Anatomy of Chest Wall and Mechanics of Breathing Flashcards
how many lobes is the right lung divided into?
3 (superior, middle and inferior lobe)
how many lobes is the left lung divided into?
2 (superior, inferior)
what are the lung extremities called?
apex and base
what surrounds the lungs?
inside two pleural membranes
what passes through the thorax?
the oesophagus and the aorta
what cavity surrounds the heart?
the pericardial cavity
what cavity is between the pleural membranes? what is it filled with?
the pleural cavity, filled with intrapleural fluid
what is the deep pleural membrane called? what does it coat?
visceral pleura, coats outer surface of lungs
what is the superficial pleural membrane called? what does it coat?
parietal pleura, coats inner surface of rib cage
the 2 pleural membranes and the pleural cavity form what?
the pleural sac
what is pleurisy?
inflammation of the pleura
how does intrapleural pressure compare with that of the atmosphere?
-3mmHg at rest (subatmospheric)
what force compensates the one applied inwards by the elasticity of the lung?
the elastic recoil o the chest wall going outwards
what is a pneumothorax?
when air flows in the interpleural space and the pressure normalises with the atmosphere. The visceral pleura looses its adherence with the parietal pleural, the lung collapses and the rib cage expands slightly (shows importance of relationship between pleural membranes)
what is Boyle’s law?
the pressure exerted by a gas is inversely proportional to its volume
why does air come in the lungs during inspiration?
the thoracic cavity increases its volume, the pressure decreases, air comes in the compensate (gases move from high pressure to low pressure)
how does the thoracic cavity increase its volume?
external intercostals muscles, the diaphragm, sternocleistomastoids and scalenes
how does the thoracic cavity decrease its volume?
expiration is passive at rest but uses internal intercostal and abdominal muscles during severe respiratory load (reducing duration of breathing cycle and allowing more breaths/min, ex: asthma)
how do external intercostals increase cavity size?
by pushing ribs forward (pump handle, sternum comes away from spine) and also up (bucket handle, lateral side of rib goes up)
what is asthma?
over-reactive constriction of bronchial smooth muscle, increases resistance, expiration difficult
what is the intra-thoracic/ alveolar pressure? (Pa)
the pressure inside the thoracic cavity (essentially inside the lungs), may be negative (inspiration, -1mmHg) or positive (expiration, +1mmHg) as opposed to the atmospheric pressure
what is the intra-pleural pressure? (Pip)
the pressure inside the pleural cavity, always negative in healthy lungs, varies between -3mmHg when resting and -6mmHg when max effort (end of inspiration, biggest volume of air moved)
what is the transpulmonary pressure (Pt)
the difference between the alveolar pressure and the intra-pleural pressure, always positive in health because Pip is always negative (Pt=Pa-Pip) (and i guess negative Pa is never lower than Pip)
what is the difference between the atmospheric and the alveolar pressure proportional to?
it is proportional to the difference between the atmospheric and alveolar pressures and inversely proportional to the airway resistance F=(Patm-Pa)/R
what are the pressure differences at the end of an unforced expiration?
Patm=Pa, no air is flowing, dimensions of lung and thoracic cage are stable as the result of opposing elastic forces (creating a subatmospherical intrapleural pressured hence a transpulmonary pressure that opposes the recoiling forces)
what does airway resistance determine? how does it vary?
it determines how much air flows into the lungs at any given pressure difference between the atmosphere and the alveoli, its major determinant is the radius of the airways
