Respiratory System Year 1 Medical Radiation

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Respiratory SystemYear 1 Medical Radiation

• Sharron King

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Learning Objectives

• Review Thoracic Anatomy
• Describe the primary functions of the respiratory
  system
• Identify the structures and functions of the
  upper and lower respiratory systems
• Identify the blood supply to the lung

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Primary functions of the respiratory system (p.
814)

• Provides extensive gas exchange surface area
  between air and circulating blood
• Moves air to and from exchange surfaces of lungs
• Protects respiratory surfaces from outside
  environment
• Produces sounds
• Participates in olfactory sense

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Respiratory structures

• The respiratory system consists of the
• Upper respiratory system
• nose
• Pharynx
• Lower respiratory system
• larynx
• trachea
• bronchi
• lungs

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Nose

• Nose serves 3 functions
• Warming, moistening and filtering air
• Olfaction
• Modifying speech vibrations

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Pharynx

• Pharynx (throat) serves the following functions
• Passageway for air and food
• Resonating chamber for speech sounds
• Houses tonsils
• Participate in immune reactions
• Nasopharynx exchanges air with eustachian tubes
• equalises air pressure across ear drum

Jenkins, Kemmitz Tortora (2007 p. 836)
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Larynx

• Larynx (voice box)
• Contains 3 sets of cartilage
• Thyroid cartilage (Adams apple)
• Cricoid cartilage
• Epiglottis
• Folds over glottis to prevent food entering
  larynx during swallowing

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Sound Production (p. 821)

• Air passing through glottis
• vibrates vocal folds
• produces sound waves
• Sound is varied by
• tension on vocal folds
• voluntary muscles
• Speech is produced by
• phonation
• sound production at the larynx
• articulation
• modification of sound by other structures

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Trachea

• Trachea
• Anterior to oesophagus
• C-shaped cartilage rings provide support
• Prevents tracheal wall collapsing during
  inhalation
• Extends into mediastinum where it branches into
  right and left pulmonary bronchi

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Revision of Thoracic Structures

• Thoracic wall
• Skeletal ribs, Tx vertebra, sternum
• Muscles
• Diaphragm
• Mediastinum includes heart, midline
• Pleural cavities either side of mediastinum,
  includes lungs

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Thorax
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Boundaries of the thorax

• Superior Thoracic inlet
• Bounded by T1 rib 1 and manubrium
• Inferior thoracic outlet (or aperture)
• Thorax continuous with abdomen but separated by
  diaphragm
• Bounded by T12, rib 12, costal cartilage
  xiphisternal joint

Thoracic boundaries (n.d.)
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Mediastinum

• Central region between 2 pleural sacs
• Contaisn all thoracic strcutures except lungs and
  pleura
• Separated into regions
• Superior
• Inferior
• Anterior
• Middle
• Posterior

Mediastinum (Norman 1999)
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Lungs

• Pleural membrane encloses each lung
• Parietal pleura
• outer layer attached to wall of thoracic cavity.
• Visceral pleura
• inner layer covering surface of lung
• Pleural cavity
• contains lubricating fluid secreted by membranes

Jenkins, Kemmitz Tortora (2007 p. 845)
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Lungs

• Right lung
• three lobes
• Separated by horizontal and oblique fissures
• Left lung
• two lobes
• Separated by oblique fissure
• cardiac notch

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Lungs

• 3 Surfaces
• Costal
• Diaphragmatic
• Mediastinal
• 3 Borders
• Anterior
• Posterior
• Inferior

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Bronchi

• Primary Bronchi
• Branch to form secondary bronchi (lobar bronchi)
• 1 secondary bronchus goes to each lobe
• Secondary bronchi divide to form tertiary bronchi

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Bronchi
CT Scan of Bronchial tree
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Bronchopulmonary segments

• 10 segments per lung
• Each segment contains lobules
• Each lobule contains
• lymphatics
• arterioles
• capillaries
• venules
• branch from terminal bronchiole (end of
  conducting zone)

Jenkins, Kemmitz Tortora (2007 p. 848)
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Respiratory zone

• Terminal bronchioles subdivide into respiratory
  bronchioles
• Marks beginning of respiratory zone
• Then branch into alveolar ducts
• Finally alveoli

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Alveoli

• Alveolus
• Cup-shaped out-pouching lined by simple squamous
  epithelium
• Supported by basement membrane
• Alveolar sac
• 2 or more alveoli with a common opening

Jenkins, Kemmitz Tortora (2007 p. 848)
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Alveoli

• Walls of alveoli consist of
• Type I alveolar cells
• Predominant cells
• Simple squamous epithelial cells
• Main sites of gas exchange
• Type II alveolar cells (septal cells)
• Cuboidal epithelial cells with microvilli
• Secrete alveolar fluid
• Surfactant reduces surface tension
• Alveolar macrophages (dust cells)
• Wandering phagocytes remove dust and debris

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Respiratory membrane

• 3 parts to membrane
• Squamous epithelial lining of alveolus
• Endothelial cells lining an adjacent capillary
• Fused basal laminae between alveolar and
  endothelial cells
• Diffusion across respiratory membrane is very
  rapid
• because distance is small
• gases (O2 and CO2) are lipid soluble

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Inflammation of lobules

• Also called pneumonia
• causes fluid to leak into alveoli
• compromises function of respiratory membrane
• Viral or bacterial pneumonia
• Symptoms
• SoB, fever, cough with yellow or green sputum,
  chest pain, fatigue, nausea, loss of appetite

• Chest X-ray
• Normal lung
• Pneumonia in right lung
• Pneumonia (2006)

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Blood supply to respiratory surfaces

• Each lobule receives an arteriole and a venule
• respiratory exchange surfaces receive blood
• from arteries of pulmonary circuit
• a capillary network surrounds each alveolus
• as part of the respiratory membrane
• blood from alveolar capillaries
• passes through pulmonary venules and veins
• returns to left atrium

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Concept check questions

• Why are the cartilages that reinforce the trachea
  C-shaped?
• List the functions of the pleura. What does it
  secrete?

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References

• Jenkins, GW, Kemmitz, CP Tortora, GJ 2007,
  Anatomy and Physiology From Science to Life,
  John Wiley Sons Inc, New Jersey.
• Martini, FH 2006, Fundamentals of Anatomy and
  Physiology, 7th edn, Pearson Benjamin Cummings,
  San Francisco.
• Pneumonia 2006, Wikipedia, viewed 12 May 2006,
  http//en.wikipedia.org/wiki/Pneumonia
• Norman, W 1999, Mediastinum, viewed 2 August
  2006, lthttp//mywebpages.comcast.net/wnor/thoraxle
  sson3.htmgt.