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Respiratory anatomy and Physiology


Respiratory anatomy and Physiology Caia Francis Chair RCN Respiratory Forum Senior Lecturer- Respiratory Specialist 0117 32 88631 – PowerPoint PPT presentation

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Title: Respiratory anatomy and Physiology

Respiratory anatomy and Physiology
  • Caia Francis
  • Chair RCN Respiratory Forum
  • Senior Lecturer- Respiratory Specialist
  • 0117 32 88631

Outline of session
  • Review and orientation to respiratory anatomy and
  • Learning outcomes
  • Understand fundamental law of diffusion and apply
    it to gas exchange.
  • Understand the mechanics of breathing and how
    this is influenced to maintain normal
    respiratory functioning.

Respiratory Physiology.
  • Lung is for gas exchange.
  • Prime function is to allow oxygen to move from
    the air into the venous blood and carbon dioxide
    to move out.
  • Metabolizes some compounds, filters toxic
    materials from the circulation and acts as a
    reservoir for blood.

  • Oxygen and carbon dioxide move between air and
    blood by simple diffusion, i.e. from an area of
    high to low partial pressure. (Ficks law of
    diffusion). Blood- gas barrier is exceedingly
    thin and has an area of between 50- 100 m2.
  • Large surface area is obtained by wrapping
    capillaries around air sacs (form alveoli). 300
    million alveoli in human lungs.

  • Airways consist of a series of branching tubes,
    becoming narrower, shorter and more numerous as
    they penetrate deeper into the lung.
  • Trachea divides into right and left main bronchi,
    divide into lobar, then segmental bronchi. This
    process continues down to terminal bronchioles,
    smallest airways outside the alveoli.

  • These make up the conducting airways. Function
    is to lead inspired air into gas exchanging
    regions of the lung.

  • Terminal bronchioles divide into respiratory
    bronchioles, finally arriving at the alveolar
    ducts, which are completely lined with alveoli.
  • This region is known as the respiratory zone.
  • Portion of lung distal to a terminal bronchiole
    forms an anatomical unit called acinus or lobule.

  • Static volumes of the lung can be measured mainly
    by spirometry.
  • Tidal volume
  • Vital capacity.
  • Minute volume.
  • But some gas remains in the lungs, residual
    volume and functional residual volume. Measured
    by body plesthysmography.

Ventilation -part 2
  • Volume exhaled with each breath is 500ml, 15
    breaths per minute total volume leaving the lung
    each minute is?
  • 50015 7500ml/min.
  • Total ventilation or minute volume.
  • But not all air that passes lips reaches the
    aleovlar gas compartment where gas exchange

Anatomic dead space.
  • Volume of the conducting airways.
  • Normal value is circa 150ml, but depends upon the
    size of inspiration and posture of subject.

Physiologic dead space.
  • Volume of the lung which does not eliminate CO2.
  • In normal subjects this is nearly the same as
    anatomic dead space.
  • However in patients with lung disease the
    physiologic dead space may be considerably larger
    because of inequality of blood flow and
    ventilation within the lung.

Regional differences in ventilation (V) (upright
  • Upper zone lowest ventilation
  • Lower zone greatest ventilation.

Blood flow (Q) through the lungs
  • Regional variations in blood flow through the
  • Lowest blood flow
  • Highest blood flow.

In well human
  • O2 will have fully diffused across alveolar
    membrane to bind with Hb within 0.25s.
  • C02 will have diffused across the alveolar
    membrane within 0.25s to be expired.
  • Blood will take 0.5s to traverse pulmonary
    capillary in association with alveolar sac.

Respiratory disease.
  • Asthma mucus, airway thickening (hypertrophy)
    will increase width of alveolar membrane and
    thus delay diffusion across membrane of both CO2
    and O2.
  • COPD as above plus pulmonary and cardiac
    circulation problems will delay the above.
  • Genetic conditions eg cystic fibrosis will
    compromise blood flow through alveolar.

What happens once oxygen is delivered to the
  • Oxygen dissociation curve.
  • Dissolved oxygen in blood, in some cases of
    significance in respiratory disease.

Oxygen dissociation curve.
  • Haemoglobin (Hb)
  • 02 forms easily reversible combination with Hb to
    give oxyhaemoglobin.
  • 02 Hb HbO2
  • Consider this in more detail.

Oxygen dissociation curve.
  • Consider
  • anaemia Hb 10gdl-1
  • Altitude.
  • Paediatrics.
  • Temperature.
  • pH.

(No Transcript)
Why do you need to know this?
  • Understand normal respiration and its
    measurement, function.
  • Establish a common frame of reference.
  • Revise known anatomy and physiology.
  • Introduce some issues of importance in
    respiratory disesase.

Mechanics of breathing.
  • Inspiration lower intra-thoracic pressure to
    allow air to pass by diffusion into lungs.
    Usually only 1cmH20 lower but in respiratory
    disease can be many times greater.
  • Diaphragm moving down in quiet breathing.
  • Expansion of rib cage in rapid deep breathing and
    using accessory muscles.

  • Expiration. Diaphragm returning to rest.
  • Ribs returning to status quo.
  • Increases slightly intra- thoracic pressure
    higher than the atmosphere and allows expiration.
    Usually only 1cmH20 higher but in respiratory
    disease can be many times greater.

  • Positive end expiratory pressure (PEEP) aides in
    complete expiration.
  • Occurs in well individuals easily and

  • Francis C., (2006) Respiratory care Blackwell
    Publishing Oxford
  • Jevon P., Ewens B., (Eds) (2002) Monitoring the
    critically ill patient Blackwell Science Oxford.
  • Levitzky M. (2002) 7th Edition Pulmonary
    Physiology McGraw Hill New York.
  • West J., (2010) 8th Edition. Pulmonary
    Pathophysiology Lippincott Williams Wilkins
  • West J., (2009) 10th Edition. Respiratory
    Physiology the essesentials Lippincott Williams
    Wilkins London.
  • Woodcock A., Partridge M., (1995) Respiratory
    Handbook Boehringer Ingelheim.