RESPIRATORY PHYSIOLOGY Anatomy review - PowerPoint PPT Presentation


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RESPIRATORY PHYSIOLOGY Anatomy review Pressures Atmospheric pressure Alveolar pressure (intrapulmonary pressure) Intrapleural pressure Boyle s Law More volume=less ... – PowerPoint PPT presentation

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  • Atmospheric pressure
  • Alveolar pressure (intrapulmonary pressure)
  • Intrapleural pressure
  • Boyles Law
  • More volumeless pressure
  • Less volumemore pressure

  • Diaphragm is chief respiratory muscle (80)
  • Intercostal muscles are secondary (20)
  • - Diaphragm is controlled by phrenic nerve
  • - Range of movement from 1 cm (normal breathing)
    to 10cm in heavy breathing.
  • Parietal pleura attaches to diaphragm
  • Visceral pleura attaches to parietal pleura (thin
    space in b/w filled with serous fluid)
  • Lungs attach to visceral pleura.

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  • Inspiration
  • Before inspiration pressure in lung equals
    atmospheric pressure 760 mm Hg or 1 atm
  • Increasing the size of the lungs will cause
    pressure to drop and air to rush in. How does
    lung increase in size?
  • Boyles law the pressure of a gas in a closed
    container is inversely proportional to the volume
    of the container.
  • - incr. in size of container pressure will
    decrease pressure..
  • Intrapleural pressure is 756 mm Hg and during
    inspiration (as diaphragm is pulling down)
    pressure drops to 754 mm Hg.
  • External intercostals contract and pull rib cage
    up and forward (anterior) causing a-p diameter to

  • When volume increases, pressure inside lung
  • (alveolar, intrapulmonic pressure) drops from
    760 to 758. A pressure gradient is established
    between the atmosphere and the alveoli.
  • Air rushes in (pressure gradient) to alveoli from
  • Expiration pressure in lungs is greater than
  • - diaphragm relaxes and dome shape muscle pushes
    up (elasticity). Internal intercostals cause a-p
    diameter to decrease
  • - lung pressure increases to 762. Air will flow
    from higher to lower pressures.

Thoracic Volume and Inspiration
Thoracic Volume and Expiration
Changes in Thoracic Volumes
Factors Influencing Pulmonary Ventilation
  • Airway Resistance
  • Amount of drag air encounters in respiratory
    passageways not significant since airway
    diameters are large and at terminal bronchioles
    gasses travel by diffusion
  • Surface Tension
  • At gas-liquid boundaries, liquids are more
    attracted to each other (cohesiveness), surfacant
    at the alveoli keeps water from being cohesive
    and allows alveoli to be more functional (less
    energy needed for breathing)
  • Lung Compliance
  • The distensibility of the lungs, ability to
    stretch higher compliance leads to better
    ventilation (fibrosis, airway blockages,
    decreased surfacant, and decreased thoracic cage
    flexibility lead to less compliance)

Respiratory Volumes and Capacities
Respiratory Volumes
  • Tidal Volume
  • The amount of air that moves in and out of the
    lungs with a normal breath at rest (500 mL)
  • Inspiratory Reserve Volume
  • The amount of air that can be inspired forcibly
    beyond the tidal volume (2100-3200 mL)
  • Expiratory Reserve Volume
  • The amount of air that can be expired forcibly
    beyond a tidal expiration (1000-1200 mL)
  • Residual Volume
  • The amount of air remaining in the lungs even
    after the most forceful expiration (1200 mL)

Respiratory Capacities
  • Inspiratory Capacity
  • Total amount of air that can be inspired after a
    tidal expiration TV IRV
  • Functional Residual Capacity
  • Total amount of air remaining in lungs after a
    tidal expiration ERV RV
  • Vital Capacity
  • Total amount of exchangeable air TV IRV ERV
  • Total Lung Capacity
  • Sum of all lung volumes

Volumes and Capacities
Dead Space
  • Anatomical dead space
  • The volume of air found in the conduits of the
    respiratory system NOT involved in gas exchange
  • Alveolar dead space
  • Regions where alveoli cease to function due to
    collapse or obstruction
  • Total dead space
  • Alveolar dead space Anatomical dead space

Non-Respiratory Air Movements
  • Cough
  • Sneeze
  • Crying
  • Laughing
  • Hiccups
  • Yawn

Regulation of Respiration
  • Medullary respiratory center
  • Dorsal respiratory center (DRC)
  • Ventral respiratory center (VRC)
  • Pontine center
  • formerly called the Pneumotaxic center
  • Hypothalamus

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Gas Transport
  • Oxyhemoglobin HbO2
  • Deoxyhemoglobin HHb
  • Carbaminohemoglobin HbCO2
  • External Respiration
  • Oxygen and Carbon Dioxide concentration is
    measured as a unit of pressure called partial
    pressure (p)
  • Blood coming into the lungs (pulmonary
    artery-capillary) is deoxygenated blood PO2 is
    40 mm Hg. PCO2 is 45 mm Hg

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  • Air in the alveoli
  • PO2 105 mm Hg
  • PCO2 40 mm Hg
  • Oxygen and Carbon dioxide are highly fat soluble
    and can diffuse through membranes with ease.
  • As gases pass from the blood pass an alveolus
    gases will diffuse from areas of higher
    concentration to lower. (diffusion gradients)
  • PO2 in blood after passing alveolus is 105 mm Hg
  • PCO2 in blood after passing alveolus is 40 mm Hg

  • Internal respiration Exchange of gases in the
  • CO2 is a byproduct of cellular metabolism.
  • PCO2 in tissue space 45 mm Hg
  • PO2 in tissue spaces 40 mm Hg
  • O2 will diffuse into tissue spaces (105) and CO2
    will diffuse into blood (45)

Gas Transport at the Tissues
  • Carbon dioxide transported to and from the lungs
    and tissues in three ways
  • Dissolved in plasma 7
  • Chemically bound to hemoglobin (carbaminohemoglobi
    n) 23
  • As Bicarbonate in plasma (Reaction between carbon
    dioxide and water, catalyzed by carbonic
    anhydrase) ? pH buffer system. 70 of CO2 is
    transported this way.
  • Chloride shift (Chloride anions diffuse into RBCs
    to counteract bicarbonate anions leaving RBCs)
  • Process results in diffusion of Oxygen from RBC
    to tissues and from Carbon dioxide from tissues
    to RBCs
  • This process is reversed in the Lungs

At the Lungs
At the Tissues
Oxygen Transport
  • Molecular oxygen carried in blood or bound to
  • HbO2- hemoglobin bound to oxygen
  • HHb O2 --? HbO2 H
  • Hb can bind 4 oxygens after first binding, there
    is a higher affinity for other 3
  • Hemoglobin is fully saturated when all 4 heme
    sites bound to oxygen

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Clinical corner
  • Eupnea - quiet breathing
  • Tachypnea - rapid breathing
  • Costal breathing - shallow Diaphragmatic
    breathing - deep Atelectasis - collapse or
    incomplete expansion of lungs
  • Cheyne-Stokes respiration - irregular breathing
    (increase/decrease in depth and rapidity)

  • Laryngitis - inflammation of the vocal cords
  • Pleurisy - inflammation of the pleura Infant
    respiratory distress syndrome (IRDS) -
    insufficient surfactant produced, surface tension
    forces collapse of the alveoli
  • Hypoxia - inadequate amount of oxygen is
    delivered to body tissues anemic - to few RBCs,
    or RBCs with inadequate hemoglobin stagnant -
    blood circulation is impaired or blocked
    interference with gas exchange
  • Hypercapnia - apnea (breathing cessation)
    increase in carbon dioxide levels in
    cerebrospinal fluid, causing pH to decrease,
    exciting chemoreceptors to increase rate of
    breathing (compensating)
  • Hypocapnia- low levels of CO2 in plasma and CSF
    due to depth and rate of breath increase

  • Chronic Obstructive Pulmonary Disease (COPD),
    common features
  • 1- Patients with history of smoking
  • 2- Dyspnea - difficult or labored breathing
  • 3- Coughing and frequent pulmonary infection
  • 4- Will develop respiratory failure
  • COPDs Obstructive emphysema - permanent
    enlargement of the alveoli, deterioration of
    alveolar walls
  • Chronic inflammation leads to lung fibrosis
    (lungs lose their elasticity)
  • Victims sometimes called "pink puffers" -
    breathing is labored, but doesn't become cyanotic
    because gas exchange remains adequate until late
    in the disease
  • Chronic bronchitis - inhaled irritants lead to
    chronic excessive mucus production by the mucosa
    of lower respiratory passageways and inflammation
    and fibrosis of that mucosa
  • Victims sometimes called "blue bloaters" -
    hypoxia and carbon dioxide retention occur