Anterior Thoracic Wall Flashcards
What are the three muscles of the intercostal space?
- External intercostals
- Internal intercostals
- Innermost intercostals
What are the three movements of the thoracic cage? Describe them.
- increase in vertical diameter (contraction of diaphragm)
- Bucket Handle movement of ribs - ribs swing out laterally to increase transverse diameter
- Pump Handle - movement of the ribs when the sternum and anterior ends are raised to increase anteroposterior diameter.
What are the parts of a typical intercostal nerve?
white and gray ramus from the ventral rami
then splits into the following branches: rami communicantes, collateral branches, lateral cutaneous branches, and anterior cutaneous branches
Where do the posterior intercostal arteries originate from?
the thoracic aorta posteriorly
Where do the anterior intercostal arteries arise from?
they are branches of the internal thoracic artery, which is off the subclavian
What are the 4 branches from the internal thoracic artery?
the pericardiacophrenic
musculophrenic, which gives off the intercostal arteries in 7-9
superior epigastric
anterior intercostal arteries
Where do the anterior intercostal veins drain?
the internal thoracic veins
Where do the posterior intercostal veins drain?
azygos and hemiazygos system of veins
Which rib pairs actually connect to the sternum and which do not?
1-7 connect
8-10 connect indirectly through costal cartilage
11 and 12 are “false” ribs in that they only connect to the costal cartilage of the rib above.
What are the two ways the vertebrae connect to the ribs?
- through the facet joints directly to the head of the ribs
2. through the costotransverse joints between the tubercle or rib and transverse process
What binds the superior thoracic aperture?
the body ot T1, rib 1 and the manubrium
What passes through the superior thoracic aperture?
the brachial blexus and the subclavian artery and veins
What is the superior thoracic aperture known as CLINICALLY?
the thoracic outlet (even though it’s technically the outlet)
What is thoracic outlet syndrome/
it’s when there’s compression of the brachial plexus and/or subclavians in the outlet
What binds the inferior thoracic aperture?
body of T12, costal margin, xiphisternal joint
What does the inferior thoracic aperture represent?
the attachment of the diaphragm
What are the sections fo the sternum?
the manubrium, body and xiphoid process
How does the sternum develop?
from 6 separate ossification centers - most of which fuse around age 25 (xiphoid is last at age 35)
The sternal angle is what type of joint?
a symphysis - secondary cartilaginous joint where the bones are united by fibrocartilage
The xiphisternal junction is what type of joint?
a synchondrosis - primary cartilaginous joint where the bones are united by hyaline cartilage temporarily and then converts to bone
What disc space lies posterior to the sternal angle?
T4-T5
What number is the intercostal space below the sternal angle?
the 2nd intercostal space
What happens with the trachea at the sternal angle? What part of the aorta is located posterior ot the sternal angle? WHat does the superior vena cava do at the sternal angle? What does the sternal angle do to the mediastinum?
trachea bifurcates
aortic arch
it enters the pericardium
divides it into inferior and superior
What is the weakest part of the rib? Which ribs are most frequently fractured?
just anterior to the angle
the middle ribs are most frequently fractured
What is contained in the costal groove just under the rib?
the intercostal VAN (vein, artery, nerve)
What vertebrae does rib #4 articulate with?
T4 (via the facet and the tubercle) and T3 (via the facet)
What happens when the external intercostals contract?
they cause the lungs to elevate, resulting in forced inspiration
The external intercostal muscle layer is incomplete anteriorly or posteriorly?
anteriorly - replaced by the external intercostal membrane
What happens when the internal intercostal contracts?
they depress the ribs, causing forced expiration
The internal intercostal muscles are incomplete anteriorly or posteriorly?
posteriorly
What muscles keep the intercostal spaces rigid and elevate or depress the ribs?
subcostals
What’s the primary movement of inspiration?
contraction of the diaphragm increasing the vertical dimension
What major artery can be seen lateral to the sternum within the intercostal spaces?
the internal thoracic artery
What is the internal thoracic artery a branch of?
subclavian
inferiorly, the internal thoracic artery branches to form what two arteries?
the superior epigastric and musculophrenic arteries
The ventral ramus of the 12th nerve forms what?
the subcostal nerve
Each intercostal nerve is connected to a ganglion of the sympathetic trunk via what?
rami communicantes
THe white ramus conteys what fibers? How about the gray ramus?
white = preganglionic sympathetic to the ganglion gray = postganglionic away from the ganglion
THe intercostal nerves carry motor fibers to the muscles and sensory fibers from the skin and ….
partietal pleura
The anterior cutaneous branches of the T7-T12 intercostal nerves carry sensation and motor to what?
the abdominal muscles and skin
The outer wall of the pericardium is called what?
the fibrous pericardium
The inner layer of pericardium is what? What are it’s two layers?
the serous pericardium
parietal is attached to the inner aspect of the fibrous pericardium and the visceral pericardium (epicardium) is attahed tot he heart
What layer of the pericardium reflects back over the great vessels?
visceral
What sinus lies behind the aorta and pulmonary trunk? What is the clinical significance?
the transverse sinus
you can clamp it to stop blood flow to the heart during surgery
What sinus is formed by the pericardial reflections on the inferior vena cava and pulmonary veins?
oblique sinus
