Respiratory Anatomy

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Respiratory Anatomy
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Muscles of Expiration

• Unlike inspiration expiration is an interaction
  between passive active forces
• active rib cage and abdominal muscles
  (opposition to diaphragm)
• passive recoil forces, gravity
• 3 relatively independent forces
• Passive forces
• Active diaphragm-abdomen forces
• Active rib cage forces

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Internal Intercostals

• Fill spaces between ribs (except in back) on the
  inside of the chest
• Connect ribs at opposite angles to external
  intercostals
• Work in opposition to each other
  (external/internal)
• Internal pull down from the pelvis through
  connection with abdominal muscles
• External Pull upward from the spine, skull, neck
  and fixate upper ribs

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Transversus Thoracis

• Upward outward from lower sternum to insert
  into 2nd-6th ribs
• Flat muscle lying along inside front wall of the
  chest
• Upper fibers run obliquely assist in pulling
  the chest downward

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Subcostal Muscles

• Along lower inside back wall of the thorax
• Originate from lower ribs near the vertebral
  attachment
• Run outward and up to insert into ribs one or
  more higher
• Pull lower ribs (bucket handle) inward downward

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Internal Rib Cage Muscles of Exhalation
Transversus Thoracis
Outside view of back wall of lower six ribs
Inside view of front wall of upper six ribs
Internal Intercostals
Subcostals
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Serratus Posterior Inferior

• Slants upward outward from lower thoracic and
  upper lumbar vertebrae
• Inserts into the lowest four ribs
• Size, angle of pull leverage to depress the
  lower ribs with strong force

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Quadratus Lumborum

• Strongly pulls down on the lowest floating rib
• Pulls from its attachment along the upper border
  of the hip (coxal bone)
• Flat vertical muscle in the posterior abdominal
  wall

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External Rib Cage Muscles of Exhalation
Serratus Posterior Inferior
Quadratus Lumborum
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Abdominal Muscles of Expiration

• Abdominal wall muscles provide major active force
  in exhalation
• Contribution to breathing is compression of
  viscera that push up on diaphragm
• Pushing displaces 60-80 of the exhaled volume
• Function as rib cage depressors (pull down on
  thorax) abdominal compressors

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Rectus Abdominus

• Large, vertical ribbon muscle
• Runs from front of pelvis along midline of belly
  to the sternum lower ribs
• Limited in amount of compression it applies
  (Pulls in a straight line)
• Downward pull on sternum provides powerful
  exhalatory force

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External Oblique

• Originates from the lower 8 ribs and sweeps down
  and forward
• Posterior fibers descend vertically to crest of
  coxal bone
• Other fibers slant obliquely forward toward
  midline
• Insert into tendinous sheath called abdominal
  aponeurosis (covers rectus abdominus)
• Contribute to exhalation by pulling down on the
  thorax while compressing viscera

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Internal Obliques

• Thinner muscle, middle layer of abdominal wall
• Course of fibers opposite to external obliques
• Originate along upper border of coxal bone, fan
  out and up
• Fan out at right angles to the external obliques
• Insert at the midline into the abdominal
  aponeurosis cartilages of the lower ribs
• External Internal pull down on the thorax and
  squeeze the viscera

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Transversus Abdominus

• Deepest layer of abdominal muscle
• Horizontal fibers sweep from the vertebrae in the
  back of the abdomen
• Insert into abdominal aponeurosis
• Attaches above to the lower border of the ribs
  (the cartilages of the lower 6 ribs)
• Attaches below to the upper border of the pelvis
  (coxal bone)- Like a corset (compress viscera)
• Corset action- Ext. Int. obliques add
• Paired muscle- Tug of war

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Abdominal Muscles of Exhalation
Rectus Abdominus
Transverse Abdominus
Internal Oblique
External Oblique
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Passive forces

• Inspiration- raises rib cage against gravity
• cartilage are twisted
• viscera compressed
• alveolar sacs inflated against surface tension
• greater the inhalation greater resistance
  (muscles)
• Muscles relax passive forces
• Untorquing
• Gravity
• Elastic recoil of lungs

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Relaxation Pressure
Ribs Raised
Exhaled
Torqued cartilage
Elastic Recoil
Inhaled
Gravity
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Assignments

• Reading
• Seikel Ch.3 (Pgs. 99-109)
• Maue-Dickson Ch.3 (116-122)