2.1thorax

• The thorax is the superior part of the trunk between the neck and the abdomen. The thoracic cage is formed by 12 pairs of ribs, sternum, costal cartilages & 12 thoracic vertebra, together with skin, fascia & muscles.
• Jugular notch


  Other name: Suprasternal notch
• Landmarks of the thorax

  • Suprasternal / jugular notch
  • Sternal angle of louis
  • Clavicle
  • Xiphoid process
  • Costal margins
• The bony thorax is made up of three parts: sternum, ribs, and thoracic vertebrae.
• The sternum is a flat bone that is shorter and thinner in females. It has three parts: manubrium, body, and xiphoid process.
• Manubrium


  Superior margin – Jugular notch which is palpable at the root of the neck. Clavicular notch on the sides for articulation with the clavicle. Articulates with the cartilage of the First rib, upper half of the second rib and body of sternum at the sternal angle.
• Sternal Angle (Angle of Louis)


  Junction between the manubrium and body of the sternum. Located where the second ribs articulate with the sternum, aortic arch begins and ends, trachea bifurcates into R/L bronchi, inferior border of superior mediastinum, and level of intervertebral disc T4-T5.
• Body of the Sternum

  Articulates with the second to seventh costal cartilages. Articulates with the xiphoid process at the XIPHISTERNAL JOINT which is at the level of T9.
• Xiphoid Process


  Flat, sword shaped cartilaginous process at birth that ossifies slowly from the central core and unites with the body of the sternum after middle age (becomes bony by 40 years). Lies at the level of T10 vertebra which marks the lower limit of the thoracic cavity in front, upper surface of the liver, diaphragm and the lower border of the heart.
• The sternum is a common site for bone marrow biopsy because it possesses hematopoietic marrow activity throughout life and because of its breadth and subcutaneous position.
• The sternal angle is an important landmark where the trachea bifurcates into R/L primary bronchi, the arch of the Aorta arises from the Ascending Aorta and continues as the Descending Aorta, and the Azygous vein drains into the SVC.
• The thorax has 12 pairs of ribs. True ribs (1st to 7th) are vertebrosternal, false ribs (8th to 12th) are vertebrochondral, with the 11th and 12th being floating ribs.
• Parts of a rib

  • Head
  • Neck
  • Tubercle
  • Shaft/Body
• The head of a rib articulates with the corresponding vertebral body and that of the vertebra immediately above. The tubercle of a rib articulates with the transverse process of the corresponding vertebra.
• Typical and atypical ribs

  • Typical ribs (3-9)
  • Atypical ribs (1, 2, 10, 11, 12)
• First rib


  Clinically important because of its close relationship to the lower nerves of the Brachial plexus and Subclavian artery/vein. Anterior to the Scalenus ant – Subclavian vein crosses the rib. Posterior – Subclavian artery and the lower trunk of the Brachial plexus cross the rib.
• Rib fractures


  Commonly occur just anterior to the angle of the rib, the weakest point. Middle ribs (5th to 10th) are most commonly fractured, usually resulting from direct blows or crushing injuries. Broken ends may cause Pneumothorax and Lung or Spleen Injury.
• Thoracic outlet


  Where the Thoracic cavity communicates with the root of the neck. Important vessels and nerves emerge from the thorax to enter the neck and upper limbs. Boundaries: Posterior - First Thoracic Vert, Lateral - Medial border First rib, Anterior - Manubrium sterni.
• Rib fractures


  • Commonly occur just anterior to the angle of the rib, the weakest point of the rib
  • Middle ribs are most commonly fractured and usually result from direct blows or crushing injuries
  • Broken ends of ribs may cause Pneumothorax and Lung or Spleen Injury
  • First rib rarely fractured
  • 5th to 10th ribs are most commonly fractured
• Thoracic outlet


  Where the Thoracic cavity communicates with the root of the neck
• Boundaries of the thoracic outlet

  • Post - First Thoracic Vert
  • Lat - Medial border First rib
  • Ant - Manubrium sterni
• Clinicians tend to use thoracic inlet and outlet interchangeably, and they are usually referring to the same structure– the superior thoracic aperture
• When anatomists refer to the thoracic outlet, they are most likely referring to the inferior thoracic aperture
• Thoracic outlet syndrome


  • Brachial plexus and the Subclavian artery and vein are closely related to the upper surface of the First rib and Clavicle
  • Symptoms caused by pressure on the lower trunk of the plexus producing pain down the medial forearm and hand; wasting of hand muscles
  • Pressure on the blood vessels may compromise the circulation of upper limb
  • Compression of the neurovascular bundle occurs as a result of Cervical ribs or abnormal insertions of the Anterior and Middle Scalene muscles
• Muscles with attachment to parts of thoracic cage

  • Vertebral spine
  • Ribs
  • Sternum
• Movements of thoracic wall

  • Vertical Diameter
  • Transverse Diameter
  • Anteroposterior diameter
• Inspiration


  Increases vertical, transverse, and anteroposterior diameters of thoracic wall
• Expiration


  Decreases vertical, transverse, and anteroposterior diameters of thoracic wall
• Muscles of thoracic wall

  • Serratus post sup
  • Serratus post inf
  • Levator costarum
  • Ext intercostal
  • Int intercostal
  • Innermost intrcostl
  • Subcostal
  • Transv thoracis
• Intercostal nerves


  Anterior rami of the First 11 Thoracic spinal nerves
• Branches of internal thoracic/internal mammary artery

  • Pericardiophrenic
  • Anterior Intercostal – 12
  • Anterior Perforating branches
  • Musculophrenic
  • Superior Epigastric artery
• Intercostal arteries


  • Posterior IC artery - branch of thoracic aorta
  • Anterior IC artery - branch of internal thoracic artery and musculophrenic artery
• Intercostal veins


  • Posterior IC artery - drain into azygous/hemiazyguos veins
  • Anterior IC artery - drain into internal thoracic vein
• Thoracocentesis


  • Needle is inserted through an intercostal space into the thoracic cavity to obtain fluid
  • To avoid damage to intercostal nerve and vessels, the needle is inserted above the rib
  • Needle passes through: Ext IC -> Int IC -> Innermost IC -> thoracic cavity
• Layers needle passes through during thoracocentesis


  • Skin
  • Superficial fascia
  • Deep fascia
  • Intercostal muscles
  • Endothoracic fascia
  • Extrapleural fatty layer
  • Parietal pleura
• Contents of an intercostal space from top to bottom: Vein, Artery, Nerve (VAN)
• Lymphatic drainage of thoracic wall

  • Parasternal/Internal thoracic nodes
  • Intercostal nodes
  • Phrenic nodes