Intercostal Muscles Flashcards
What are intercostal muscles?
Cover the spaces between the ribs (intercostal spaces)
What are the layers to the intercostal muscles?
3
External - most superficial
Internal
Innermost intercostals - deepest - lined by endothoracic fascia
Where do the intercostal muscles extend to?
Internal - Extends between the sternum and the angle of the rib
External - Extends between the tubercle and the costochondral junction
What fibres replaced by in intercostal muscles?
Internal - Fibres replaced posteriorly by the intercostal membrane
External - Fibres replaced anteriorly by the intercostal membrane
Where do the fibres of intercostal muscles run?
Internal - Fibres run in a posterio-inferior direction
External - Fibres run in an anterio-inferior direction
What do the intercostal muscles do?
Internal - depress the ribs
External - elevate the ribs
Where does the neuromuscular structure of the thoracic wall run?
Runs within the intercostal spaces between the internal intercostal and innermost intercostal muscles.
Structures lie in the upper aspect of the intercostal space and are partially protected by the costal groove.
Where does the intercostal vein lie?
Superior, and the nerve inferior, to the artery (VAN)
Where are the intercostal nerves formed?
From the ventral rami of T1-T11 and the subcostal nerve from T12
What does each typical intercostal nerve give off?
A number of branches; rami communicantes, collateral, lateral cutaneous, anterior cutaneous and muscular
What does the rami communicates connect?
The nerve to the sympathetic chain
Where does the collateral nerve arise from?
Arises at angle of the rib, courses along the superior margin of the rib below and supplies intercostal muscles and parietal pleura
Where does the lateral cutaneous arise from?
Arises near the midaxillary line, pierces the internal and external intercostals, divides into anterior and posterior branches and supplies skin on lateral aspect of thorax and abdomen
Where does the anterior cutaneous do?
Pierces the muscles at the side of the sternum, divides into medial and lateral branches to supply skin on anterior aspect of thorax and abdomen
What does the muscular supply?
Supplies the intercostal muscles
Which structures does the superior part of T1 contribute to?
Brachial plexus
What is each intercostal space supplied by?
A posterior intercostal artery (plus collateral branch) and 2 anterior intercostal arteries
Where does the posterior artery in the superior two spaces arise from?
Superior thoracic branch of the costocervical trunk
Where doe the remaining posterior intercostal arteries arise?
Thoracic aorta
Where does the anterior intercostal arteries of the upper six intercostal spaces arise from?
Internal thoracic artery
The remaining vessels arise from one of the terminating branches of the internal thoracic artery?
Musculophrenic
What is each intercostal space drained by?
Posterior intercostal vein
Most of these vessels empty into the azygos system of veins
What does the posterior intercostal veins anastomose with?
Anterior intercostal veins
Where do the anterior intercostal vessels empty?
Musculophrenic
