Body Walls Flashcards
Thoracic wall boundaries
Anterior: sternum and costal cartilage
Posterior: vertebral column
Lateral: ribs and intercostal spaces
Thoracic cage superior appreture
Posteriorly: body of first thoracic vertebra
Anteriorly: manubrium
Medial margin of first rib on each side
Thoracic inferior appreture
Closed by diaphragm
Posteriorly: body if the 12th vertebra
Anteriorly: Xiphoid process
Posterio-lateral: 12th rib and distal end of 11th rib
Anterio-lateral: Distal cartilaginous ends of ribs 7 to 10
External intercostal muscle Origin Insertion Direction Extension Action
Inferior margin of the ribs above
Superior margin of the rib below
Fibres run obliquley anteroinferiorly (downward and forward)
from the tubercles of the ribs to the costal cartilage then continues as external intercostal membrane
Most active during inspiration
Internal intercostal muscle Origin Insertion Direction Extension Action
Inferior lateral edge of the costal groove of rib above
Superior margin of the rib below
Fibres pass obliquely posterioinferiorly (downward and to the back)
From the parasternal region to the angle of the ribs where it continues as internal intercostal membrane
Mostly active during forced respiration
Sternocostalis muscle
Origin
Insertion
Direction
Lower 1/3 of posterior surface of the body of the sternum and the xiphoid process
To the lower border of the 2nd to the 6th (3rd to 6th) costal cartilage
Pass superiorly and laterally
Subcostalis muscle
Origin
Insertion
Extension
From inner surface of the rib above
to the superior surface of the 2nd or 3rd rib below
Lies in the inner aspect of the posterior thoracic wall medial to the angle of ribs
Intercostalis intimis muscle Origin Insertion Direction Action
From inner surface of the rib above
to the superior surface of the 2nd or 3rd rib below
Pass posterioinferiorly
Exporation
Posterior intercostal arteries
1st and 2nd arteries origin is from the supeior intercostal artery which arise from the costo-cervical trunk of the sub-clavian artey
The remaining 9 posterior intercostal arteries arise from the descending aorta
Internal thoracic artery origin and termination
Origin: A major branch of the sub-clavian artery
Ends at the level of the 6th intercostal space when it divides to musclo-phrenic artery and Superior epigastric artery
Anterior Intercostal arteries
In the upper 6 spaces arise from the internal thoracic artery
In the 7th,8th and 9th space, it arise from the musculo-phrenic artery
In the 10th and 11th space there is no anterior intercostal arteries
Venous drainage of the posterior and anterior
Posterior thoracic veins drain into the azygos and hemiazygous veins
Anterior thoracic arteries drain into the musculo-phrenic and internal thoracic veins
Nerve supply of the thoracic wall (generally)
Innervation of the thoracic wall is mainly by the intercostal nerves which are the anterior rami of spibal nerves T1 to T11. The anterior ramus of T12 is called the subcostal nerve
Typical intercostal nerves
From 3rd to the 6th
The intercostal nerve gives a lateral and anterior cutaneous branches to supply the skin above the intercostal space
Atypical intercostal nerves
Anterior ramus of T1 contributes to the brachial plexus to supply the upper limb
Lateral cutaneous branch of T2 (intercostobrachial) contributes to the innervation of the medial surface of the upper arm
Lower 5 intercostal nerve supply muscles, skin and peritoneum of the abdominal wall