Presentation on theme: "Functional Anatomy of the Respiratory System"— Presentation transcript:
1 Functional Anatomy of the Respiratory System Dr. Meg-angela Christi Amores
2 Pulmonary Ventilation Pulmonary Ventilation – inflow and outflow of air between the atmosphere and the lungsMuscles for Respiration:DiaphragmExternal Intercostal musclesSternocleidomastoid MusclesAnterior SerratiScalene musclesAbdominal Rectus muslesInternal Intercostals
3 Lung Expansion and Contraction 2 ways:Diaphragm Movementor – lengthen or shorten chest cavityRibsElevate or depress – increase or decrease antero-posterior diameter of chest cavityNormal quite breathing is accomplished almost entirely by first method.
5 Diaphragm Movement During INSPIRATION: During EXPIRATION: Diaphragm contracts and pulls lower surface of the lung downwardDuring EXPIRATION:Diaphragm relaxes accompanied by elastic recoil of lungs, chest wall and abdominal structuresDuring heavy breathing, extra force is achieved mainly by contraction of abdominal muscles
6 Ribs Movement During INSPIRATION Ribs project almost entirely forward from an original downward positionSternum also moves forward away from spineAnteroposterior (AP) diameter increases to 20%Muscles that elevate ribs:External intercostalsSternocleidomastoidAnterior SerratusScalene Muscles
8 PRESSURESLungs are “elastic” – collapses like a balloon when there is no force to keep it inflatedThere are no attachments between the lungs and the ribcage except at hilumLungs float in pleural fluidLymphatics provide slight suction between visceral surface of lung pleura and parietal surface of thoracic cavity
9 Pleural PresurePressure of fluid in the narrow space between lung pleura and chest wall pleuraSlightly negative pressureAt beginning of inspiration: -5 cmH20The amount needed to hold the lungs openDuring inspiration: -7.5cmH20As negativity increases, lung volume increases to 0.5L
10 Alveolar Pressure Pressure of air inside the lung alveoli Open glottis – pressures are equal at 2 atmFor inspiration – inward flow of air into alveoli the pressure must fall to a value slightly below atmospheric pressure (below 0)During inspiration: alv pressure drops to -1cmH20 = 0.5 L of air
12 ComplianceCompliance is the extent to which lungs expand for each unit of increase in transpulmonary pressure= 200mL/ 1 cmH20 change in transpulmonary pressure
13 Work of breathing Equivalent to Work of Inspiration 3 fractions: That required to expand the lungs against the lung and chest elastic forces = compliance workThat required to overcome the viscosity of the lung and chest wall structures =tissue resistance workThe required to overcome airway resistance during the movement of air into the lungs = airway resistance work
14 Pulmonary volumes and capacities Spirometry – process of studying pulmonary ventilation, recording the volume movement of air into and out of lungsPulmonary Volumes:Tidal Volume: vol. of air inspired/expired with each normal breathing = 500 mLInspiratory Reserve Volume – maximum extra volume of air that can be inspired over and above normal tidal volume = 300 mL
15 Pulmonary volumes and capacities 3. Expiratory Reserve Volume : maximum extra volume of air that can be expired forcefully after end of a normal tidal expiration = 1.1LResidual Volume : volume of air remaining in the lungs after most forceful expiration = 1.2L
16 Pulmonary volumes and capacities Pulmonary CapacitiesTwo or more volumes togethereInspiratory Capacity : TV + IRV = 3.5LFunctional Residual Capacity: ERV+RV = 2.3LVital Capacity : IRV + TV + ERV = 4.6LTotal Lung Capacity: VC + RV = 5.8LAll pulmonary volumes and capacities are about 20-25% less in women than in men.
17 For the next meeting, read on Pulmonary Gas exchange and Gas transport Guyton Textbook of Medical Physiology