THORACIC CAGE
The thorax (thoracic cage) is formed by the sternum
anteriorly, twelve pairs of ribs forming the lateral bony cages, and the twelve
thoracic vertebrae.
STERNUM (BREAST BONE)
This flat bone can be felt just under the skin in the middle
of the front of the chest.
The manubrium is the uppermost section and articulates with
the clavicles at the sternoclavicular joints and with the first two pairs of
ribs.
The body or middle portion gives attachment to the ribs.
The xiphoid process is the tip of the bone. It gives
attachment to the diaphragm, muscles of the anterior abdominal wall and the
linea alba.
RIBS.
The 12 pairs of ribs form the lateral walls of the thoracic
cage.
They are elongated curved bones that articulate posteriorly with the vertebral column.
Anteriorly, the first 7 pairs of the ribs articulate directly with the sternum and are known as the true ribs.
The next 3 pairs articulate only indirectly. In both cases, costal cartilage attach the ribs to the sternum.
The lowest 2 pairs of ribs, referred to as floating ribs, do not join the sternum at all, their anterior tips being free.
They are elongated curved bones that articulate posteriorly with the vertebral column.
Anteriorly, the first 7 pairs of the ribs articulate directly with the sternum and are known as the true ribs.
The next 3 pairs articulate only indirectly. In both cases, costal cartilage attach the ribs to the sternum.
The lowest 2 pairs of ribs, referred to as floating ribs, do not join the sternum at all, their anterior tips being free.
Each rib forms up to three joints with the vertebral column.
Two of these joints are formed between facets on the head of the rib and facets on the bodies of two vertebrae, the one above the rib and the one below.
Ten of the ribs also form joints between the tubercle of the rib and the transverse process of (usually) the lower vertebra.
Two of these joints are formed between facets on the head of the rib and facets on the bodies of two vertebrae, the one above the rib and the one below.
Ten of the ribs also form joints between the tubercle of the rib and the transverse process of (usually) the lower vertebra.
The inferior surface of the rib is deeply grooved, providing
a channel along which intercostals nerves and blood vessels run.
Between each rib and the one below are the intercostal muscles, essential for breathing.
Because of the arrangement of the ribs, and the
quantity of cartilage present in the ribcage, it is flexible structure that can
change its shape and size during breathing.Between each rib and the one below are the intercostal muscles, essential for breathing.
The first rib is firmly fixed to the sternum and to the first thoracic vertebra, and does not move during inspiration.
Because it is a fixed point, when the intercostals muscles contract, they pull the entire ribcage upwards towards the first rib.
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