Anatomy

• Thorax


  The part of the body between the neck and abdomen
• Thoracic cavity and its wall

  • Shape of a truncated cone, narrowest superiorly, circumference increasing inferiorly, reaching maximum size at junction with abdomen

  
• Contents of the thoracic cavity

  • Primary organs of the respiratory system
  • Primary organs of the cardiovascular system

  
• Thoracic cavity


  • Divided into three major spaces: central compartment (mediastinum) housing thoracic viscera except lungs, right and left pulmonary cavities housing the lungs

  
• The majority of the thoracic cavity is occupied by the lungs, which provide for the exchange of oxygen and carbon dioxide between the air and blood
• Most of the remainder of the thoracic cavity is occupied by the heart and structures involved in conducting the air and blood to and from the lungs

  
• Components of the thoracic wall

  • Thoracic cage
  • Intercostal muscles
  • Skin
  • Subcutaneous tissue
  • Muscles
  • Fascia covering anterolateral aspect

  
• Components of the thoracic cage

  • Sternum anteriorly
  • 12 pairs of ribs and associated costal cartilages laterally
  • 12 thoracic vertebrae and intervertebral discs posteriorly

  
• Ribs and costal cartilages


  Form the largest part of the thoracic cage, identified numerically from most superior (1st) to most inferior (12th)

  
• Sternum


  Flat, elongated bone that forms the middle of the anterior part of the thoracic cage, directly overlies and affords protection for mediastinal viscera and much of the heart

  
• Parts of the sternum

  • Manubrium
  • Body
  • Xiphoid process
• Manubrium

  • Roughly triangular in shape, widest and thickest of the three parts of the sternum, has jugular notch, facets for clavicle and first costal cartilage

  
• Sternal angle (angle of Louis)

  • Angle formed by the junction of the manubrium and the body of the sternum, marks the site of articulation of rib II with the sternum, separates the superior and inferior mediastinum

  
• Rib I is not palpable, because it lies inferior to the clavicle and is embedded in tissues at the base of the neck

  
• Rib II is used as a reference for counting ribs and can be felt immediately lateral to the sternal angle

  
• Body of the sternum

  • Longer, narrower, and thinner than the manubrium, has articular facets for costal cartilages

  
• Xiphoid process


  • Smallest and most variable part of the sternum, cartilaginous in young people but more or less ossified in adults older than age 40, may fuse with the sternal body in elderly people
• Types of ribs


  • True (vertebrosternal) ribs (1st-7th)
  • False (vertebrochondral) ribs (8th-10th)
  • Floating (vertebral, free) ribs (11th-12th)

  
• Typical ribs (3rd-9th)


  • Have head, neck, tubercle, and body (shaft)
  • Head has two facets for articulation with vertebrae
  • Neck connects head to body at level of tubercle
  • Tubercle has articular and non-articular parts
  • Body is thin, flat, and curved with a costal groove

  
• Atypical ribs (1st, 2nd, 10th-12th)


  • Dissimilar to typical ribs, 1st rib is broadest and most sharply curved, 2nd rib has tuberosity for serratus anterior, 10th-12th ribs have only one facet on head and no neck or tubercle

  
• Costal cartilages


  Prolong the ribs anteriorly and contribute to the elasticity of the thoracic wall, providing a flexible attachment for their anterior ends

  
• The cartilages increase in length through the first 7 and then gradually decrease
• Attachment of costal cartilages

  • 1st-7th attach directly and independently to the sternum
  • 8th-10th articulate with the cartilage just superior to them
  • 11th and 12th form caps on the anterior ends of the corresponding ribs and do not reach or attach to any other bone or cartilage

  
• Intercostal spaces


  Separate the ribs and their costal cartilages from one another, named according to the rib forming the superior border

  
• There are 11 intercostal spaces and 11 intercostal nerves
• Intercostal spaces are occupied by intercostal muscles and membranes, and two sets of intercostal blood vessels and nerves
• The space below the 12th rib is referred to as the subcostal space, and the anterior ramus of spinal nerve T12 is the subcostal nerve
• The intercostal spaces are widest anterolaterally, and they widen further with inspiration. They can also be further widened by extension and/or lateral flexion of the thoracic vertebral column to the contralateral side
• Thoracic vertebrae


  The second segment of the vertebral column, located between the cervical and lumbar vertebral segments, consists of twelve vertebrae separated by intervertebral discs

  
• Thoracic vertebrae increase in size as they descend towards the lumbar vertebrae
• Intercostal space


  • Lies between ribs 4 and 5
  • There are 11 intercostal spaces and 11 intercostal nerves
  • Occupied by intercostal muscles and membranes, and two sets (main and collateral) of intercostal blood vessels and nerves
• Subcostal space


  The space below the 12th rib does not lie between ribs and thus is referred to as the subcostal space

  
• The anterior ramus (branch) of spinal nerve T12 is the subcostal nerve
• Intercostal spaces


  • Widest anterolaterally
  • Widen further with inspiration
  • Can be further widened by extension and/or lateral flexion of the thoracic vertebral column to the contralateral side

  
• Thoracic vertebrae

  The second segment of the vertebral column, located between the cervical and lumbar vertebral segments

  
• The thoracic vertebrae consist of twelve vertebrae, which are separated by intervertebral discs
• Thoracic vertebrae increase in size as they descend towards the lumbar vertebrae


  The lower vertebrae must be able to support more of the body's weight when a person is standing due to the effects of gravity
• Main anatomical components of a thoracic vertebra

  • Body of vertebrae
  • Pedicle
  • Lamina
  • Transverse process
  • Spinous process
  • Superior and inferior articular facets

  
• Body of vertebrae


  The largest part, simulating a short cylinder, with two costal facets (one along the upper margin and the other indenting its lower margin)
• T10, 11, & 12 vertebrae


  Have single costal facets located at the upper border of body