Ventilation and the mechanisms of breathing Flashcards
Define ventilation
the exchange of air between the lungs and the atmosphere so that gas exchange can occur in the alveoli
What is the role of ventilation?
-maintains blood gases and PH
-ventilation brings air from the atmosphere to the terminal bronchioles
-bring gas and blood into contact
-permits gas exchange of oxygen and carbon dioxide
What two things must match in order for efficent gas exchange?
ventilation and perfusion
What generates a total pressure gradient?
respiratory muscles
Name the four main respiratory muscles
-diaphragm
-intercostal muscles
-accessory muscles
-muscles of the abdominal wall
Name the intercostal muscles
-internal
-external
Name the accessory muscles
-scalenus
-sternocleidomastoid
-pectoralis major and minor
-trapezius
Name the muscles of the abdominal wall
-rectus abdominus
-external abdominis obliquus
-internal abdominus obliquus
-transversus abdominis
What is the structure of the diaphrgam?
-membranous domed shaped muscle
-composed of two muscles (hemidiaphragms) joined at the centre
-innervation from phrenic nerves
-surface area about 900cm2
What are some functions of the diaphragm?
-can shorten by 40%
-spend 45% of the day contracting
-unilateral paralysis causes little detriment and bilateral paralysis still consistenet with good ventilation
Where do you find the sternocleidomastoid muscles?
either side of the neck
where do you find your pectoralis major muscles?
chest
Where do you find your trapezius muscles?
top of your back
Where is the transverse abdominis located?
under the obliques, it is the deepest abdominal muscle and wraps around your spine for protection
Where is the internal abdominal oblique located?
under the external obliques running in opposite directions
where are external abdominal obliques located?
side and front of the abdomen
Where is the rectus abdominis muscle located?
along the front of the abdomen.
(known as the six pack)
What muscles are used during active forced respiration when inhaling?
-diaphragm
-external intercostals
-pectorals
-sternocleidomastoid
-scalene
-trapezius
What muscles are used during active forced respiration when exhaling?
-internal intercostals
-rectus abdominus
-internal/external oblique muscles
-transverse abdominal muscles
Describe accessory muscles of inspiration
-sternocleidomastoid-elevates sternum
-scalenes group-elevaate upper ribs
-pectoralis minor
Describe the principal muscles of inhalation
-external intercostals interchondral part of internal intercostals-elevates ribs
-diaphragm-dome descends thus increasing vertical dimensions of thoractic cavuty-elevates lower ribs
Describe quiet breathing using muscles of expiration
-passive elastic recoil of the lungs
-rib cage and diaphragm
Describe active breathing with muscles of expiration
-internal intercostals except interchondrial part pull ribs down
-abdominals-pulls ribs down, compress abdominal contents thus pushing diaphragm up
-quadratus lumborum
-pulls ribs down
describe the basics of breathing in
-increase in volume, decrease in pressure
-ribs move up and out
-diaphragm flatterns
-volume of chest increases
Describe the basics of breathing out
-decrease in volume,higher pressure
-ribs fall
-diaphragm moves up
-volume of chest decreases
atmospheric pressure is 101kpa what is the lung pressure if its the same as atmospheric?
0kpa
what is the pressure of the lungs when its less than atmospheric?
-1kpa
if the pressure is greater than atmospheric what is the pressure in the lungs?
+2kPa
Why does air flow into lungs because the thoracic cage expands?
-inspiratory muscles contract and increase the thoracic cavity volume
-gas moves from areas of high to low pressure
-gas flows from outside to inside of the thoracic cavity
-only small pressure changes of about +/ - 0.1kPa are needed
What does FRC stand for?
functional residual capacity
Define FRC
the volume of gas in lungs and airways at the end of a normal expiratory breath
-measured in litres
How do lungs balance at the FRC?
outward recoil of the chest wall is balanced by the inward recoil of the lung
Describe the mechanisms of ventilation
-thoracic wall and lungs are held closely together by pleural membranes
-lungs and chest wall pull in opposite directions creating a negative pressure in pleural space
-lung is pulled outwards
-chest walls inwards
-intrapleural pressure is usually negative
-when thoracic cavity expands, vaccum in the interpleural space forced lungs to follow
What is alveoli pressure at FRC?
-at FRC there is no flow so alveoli pressure is the same as atmospheric
Describe pressure changes during inspiration
-thorax expands following contractions of inspiratory muscles
-lungs stretch to fill expanded thorax
-air flows into lung down pressure gradient
(alveolar pressure drops as volume of thorac increases, pleural pressure becomes more negative)
Describe pressure changes during expiration
-thorax decreases in size following relaxation of inspiratory muscles
-lungs decrease in size as they recoil
-increased alveolar pressure
Give an overall description of pressure change during breathing
-pleural pressure is sub atmospheric
-becomes more negative at higher volumes
-intrapleural pressure helps to prevent lung from completley deflating
