Intercostal muscles and diaphragm Flashcards
Where are the intercostal muscles located?
Between the ribs
What are the different intercostal muscles?
External intercostal
Internal intercostal
Innermost intercostal
Where are the external intercostal muscles most developed?
Most developed posteriorly
Where are the external intercostal muscles least developed?
Least developed anteriorly
What is the direction of the external intercostal muscle fibres?
Antero-medially
What is the action of the external intercostal muscles?
Move the ribs upwards and outwards
What are the external intercostal muscles continuous with?
The external oblique
Where are the internal intercostal muscles most developed?
Most developed anteriorly
Where are the internal intercostal muscles least developed?
Least developed posteriorly
What is the direction of the internal intercostal muscle fibres?
Perpendicular to external intercostal muscles
What is the action of the internal intercostal muscles?
Move the ribs downwards and backwards
What are the internal intercostal muscles continuous with?
Internal oblique
Where are the innermost intercostal muscles most developed?
Laterally
Where are the innermost intercostal muscles least developed?
Anteriorly and posteriorly
What is the direction of the innermost intercostal muscles?
Perpendicular to external intercostal muscles
What is the action of the innermost intercostal muscles?
Move the ribs downwards and backwards
What is located between the internal and innermost intercostal muscles?
Neurovascular bundle
What is the neurovascular bundle located between the internal and innermost intercostal muscles made up of?
Collateral artery
Collateral vein
Collarteral nerve
What does the neurovascular bundle between the internal and innermost intercostal muscles supply?
Intercostal muscles
What is the neurovascular supply of the intercostal muscles?
Main supply is by intercostal artery, vein and nerve
Minor supply is by collateral artery, vein and nerve
What type of muscle is the diaphragm made up of?
Skeletal muscle
What does the diaphragm originate from?
The borders of the inferior thoracic aperture
What does the diaphragm insert into?
Inferior surface of fibrous pericardium
What innervates the diaphragm?
Right diaphragm by right phrenic nerve
Left diaphragm by left phrenic nerve
What are the roots of the phrenic nerve?
C3, C4, C5
What is the clinical signifiance of the diaphragm being innervated by the phrenic nerve?
Pain from the diaphragm is carried by the phrenic nerve to C3, C4, C5 levels of spinal cord
CNS interprets this pain as coming from the C3, C4, C5, cervical dermatomes
gives referred pain to shoulder
What shape is the diaphragm?
Dome-shaped
What happens to the diaphragm when it contracts?
It moves downwards and flattens
What part of the thorax is the diaphragm located at?
Floor of thorax
What part of the abdominal cavity is the diaphragm located at?
Roof of abdominal cavity
What is the direction of the muscle fibres of the diaphragm?
Run centrally
What do the muscle fibres of the diaphragm converge into?
Central tendon
What is the level of the right diaphragm?
Fourth intercostal space
What is the level of the left diaphragm?
Fifth intercostal space
Why is the right diaphragm higher than the left?
Because the right side has to accommodate for the liver, which is a large organ
How many openings are there in the diaphragm?
Three
What are the openings in the diaphragm?
Oesophageal opening
Aortic opening
Caval opening
What is the vertebral level of the oesophageal opening?
T10
What is the vertebral level of the aortic opening?
T12
What is the vertebral level of the caval opening?
T8
What passes through the caval opening of the diraphagm?
Inferior vena cava
What passes through the aortic opening of the diaphragm?
Descending aorta
Azygos vein
Thoracic duct
What passes through the oesophageal opening of the diaphragm?
Oesophagus
Vagus nerves
Where do the phrenic nerves travel?
From the neck
alongside lateral side of fibrous pericardium
to the diaphragm
What does the intercostal artery posteriorly arise from?
The thoracic aorta
What does the intercostal artery anteriorly arise from?
Internal thoracic artery
What does the intercostal vein posteriorly drain into?
Above heart, superior vena cava
At the level of the heart, the azygos vein on the right side and the hemiazygos vein on the left side
Below the heart, inferior vena cava
What does the intercostal vein anteriorly drain into?
Internal thoracic vein
What does the azygos vein drain into?
Superior vena cava
What does the hemiazygos vein drain into?
Azygos vein
What does the collateral artery running between the internal and innermost intercostal muscles arise from?
Branches off the intercostal arteries anteriorly and posteriorly
What do the collateral veins running between the internal and innermost intercostal muscles drain into?
Drain into intercostal veins anteriorly and posteriorly
