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Chapter 13
Respiration

Pulmonary ventilation (breathing)
 Air moving in and out of lungs so gas exchange
can occur

External respiration
 Gas exchange between pulmonary blood and
alveoli

Respiratory gas transport
 Gas transported to and from lungs and tissue
cells in body

Internal respiration
 At systemic capillaries, gas exchange between
blood and tissue cells (cellular respiration)
Mechanics of Breathing

Mechanical process (pulmonary
ventilation)
 Inspiration- air flowing into lungs
 Expiration- air leaving lungs
Inspiration
Diaphragm contracts (moves downward)
 Inspiratory muscles contract
 external intercostals contract lifting rib cage

 Both cause size of thoracic cavity to increase
Since lungs adhere tightly to thorax walls
due to the surface tension between pleural
membranes, lungs expand
 Decrease in gas pressure causes air to be
sucked into lungs

Expiration
Muscles relax, rib cage descends, lungs
recoil
 Thoracic volume decreases, causing an
increase in pressure
 Air flows out of lungs

Respiratory Volumes &
Capacities
Tidal volume- normal
amount of air take in
and out during a breath
(~500 ml)
 Inspiratory reserve
volume (IRV)- amount
of air that can be
forcible taken in above
the tidal volume (~2100
– 3200 ml)

Expiratory reserve volume
(ERV)- amount of air that can
be exhaled above the tidal
volume (~1200 ml)
 Residual volume- air that
cannot be expelled, needed
for gas exchange to continue
in lungs in between breaths
 Vital capacity (VC)- total
amount of exchangeable air

 = TV + IRV + ERV
Respiratory Sounds

Bronchial sounds
 Air rushing through large respiratory
passageways (trachea & bronchi)

Vesicular breathing sounds
 Occurs as air fills alveoli
 Soft and resemble muffled breeze
External Respiration


Exchange of gas between lungs and blood
Gas exchange always diffuses from area of high
concentration to low concentration
 Oxygen concentration
○ high in lungs, low in capillaries
 Carbon dioxide concentration
○ high in blood, low in lungs
Internal Respiration
 Exchange of gases between blood and cells
○ Oxygen concentration
 High in capillaries, low in cells
○ Carbon dioxide concentration
 High in cells, low in blood