Thoracic Wall Flashcards
What are the true ribs, false ribs, and floating ribs?
True ribs: 1-7
False ribs: 8-12
Floating ribs: 11-12 (in abdominal muscles)
What ribs are not palpable?
1, 11, 12
What intercostal space is located at the nipple?
4
What are the three layers of intercostal muscles?
External, Internal, Innermost
What is the function of the external intercostal muscles?
Most active during inspiration, moves ribs superiorly
What is the function of the internal intercostal muscles?
Most active during expiration, moves ribs inferiorly
What is the function of the innermost intercostal muscles?
Acts with internal intercostals
What are the contents of each intercostal space?
Three layers of intercostal muscles
Intercostal neurovascular supply
What is the external intercostal membrane?
Thin layer of connective tissue aponeurosis that replaces the external intercostal muscles in the anterior part of each intercostal space adjacent to the sternum
What is the internal intercostal membrane?
Thin connective tissue aponeurosis that replaces the internal intercostal muscles in the posterior intercostal space adjacent to the vertebral columns
What are the transversus thoracis muslces?
Located on deep surface of anterior thoracic wall, deep to internal thoracic vessels
Attaches to lower sternum and ribs 3-6
Depresses costal cartilage
What are the subcostal muscles?
Located at lower regions of posterior thoracic wall
Depresses ribs
May span multiple ribs
What is the intercostal neurovascular bundle?
Located between internal and innermost muscles at the inferior border of the rib in the costal groove
Order of structures superior to inferior: VAN
Vein ->artery->nerve (all intercostal)
Where is a thoracostomy performed and why?
Directly above the rib at the 4th or 5th intercostal space
To avoid the neurovascular bundle
What are the three movements of the thoracic wall during inspiration?
Vertical diameter - contraction of the diagphragm
Anteroposterior diameter - intercostal muscles
Transverse diameter - intercostal muscles
Describe the posterior intercostal arteries
Branch from the aorta (except 1 and 2)
Supply each intercostal space
Larger than anterior intercostal arteries
Describe the anterior intercostal arteries
Upper 6 originate from the internal thoracic artery
7-9 originate from the musculophrenic artery
There are none in the 10th and 11th spaces
Where do the 1st and 2nd intercostal arteries arise from?
Superior intercostal artery, a branch of the costocervical trunk of the subclavian
Describe the internal thoracic artery
Located parasternally, between the internal intercostal and transversus thoracis muscles
Divides into musculophrenic and superior epigastric arteries at the 6th intercostal space
What is the musculophrenic artery?
Terminal artery that follows the costal margin and supplies the anterior intercostal arteries of 7-9 and adjacent diaphragm
What is the superior epigastric artery?
Supplies the anterior abdominal wall
Travels through the sternocostal hiatus (gap in diaphragm)
Where do the posterior and anterior intercostal veins drain?
Posterior - into azygous vein on the right side, hemiazygous and accessory hemiazygous veins on the left side
Anterior - internal thoracic and musculophrenic veins
Where do the intercostal nerves originate?
Ventral rami of thoracic spinal nerves
What do internal costal nerves carry?
Somatic motor innervation to thoracic wall muscles
Somatic sensory innervation for skin and parietal pleura
Posganglionic sympathetic fibers to the periphery
