Lecture 17 Flashcards
3 basic steps of respiration
- Pulmonary ventilation
- External ventilation
- Internal ventilation
What is pulmonary ventilation/breathing (inhalation/exhalation)
Exchange of air bet atmosphere and alveoli of lungs
What is external (pulmonary) respiratory
Exchange of gases between air in alveoli and blood in capillaries across respiratory membrane
What is internal (tissue) respiration
Exchange of gases between blood in systemic capillaries and tissue cells
How does flow of air between atmosphere and lungs occur
Difference in air pressure (high to low)
When diaphragm is relaxed, what is the diff between alveolar air pressure and atm pressure
0, both at 760mmHg
During inhalation, pressure in lung decr or incr
Decrease (more space, same amount of gas)
Bc during inhalation pressure lowers in lungs, air moves
Into lungs
When diaphragm contracts (inhalation), alveolar pressure drops to
757 mmHg
Body parts during inhalation
Thoracic cavity expands, external intercostal muscles and diaphragm contract
Why does contraction of diaphragm increases thoracic cavity
Bc it flattens and lowers the dome -> more space for lungs
When intercostal muscles contract,
Elevates ribs
Why is inhalation said to be an active process
Bc involves muscular contraction
Why is exhalation not a passive process
Bc no muscular contraction
What results from elastic recoil of chest wall and lungs
Exhalation
Body mvmt during exhalation
External IM relax, diaphragm relaxes, ribs are depressed
When exhalation decreases thoracic cavity, pressure in lungs increases to
763 mmHg
During exhalation, atm 760 and lungs 763 so air
Flows out
Ventilation steps
- Respiratory center in brain stimulates phrenic and intercostal nerves
- Nerves send impulses to resp muscles
- IM and D contract
- Thoracic cav V incr
- Lungs expand so intrapleural and intrapulmonary P decreases
- Air sucked in lungs (inhale)
- Muscles relax, air out of lungs (exhale)
Negative pressure and positive pressure mean
Negative: lower than atm P
Positive: higher than atm P
Atm pressure at sea level (normal atm P)
760 mmHg
Intrapulmonary/intra alveolar P is
P of air within alveoli (equalizes atm bet breaths but doesn’t stay there)
Intrapleural P
P within pleural cav, changes at diff phases of breathing, ALWAYS 4 mmHg LESS than intrapulmonary P
If intrapleural P wasn’t negative to lungs, they would
Collapse bc air would flow to low P
At rest, three P are at
Atm: 760
Intra alveolar: 760
Intrapleural: 756
Lungs tend to get pulled inward bc of the
Recoil of elastic tissue in them