-
non-respiratory functions of respiratory system
- water loss and heat elimination
- enhances lymph flow and venous return
- helps maintain normal acid-base balance
- enables speech, singing and other vocalizations
- defends against foreign matter
- removes, modifies, activate, or inactivates various materials passing through the pulmonary circulation
- nose: organ of smell
- helps expel abdominal contents during urination, defecation, and childbearth
-
3 meanings of respiration
- ventilation of the lungs ( breathing, pulmonary and alveolar)
- the exchange of gases btwn the air and blood and btween blood and tissue fliud
- the use of oxygen in cellular metabolism
-
alveoli
- incoming airs stops at the alveoli
- millions of thin-walled, microscopic air sacs
- exchanges gases with the bloodstream through the aveolar wall, and then flows back out
-
conducting division
- passages that serve only for airflow
- no gas exchange
- nose, pharynx, larynx, trachea, and major bronchi
-
respiratory division
consists of the alveoli and other gas exchange regions
-
upper resiratory tract
- in head and neck
- nose, pharynx and larynx
-
lower respiratory tract
- organs of the thorax
- trachea, bronchi, and lungs
-
3 important pressures in ventilation
- atomostpheric: barometric 760 mmhG
- intra-aveolar: intrapulmonary
- intrapleural: intrathoracic
-
intra-aveolar
- intrapulmonary
- pressure within the alveoli
- usually the same as atmospheric pressure
-
intrapleural
- intrathoracic
- pressure within the pleural sac
- the pressure exerted outside the lungs within the thoracic caivity
- usually less than atomospheric pressure
-
changes in the intra-alveolar pressure
- produce flow of air into and out of lungs
- if pressure is less than atomospheric pressure air will enter the lungs
- it pressure is greater than atomospheric pressure air exits the lungs
-
boyles law
- at constant temperature
- pressure of of a given quanity of gas is inversely related to its volume
- quantity and temperature remains constant
-
boyles law related to lungs
- lung volume increases, then their internal pressure or intrapulmonary pressure with fall
- if the pressure falls below atmostpheric pressure that air will move into the lungs
- if the lung volum decreases, intrapulmunary pressure rises
- if pressure rises above atmospheric pressure the air moves out of th lungs
-
inspiration
- the 2 pleural layers, their cohesive attractive to eachother and their connections to the lungs and their linging of the rib cage cause inspiration
- when ribs swing upward and outward, the parietal pleura follows
- the visceral pleura clings to it by the cohsion of water and it follows the parietal pleura
- it stretches the aveoli within the lungs
- the entire lung expands along the thoracic cage
- as the volume increases, its internal pressure drops and air flows in
-
intrapleural pressure and inspiration
- slight vacuum exists btwn 2 pleural layers
- about -4 mmHg
- drops to -6 mmHg during inspiration as the parietal pleura pulls away
- some of the pressure change transfer to the interior of the lungs
- intrapulmonary pressure drops (in alveoli) allows the air to flow into the lungs (less than atmospheric pressure)
-
charles law
the given quantity of gas is directly proportional to is absolue pressure
-
charles law and inspiration
- on cold day inspiration will increas temp of air
- it will warm by the time is reaches the alveoli and the thermal expansion with contribute to the inflation of the lungs
-
quiet breathing
dimensions of the thoracic cage increases only a few millimeter in each direction
-
muscles of respiration in inspiration
active diaphram and external intercostals
-
expiration
relaxed and forced breathing
-
relaxed breathing
- passive process achieved mainly by the elastic recoil of the thoracic cage
- recoil compresses the lungs
- volume of the thoracic cavitiy decreases
- raise intrapulmonary pressure about + 3 mmHg
- air flows down the pressure gradient and out of the lungs
- elastic properties of the lung
-
forced breathing
- accessory muscles rais the intrapulmonary pressure as high as +30 mmHg
- massive amounts of air moves out of the lungs
-
active respiration
- active exhalation abdominal compression
- active inspiration abdominal relaxation
-
pneumothorax
- presence of air in pleural caivity
- thoracic wall is punctured
- inspiration sucks air through the wound and into the pleural cavity
- potentail space becomes an air filled cavity
- loss of negative intrapleural pressure allows the lungs to recoil and collapse
-
atelectasis
- collapse of part or all of the lung
- can also result from an airway obstruction
-
cell types in alveoli
- capillary endothelial cells
- alveoli epithelial cells (type I and II)
- fibroblasts (surfactant)
- macrophages
- mast cells
-
controll of brochiolar diameter
- 1. nervous
- sympathetic: β2 receptors dilate
- parasympathetic: Ach constricts
- 2. Humoral
- histaminend Ach constrict
- Adrenergic (β agonists) relax
-
resistance to airflow
the greater resistance, the slower the flow
-
3 factors that influence airway resistance
- diameter of the bronchioles
- pulmonary compliance
- surface tension of the alveoli and distal bronchioles
-
bronchodilation
- increases the diameter of a bronchus or bronchiole
- decrease resistance
- epinephrine and sympathetic stimulation stimulates bronchodilation
- increase air flow
-
bronchoconstriction
- decrease the diameter of a bronchus or bronchiole
- histamine, parasympathetic nerves, cold air, and chemical irritants stimulate bronchoconstriction
- suffocation from extreme bronchconstriction is brought about by anaphylactic shock and asthma
- inscrease resistance and decreases the flow
-
pulmonary compliance
- the ease with which the lungs can expand
- the change in lung volume relative to a given pressure change
- compliance reduced by degenerative lung diseases in which lungs are stiffened by scar tissue
-
surface tension of the alveoli and distal bronchioles
- surfactant: reduces surfaces tensions of water
- infant respiratory distress syndrome (IRDS) premature babies
-
elastic recoli
- lung compliance
- how readily the lungs rebound after stretch
- responsible for lungs returning to their preinspiratory volume when inspiratory muscles relax at the end of inspirationo
- depends on 2 factors: 1. high elastic connective tissue in the lungs 2. alveolar surface tesion
-
alveolar surface tension
- thin liquid film lines each alveolus
- thin film of water is needed for gas exchange
- reduces tendency of alveoli to recoil
- helps maintain lung stability
- if too much tension will collapse the alveoli
- prevented by surfactant
-
pulmonary surfactant
- produces by the great alveolar cells
- decreases surface by disrupting H bonding in water
-
infant respiratory distress syndrome
- premature infants that that lack surfactant
- great difficulty breathing
- treated with artificial surfacnt until lungs can produce their ow
-
alveolar ventilation
only air that enters the alveoli is available for ga exchange
-
anatomic dead space
- conducting division of the airway where there is not gas exhange
- can be alertered somewhat by sympathetic and parasumpathetic stimulation
-
pulmonary disease
some aveoli may be unable to exchange gases bc they lack blood flow or their respiratory membrane has been thicked by edema or fibrosis
-
if a person inhales 500 ml of air
- 150 stays in anamical dead space
- 350 mL reaches the aveoli
-
AVR: alveolar ventilation rate
- air that ventilates alveoli, respiratory rate
- relavent to the body's ability to get oxygen to the tissues and dispose of carbon dioxide
-
lung volumes and capacities
can be measure by spirometer
-
spirogram
graph that records inspiration and expiration
-
spirometer
a devicethat recaptures expired breath and records such variables such as rate and depth of breathing, speed of expiration and rate of 02 consumpion
-
tidal volume
- volume of air inhaled and exhaled in one cycle of quiet breathing
- average - 500 mL
-
inspiratory reserve volume
- air in excess of tidal volume that can be inhaled with maximum effore
- IRV
- average - 3000 mL
-
expiratory reserve volume
- air in excess of tidal volume that can be exhaled with max effort
- ERV
- average about 1000 mL
-
residual volume
- air remaining in the lungs after maximum expiration
- RV
- average about 1200 mL
-
vital capacity
- total amount of air that can be inhaled and then exhaled with max effort
- VC = ERV + TV + IRV
- important measure in pulmonary health
- average about 4500 mL
-
inspiratory capacity
- max amount of air that can be inhaled after a normal tidal expiration
- IC = TV + IRV
- about 3500 mL
-
functional residual capacity
- amount of air remaining in lungs after normal tidal expiration
- FRC = R + ERV
- average about 2200 mL
-
total lung capacity
- max amount of air that the lungs can contain
- TLC = RV + VC
- average about 5700 mL
-
forced expiratory volume
- FEV
- percentagof vital capacity that can be exhaled in a given time interval
- healthy adult range: 75-85% in 1 sec
-
peak flow
- max speed of expiration
- blowing into a handheld meter
-
minute respiratory volume
- MRV
- amount of air inhaled per minute
- TV x respiratory rate
-
maximum voluntary ventilation
MVV = MRV during heavy exercise
-
restrictive disorders
- reduce pulmonary compliance
- limit amount that the lungs can be inflated
- any disease that produces pulmonary fibrosis
- black-lung, tuberculosis
-
obstructive distorders
- disorders that interfere with airflow by narrowing or blocking the airway
- make it harder to inhale and exhale a given amount of air
- asthma, chronic bronchitis
-
emphysema
combines both elements fo restricive and obstructive disorders
-
conditions affecting respiratory fucntion
- diseases affecting diffusion of 02 and co2 across pulmonary membranes
- reduced ventilation due to mechanical failure
- inadequate pulmonary blood flow
- ventilation/ perfusion abnormalities involving a poor matching of air and blood so the efficient gas exchange does not occure
-
eupnea
- relaxed quiet breathing
- tidal volume of 500 mL and the respiratory rate of 12 - 15 bpm
-
apnea
temporary cessation of breathing
-
dyspnea
- labored, gasping breathing
- shortness of breath
-
hyperpnea
increased rate and depth of breathing in response to exercise, ain or other conditions
-
hyperventolation
increase pulmonary ventilation in excess of metabolic demand
-
hypoventilation
reduced pulmonary ventilation
-
kussmual respiration
deep, rapid breathing often induced by acidosis
-
orthopnea
dyspnea that occure when a person is laying down
-
respiratory arrest
permanent cessation of breathing
-
tachyphnea
accelerated respiration
-
systemic gas exchange
the unloading of 02 and loading of co2 at systemic capillaries
-
co2 loading
- co2 diffuses into blood
- carbonic anhydrace in RBC catalyzed
- Co2 + H20 > H2CO3 > HCO 3 - + H+
- chloride shift: keeps reaction proceeding exhanges HCO3- for Cl-
- H+ bings to hemoglobin
-
O2 unloading
- H+ bings to HbO2 reduces affinity for 02
- tends to make hb release o2
- Hbo2 arrives at systemic capillaries 97% and leaves 75% saturated
- utilization coefficient: given up 22% of its o2 load
-
venous reserve
o2 remaining in the blood after it passes thorugh the capillary beds
-
Co2 unloading
- as Hb loads 02 affinity for H= decreases , H+ dissociates from Hb and binds with HCO3+
- reverse rxn: co2 + h20 < h2CO3 < hco3 - + H+
- reverse chloride shift: Hco3- diffuses ack into RBC in exchange for Cl-, free co2 generated diffuses into alveolus to be exhaled
-
carbon monoxide
- CO
- competes for o2 binding sites on Hb molecule
- colorless, odorless gas in cigarette smoke, engine exhaust fumes from furances and space heaters
-
carboxyhemoglobin
- CO bings to ferrous ion of hb
- bings 210x tightly as o2
- ties ub hb for a long time
- non-smokers: less than 1.5% hb occupied by CO
- smokers: 10%
- atmospheric concentrations of 0.2% CO is quickly lethal
-
rate and depth of breathing adjust to main levels of
- pH : 7.35- 7.45
- Pco2: 40 mmHg
- Po2: 95 mmHg
-
brainstem respiratory centers
recieve iput form the central and peripheral chemoreceptors that monitor the composition of blood and CSF
-
most potent stimulus for breathing
pH, then Co2 then O2
-
maintain pH in the brain
- pulmonary ventilation is adjusted
- central chemoreceptors in the medulla oblongata produce about 75% change in respiration induced by pH shift
- H+ does not cross BBB easily
- CO2 does and is CSF reeacts with water and produces carbonic acid, it will dissociate into bicarbonate and hydrogen ions
- most H+ remains free and greatly stimulates the central chemoreceptors
-
peripherial chemoreceptors
- H+ ions potent stimulus
- will product 25% of the respiratory response to pH change
-
respiratory acidosis and alkalosis
pH imbalances resulting from a mismatch between the rate of pulmonary ventilation and the rate of co2 prodcution
-
hyperventilation is correctic homeostatic
- in response to acidosis
- "blowing off" Co2 faster that the body produces
- it pushes rxn to the ledtreduces H+,
- reduce acid and raise blood pH towards normal
-
hypoventilation is a corrective homeostatic
- respsonse to alkalsis
- allows co2 to accumlate in body fluids faster that we exhale it
- shift rxn to the right
- raisin H+ concentration and lowering pH to normal
-
ketoacidosis
- acidosis brought about by rapid fat oxidation releasing acid ketone bodies
- diabetes mellitus
- insuces Kussmaul respiration
- hyperventilation cannot remove ketone bodies
- but blowing off co2 can reduce the co2 concentration and can compensate for the ketone bodies to some degress
-
carbon dioxide indirect effects on respiration
pH
-
direct effects of CO2 on respiration
- increase of co2 at begining of exercise directly stimulates peripheral chemoreceptors
- triggers and increase in ventilation more quickly than central chemoreceptors
-
effects of O2 on respiraton
- Po2 usually has little effect on respiration
- chronic hypoxemia ( po2 < 60 mmHg) can significantly stimulate ventilation
-
hypoxic drive
- respiration driven more by low Po2 thatn CO2 or pH
- emphysema and pnueumonia
- high elevations after several days
-
hypoxia
- a deficiency of 02 in the tissue or the inabilitto use o2
- consequence of respiratory disease
-
hypoxemic hypoxia
- state of low arterial Po2
- usually due to inadequate pulmonary gas exchange
- o2 deficiency at high elevations, impaired ventilation
- drowning, aspiration of a foreign body, respiratory arrest, degenerative lung diseaese
-
ischemic hypoxia
- inadequate circulation of blood
- CHF
-
anemic hypoxia
due to anemia resulting from the inability of blood to carry adequat o2
-
histotoxic hypoxia
metabolic poisons such as cyanide that prevent the tissues from using o2 delivered to them
-
cyanosis
- blueness of the skin
- sign of hypoxia
-
oxygen toxicity
- pure o2 breath at 2.5 atm or greater
- safe to breath 100% oxygen at 1 atm for a few hours
- generates free radicals of H2O2
- destroys enzymes
- damages nerous tissue
- leads to seizures, coma, and death
-
hyperbaric oxygen
- formly used to treat premature infants
- causes retinal damage
-
COPD
- chronic obstructive pulmonary disease
- refers to any disorder in which there is a long-term obstruction of airflow and substantial reduction of pulmary ventilation
- chronic bronchitis
- emphysema
- usually associated with smoking
- other risk factors are air pollution or occupation exposure to airbone irritants
-
chronic bronchitis
- COPD
- inflammation and hyper plasis of bronchial mucosa
- cilia immobilized and reduced in number
- goblet cells enlarge and produce excess mucus
- develop chronic cough to bring up extra mucus with less cilia to move it up
- sputum formed (mucus and cellular debris): ideal growth media for bateria, incapacitates alveolar macrophages
- leads to chronic infection and bronchial inflammation
- symptoms: dyspnea, hypoxia, cynosis, and attack of coughing
-
emphysema
- COPD
- aveolar walls break down
- lung has larger but fewer alveoli
- much less respiratory membrane for gas exchange
- lungs fibrotic and less elastic
- healthly lungs are like a sponge, emphysema lungs are more like a rigid ballon
- air passages collapse and obstructs outflow of air and air is trapped in lungs
- weaken thoracic muscles, spend 3 - 4x times about of energy just to breathe
-
pulmonary artery
supply blood capillaries that surround the aveolus
-
respiratory membrane
- the barrier btwn the alveolar air and the blood
- consists of: squamous alveolar cells, endothelial cells of blood capillary, their shared basement membrane
- important to prevent fluid accumulating in alveoli
- gases diffuse too slowly through liquid to sufficiently aerate the blood
- alveoli are kept dry by absorption of excess liquid by the blood capillaries
- lungs has more extensive lymphatic drainage
- low capillary bp prevents rupture of the delicate respiratory membrane
-
composition of air
- nitrogen: 78.6%
- oxygen: 20.9%
- Co2: 0.04%
- water vapor: 0-4% depending on temp and humidity
- minor gases: argon, neon, helium, meathane and ozne
-
daltons law
- the total atmospheric pressure is the sum of the contributions of the individl gases
- at sea level 1 atm = 760 mmHG
-
composition of inspired air and alveolar air is different bc
- air humidifies by contact with the mucous membrane: alveolar Ph20 is more than 10x greated than inhaled air
- freshly inspired air mixes with residual air left from the previous respiratory cycle: oxygen is diluted and enriched with c02
- alveolar air exhanges o2 and co2 with blood: po2 of alveolar is about 65% that of inspired air and pCO2 is more than 130x higher
-
alveolar gas exchange
- the back and forth traffic of o2 and co2 across the respiratory membrane
- air in the alveolus is in contact with a film of water covering the alveolar epithelium
- for o2 to get int the blood it must dissolve in water
- pass through the respiratory membrane seperating the air from the blood stream
- for co2 to leave the blood it must pass the other way and diffuse out of the water into the alvolar air
- gases diffused down their own concentration gradient until the ppof each gas in the air is equal to the pp in water
-
henrys law
- at air-water interface, for a given temp, the amout of gas that dissolves in water is determined by its solubility in water and its pp in the air
- the greater the po2 in alveolar air, the more o2 blood picks up
- since blood arriving at an alveolus has a high pco2 than air, it releases co2 into the air
- at alveolus blood unloads co2 and loads o2 which involces erthrocytes
- efficiency depends on how long RBC stays in alveolar capillaries 0.25 sec to reach equilidrium, at rest RBC spend.75 sec, strenous exercise .3 secs
- each gas in a mixture behaves independently
- one gas DOES NOT influence the diffusion of another
-
pressure gradient of the gases
- po2: 104 mmHg in alveolar air and 40 mmhg in blood
- Pco2: 46 mmHg in blood ariving and 40 mmHg in alvelar air
-
hyperbaric o2 therapyse
- treatment with o2 greater than one atm pressure
- gradient differences are more, more o2 diffuse to blood
- treats gangrene and co posioning
-
high altitudes
- the pp of gases are lower
- gradient difference is less
- less o2 diffuses into blood
-
solubility of gases
- CO2 is 20x more soluble as 02
- equal amounts of o2 and co2 are exchanged across the respiratory membrane bc co2 is much more soluble is diffuses more rapidly
- o2 twice as soluble as n2
-
membrane thickness
- 0.5μm thick
- little obstcale for diffusion
- pulmonary edeman in the left side of the ventricular failure causes edema and thickening of the respiratory membrane
- pneumonia causes thickening of respiratory membrane
- thicker mebrame: farther travel btwn blood and air and cannot equilibrate fast enought to keep up with blood flow
-
membrane SA
- 100 mL blood in alveolar capillaries spread thingly over 70 m2
- emphysema, lung cance, and tb decrease SA for gas exchange
-
ventilation-perfusin coupling
- ability to match ventilation and perfusion
- gas exchange requires both good ventilation of alveolus and good perfusion of the capillaries
- at rest ratio 0.8: flow of 4.2 L air and 5.5 L of blood per minute
-
pulmonary edema
- caused by left heart failure and damage to pulmonary membrane
- safety factor: negative interstitial pressure, lumphatic pumping,and decreases interstitial osmotic pressure
-
gas transport
process of carrying gases from the aveoli to the systemic tissues and vice versa
-
o2 transport
- 98.5% bound to hb
- 1.5% dissolved in plasma
- arterial blood carries about 20 mL of o2 per deciliter
-
co2 transport
- 60% as bicarbonate ion
- 30% boung to hb
- 10% dissolved in plasma
-
oxyhemoglobin
- hbo2 o2 bound to hemoglobin
- 100% saturated with 4 o2 molecules
- 50% saturated with 2 o2 molecules
-
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