Respiratory system

1
Respiratory system
2
What is respiration?

• Multiple definitions
• Ventilation of lungs (breathing)
• Exchange of gases between air and blood
• Also between blood and tissues
• Oxygen consumption during metabolic activities
• Happens in what organelle?

3
What organs are involved?

• Conducting regions
• Nose
• Larynx
• Epiglottis
• Trachea
• Bronchi
• Lungs
• Bronchioles
• Respiratory region
• Alveoli
• Upper respiratory
• Head and neck
• Lower respiratory
• Trachea to lungs

4
What does the nose do?

• Receive and humidify incoming air
• Smells
• Voice resonating chamber
• Filter out bacteria

5
Why do I only breath out of one chamber at a time?

• Nasal fossa chamber
• Divided by nasal septum
• Lamina propria of inferior concha swell
• Every 30-60 minutes
• Alternate chambers
• Allows for rehydration
• Epistaxis
• Nose bleed most common in inferior concha

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Whats up with the pharynx and larynx?

• Pharynx extends from nose/mouth to larynx
• Good at trapping large dust particles
• Larynx voice box
• Job keep food/water out of trachea
• Also produces sound
• Glottis (opening) guarded by epiglottis

7
What does the trachea do?

• Hyaline cartilage rings stiffen tube
• Directs air to lungs via bronchi
• Pseudostratified epithelium
• Mucociliary escalator cilia sweep mucus upward
  to pharynx

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What parts make up the lungs?

• Right lung superior, middle, inferior lobes
• Left lung superior and inferior lobes only
• Bronchial tree
• Branched air tubes from primary bronchi (two) to
  secondary bronchi to tertiary bronchi to
  bronchioles
• Overlapping plates of cartilage give shape

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What parts make up the lungs?

• Bronchioles (no cartilage) have smooth muscle to
  dilate/contract
• Asthma
• Bronchiolconstriction (irritants, cold air,
  histamine) and bronchioldilation
• Click below for asthma movie!

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What parts make up the lungs?

• Terminal bronchioles follow after bronchioles
• Final branches of conducting division (region)
• Cilia prevent congestion via mucociliary
  escalator
• Next are respiratory bronchioles
• Beginning of respiratory division
• Divide into alveolar ducts
• End in alveolar sacs

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What do the alveoli do?

• Approx. 150 million great S.A.
• Mostly squamous alveolar cellswhy?
• A few cuboidal cells (great alveolar cells)
• Secrete pulmonary surfactant
• Disrupts hydrogen bonds
• Prevents alveolar collapse during expiration
• Premature infants lack

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What do the alveoli do?

• Alveolar macrophages consume anything mucus
  doesnt strain out
• Items smaller than 2 micrometers
• Capillaries surround each alveolus
• Distance air must travel
• Called respiratory membrane
• Squamous alveolar cell, basement membrane,
  capillary squamous cell

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What are the pleurae and why are they there?

• Moist serous membrane covering outside of lungs
• Visceral pleura inside
• Folds out at hillum to form outer parietal pleura
• Pleural cavity between parietal and visceral
  layers
• Filled with pleural (serous) fluid
• Pleurae functions
• Reduce friction
• Create pressure gradient to help with lung
  inflation
• Compartmentalization prevent infection spread to
  neighboring organs

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How does breathing occur?

• Atmospheric pressure drives respiration
• Atm. pressure weight of air column
• 1 atm. 760 mmHg
• Boyles law pressure and volume are inversely
  proportional
• Intrapulmonary pressure changes opposite to
  volume load
• Lower intrapulmonary pressure below 760 mmHg to
  draw breath

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What happens during inspiration?

• Diaphragm does most of the work
• Phrenic nerves cause diaphragm to flatten
• External intercostals also contract, elevating
  (expanding) ribcage
• Increases lung volume so pressure ______
• Parietal pleurae cling to external intercostals
• Visceral pleurae cling to parietal pleurae
• Helps increase volume

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What happens during inspiration?

• Air is warmed to assist volume expansion
• 500 ml air inhaled during resting inspiration
• 150 ml is dead air (held in conducting regions)
• Thus only 350 ml to alveoli (respiratory
  division)
• Alveolar ventilation rate (AVR) 350 ml (or
  whatever value) X number of breath per minute

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What happens during expiration?

• Passive process
• Diaphragm and external intercostals allowed to
  relax
• Natural elasticity of ribcage, lungs and tendons
  assist via recoil
• Boyles law volume decreases so pressure
  ___________ and air ______
• Hard exhale use internal intercostals to depress
  ribcage

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Why does a lung collapse?
From http//www.lunge.no/files/news/pneumothorax.
gif

• Pneumothorax air in the pleural cavity
• Can happen if thoracic wall is punctured
• Separates visceral and parietal pleurae
• Result? Lung collapse atelectasis
• Can also happen if area of lung is blocked
• Blood absorbs air and lung collapses

From http//medinfo.ufl.edu/bms5191/pulmon2/imag
es/1a.jpg
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How is ventilation measured?

• Spirometer
• Measures respiratory volumes
• Tidal volume amount of air inhaled or exhaled
  when relaxed
• Inspiratory reserve volume amount can breath in
  above tidal volume with maximum effort
• Expiratory reserve volume
• Residual volume what remains in lungs after
  maximum expiration (keeps alveoli inflated)

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What are some breathing variations?

• Apnea temporary breath cessation
• Dyspnea gasping, labored breathing, shortness of
  breath
• Orthopnea dyspnea while lying down
• Eupnea normal, quiet breathing
• Hyperpnea increased rate and depth of breathing
• Tachypnea accelerated respiration
• Hyperventilation expels too much CO2, raising pH
• Hypoventilation increases CO2, lower pH

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What controls breathing?

• Medulla oblongata
• Inspiratory neurons
• Expiratory neurons (dont fire during eupnea)
• Unknown how rate of breathing is set
• Pons
• Regulates ventilation via pneumotaxic center
• Sends inhibitory signals to med. Obl. inspiratory
  center
• More impulses shorter breath
• Voluntary control motor cortex of frontal lobe
• Automatic controls can override to protect
  organism

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What happens during gas exchange?

• Air composition O2, N2, H2O, CO2
• Daltons law partial pressure of each adds up to
  total pressure
• What should they add up to at sea level?

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What affects gas exchange?

• Takes about 0.25 secs to create equilibrium
• Erythrocyte takes 0.75 sec to pass through
  alveolar cap.
• During exercise erythrocyte present for 0.3 sec

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What affects gas exchange?

• Concentration gradients of gases
• Blood entering lungs
• PO2 40 mmHg
• PCO2 46 mmHg
• Blood leaving lungs
• PO2 95 mmHg
• PCO2 40 mmHg
• Solubility Same amount of gases exchange,
  though, bec. CO2 is about 20 times as soluble in
  water

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What affects gas exchange?

• Membrane thickness respiratory membrane v. thin
• Left ventricular failure edema and thickened
  resp. memb.
• Result gases cant equilibrate fast enough
• Membrane area more resp. memb. S.A. better gas
  exchange
• Emphysema, tuberculosis decrease S.A.

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How is oxygen transported?

• Oxygen 98 bound to hemoglobin
• Review hemoglobin structure
• How many molecules of oxygen can one hemoglobin
  hold?
• As more oxygen bind to hemoglobin, affinity for
  oxygen increases
• Oxyhemoglobin vs. deoxyhemoglobin
• CO poisoning carboxyhemoglobin (HbCO) competes
  with oxygen for binding site
• Binds 210 times more tightly than oxygen to heme
  group

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How is carbon dioxide transported?

• Three ways
• Carbonic acid
• 70 of CO2 is hydrated
• CO2 H2O ? H2CO3 ? HCO3- H
• Carbamino compounds (23)
• To plasma proteins and hemoglobin to form
  carboaminohemoglobinHbCO2 (different from
  carboxyhemoglobin)
• Binds to polypeptides, not to heme groups
• Dissolved gas (7)
• Dissolves in plasma like CO2 in soda pop

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What is carbon dioxide loading?

• Carbonic acid reaction occurs in plasma and
  erythrocytes
• Carbonic anhydrase in RBCs speeds reaction
• Chloride shift HCO3 diffuse out of RBCs,
  replaced with Cl-
• H binds to Hb (this buffers RBC pH)

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What is oxygen unloading?

• H bound to HBO2 decreases affinity for O2
• Causes RBC to offload oxygen more easily
• Under what conditions would this happen?
• Venous reserve oxygen not offloaded
• Can sustain life for up to five minutes

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What happens in exhalation?

• Carbon dioxide offloading
• Exact reverse of loading process
• Oxygen loading
• Reverse of offloading

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Does Hb always offload the same amount of O2?

• No!
• If PO2 of tissue is lower, more is offloaded
• Higher temp more offloaded
• Bohr effect active tissues put off more CO2
  which lowers blood pH
• This causes more O2 offloading Bohr effect
• BPG (bisphosphoglycerate) binds to Hb and
  promotes O2 offloading
• RBS anaerobic fermentation intermediate
• Fever, growth hormone, NE stimulate BPG synthesis

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Does Hb always load the same amount of CO2?

• No!
• Haldane effect low HbO2 allows more CO2
  transport
• HbO2 doesnt bind CO2 as well as deoxyhemoglobin
  (HHb)
• HHb binds more H which removes H from solution
• How does this affect the reaction CO2 H2O ?
  H2CO3 ? HCO3- H?

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How does blood chemistry affect ventilation?

• Peripheral chemoreceptors monitor
• Carotid bodies and aortic bodies
• Central chemoreceptors also monitor
• In brainstem
• Both monitor blood pH
• How does this relate to O2 and CO2 levels?

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How does blood chemistry affect ventilation?
Recall CO2 H2O ? H2CO3 ? HCO3- H

• H in CSF is main site of monitoring
• H doesnt cross blood-brain barrier but CO2
  does, then reacts with water
• Problem few proteins present to buffer H
• Acidosis blood pH lower than 7.35
• Common cause hypercapnia (high CO2 value)
• To correct blow off CO2 rapidly
  (hyperventilation)
• Alkalosis above 7.45
• Common cause hypocapnia
• To correct take up CO2 rapidly (hypoventilation)

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How does blood chemistry affect ventilation?

• Ketoacidosis from diabetes mellitus
• Lipid oxidation produces ketone bodies
• Leads to low pH
• Hyperventilation called Kussmaul respiration
• Blowing off CO2 helps remove H and compensate
  for ketone body H production

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What are some respiratory disorders?

• Hypoxia oxygen deficiency
• Hypoxemic hypoxia low arterial PO2
• High altitude, impaired pulmonary function,
  respiratory arrest, lung disease
• Ischemic hypoxia inadequate blood circulation
• e.g. from congestive heart failure
• Anemic hypoxia from anemia
• Histotoxic hypoxia from metabolic poison (e.g.
  cyanide)
• Hyperoxia produces hydrogen peroxide and free
  radicals

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What are some respiratory disorders?

• Chronic obstructive pulmonary disease (COPD)
• Long-term obstruction of airflow
• Asthma
• Chronic bronchitis cilia immobilized and reduced
  in number
• More goblet cells present produces sputum
• Emphysema alveolar walls destroyed
• Smokers often have one or more of these

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How does smoking and cancer affect the lungs?

• Lung cancer accounts for the most cancer-related
  deaths
• Causes smoking, followed by pollution
• Tobacco more than 15 carcinogens

From http//www.aafp.org/afp/991201ap/photo.html