physiology of the pulmonary system Flashcards
what are the four steps involved in gas transport from atmosphere to the tissue
- ventilation: inspired air to alveoli
- external respiration: transfer from alveoli to capillary (diffusion)
- Transport: gas transport in blood to tissue
- internal respiration: exchange of gases between the capillary and tissue mitochondria
Circulation
- passage of blood through the heart, blood vessels, organs and tissue
- transport system
perfusion
- refers to the blood flow at the capillary level
- without this you get cyanotic
ventilation
mechanical movement of gas in and out of the lungs (getting to and from alveoli)
respiration
- exchange of O2 and CO2 across a membrane at the cellular level
- occurs via diffusion across a semipermeable membrane
compliance
- a measure of the lungs ability to stretch and expand
- COPD = high compliance
- decreased compliance in restrictive pulmonary diseases
Elasticity
- refers to the lungs ability to return to initial size after distension
Surfactant
- a lipoprotein that REDUCES surface tension to keep alveoli open
Partial pressure
- portion of the total pressure exerted by the presence of a single gas molecule
Neural control of breathing
- automatic by pons (rate) and medulla (depth)
- voluntary = cerebal cortex (integrates with singing, talking, laughing)
- influenced by the hypothalamus (pH) and limbic system (emotion)
Vagus nerve and respiration
- has stretch receptors to monitor when it is overstretched
- irritant receptors to initiate coughing
- j receptors
- hiccups stem from stimulation of the vagus nerve
chemical control
- chemoreceptors in the brainstem, peripheral arteries, carotids and aorta
- sense changes in oxygen and carbon dioxide and pH
- more sensitive to CO2 changes
- feed into pons and medulla
when is dyspnea most likely to occur
- when there is a discrepancy between neural drive to breathe and the level of ventilation achieved
Describe the pump handle and bucket handle effects
- pump handle: refers to the up/anterior movement of the sterum and ribs
- bucket handle: refers to the lateral movement of the rib cage
Mechanisms of inhalation
- the diaphragm contracts and moves down
- external intercostals contract lifting/rotating ribs, lift sternum and thoracic vertebrae
- lungs stretch
- pressure inside lungs is lower than pressure outside
- air gets pulled into lungs
- diaphragm pushes down into abdominal contents = abdomen expands
Mechanics of exhalation
- lungs recoil
- rib cage gets pulled inward
- diaphragm gets pulled upward
- pressure inside lungs is higher than pressure outside
- air is forced out of respiratory tract
- diaphragm no longer pushes abdominal contents
- abdomen is pulled in
TV
- tidal volume
- air inhaled and exhaled during quiet breathing
IRV:
air that can be forcefully inhaled over normal breathing
ERV:
air that can be forcefully exhaled over normal breathing
RV:
the amount of air that cannot be forcefully exhaled
Capacities:
TLC:
the total amount of air that the lungs can hold (IRV+TV+ERV+RV)
IC:
maximum amount of air that can be inhaled following a normal expiration
VC:
amount of air that can be forcefully exhaled following max inspiration
FRC:
amount of air remaining in the lungs following a normal expiration
Minute ventilation
- norms
= respiratory rate x tidal volume
- normal 4-6 L/min
- tidal volume can increase more than RR
Describe pressures in the lungs during
1) resting
2) inspiration
3) expiration
1) atmospheric pressure = intrapulmonic pressure and intrapleural pressure is lower than atmospheric pressure
2) Atmospheric pressure>intrapulmonic pressure (air flows in) intrapleural pressure becomes more negative
3) atmospheric pressure <intrapulmonic pressure (air pushed out) intrapleural pressure remains negative
Describe transport and cellular respiration
- at alveoli: capillary Po2<alveoli Po2
- at tissue: capillary Po2>tissue pO2
Ventilation/perfusion ratio
- Ratio of the amount of air entering the alveoli and the blood flowing available to the alveoli
- Norm is 0.8 or greater
- Alterations result in hypoxia
Types of barriers in V/Q
- dead space
- shunt
Dead space as a barrier
- Air that does not participate in gas exchange
- Ventilation but not perfuses
- Anatomic dead space such as trachea and bronchi
- alveolar/physiologic dead space: ex = pulmonary embolism that blocks blood flow to the lung
Shunt as a barrier to V/q
- Blood flow that returns to the left side of the heart without picking up oxygen
- Perfused but not ventilated
- Pneumonia (lung has gunk in it and get clogged so gas does not diffuse as well)
V/Q in relation to body position
- Air and pulmonary blood flow are related to gravity
- Body position has a significant effect on the distribution of pulmonary blood flow
- Greatest volume of pulmonary blood flow will occur in gravity dependent areas of the lungs
- More in the bases than apices in upright position
- Patients that are bed bound need to be put in different positions to use different portions of their lungs → we normally change positions throughout our day
