Myology

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Myology
Bony Anatomy of the Thorax
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Gross Anatomy
Osteology of the Thorax
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Thorax

• Thorax refers to the entire chest
• Functions
• Protect organs in chest and upper abdomen
• Provides support for bones of upper limbs
• Bony cage flattened from front to back
• Formed by
• Sternum
• Ribs
• Costal cartilages
• Bodies of thoracic vertebrae.

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• Sternum (breastbone)
• Manubrium upper portion
• Suprasternal (Jugular) notch depression in the
  upper part of the manubrium
• Clavicular notches lateral sides of manubrium,
  for articulation with the clavicle.
• Body middle and largest portion
• Xiphoid inferior and smallest portion
• Sternal angle formed by the junction of the
  manubrium and body
• Ribs
• Ribs 1-7 are true ribs direct anterior
  attachment to sternum
• Ribs 8-12 are false ribs attaches indirectly to
  sternum or doesnt attach to sternum at all
• Ribs 11-12 are floating ribs ends of ribs do not
  attach to sternum

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Palpation of the Thorax
Sternum Supine place your fingers on the
center of the chest. Then slide superiorly
toward the jugular notch at the top. Then move
your fingers slightly lateral and palpate the
sternoclavicular joints (confirm by having your
partner move their upper extremity). Return to
the sternum and palpate inferiorly onto the
manubrium and body. Finally, slide your fingers
down onto the xiphoid process feeling the tip
between the costal cartilages. Ribs Supine
slide laterally from the sternum onto the costal
cartilages. Roll off the cartilage into the
spaces between. Follow the costal cartilages
laterally on to the ribs.
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Pectoralis Major

• Pec major along with the lats are important when
  performing a pull-up.
• Both pec major and lats are powerful muscles
  which attach from the trunk to the arm.
• Synergistic to each other with respect to their
  arm action in that they both adduct and medially
  rotate the arm
• However they are antagonistic with respect to
  their sagittal plan arm actions pec major (being
  anterior) flexes the arm and the lats (being
  posterior) extends the arm.
• Pectoralis major has layers clavicular fibers
  are most superficial (anterior) the sternal
  fibers are deep to the clavicular fibers and the
  costal and abdominal fibers attach more
  proximally on the humerus.
• Makes up the vast majority of the anterior
  axillary fold of tissue, which borders the
  armpit anteriorly.
• Can only create flexion of the arm at the
  shoulder joint up to 60.
• Powerful horizontal flexor of the arm at the
  shoulder joint.

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Pectoralis Major
O Clavicular Head Medial clavicle Sternal
Head Sternum and the upper costal cartilages I
Lateral lip of the bicipital groove A
Adduction, medial rotation, and horizontal
adduction of the arm. The clavicular head also
causes flexion of the arm. Secondarily depresses
and protracts the scapula. Reversed muscle
action causes elevation of the trunk, lateral
deviation, and ipsilateral rotation. N Medial
and Lateral Pectoral nerves
Palpation page 260
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Pectoralis Minor

• When contracting it pulls on the coracoid process
  and pulls scapula in such a manner that the
  lateral border is pulled in toward the lateral
  body wall and the medial border moves away from
  posterior body wall.
• This movement is called lateral tilt.
• Rounded shoulders is a common postural condition
  in which the scapulae are protracted and
  depressed and the humeri are medially rotated.
• Given the pec minors action of both protraction
  and depression, when pec minor muscles are tight,
  they can contribute to this condition.
• By elevating ribs 3-5, this muscle can expand the
  ribcage during inspiration (accessory muscle of
  inspiration)

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Pectoralis Minor

• O Anterior borders of ribs 3 through 5
• I Coracoid process of the scapula
• A Protracts, Depresses, and
• downwardly rotates the scapula
• Reversed muscle action
• includes elevation of the 3rd
• through 5th ribs
• N Medial pectoral nerve

Palpation page 264
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Subclavius

• If clavicle is fixed to the scapula, then
  subclavius can also depress the scapula at the
  scapulocostal joint
• Many believe main function is to act as a fixator
  of the clavicle during arm/shoulder movements.
• Common entrapment site for nerves of brachial
  plexus and subclavian artery called
  costoclavicular syndrome

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Subclaviusmuscle is under the clavicle

• O 1st rib
• I Inferior surface of the clavicle
• A Depression of the clavicle and Elevation of
  the 1st rib
• N Nerve to the subclavius from
• the brachial plexus

Palpation page 267
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External Intercostals

• Oriented in the same direction as the external
  oblique abdominal muscles.
• Appear to be extensions of external obliques
• Involved in respiration
• These muscles should be addressed in any client
  who has a respiratory condition.
• This is the meat which is eaten when one eats
  spare ribs.

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External Intercostals

• O Inferior borders of ribs 1-12
• I Superior border of the rib below
• A Elevation of ribs 2-12
• N Intercostal nerves

Palpation page 270
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Internal Intercostals

• Oriented in the same direction as fibers of the
  internal abdominal obliques.
• Generally thinner then external intercostals.
• Involved in respiration
• There is another layer of muscles called the
  innermost intercostals which are located deep to
  the internal intercostals.

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Internal Intercostalslocated between the ribs
and internal to external intercostals

• O Superior border of the rib below
• I Inferior border of the rib above
• A Depresses ribs 1-11
• N Intercostal nerves

Not palpable
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Transversus Thoracis

• Superior fibers run primarily vertically but
  inferior fibers run horizontally
• Located internally i.e. located within thoracic
  cavity
• Primary role is as a respiratory muscle.

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Transversus ThoracisRuns transversely across the
thoracic region

• O Internal surfaces of the sternum, xiphoid and
  adjacent costal cartilages
• I Internal surfaces of costal cartilages 2-6
• A Depression of ribs 2-6
• N Intercostal nerves

Not palpable
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Diaphragm

• Separates the thoracic and abdominal cavities.
• Number of openings to allow passage of structures
  between thoracic and abdominal cavities.
• Largest openings for esophagus, aorta and
  inferior vena cava
• Only muscle that must contract for quiet, relaxed
  inspiration.
• Usually under both conscious and unconscious
  control.
• Innervation is phrenic nerve composed of spinal
  nerves
• C3, 4, 5.
• C3, 4, 5 keeps the diaphragm alive!
• Clinically a Hiatal hernia is when part of the
  stomach herniates through the diaphragm into the
  thoracic cavity.

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Diaphragm

• O Internal surfaces of ribcage, sternum and
  spine
• I Central tendon of diaphragm
• A Increases volume of thoracic cavity during
  inspiration
• N Phrenic nerve

Palpation page 293
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Muscles of the Anterior Abdominal Wall

• Rectus abdominis located anteromedially
• External/internal oblique and transversus
  abdominis located anterolaterally
• All four muscles compress the abdominal contents.
• All except transversus abdominis can flex the
  trunk.
• External oblique of one side is synergistic with
  internal oblique of opposite side with trunk
  rotation.

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Rectus Abdominis

• Three fibrous bands known as tendinous
  inscriptions transect the rectus abdominis
  muscles and divide each into four sections or
  boxes.
• For this reason, this muscle in a well developed
  person is often known as the eight-pack muscle
  (it is more often incorrectly labeled as the
  six-pack since six of eight compartments are more
  visible.
• The two rectus sheaths which encase the rectus
  abdominis meet in the midline and form the linea
  alba.
• When old-fashioned straight legged sit-ups are
  done, the movement occurs at the hip joint and
  not a the spinal joints.

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Rectus Abdominismuscle runs straight up the
abdomen

• O Pubis
• I Xiphoid and cartilages of ribs
• 5-7
• A Bilateral contraction Flexion of trunk,
  Posterior tilt of pelvis, and compresses the
  abdominal contents
• Unilateral contraction lateral flexion of the
  trunk
• N Intercostal nerves, iliohypogastric, and
  ilioinguinal nerves

Palpation page 281
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External Obliques

• Located lateral to rectus abdominis
• Most powerful of the 3 layers of the
  anterolateral abdominal wall
• Directly deep to external oblique is internal
  oblique and deep to that is the transversus
  abdominis
• If you put your hands in your coat pocket, your
  fingers would be pointing along the direction of
  this muscle.

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External Abdominal Obliquelocated externally and
fibers oriented obliquely

• O Anterior iliac crest pubic bone and abdominal
  aponeurosis
• I Lower 8 ribs
• A Bilateral contraction Trunk flexion,
  Posterior tilt of pelvis, and compression of the
  abdominal contents.
• Unilateral contraction Lateral trunk flexion,
  Contralateral trunk rotation, and elevation of
  the pelvis.
• N Intercostal nerves, iliohypogastric, and
  ilioinguinal nerves

Palpation page 284
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Internal Obliques

• If you were to put your hands in your back
  pockets, your fingers would be pointing along the
  direction of this muscle.
• It is an ipsilateral trunk rotator and
  antagonistic to its external oblique partner on
  the same side.

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Internal Abdominal Obliquelocated internally and
fibers oriented obliquely

• O Inguinal ligament, iliac crest and
  thoracolumbar fascia
• I Lower 3 ribs and the abdominal aponeurosis
• A Bilateral contraction Trunk flexion,
  Posterior tilt of pelvis, and compresses the
  abdominal contents.
• Unilateral contraction Lateral trunk flexion,
  Ipsilateral trunk rotation, and elevation of the
  pelvis
• N Intercostal nerves, iliohypogastric, and
  ilioinguinal nerves

Palpation page 287
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Transversus Abdominis

• Is the only abdominal muscle that cannot act as a
  mover of a skeletal action.
• Primary purpose is to compress the abdominal
  contents.
• Upper fibers are contiguous with the diaphragm
  and the transversus thoracis.
• Sometimes called the corset muscle because it
  wraps around the abdomen.

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Transversus Abdominis

• O Inguinal ligament, iliac crest, thoracolumbar
  fascia and lower costal cartilages
• I Abdominal aponeurosis
• A Compression of abdominal contents
• N Intercostal nerves, iliohypogastric, and
  ilioinguinal nerves

Palpation page 287