Thoracic Wall Flashcards
Intrinsic muscles, superficial to deep
External intercostal Internal intercostal Transversus thoracis (innermost)
External intercostal muscle, origin and insertion
From lower lip of rib above to outer lip of upper border of rib below
External intercostal muscle, direction of fibres
Downwards, fwds and medially
Internal intercostal muscle, origin and insertion
From floor of costal groove of upper rib to inner lip of upper border of rib below
Internal intercostal muscle, direction of fibres
Upwards, fwds, right angle to that of external
Parts of transversus thoracis
Intercostalis intimus
Subcostalis
Sternocostalis
Intercostalis intimus, origin insertion
From inner surface of rib above to inner surface of rib below
Extent of external intercostal muscle.
From tubercle of the rib behind to the costochondral Junction in front where it is replaced by anterior intercostal membrane
Extent of Internal intercostal muscle.
From the lateral border of sternum in front to the angle of rib behind where it is replaced by the posterior intercostal membrane
Contents of a typical intercostal space
- the three intercostal muscles
- intercostal veins
- intercostal arteries
- intercostal nerves
- intercostal lymph vessels and lymph nodes.
(NV bundle in intercostal space is b/w internal and innermost intercostal: in the order from above to downwards- VAN)
Actions of intercostal muscle
- Strong support of ribs, preventing their separation.
2. Elevators of ribs during respiration
Intercostal nerve is:
Ventral ramii of typical spinal nerve
Ventral primary ramus of 12th thoracic spinal nerve, running in abdominal wall is called:
Subcostal nerve.
Nerve in posterior part of intercostal space
B/w pleura and posterior intercostal membrane
Nerve In the remaining greater part of intercostal space
B/w internal intercostal muscle and intercostalis intimus
Describe first intercostal nerve
Most of it joins ventral ramus C8 to form lower trunk of brachial plexus. Rest of it is very small and lacks lateral and anterior cutaneous branches
Lateral cutaneous branch of second intercostal nerve is known as ________________
Intercostobrachial nerve
Intercostobrachial nerve supplies _____________ & ______________
Skin of floor of axilla & upper part of medial side of arm
Applied anatomy for intercostobrachial nerve.
In coronary artery disease, cardiac pain is referred along this nerve to medial side of arm
What are thoraco-abdominal nerves
7th to 11th intercostal nerves. Supply muscles of corresponding intercostal space
+ muscles of anterior abdominal wall and skin, parietal peritoneum covering abdominal wall
Root pain/girdle pain
Irritation of intercostal nerves due to disease of thoracic vertebrae.
Severe pain around trunk along cutaneous distribution of affected nerve
Sites of eruption of cold abscess on body wall
Pus from tuberculous thoracic vertebrae (Pott's disease) # just lateral to sternum # midaxillary line # lateral to erector spinae muscle
Herpes Zoster (shingles)
Cutaneous vesicles appear in dermatomal area of distribution of intercostal nerve
Intercostal nerve block
Is given to produce local anesthesia in intercostal space by injecting anesthetic agent around nerve trunk, just lateral to Vertebrae.
Conventional thoractomy
Posteriolateral
Along 6th rib
NV bundle protected from injury by lifting periosteum of rib
Paracentesis thoacis
Aspiration of fluid from the pleural cavity. Needle should not be inserted medial to angle of rib as posterior intercostal artery passes oblique from below upwards.
Coarctation of aorta
Narrowing of arch of aorta. PIA enlarged, notching of ribs, especially in posterior parts
PIA Origin
1st and 2nd- superior intercostal artery, branch of costocervical trunk
3rd-11th- descending thoracic aorta
PIA Termination
Anastomose with upper ant. Intercostal artery. At costochondral junction
Collateral branch of PIA
Arises near angle of rib. Ends by anastomosis with lower anterior intercostal artery
Ant. Intercostal arteries origin
1st-6th spaces- internal thoracic artery
7th-11th spaces- musculophrenic
Internal thoracic artery origin
1st part of Subclavian artery (lower surface) about 2.5 cm above the medial end the medial end of the clavicle opposite the origin of thyrocervical trunk
Int. Thoracic artery course
Behind medial end of clavicle
Upper 6 costal cartilages
1 cm away from lateral margin of sternum
At 6th space, into superior epigastric and musculophrenic arteries
Role of internal mammary artery in treatment of coronary heart diseases
When the segment of coronary artery is blocked by atherosclerosis, The diseased arterial segment is bypassed by inserting a graft .
The myocardium is revascularized by mobilizing internal thoracic artery and joining its distal cut end to the coronary artery distal to diseased segment.
IMA graft is preferred. Why?
Lasts long.
Less prone to developing atherosclerosis due to histological peculiarity. Walls contain only elastic tissue.
Cells of endothelial lining secrete chemicals that prevent atherosclerosis.
Left IMA is preferred due to easier access.
