Respiratory System

Question 1

INHALATION

Answer 1

• Unforced: contraction of diaphragm (flattens out) and ext. intercostals (pull ribs up- and outwards) → volume of lungs expand → alveolar pressure lower than atmospheric → air flows in
• Forced: contraction of sternocleidomastoid (elevating sternum), scalene muscles (elevate 2 uppermost ribs), and pectoralis minor (elevate 3-5 ribs)

Question 2

EXHALATION

Answer 2

• Unforced: no muscle contraction → diaphragm and ext. intercostals relax → decreased lung volume → alveolar pressure greater than atmospheric → airflow out
• Active: contraction of int. intercostals, ext./int. oblique, transverse abdominis, and rectus abdominis → lower ribs downwards → force diaphragm upwards → decreased lung volume…
• Alveoli and airways do not completely collapse → still some air left

Question 3

LUNG VOLUMES

Answer 3

• Tidal volume (TV) = air in- and exhaled per breath, unforced ~ 500 ml
• In-/exspiratory reserve volume = extra air during a forced inhalation/forced exhalation
• Residual volume = remaind air in lungs after a forced exhalation
• Minute volume (MV) = TV during 1 minute
• 70% of TV → bronchiols and alveolar → gas exchange = Alveolar ventilation (VA); 30% remains in airways = dead space

Question 4

Spirometry

Answer 4

• Messurment of air volume during breathing (in- and exhaled)
• MV = TV × respiratory rate (breath/min ~ 12)
• VA = (TV - dead space) × respiratory rate

Question 5

GAS EXCHANGE - external

Answer 5

• The exchange of gases between alveolar and pulmonary capillaries
• O2 in alveoli diffuse to blood and CO2 in blood diffuse to alveoli → deoxygenated blood becomes oxygenated → into left atrium

Question 6

GAS EXCHANGE - Internal

Answer 6

• Exchange of gases between systemic tissue capillaries →← systemic tissue cells
• O2 leaves blood and CO2 from cells enters blood → oxygenated blood becomes deoxygenated

Question 7

TRANSPORT - Oxygen

Answer 7

• Heme part in hemoglobin bind most O2
• High Po2 → easier O2 bonding to hemoglobin
• Partial pressure = Px = exerted pressure by 1 gas in a gas-mix
• Low Po2 → easier O2 release from hemoglobin

Question 8

TRANSPORT - Carbon dioxide

Answer 8

• Dissolved in blood plasma (7%)
• Bound to hemoglobin (23%)
• Bicarbonate ions in blood plasma (70%)

Question 9

RESISTANSE AND LUNG COMPLIANCE

Answer 9

• Lung compliance = mussure of elasticy of lungs
• Resistance = resistance to airflow in respiratory tract; depend on lung volume → body position
• Standing/forward tilted sitting → increase volume
• Suspine position → decreased volume

Question 10

REGULATION

Answer 10

• Nerve impulses from respiratory center → muscles contract → extend thorax (muscles relax in absence of impulses)
• Medallary = unforced and forced breathing and their rythm
• Pontine = modifies breathing rythm
• Changes in CO2, H+, or O2 level → chemoreceptors detect → impulse to medullary respiratory center → output
Hyperventilation if increased Pco2 and H+ → more exhalation of CO2; hypoventilation in opposite