Functional Anatomy of the Respiratory System Dr. Meg-angela Christi Amores.
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Transcript of Functional Anatomy of the Respiratory System Dr. Meg-angela Christi Amores.
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Functional Anatomy of the Respiratory System
Dr. Meg-angela Christi Amores
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Pulmonary Ventilation
• Pulmonary Ventilation – inflow and outflow of air between the atmosphere and the lungs
• Muscles for Respiration:– Diaphragm – External Intercostal muscles– Sternocleidomastoid Muscles– Anterior Serrati– Scalene muscles– Abdominal Rectus musles– Internal Intercostals
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Lung Expansion and Contraction
2 ways:• Diaphragm Movement– or – lengthen or shorten chest cavity
• Ribs– Elevate or depress – increase or decrease antero-
posterior diameter of chest cavity
Normal quite breathing is accomplished almost entirely by first method.
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Diaphragm Movement
• During INSPIRATION:– Diaphragm contracts and pulls lower surface of
the lung downward• During EXPIRATION:– Diaphragm relaxes accompanied by elastic recoil
of lungs, chest wall and abdominal structures
During heavy breathing, extra force is achieved mainly by contraction of abdominal muscles
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Ribs Movement• During INSPIRATION– Ribs project almost entirely forward from
an original downward position– Sternum also moves forward away from
spine– Anteroposterior (AP) diameter increases
to 20%– Muscles that elevate ribs:
• External intercostals• Sternocleidomastoid• Anterior Serratus• Scalene Muscles
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PRESSURES
• Lungs are “elastic” – collapses like a balloon when there is no force to keep it inflated
• There are no attachments between the lungs and the ribcage except at hilum
• Lungs float in pleural fluid• Lymphatics provide slight suction between
visceral surface of lung pleura and parietal surface of thoracic cavity
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Pleural Presure
• Pressure of fluid in the narrow space between lung pleura and chest wall pleura
• Slightly negative pressure• At beginning of inspiration: -5 cmH20
• The amount needed to hold the lungs open
• During inspiration: -7.5cmH20
As negativity increases, lung volume increases to 0.5L
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Alveolar Pressure
• Pressure of air inside the lung alveoli• Open glottis – pressures are equal at 2 atm• For 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
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Transpulmonary Pressure
Se-ries
1
-10
-8
-6
-4
-2
0
2
pleural PAlveolar PLung vol
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Compliance
• Compliance is the extent to which lungs expand for each unit of increase in transpulmonary pressure
• = 200mL/ 1 cmH20 change in transpulmonary pressure
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Work of breathing
• Equivalent to Work of Inspiration • 3 fractions:
1. That required to expand the lungs against the lung and chest elastic forces = compliance work
2. That required to overcome the viscosity of the lung and chest wall structures =tissue resistance work
3. The required to overcome airway resistance during the movement of air into the lungs = airway resistance work
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Pulmonary volumes and capacities
• Spirometry – process of studying pulmonary ventilation, recording the volume movement of air into and out of lungs
• Pulmonary Volumes:1. Tidal Volume: vol. of air inspired/expired with
each normal breathing = 500 mL2. Inspiratory Reserve Volume – maximum extra
volume of air that can be inspired over and above normal tidal volume = 300 mL
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Pulmonary volumes and capacities3. Expiratory Reserve Volume : maximum extra
volume of air that can be expired forcefully after end of a normal tidal expiration = 1.1L
4. Residual Volume : volume of air remaining in the lungs after most forceful expiration = 1.2L
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Pulmonary volumes and capacities
• Pulmonary Capacities– Two or more volumes togethere1. Inspiratory Capacity : TV + IRV = 3.5L2. Functional Residual Capacity: ERV+RV = 2.3L3. Vital Capacity : IRV + TV + ERV = 4.6L4. Total Lung Capacity: VC + RV = 5.8L
All pulmonary volumes and capacities are about 20-25% less in women than in men.
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• For the next meeting, read on Pulmonary Gas exchange and Gas transport
• Guyton Textbook of Medical Physiology