THE RESPIRATORY SYSTEM

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THE RESPIRATORY SYSTEM

• Chapter 23 24

http//www.youtube.com/watch?vp4zOXOM6wgE
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• Function
• Air distributor (breathing)
• Gas exchanger b/t blood alveoli
• Filters, warms humidifies air
• Speech
• Smell
• Regulates pH (homeostasis)

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• Structure
• Upper Tract
• Nose
• Parts
• external nares,
• internal nares,
• nasal cavities separated by nasal septum,
  sinuses

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Functions of Nose

• Moistens, warms filters- mucosa, highly
  vascular, hairs (vibrissae)
• Nasal cavities w/olfactory receptors turbinates
• Resonating chamber for speech
• Olfactory receptors
• Pathology rhinitis, sinusitis

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Pharynx (throat)

• Pharynx muscular
• tubelike (12.5 cm)
• back of mouth
• 3 Divisions
• Nasopharynx (air passageway, uvula, drainage for
  internal nares , eustachian tubes of ears
  adenoids )

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• Oropharynx air food passageway palatine
  lingual tonsils here
• Laryngopharynx from hyoid bone to larynx where
  it becomes the esophagus

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• Larynx with epiglottis (voice
  Box)
• Provides permanently
  open air passageway
• Switching station for
  food air
• Voice production
  (laryngitis)
• Composed of nine cartilage rings (epiglottis
  being one) membrane ligaments

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Two pairs of folds form divisions

• Vestibular Vocal Folds (false)- upper pair no
  part in vocalization
• True Vocal Cords- lower pair w/rima glottidis
  (slitlike space) glottis

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• Lower Tract
• Trachea (windpipe)
• Tubelike 11 cm long
• 2.5 cm diameter from
• lower larynx to primary
• bronchi where it divides
• Cartilage rings- C shaped
• hold trachea open
• Mucous membranes w/cilia
• (destroyed by smoking)

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http//www.youtube.com/watch?vd_5eKkwnIRs

• Tracheal obstruction -
• tracheotomy/
• tracheostomy

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• Bronchial tree
• Right left
  bronchi,
  branch into
  secondary
  (lobar) bronchi 3 on
  right, 2 on left each serving a long lobe
  branch into tertiary bronchi branch into
  terminal bronchioles

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• As branching occurs
• cartilage rings diminish
• mucosal membranes diminish
• smooth muscle increases
• more autonomic control of
• bronchiole diameter

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• Alveoli
• Respiratory bronchioles terminate at alveolar
  ducts, to alveolar sacs, to alveoli
• Composed of thin
• membrane covered
• with cobweb of
• capillaries

http//www.youtube.com/watch?vsU_8juD3YzQfeature
player_embedded
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• Efficient gas exchange-
• - moist
• - thin-wall
• - blood capillaries
• - increased of alveoli
• - liquid surfactant produced by Type
• II cells (reduce surface tension)
• - shape increases surface area

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• Type II cells in premature babies
• not sufficiently developed to produce enough
  surfactant (hyaline membrane is not yet formed)
• run an increased risk of breathing problems due
  to collapsed lung(s)

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• Lungs
• Occupy the thoracic cavity
• each surrounded by pleural membrane
• 2 lobes on left
• 3 lobes on right
  
• separated by mediastinum

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• Composed of elastic connective tissue air
  spaces
• weigh 2.5 pounds

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• Blood to be oxygenated pulmonary arteries,
  blood that is oxygenated pulmonary veins
• Blood nourishing the lung tissue bronchial
  arteries blood carrying lung tissue waste
  bronchial and pulmonary veins

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• Pleura secrete lubricant
• Visceral- covers outer surface of lungs
• Parietal- lines thoracic cavity
• Pleurisy-
• Pleural
• inflammation

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Physiology of the Respiratory System

• Respiratory Physiology- processes that interact
  to maintain a stable internal environment

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Pulmonary Ventilation

• Breathing
• Inspiration- moves air into lungs inhaling
• Expiration- moves air out of lungs exhaling

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MECHANICS

• Pressure relationships
• Intrapulmonary pressure
• pressure within the alveoli of lungs
• always equal to the atmospheric pressure

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• The pressure exerted by gases in the atmosphere
  outside the body at sea level is
• 760 mm Hg
• This is the pressure required to move a given
  amount of mercury 760 mm up a glass column
• Written as 1 atm

http//www.youtube.com/watch?vq6-oyxnkZC0
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• Intrapleural pressure - pressure between parietal
  visceral pleura lt4 mm Hg
• gt the intrapulmonary pressure
• said to be negative pressure
• due to factors which hold lungs to thorax
  opposed by factors acting to pull lungs from
  thorax

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• Actelectasis (pneumothorax) lung collapse
• occurs when pressure between intrapulmonary
  intrapleural pressure is equalized
• Occurs when air is introduced into
  intrapleural space
• usually due to a
  rupture of visceral
  pleura or wound to chest
  (President Reagan)

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PULMONARY VENTILATION

• Volume changes lead to pressure changes which
  lead to the flow of gases to equalize the
  pressure
• Inspiration
• diaphragm contracts to drop flatten
• external intercostals elevate to expand the ribs

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• thoracic volume increases
• lungs attached to thoracic wall are stretched
• pulmonary pressure drops 1-3 mm Hg and air
  rushes in (about 500 ml of air will move with
  this pressure change) until pressure is again
  equalized

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• Forced inspiration requires other skeletal
  muscles (intercostals)

http//www.youtube.com/watch?vdMxE9tGRsaw
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• Expiration
• passive process (rather than muscular in origin)
• dependent on the elasticity of lungs
• muscle relax
• lungs recoil causing thoracic
• lung volumes to decrease, compressing alveoli
• pressure rises 1-3 mm Hg above atmospheric
  pressure air rushes out

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• Influencing Physical Factors
• Resistance due to obstruction or constriction
• Compliance deformities ossification or costal
  cartilages)

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• lung elasticity (recoil properties) which is
  hindered in those with emphysema (elasticity
  replaced with fibrous tissue)
• alveolar surface tension (produced by water
  molecules in the alveoli ) this is a problem in
  premies

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GAS EXCHANGE IN THE BODY

• Gas Laws
• Daltons Law Total gas pressure exerted by a
  mixture of gases is equal to the sum of the total
  pressures exerted by the individual gases in the
  mixture.
• p1 p2 p3 Pt

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• Pressure exerted by each gas (its partial
  pressure P) is proportional to its percentage
  in the total gas mixture
• Total gas pressure sum total of pressure of
  each gas

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• Henrys Law
• Gases diffuse from high to low pressure
• dependent on temperature membrane types
• Gas mixtures will diffuse in proportion to its
  percentage solubility.

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• Example Divers N2 at increasing depth, more
  more N2 is forced to dissolve into the system
  (much like carbonation in a soda)
• CO2 gt CO gt O2 gt N2
• To summarize
• Gases go from high to low concentrations
• Gases diffuse in proportion to their percentage
  and solubility

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• Hyperbaric Conditions
• used in treating asphyxia, CO poisoning, tetanus,
  the bends, etc
• forces more O2 into the system due to pressure
  exerted on the body.

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EXCHANGE BETWEEN BLOOD TISSUES

• External Gas Exchange (b/t blood lungs)
• gas flows along a concentration gradient
• dependent upon solubility
• PO2 in lungs is higher than in blood (104 mm Hg
  vs. 30 mm Hg)

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• PCO2 is lower in lungs than blood (40 mm Hg vs.
  45 mm Hg in blood)
• Capillaries assist this exchange
• Ex with poor
  alveolar
  ventilation
  
  PO2 is low
  PCO2 is high
  small capillaries
• larger airways

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• Internal Gas Exchange (b/t blood tissues)
• essentially the same as external
• ependent upon simple, diffusion partial
  pressure gradients

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TRANSPORT OF GASES BY BLOOD

• Oxygen Transport
• 2-3 is dissolved in blood
• 98.5 is carried by hemoglobin on RBCs
• Each hemoglobin molecule can carry 4 O2
• Each RBC has 250,000 Hb molecules
• Each RBC can carry 1,000,000 O2 molecules!!!!!!!!

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• At resting levels
• 25 of O2 is unloaded into tissues, leaving 75
  still bound to Hb
• therefore there is always reserve O2 for the
  tissues
• inhaling deeply does not increase saturation of
  blood by O2

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• Affects of temperature
• high temps low HbO2- and vice versa
• Affinity of O2 for hemoglobin decreases at higher
  temps
• tissues are hot from work high unloading of O2
• Affects of pH Bohr effect
• Acids (H) bases (OH-) weaken the HbO2 bond

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• Hypoxia inadequate O2 supply to tissues
  cyanotic color (blue)
• Anemic hypoxia not enough RBCs or amount of
  hemoglobin
• Stagnant hypoxia blood is impaired or blocked

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• CO Poisoning
• CO has more an affinity for hemoglobin than O2
• HbCO turns skin a bright pink

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• CO2 Transport
• Active body cells produce 200 ml CO2/min which is
  carried to lungs
• 10 - Dissolved as a gas in plasma
• 30 - Bound to globin (not heme which would
  interfere with HbO2 transport)
• 60 - Converted to bicarbonate ion and carried by
  plasma

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CONTROL OF RESPIRATION

• Neural Mechanisms
• Neurons in medulla depolarize rhythmically
  produce oscillating breathing patterns
• Impulse travels along phrenic intercostal
  nerves to diaphragm external intercostal
  muscles contraction

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• Medulla becomes dormant expiration occurs
  passively
• 12-15 bpm (2 second lapse b/t inspirations with 3
  seconds to expire eupnea

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• Pons produces smooth transitions btw inspiration
  expiration. When pons medulla are severed,
  breathing becomes erratic requiring artificial
  ventilation

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• Factors controlling rate depth
• Irritants
• Hering-Breuer Reflex stretch receptors in
  pleural membrane trigger expiration (prevent
  over-inflation)
• Hypothalmic control in response to emotion /or
  pain

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• Cortex control during singing or swallowing
• Chemical factors
• chemoreceptors in medulla, in great vessels of
  neck
• read increasing CO2 levels

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• Hypercapnia
• H ions that diffuse into cerebrospinal fluid
• trigger rate increase from respiratory center
  hyperventilation
• Explains panting observed in diabetics who have
  elevated blood sugar levels

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• Low CO2 (NOT low O2 levels) levels triggers
  apnea or periods of breath holding.
• Chronic respiratory diseases will cause a shift
  in way medulla monitors blood.

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• Metabolic factors drop in blood pH due to
  accumulation of lactic acid or fatty acids (of
  diabetics) will trigger a respiratory rate
  increase

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• Adjustments from exercise
• Deep breathing from exercise is due to the muscle
  inability to utilize available O2 lactic acid
  buildup, repayment of O2 debt

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• At high altitudes
• Air pressure is lower, therefore PO2 is lower
  acclimatization is necessary
• Decrease in PO2 causes receptors to be more
  responsive to increased CO2 hyperventilation to
  restore previous gas levels

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• Within a few days, minute respiratory volume is
  stabilized at 2-3L/min higher than before
• Slightly lower hemoglobin saturation at higher
  altitudes because
• less O2 is available
• Hemoglobin has lower affinity for O2 at high
  altitudes so more O2 is unloaded at one time

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• This is all okay at rest, but during physical
  activity, hypoxia of tissues occurs
• To compensate, the body produces more RBCs,
  which takes some time

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SMOKING GALLERY
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