Dr. Kamal Motawei
College of Medicine Anatomy Dept. 2013-2014
The thoracic wall is formed by:
Posteriorly: thoracic vertebrae
Laterally: ribs and intercostal spaces
Anteriorly: sternum & costal cartilages.
Superiorly: thoracic outlet and suprapleural membranes
Def.: spaces between the ribs (also, between the costal cartilages anteriorly).
So, they are 11 in number.
Each space contains:
Intercostal muscles: external, internal and innermost.
Intercostal vein, artery and nerve (VAN) in the neurovascular plane; between the internal intercostal and the innermost intercostal muscles.
Superficial layer; its fibers are directed downward and forward from the inferior border of the rib above to the upper border of the rib below.
It extends from the rib tubercle behind to the costochondral junction in front, where it is replaced by the anterior intercostal membrane.
Intermediate layer; its fibers are directed downward and backward from the subcostal groove of the rib above to the upper border of the rib below.
It extends from the sternum in front to the angles of the ribs behind, where it is replaced by the posterior intercostal membrane.
deepest layer; it is incomplete layer.
It is represented by three patches; anterior, lateral and posterior.
It crosses more than one intercostal space.
1) narrow the intercostal spaces.
So, they either raise or lower ribs according to which rib is more stable, the 1st or the 12th
This means they are responsible for inspiration and forced expiration.
2) Their tone prevents sucking and bulging of the intercostal spaces during inspiration and expiration.
Intercostal nerves and their collateral branches
Posterior Intercostal Arteries:
Upper 2: br. from the superior intercostal a. of the costocervical trunk of the subclavian a.
Lower 9: from the descending aorta
Anterior intercostal arteries: (2 in each space)
Upper 6: from the internal thoracic a.
Lower 5: from the musculophrenic a.
Posterior Intercostal veins:
Rt. side: into azygos vein
Lt. side: hemiazygos veins
Anterior intercostal veins:
Drain into the internal thoracic vein & the musculophrenic v.
Internal thoracic artery:
Origin: 1st part of the subclavian artery
Course: deep to the costal cartilages a finger breadth lateral to the edge of the sternum
Ends in the 6th intercostal space by dividing into 2 branches.
Anterior intercostal arteries
Superior epigastric a
The 1st intercostal nerve has no cutaneous branches. Also, most of the primary ramus share in the brachial plexus
The lateral cutaneous br. of the 2nd intercostal nerve is called intercostobrachial nerve as it communicates with medial cutaneous nerve of the arm
The 7th to the 11th nerves supply the anterior abdominal wall.