18. anatomy of ventilation Flashcards
what is pulmonary ventilation (breathing)
the physical movement of air into and out of the respiratory tract
what is the function of pulmonary ventilation
to ensure a continuous supply of oxygen
to prevent build up of CO2
how is pressure made
by gas particles bouncing off each other and walls of containers
what is boyles law
the pressure of a given quantity of gas is inversely proportional to its volume
how does air flow
from an area of high pressure to an area of low pressure
if we pull a plunger back does air move out or into the syringe
pulling plunger back increases the volume so the pressure in syringe decreases so air moves in
when will air enter the lungs in inspiration
when the atmospheric pressure Is greater than the intrapulmonary/intra alveolar pressure due to lung volume increasing
how can we increase thoracic volume (3)
increasing the
vertical diameter
the anterior posterior diameter
the transverse diameter
how can we increase vertical diameter
contraction of the diaphragm
responsible for 75% increase in thoracic capacity
how can we increase the anteroposterior and transverse diameters
elevation of the ribs
responsible for 25% of the increase in thoracic capacity
why does elevation of the ribs increase A diameter
elevation of the ribs at the sternal end makes them more horizontal and pushes the sternum forward
pump handle movement (pulling handle up)
why does elevation of the ribs increase the transverse diameter
many ribs are lowest at their middle and rise at each end like the handle of a bucket.
if the middle of the rib rises it moves away from the midline of the body making the chest wider from left to right
what is the role of pleura in ventilation
the surface tension created by the layer of serous fluid between the visceral and parietal pleura means they cant be pulled apart
and so when the thorax increases in the volume the lungs also increase in volume
what is the interpleural pressure and how is it generated
pressure within the pleural cavity
is always lower than the atmospheric and intrapulmonary pressure
is created by the elastic recoil of the lungs
what is pneumothorax
accumulation of air or gas in the pleural cavity
occurs as a result of disease or injury
loss of negative interpleural pressure causes the lungs to collapse
inspiration is an _____ process
ACTIVE
what are the muscles of quiet inspiration and what do they do
diaphragm- contracts and flattens, increasing vertical diameter
external intercostals- elevate the ribs and increase AP + transverse diameter
what are the muscles of forced inspiration
pectoralis major pectoralis minor scalenes serratus anterior sternocleidomastoid
what do the muscles of forced inspiration do
assist in rib elevation , increase the speed and amount of movement
is expiration an active or passive process
it is both
when at rest expiration is passive
but when forced is active
quiet expiration
relaxation of the diaphragm and external intercostal muscles
muscles of forced expiration
internal and innermost intercostals depress the ribs, reducing the size of the thoracic cavity
abdominal muscles compress the abdomen and force the diaphragm upwards
neural control of ventilation
chemoreceptors detect changes in PO2, PCO2 and pH
sends signal through afferent nerve pathways to the respiratory centres in the brain stem
then sends signal down efferent pathways (eg phrenic nerve) to the muscles of ventilation
