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									         Myology



Bony Anatomy of the Thorax




                             1
   Gross Anatomy


Osteology of the Thorax




                          2
                       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.



                                                 3
• 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
     doesn’t attach to sternum at all
   – Ribs 11-12 are floating ribs: ends of ribs do not attach to
     sternum

                                                                   4
5
                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.




                                                                                 6
                      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.          7
                           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   8
                  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 minor’s 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)



                                                                  9
                  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

                                           10
                     Palpation: page 264
                       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




                                                                11
             Subclavius
          muscle 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

                                                                 12
                                           Palpation: page 267
               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.




                                                              13
             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   14
            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.



                                                        15
               Internal Intercostals
          located 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
                                                                           16
               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.




                                                                     17
    Transversus Thoracis
       Runs 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   18
                       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.

                                                                   19
       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   20
   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.
                                       21
               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.



                                                              22
    Rectus Abdominis
        muscle 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                                          23
                                              Palpation: page 281
                 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.




                                                                 24
    External Abdominal Oblique
             located 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
                                                                  25
                                            Palpation: page 284
                 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.




                                                               26
          Internal Abdominal Oblique
                  located 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   27
         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.




                                                            28
      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   29

								
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