Bones and Joints in the Thoracic Region
The thoracic cage is made up of bones and cartilage along with joints and an assortment of muscles and other soft tissues. The part that opens into the neck is called the superior thoracic aperture, and the bottom of the thoracic cage (the inferior thoracic aperture) is closed by a muscle called the diaphragm. Its main function is to protect your heart, lungs, and major blood vessels located inside.
The thoracic bones
The bones that create the architecture of the thoracic cage include the sternum, the ribs, and the thoracic vertebrae.
The sternum: The sternum is a flat, long bone that forms the medial and anterior part of the thoracic cage. It has three parts:
Manubrium: The manubrium forms the upper part of the sternum. It articulates with the clavicles and attaches to the cartilage of the first two ribs.
Body: This part of the sternum articulates with the costal cartilages of the 2nd through 7th ribs on its sides and with the xiphoid process.
Xiphoid process: This small piece of cartilage turns into bone during adulthood. It’s located at the inferior end of the sternal body at the xiphisternal joint.
The ribs: The ribs are 12 pairs (left and right) of flat, curved bones that give the thoracic cage its shape. They articulate with the thoracic vertebrae in your back, and most of them are attached directly or indirectly to your sternum by costal cartilages. These cartilages help hold the thoracic cage to the sternum and add elasticity to the thoracic cage.
Each rib is separated from neighboring ribs by an intercostal space that runs between the ribs along their full lengths. The space below the 12th rib is called the subcostal space.
The thoracic joints
The cartilaginous joints in your thoracic cage allow you to breathe. The 1st ribs don’t move at all, but the act of breathing requires the other ribs to move up and down a bit, so the joints formed between the rest of the ribs and thoracic vertebrae allow for some movement:
Manubriosternal joint: The joint between the manubrium and the body of the sternum; forms the sternal angle
Xiphisternal joint: Formed between the sternal body and xiphoid process
Costovertebral joints: Formed between the heads of the ribs and the bodies of the vertebrae and the necks of the ribs and the transverse processes of the vertebrae
Sternocostal joints: Join the sternum to the costal cartilages
Sternoclavicular joints: Join the sternum and clavicles
Costochondral joints: Attach the ribs to the costal cartilages
Interchondral joints: Join cartilage to cartilage