B

• The thorax refers to the region of the body between the neck and the abdomen
• The thoracic cavity is enclosed by the musculoskeletal walls of the thorax and the diaphragm
• The thoracic wall consists of the sternum anteriorly and the 12 thoracic vertebrae and their intervening intervertebral discs posteriorly
• The thoracic wall laterally consists of the ribs, each rib’s associated costal cartilages, and muscles that span the space between adjacent ribs/costal cartilages
• The diaphragm forms the physical boundary between the thoracic cavity and the abdominal cavity inferiorly
• The sternum is a flat bone located at the anterior aspect of the thorax, with a 'T' shape
• The sternum can be divided into three parts: the manubrium, body, and xiphoid process
• Manubrium:

  • Most superior portion of the sternum, trapezoid in shape
  • Jugular notch visible underneath the skin, articulates with clavicles forming sternoclavicular joints
  • Articulates with the body of the sternum, forming the sternal angle
• Body:

  • Flat and elongated, largest part of the sternum
  • Articulates with the manubrium superiorly and the xiphoid process inferiorly
  • Articular facets articulate with the costal cartilages of ribs 3-6
• Xiphoid Process:

  • Most inferior and smallest part of the sternum
  • Tip located at the level of the T10 vertebrae
  • Largely cartilaginous in structure, ossifies around age 40
  • In some individuals, articulates with part of the costal cartilage of the seventh rib
• Sternal fractures are associated with severe blunt trauma to the chest, classified as comminuted fractures
• Rib structure includes typical ribs with a head, neck, and body, and atypical ribs (1, 2, 10, 11, 12)
• Typical Ribs:

  • Head articulates with corresponding vertebra and vertebra above
  • Neck connects head with body, contains tubercle
  • Body is flat and curved, with a groove for neurovascular supply
• Atypical Ribs:

  • Rib 1 shorter and wider, only one facet on head
  • Rib 2 thinner and longer, roughened area for muscle origin
  • Rib 10 only has one facet
  • Ribs 11 and 12 have no neck, one facet for articulation
• The thoracic spine consists of twelve vertebrae, separated by intervertebral discs
• Thoracic vertebrae have four features distinguishing them: heart-shaped vertebral body, demi-facets on sides for rib articulation, costal facets on transverse processes, and long slanting spinous processes
• Superior and inferior costal facets articulate with the heads of the ribs, with demi-facets in vertebrae T2-T9
• Unique joints of the thoracic spine include costovertebral and costotransverse joints for rib articulation
• Costovertebral joints consist of the head of the rib articulating with superior costal facet of corresponding vertebra, inferior costal facet of superior vertebra, and intervertebral disc
• Costotransverse joints are formed by the articulation of transverse processes of a thoracic vertebra and the tubercle of the adjacent rib
• The thoracic spine is strengthened by ligaments, including anterior and posterior longitudinal ligaments
• The thoracic spine is strengthened by numerous ligaments
• Ligaments present throughout Vertebral Column:

  • Anterior and posterior longitudinal ligaments: Long ligaments that run the length of the vertebral column, covering the vertebral bodies and intervertebral discs
  • Ligamentum flavum: Connects the laminae of adjacent vertebrae
  • Interspinous ligament: Connects the spinous processes of adjacent vertebrae
  • Supraspinous ligament: Connects the tips of adjacent spinous processes
• Ligaments unique to the Thoracic Spine:

  • Radiate ligament of head of rib: Fans outwards from the head of the rib to the bodies of the two vertebrae and intervertebral disc
  • Costotransverse ligament: Connects the neck of the rib and the transverse process
  • Lateral costotransverse ligament: Extends from the transverse process to the tubercle of the rib
  • Superior costotransverse ligament: Passes from the upper border of the neck of the rib to the transverse process of the vertebra superior to it
• Various diseases can lead to kyphosis in adults, with osteoporosis being the most common cause
• Kyphosis is an excessive curvature of the thoracic spine, causing the back to appear “hunched”
• The thoracic cavity contains the superior thoracic aperture (Thoracic inlet) and the inferior thoracic aperture (thoracic outlet)
• The superior thoracic aperture is bounded anteriorly by the superior surface of the manubrium, posteriorly by the internal margins of the T1 vertebra, and laterally by the first pair of ribs
• The inferior thoracic aperture is the large, irregularly shaped inferior opening of the thoracic cavity, with the diaphragm enclosing it
• The mediastinum is the central compartment of the thoracic cavity, divided into superior and inferior parts
• The superior mediastinum extends upwards, terminating at the superior thoracic aperture, and contains neural, vascular, and respiratory structures
• The superior mediastinum contains the arch of Aorta, Great Vessels, Right and Left vagus nerve, and Phrenic Nerve
• The middle mediastinum contains the heart, pericardium, tracheal bifurcation, and the left and right main bronchi
• The middle mediastinum is associated with the origins of the great vessels like Ascending aorta, Pulmonary trunk, and Superior Vena Cava
• The posterior mediastinum contains the thoracic Aorta, Oesophagus, and Thoracic Duct
• The thoracic aorta begins at the lower edge of the T4 vertebra and descends through the posterior mediastinum to the left of the vertebrae
• The oesophagus connects the pharynx to the stomach, passing into the posterior mediastinum from the superior mediastinum
• The thoracic duct allows the return of lymph from most of the body into the venous system