Thoracic Wall

External Intercostal muscle origin

lower margin of rib above

External Intercostal muscle insertion

upper border of rib below

External Intercostal muscle nerve supply

intercostal nerves

External Intercostal muscle fibers

run downwards + forward

Internal Intercostal muscle origin

from subcostal groove of rib above

Internal Intercostal muscle insertion

upper border of rib below

Internal Intercostal muscle nerve supply

intercostal nerves

Internal Intercostal muscle fibers

downward, backward

forms an incomplete layer, and is only present in the lateral part of thoracic wall

Innermost Intercostal muscle

intercostal nerve and vessels are superficial to it

Innermost Intercostal muscle

transversus thoracis muscle (Sternocostalis) origin

lower 1/2 of posterior surface of the sternum and xiphoid process

transversus thoracis muscle insertion

posterior surfaces of the costal cartilages from 2nd to 6th

typical intercostal nerves

T3 to T6

Typical intercostal nerve (3rd to 6th) origin

anterior (ventral) ramus of thoracic spinal nerve

Typical intercostal nerve branches

1. branches to sympathetic trunk


1. muscular branch to the intercostal muscles
2. lateral cutaneous branch (divides into anterior and posterior branches)
3. anterior cutaneous branch (divides into medial and lateral branches)
4. sensory branch to the parietal pleura
5. collateral branch (runs on the upper border of rib below)

Internal Thoracic artery origin

from 1st part of subclavian artery in the neck

Internal Thoracic artery termination

in the 6th intercostal space by dividing into:

* superior epigastric artery
* musculophrenic artery

\

Internal Thoracic artery branches

1. anterior intercostal arteries
2. perforating arteries
3. pericardiacophrenic artery
4. mediastinal artery
5. superior epigastric artery
6. musculophrenic artery

Anterior intercostal arteries

1. in the 1st to 6th spaces are branches from: internal thoracic artery
2. lower 3 spaces (7th to 11th) are branches from: musculophrenic artery

Posterior intercostal arteries

1. 1st and 2nd arteries from: superior intercostal artery
2. arteries from 3rd to 11th branches from: descending thoracic aorta

Anterior intercostal veins drain into

internal thoracic vein

internal thoracic vein origin

formed at 3rd intercostal space ( by union of vena comitants)

internal thoracic vein ending

ends in brachiocephalic vein

Posterior intercostal veins drain into

__azygos vein (in the right side)__ and to __hemiazygos veins (in the left side)__

Azygos vein origin

begins in the abdomen : from inferior vena cava

Azygos vein ending

the superior vena cava in the thorax