Presentation on theme: "Section A: Applied Anatomy and Physiology"— Presentation transcript:
1 Section A: Applied Anatomy and Physiology 11. Structure and function of the respiratory system
2 SyllabusStructure of the nasal passages, trachea, bronchii, bronchioles, and alveoliLobes of the lung and pleural membraneMechanics of breathing at rest and during exerciseRespiratory muscles, to include: diaphragm, external intercostals, sternocleidomastoid, pectoralis minor, internal intercostals, and abdominal musclesControl of ventilationDefinitions, values and measurement of respiratory volumes at rest and during exerciseEffect of exercise on respiratory volumes and pulmonary ventilationGaseous exchange, partial pressures and tissue respirationThe effect of altitude on the respiratory system
3 External RespirationInvolves the movement of gases into and out of the lungs.The exchange of gases between the lungs and blood is known as pulmonary diffusion.
4 Nasal PassagesNasal cavity is divided by a cartilaginous septum that forms the passages.Interior structures aid the process by:Mucous membranes and blood capillaries moisten and warm the inspired airCiliated epithelium filters and traps dust particlesSmall bones (chonchae) increase the surface area to improve efficiency
5 Oral Pharynx and Larynx Air entering the larynx passes over the vocal chords and into the tracheaSwallowing – the larynx is drawn upwards and forwards against the base of the epiglottis (preventing entry of food)
7 Trachea Approx. 10cm in length and lies in front of the oesophagus. Composed of 18 ‘rings’ of cartilage, which are also lined by a mucous membrane and ciliated cells.Extends from larynx and directs air into the right and left primary bronchi.
11 Bronchi and Bronchioles Trachea divides into right and left bronchi, which further subdivide into lobar bronchiThree feeding the lobes of the right lungTwo feeding the lobes of the left lungFurther subdivision of these form bronchiolesBronchioles enable the air to pass into the alveoli via the alveolar ducts
12 AlveoliResponsible for the exchange of gases between the lungs and the bloodThe alveolar wall are extremely thin, are lined by a film of waterEssential for dissolving oxygen from inspired airAlveoli walls also contain elastic fibres further increasing surface areaSurrounding each alveolus is an extensive capillary network
18 BreathingLungs are surrounded by pleural sacs containing pleural fluid, which reduces frictionSacs are attached to both the lungs and the thoracic cage, which enables the lungs to inflate and deflate as the chest expands and flattens
20 Inspiration Active Occurs as a result of contraction of; External intercostalsDiaphragmAs the chest expands through these muscular contractions, the surface tension created by the film of pleural fluid causes the lungs to be pulled outwards
21 Inspiration During Exercise Additional muscles;SternocleidomastoidScalenesPectoralis major
22 Expiration Generally a passive process During exercise, the process becomes more active;The internal intercostalsAbdominalsLatissimus dorsi
25 Respiratory Regulation Controlled by nervous systemBasic rhythm is governed and co-ordinated by the respiratory centre (medulla)Inspiration generally lasts up to 2 seconds after which impulses cease and expiration occurs by elastic recoil of lungs
26 Factors Controlling Rate of Breathing ChemoreceptorsCO2 levelsProprioceptors and MechanoreceptorsStretch receptorsHering-Breur reflex (prevents overinflation)ThermoreceptorsTemperature of bloodBaroreceptorsState of lung inflation
27 Neural ControlThe respiratory centre in the medulla of the brain controls breathing.It is made up of two main areas:The inspiratory centre is responsible for the rhythmic cycle of inspiration and expirationThe expiratory centre is inactive during quiet ventilation. When the rate and depth of breathing increases (detected by stretch receptors in the lungs) the expiratory centre inhibits the inspiratory centre and stimulates expiratory muscles.
29 Cont.In most circumstances the neural control of breathing is involuntaryThe resp centre sends out impulses via the phrenic and intercostal nerves to the respiratory musclesThe muscles are stimulated for a short period, causing insiprationThen when the stimulus stops, expiration occurs
30 Other factors influencing the neural control of breathing include: A large drop in oxygen tension.This is monitored by chemoreceptors in the aorta and carotid arteries and results in an increase in the rate and depth of breathing.A rise in blood pressure, monitored by baroreceptors in the aorta and carotid arteries, resulting in a decrease in ventilation rateProprioceptors in the muscles responding to movement stimulate the respiratory centre, increasing the rate and depth of breathingThe respiratory centre can also be affected by higher centres in the brain, e.g. emotional influences
31 Chemical ControlThe respiratory centre responds mainly to changes in the chemistry and temperature of the bloodThe most significant factor is a lowering in pHThis occurs when there is an increase in the amount of CO2 being produced by the cellsThe increase is detected by the respiratory centre (in the brain)It results in an increase in the rate and depth of breathingA rise in body temperature will cause an increase in the rate but not the depth of breathing
32 Reminder Pulmonary diffusion – gaseous exchange at the lungs Its functionsReplenish oxygenRemove carbon dioxide
33 Partial Pressure of Gases Central to understanding of gaseous exchange is the concept of partial pressure“the individual pressure that the gas exerts when it occurs in a mixture of gases”The pressure is proportional to its concentrationPartial pressures added together = total pressure of gas
34 Composition of Air Nitrogen = 79% Oxygen = 20.9% Carbon dioxide = 0.03%The percentages are obviously the relative concentrations!
39 Effect of AltitudeWith altitude there is a decrease in atmospheric pressure BUT the percentages of gases within the air remain identical to those found at sea levelIt is the partial pressure of the gases that changes in direct proportion to an increase in altitude
40 Effect of Altitude cont. E.G. – at rest the pO2 of arterial blood is approx 100mmHg, while in the resting muscles and tissues it is 40mmHg.The difference between the two indicates the pressure gradient.The pO2 of arterial blood at an altitude of 8000ft drops to 60mmHg, while that in the muscles remains at 40mmHg!
41 Altitude Training The principle: With an increase in altitude, the partial pressure of oxygen in the atmosphere decreases by about a half, causing the body to adapt by INCREASING RED BLOOD CELL MASS AND HAEMOGLOBIN LEVELS to cope with a lower pO2
42 Altitude TrainingIt is widely used by endurance athletes to enhance their oxygen-carrying capacityRecent evidence:Living at altitude and training at sea level produces the greatest endurance performanceCan increase the oxygen-carrying capacity of the blood by up to 150%
43 Altitude Training Disadvantages: Expensive Can cause altitude sickness Due to lack of oxygen , training at higher intensities is difficultAny benefits are soon lost on return to sea level
45 Transport of OxygenEach molecule of haemoglobin can combine with 4 molecules of oxygenThe amount of oxygen that can combine with haemoglobin is determined by the partial pressure of oxygenHigh pO2 = complete saturationLow pO2 = saturation decreases
46 Transport of Oxygen and Dissociation Hb is totally saturated at the lungs (alveoli)As the pO2 is reduced, Hb saturation decreases accordingly.This is largely due to the increased acidity of the blood (decrease in blood pH), caused by an increase in CO2 or LA and the increase in body temperature, which causes a shift to the right in the haemoglobin saturation curve.
47 The Release of Oxygen from Haemoglobin At restThe pO2 in the alveoli is approx 100mmHg100% saturationIn resting muscle and tissue the pO2 is 40mmHg75% saturationMeans that 25% of the oxygen picked up at the lungs is released into the muscle to help in energy production
48 The Release of Oxygen from Haemoglobin During exerciseThe pO2 in the alveoli remains at approx 100mmHg100% saturationIn working muscles the pO2 can be greatly reduced, up to 15mmHg25% saturationMeans that 75% of the oxygen picked up at the lungs is released into the muscle to help meet the extra energy demands
49 The Bohr ShiftIncreased oxygen released to tissues!
50 Gas Exchange at Muscles and Tissues High pO2 in arterial blood and relatively low pO2 in muscles causes a pressure gradientHigh pCO2 in tissues and low pCO2 in arterial blood causes a movement of CO2 in opposite directionProduction of CO2 stimulates the dissociation of oxygen from haemoglobinMyoglobin has a much higher affinity for oxygen than haemoglobin
51 a-VO2 differenceThe arterial-venous oxygen difference is the difference in oxygen content of the blood in the arteries and the veins.It is a measure of the amount of oxygen consumed by the muscles
52 Lung Volumes LUNG VOLUME DEFINITION TYPICAL REST VALUE CHANGE DURING EXERCISETidal volume (TV)Volume inspired or expired per breath500mlIncreaseInspiratory reserve volumeMaximal volume inspired following end of resting inspiration3100mlDecreaseExpiratory reserve volumeMaximal volume expired following end of resting expiration1200mlResidual volume (RV)Volume of air remaining in the lungs at the end of maximal expirationRemains the same
53 Lung Capacities LUNG CAPACITIES DEFINITION TYPICAL REST VALUE CHANGES DURING EXERCISEInspiratory capacity (TV + IRV)Maximum volume of air inspired from resting expiratory levels3600mlIncreaseVital capacity (TV + IRV + ERV)The maximum volume forcibly expired following maximal inspiration5000mlSlight decreaseTotal lung capacity (VC + RV)The volume of air that is in the lungs following maximal inspiration6000mlMinute ventilation (TV * f)The volume of air inspired or expired per minute7500mlDramatic increase
56 Adaptive Responses of Respiratory System to Training SMALL INCREASES IN LUNG VOLUMESResult from increased strength in respiratory musclesIMPROVED TRANSPORT OF RESPIRATORY GASESIncreased amount of RBC’s (haemoglobin)Increased blood plasma reduces viscosityENHANCED GASEOUS EXCHANGE AT THE ALVEOLI AND TISSUESIncreased capillary densityGREATER UPTAKE OF OXYGEN BY THE MUSCLESIncreased myoglobin and mitochondrial densityIncrease in a-VO2 difference