The document summarizes the anatomy of the thoracic wall. It is formed posteriorly by thoracic vertebrae, laterally by ribs and intercostal spaces, and anteriorly by the sternum and costal cartilages. The intercostal spaces contain intercostal muscles and neurovascular bundles. The document further describes the layers of intercostal muscles, blood supply, innervation, and clinical procedures relevant to the thoracic wall.

1. Prepared by:
Dr. Kamal Motawei
THORAX
Thoracic Wall
College of Medicine Anatomy Dept. 2013-2014

2. The thoracic wall is formed by:
Posteriorly: thoracic vertebrae
Laterally: ribs and intercostal spaces
Anteriorly: sternum & costal cartilages.
Superiorly: thoracic outlet and suprapleural membranes
Inferiorly: diaphragm

3. 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.

6. 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.

7. 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.

8. deepest layer; it is incomplete layer.
It is represented by three patches; anterior, lateral and posterior.
It crosses more than one intercostal space.

9. Action
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.
Nerve supply:
Intercostal nerves and their collateral branches

11. 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.

12. Posterior Intercostal veins:
Rt. side: into azygos vein
Lt. side: hemiazygos veins
Anterior intercostal veins:
Drain into the internal thoracic vein & the musculophrenic v.

14. 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.
Branches:
Anterior intercostal arteries
Perforating arteries
Mediastinal a.
Pericardiacophrenic artery
Superior epigastric a
Musculophrenic a

16. Anterior primary rami of the upper 11 thoracic nerves.
Branches:
White and gray rami communicants
Collateral br.
Lateral cutaneous br.
Anterior cutaneous br.
Muscular br.
Pleural sensory branches
Peritoneal sensory branches (7th -11th)

17. 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.

18. Needle thoracostomy
Tube thoracostomy
Thoracotomy
Intercostal nerve block

19. Intercostal muscles
Diaphragm
Levator costarum
Serratous posterior superior
Serratous posterior inferior