Lecture 7: The Respiratory System; Respiratory Physiology Flashcards
what is atmospheric pressure (Patm)
-pressure exerted by air surrounding the body
-760 mmHg at sea level = 1 atmosphere
-respiratory pressures are described relative to Patm
what does + - & 0 respiratory pressure mean in relation to Patm
-ve repiratory pressure: < Patm
+ve respiratory pressure: >Patm
0 respiratory pressure: = Patm
what is intrapulmonary pressure (Ppul) (intra-alveolar pressure)
-pressure in alveoli
-fluctuates with breathing
-always eventually equalizes with Patm
what is intrapleural pressure (Pip)
pressure in pleural cavity
-fluctuates with breathing
-always a negative pressure (<Patm and < Ppul)
-usually always 4mmHg<Ppul
-fluid level must be kept at a minimum
-excess fluid pumped out by lymphatic system
-if fluid accumulates, positive Pip pressure develops-> lung collapses
whathappens if fluid accumulates in the thoracic cavity
the lung will collapse
what two inward forces promoite lung collapse
- lungs’ natural tendency to recoil because of elasticity, lungs always try to assume smallest size
- surface tension of alveolar fluid, surface tension pulls on alveolu to try to reduce alveolar size
what is transpulmonary pressure = (Ppul - Pip)
-pressure that keeps lung spaces open (keeps them from collapsing)
-greater transpulmonary pressure the larger the lungs will be
lungs will collapse if Pip = ?
-Pip = Ppul
-Pip = Patm
-negative Pip must be maintained to keep lungs inflated
what is pulmonary ventilation
breathing
-consists of inspiration and expiration
-mechanical process that depends on volume changes in thoracic cavity
-volume changes lead to pressure changes
-pressure changes lead to flow of gases to equalize pressure
what is Boyle’s Law
-relationship between pressure and volume of a gas
-gases always fill the container they are in
-if the amount of gas is the same and container size is reduced, pressure will increase
-so pressure (P) varies inversely with volume (V)
-mathematically: P1V1= P2V2
what are the primary repsiratory muscles
external intercostal muscles & diaphragm
what are the accessory repsiratory muscles
sternocleidomastoid, scalenes, pectoralis minor, serratus anterior, internal intercostal muscles, transversus thoracis, external oblique, rectus abdominis, interal oblique
what does the body look like at resting state
-disphragm remained dome shapes
-pressure inside lungs (alveolar pressure) = Patm, 760 mmHg
-net effect- “no flow of air”
what are the events in inspiration
-diaphragm contracts and thoracic cavity floor becomes flattened
-thoracic cavity volume increases; pressure within lungs decreases. Patm is higher, air moves from outside to inside the lungs
-external intercostal muscles contract-> elevates the rib cage
-accessory muscles may contract to assist external intercostal muscles to elevate the ribs
what are the events in expiration
-diaphragm relaxes; rib cage returns to original position
-thoracic cavity volume decreases; pressure within the lungs increases-> outflow of air; pressure inside >Patm
-rib cage is lowered by internal intercostal muscles and transversus thoracis; thoracic cavity volume decreases
-external intercostal muscles can be aided by the abdominal muscles by condensing the abdomen, thereby pushing the diaphragm upwards
intrapulmonary pressure during inspiration and expiration
pressure inside the lunds decreases as lung volume increases during inspiration; pressure increases during expiration
intrapleural pressure during inspiration and expiration
pleural cavity pressure becomes more negative as chest wall expands during inspiration. returns to initial value as chest wall recoils
volume of breath during inspiration and expiration
during each breath the pressure gradients move 0.5 liters of air into and out of the lungs
what is non-repsiratory air movements
-many processes can move air into or out of lungs besides breathing
-may modify normal repsiratory rhythm
-most reslt from reflex action, although some are voluntary
what are some examples of non-respiratory air movements
coughing, sneezing, sighing, yawning, sobbing, crying, laughing, hiccupping, valsalva maneuver, pressurizing the middle ear
what is assessing ventilation
-several respiratory volumes (RVs) can be used to assess respiratory status
-combinations of RVs-> respiratory capacities, which can give information on a person’s respiratory status
-RVs and capacities are usually abnormal in people with pulmonary disorders
what is spirometry
-clinical tool used to measure respiratory volumes
what is tidal volume
amount of air moved into nad out of lung with each breath (normal quiet breathing)- avergaes ~500 ml
what is inspiratory reserve volume (IRV)
amount of air that can be inspired forcibly beyond the tidal volume (1000- 1200 ml)
