Thoracic Cage

• Thoracic Cage


  anatomically, the thorax is the chest + its bony underpinnings = thoracic cage

  elements of the thoracic cage inc the the thoracic vertebrae posteriorly, ribs laterally, the sternum + costal cartilages anteriorly

  the costal cartilages secure the ribs to the sternum

  
• Functions of the Thoracic Cage

  roughly cone-shaped w its broad dimension positioned inferiorly, the thoracic cage forms a protective cage around the vital organs of the thoracic cavity - heart, lungs + great blood vessels)

  supports the shoulder hirdles + upper limbs

  provides attachment points for many muscles of the neck, back, chest + shoulders

  the intercostal spaces between the ribs r occupied by the intercostal muscles, which lift + depress the thorax during breathing
• Sternum


  the sternum (breastbone) lies in the anterior midline of the thorax

  it is a flat bone, resulting from the fusion of 3 bones:

  manubrium, the body + xiphoid process

  
• Sternum - Manubrium


  the manubrium is the superior portion

  it articulates via its clavicular notches w the clavicles laterally

  it also articulates w the 1st 2 pairs of ribs

  
• Sternum - Body


  the body, or midportion, forms the bulk of the sternum

  the sides of the body r notched where it articulates w the costal cartilages of the 2nd to 7th ribs
• Sternum - Xiphoid Process

  the xiphoid process forms the inferior end of the sternum

  articulates only w the sternal body + serves as an attachment point for some abdominal muscles
• Anatomical Landmarks of the Sternum

  the sternum has 3 important anatomical landmarks:

  jugular notch

  sternal angle

  xiphisternal joint

  
• Sternal Anatomical Landmarks - Jugular Notch

  the jugular notch = central indentation in the superior border of the manubrium

  generally in line w the disc between the 2nd + 3rd thoracic vertebrae

  
• Sternal Anatomical Landmarks - Sternal Angle

  sternal angle = horizontal ridge across the front of the sternum, where the manubrium joins the sternal body

  this cartilaginous joint acts like a hinge, allowing the sternal body to swing anteriorly when we inhale
• Sternal Anatomical Landmarks - Xiphisternal Joint

  the xiphisternal joint = point where the sternal body + xiphoid body fuse

  lies at the level of the 9th thoracic vertebra
• Ribs


  12 pairs of ribs form the flaring sides of the thoracic cage

  all ribs attach posteriorly to the thoracic vertebrae (bodies + transverse processes) + curve inferiorly toward the anterior body surface
• True Ribs


  the superior 7 rib pairs attach directly to the sternum by individual costal cartilages (bars of hyaline cartilage)
• False Ribs


  the remaining 5 pairs ribs = false ribs cos they either attach indirectly to the sternum or entirely lack a sternal attachment

  rib pairs 8-10 attach to the sternum indirectly, each joining the costal cartilage immediately above it

  the inferior margin of the rib cage, costal margin, is formed by the costa cartilages of rib 7-10

  rib pairs 11-12 = floating ribs cos they have no anterior attachments

  instead their costal cartilages lie embedded in the muscles of the lateral body wall
• Typical Rib - Shaft & Costal Groove

  a typical rib is a bowed flat bone

  the bulk of a rib = shaft

  its superior border is smooth, but its inferior border is sharp + thin + has a costal groove on its inner face that lodges the intercostal nerves + blood vessels

  
• Typical Rib - Head

  the wedge-shaped head, the posterior end, articulates w the vertebral bodies by 2 facets - one joins the body of the same thoracic vertebra, the other articulates w the body of the vertebra immediately superior

  
• Typical Rib - Neck & Tubercle

  the neck is the constricted portion of the rib just beyond the head

  lateral to this, the knob-like tubercle articulates w the costal facet of the transverse process of the same thoracic vertebra

  beyond the tubercle, the shaft angles sharply forward + then extends to attach to its costal cartilage anteriorly

  the costal cartilages provide secure but flexible rib attachments to the sternum

  
• Atypical Ribs


  the 1st pair of ribs is atypicalthe 1st pair of ribs is atypicalthe 1st pair of ribs is atypicalthe 1st pair of ribs is atypicalthe 1st pair of ribs is atypicalthe 1st pair of ribs is atypicalthe 1st pair of ribs is atypicalthe 1st pair of ribs is atypical

  they r flattened superiorly to inferiorly + r quite broad, forming a horiz table that supports the subclavian blood vessels that serve the upper limbs

  rib 1 + ribs 10-12 only articulate w only one vertebral body

  ribs 11-12 do not articulate w a vertebral transverse process