Sternum and Ribs

Components of the thoracic wall

sternum, ribs, costal cartilages, thoracic vertebral column

primary functions of the thoracic wall

protect thoracic viscera (heart and lungs) and provide attachments for the muscles of the thorax, upper limbs, abdomen, and back

sternum

most anterior portion of the thoracic wall and articulates with the cartilages of the first 7 ribs and clavicles

segments of the sternum

manubrium, body, xiphoid

muscles attached to the sternum

pectoralis major and sternoclastal mastoid

sternal angle

transverse ridge between the manubrium and the body; point of articulation for rib 2; level at which the trachea divides into left and right main bronchi

costal facets

run along the sides of the sternum where ribs 1-7 articulate

costal cartilages

connect the ribs to the costal facets; flexible and allows for the elasticity of the thoracic cage thats needed for breathing

costal margin

lower border of costal cartilages from ribs 7-10; most inferior extent of the thoracic wall; anterior attachment of the diaphragm

intercostal spaces

occupied by intercostal muscles, blood vessels, and nerves

Which ribs are the typical ribs

ribs 2-9

head of a typical rib

has 2 articular facets that joins facets on adjacent vertebral bodies and intervertebral discs to form the costovertebral joint

tubercle of the rib

has one articular facet that joins a facet on the transverse process to create the costotransverse joint

costal groove

runs along the internal aspect of the inferior surface and partially overhangs to protect the intercostal vessels and nerves

Rib angle

region just lateral to the tubercle where the shaft turns anterolaterally and marks the lateral attachment of the erector spinae muscles

Rib 1 (atypical rib)

only has one facet on the head that articulates with only T1; shallow grooves for subclavian artery and subclavian vein; small tubercle where anterior scalene muscle attaches

Ribs 10-12 (atypical ribs)

each has only one facet on their head; ribs 11-12 do not have tubercles because they do not articulate with a transverse process and they end in the muscles of the posterior abdominal wall