Gas Exchange in Respiration Flashcards
what is the tidal volume
the volume breathed in and expired.
how do gases move along pressure gradients
downward. from high to low
on average, how many ml/min of oxygen are consumed
250
on average, how many ml/min of carbon dioxide are expired
200
what is the partial pressure of oxygen
150mmHg
is partial pressure of oxygen in the blood greater before going into the lungs are after
after
what do pressure gradients show
the direction of movement of oxygen and carbon dioxide in the respiratory system
what is the partial pressure
pressure a gas exerts in a particular environment, taking into account if the environment is wet or dry
what must the sum of partial pressures of a gas be equal to
total pressure
what do pressure changes in the environment depend on
weather patterns and the time of day
what is barometric pressure
the pressure outside the body
what is the equation to calculate partial pressure
fraction of the gas in the gas mixture times by the barometric pressure
what is the pressure of water vapour in the body
47mmHg
how many ml of air breathed in per breath on average at rest
500ml
how many ml of air remains in the airways after expiration
150ml
describe the respiratory tree
trachea
bronchi
non respiratory bronchioles
respiratory bronchioles
alveolar ducts
what happens at each division of the respiratory tree
increase in number, an increase in surface area
do the conducting airways participate in gas exchange
no
what are the respiratory airways
bronchioles with the alveoli where gas exchange occurs, from the terminal bronchioles to the alveoli
what is a respiratory unit
basic physiological unit of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli
how many alveolar sacs in average adult
300-400 million
describe alveoli
polygonal
type 1 and type 2 epithelial cells
what feature of alveoli encourages gas exchange the most
its close connection with capillary networks
describe type 1 epithelial cells in alveoli
97% of surface area of alveoli.
primary site of gas exchange
describe type 2 epithelial cells of the alveoli
septal cells
3% surface area
produce pulmonary surfactant (this reduces surface tension)
alveolar macrophages remove debris
describe the key features of alveolar
large surface area of 100m2
very thin walls
good diffusion characteristics
what are the blood supplies of the lungs
pulmonary circulation
bronchial circulation
describe pulmonary circulation
brings deoxygenated blood from the heart to lung and oxygenated blood from lungs to the heart and then the rest of the body
describe bronchial circulation
brings oxygenated blood to the lung parenchyma
function of the lymphatic system
defence and removal of lymph fluid
what is the total blood volume in pulmonary circulation
500ml
how many ml of blood in the alveolar capillary network at rest
75ml
what is the blood volume in the alveolar capillary network during exercise and how does this happen
increases from 75 to 200.
recruitment of new capillaries secondary to an increase in pressure and flow
describe arteries
thin walled
highly compliant
large diameter
low resistance
how does gas exchange occur
dense mesh like network of capillaries and alveoli
how many seconds for blood cells to pass through capillaries
one second
describe the gas gradient of pulmonary circulation
oxygen enters
carbon dioxide leaves
describe the gas gradients of systemic circulation
oxygen leaves blood
carbon dioxide enters blood
what are gas concentration gradients important for
direction of flow
do blood and air have a close contact
yes
how do the volumes of carbon dioxide and oxygen that move each minute differ
they are similar
is the pressure gradient of oxygen lesser or greater than carbon dioxide
greater
is carbon dioxide or oxygen more diffusable
carbon dioxide
describe volume and pressure of pulmonary circulation
large volumes at low pressure
what is ventilation
process by which air moves in and out of the lung
what is perfusion
process by which deoxygenated blood passes through the lung and becomes oxygenated
what is the level of partial pressure in oxygen and carbon dioxide related to
the relationship between ventilation and perfusion
what is the V/Q ratio
the relationship between ventilation and perfusion
describe the distribution of ventilation
not uniform due to gravity
describe ventilation in the upright position
alveoli in the apex is more expanded than at the base
describe graviy’s impact on ventilation distribution in the lungs
gravity pulls the lung down and away from the chest wall
pleural pressure is more negative at the apex than at the base
transpulmonary pressure is greater at the apex than at the base
increased alveolar volume in the apex
what is compliance
this refers to how much effort is required to stretch the lungs and chest wall
what does high compliance mean for breathing
it means that the lungs and the chest wall expand easily
what is resistance
narrowing or obstruction of airways
reduced lumen
increased resistance that can lead to decreased ventilation
what does decreased compliance mean for breathing
common feature when there are pulmonary conditions, leads to:
- scarring in the lung tissue (like in TB)
- lung filled with fluid (edema)
- deficiency in surfactant production
- destruction of elastic fibres (emphysema)
what is an increased resistance a common feature in
pulmonary conditions
what can increased resistance lead to
- asthma
- COPD due to obstruction or collapse of airways
is pulmonary influenced more or less by gravity compared to systemic circulation
more
describe upright pulmonary blood flow
there is greater blood flow the base than the apex
describe pulmonary circulation
low pressure and low resistance
what defines the V/Q ratio of a single alveolus
alveolar ventilation divided by capillary flow
what defines the V/Q ratio of the lung
total alveolar ventilation divided by cardiac output
what is the average alveolar ventilation of healthy individuals
4-6 litres per minute
what is the pulmonary blood flow on average in healthy individuals
5 litres per minute
what is the V/Q for a lung in a healthy individual
0.8 to 1.2
what is the V/Q ratio when the ventilation exceeds the perfusion
greater than one
what is the V/Q ratio when perfusion exceeds ventilation
less than one
what does V/Q mismatching lead to
arterial hypoxemia in patients with respiratory disorders
what is the V/Q ratio a ratio of
ventilation to blood flow
what does it mean if V/Q ratio is 1
this is the perfect model, where the inspired gas and cardiac output partial pressures are shared equally
what does V/Q mismatching result in
varying alveolar and capillary gas contents
what are the regional differences in ventilation and perfusion largely down to
gravity
