratory Reserve VolumeThe amount of space that is available to draw in more airEg; Breathe in normally, then breathe in more. This extra capacity is your IRVExpiratory Reserve VolumeThe amount of space that is available to breathe out, once you have exhaled normallyEg: Breathe out normally, then force out more air. This is your ERV.
11 Respiratory volumes Residual Volume Vital Capacity Total Lung Capacity Take in as much breath as possibleThis is your total lung capacityERV+IRV+TV+RV (Approx 6000ml)Residual VolumeBreathe out as much as possibleThere is always some air left in your lungsThis is your RV (Approx 1200ml)Vital CapacityBreathe in as much as you can, and then force as much air out of your lungs as possible.This is your IRV+ERV+TV, and is your Vital Capacity