sternal angle
2nd pair of costal cartilages and ribs - IV disc of T4/T5, also includes the manubrium, which is angled posteriorly on the body of the sternum at the manubriosternal joint
superior thoracic opening
aka thoracic inlet - communicates with the neck and upper extremities and is bounded by: 1st body of thoracic vertebra, 1st pair of ribs and their costal cartilages, jugular notch of the sternum
inferior thoracic opening
aka thoracic outlet - closed by the diaphragm and is bounded by: 12th thoracic vertebra, 11th and 12th pair of ribs, costal cartilages of ribs 7-10, xiphisternal joint
diaphragm
closes inferior thoracic aperture - it is the septum between the thoracic and abdominal cavity that is the major muscle of respiration. it is innervated by the phrenic nerve (C3-C5 - somatic nerves)
it has 2 portions:
peripheral - muscular part (sternal, costal, lumbar)
central - aponeurotic - central tendon
central portion of diaphragm
has a left and right leaflet of the central tendon covering the muscular portions and a middle leaflet of the central tendon that is fused with the pericardium where the heart rests on top of
dorsal mesentery
gives rise to the crura of the diaphragm (left crus which runs along left side of abdominal aorta, right crus which runs along right side of abdominal aorta and wraps around esophagus)
congenital hiatal hernia
esophageal hiatus may be abnormally large - portions of the diaphragm that encircle the esophagus lose their rigidity
congenital diaphragmatic hernia/Bochdalek's hernia
large postero-lateral defect caused by a defective or absent pleuroperitoneal fold (more common on the left side) - abdominal contents pass into the thorax, may cause lung hypoplasia (failure of the development of the lungs) from pushing and compressing the lung. the abdomen is also empty when lying flat and the heart is pushed to the right
retrosternal/parasternal hernia/Morgagni's hernia
in the hiatus located between the sternal and costal parts of the diaphragm, there is a herniation of the intestine into the pericardial sac
eventration of the diaphragm
caused by a defective musculature in one half of the diaphragm (loses muscular rigidity and becomes more flexible and moves backwards). that half goes up with contraction of the diaphragm during respiration - paradoxical respiration. results in dyspnea (difficulty breathing) because the lung becomes compressed
thoracic outlet syndromes
compress the brachial plexus: pain in the 4th and 5th finger from pressure on the lower trunk of the brachial plexus (C8/T1) OR the subclavian artery: ischemic muscle pain in the upper limb. the pulse increases when the limb is elevated - Holsen maneuver
incidence of cervical rib: 0.5-1%
superficial muscles of the anterior thoracic wall
pectoralis major (medial/lateral pectoral nn.)
subclavius (nerve to subclavius)
pectoralis minor (medial pectoral n.) - covered by clavipectoral fascia
serratus anterior (long thoracic n.)
superficial deep muscles of the thoracic wall
exterior intercostal muscles - direction of the fibers of these muscles is medial and downward (like hands in the front pockets). prolongation of external fibers will form a letter X on your abdomen just like eXternal. these muscles extend around the thoracic wall from the tubercles of the ribs to the costochondral joints, where they become membranes covering the internal intercostal muscles - most active during INSPIRATION
middle deep muscles of the thoracic wall
internal intercostal muscles - direction of the fibers of the external oblique is lateral and upward (like hands in the back pockets) opposite to fibers of the external intercostal muscles. they extend from the parasternal regions, where the muscles course between adjacent costal cartilages, to the angle of the ribs posteriorly where they continue medially toward the vertebral column as membranes - most active during EXPIRATION
deep deep muscles of the thoracic wall
transversus thoracis muscles - near the sternum
innermost intercostal muscles - in parallel direction with the internal intercostal muscles (best seen in mid-axillary line)
subcostal muscles - near the angles of the ribs
transversus thoracis muscles
originate posterior to xiphoid process and attach to the costal cartilages of ribs 3-6, pulling them interiorly and securing the internal thoracic vessels to the thoracic wall
pump handle breathing
increases the anterior-posterior dimension of the thorax - contraction of the diaphragm increases the vertical dimension
bucket handle breathing
increases the later dimension of the thorax by rotating the ribs in axis - opera singers have a greater ability for this type of breathing while children/babies have no ability for this type of breathing
intercostal nerves
ventral primary rami - gives two branches: lateral cutaneous branch and anterior cutaneous branch
function: sensory and motor innervation of the thoracic wall and upper abdomen, also lateral limb of the diaphragm (only sensory) and parietal pleura
dermatome (skin) and myotome (muscles) are innervated by a single pair of spinal nerves
intercostal nerve branching
starts as primary ventral ramus of spinal nerve, branches to lateral cutaneous nerve with a posterior and anterior branch, and anterior cutaneous nerve which exits at sternum to medial and lateral branches
neurovascular bundle orientation
VAN - Vein is located superiorly, Artery is located between the vein and nerve, Nerve is located inferiorly
occupies the costal groove (inferior edge of rib) and is situated between the internal intercostal and innermost intercostal muscles
Herpes Zoster
Varicella Zoster virus - initial infection is chicken pox. it then lies dormant in the dorsal root ganglia at the sensory fibers of intercostal nn. reactivation along a ganglion's distribution causes shingles
anterior intercostal arteries
internal thoracic artery (ITA) - branch of subclavian artery, runs on the internal surface of the thorax, laterally to the sternum, anteriorly to the pleura. it divides into the musculophrenic artery and superior epigastric artery
2 pairs of anterior intercostal arteries that anastamose with ITA
azygos venous system
azygos vein - runs vertically down the interior of the posterior wall of the thorax
hemiazygos vein - branches off the azygos vein to run down the left side of the interior of the posterior wall
accessory hemiazygos vein - branches off the azygos vein to run up the left side of the interior of the posterior wall
thoracic cavity
contains: 2 pulmonary cavities (right and left lung) and a mediastinum (between pulmonary cavities containing all other structures)
pleura
mesothelial (serous) membrane of cells that surrounds the lung (Bursa-like fluid bags). it produces a little bit of fluid and is a continuous closed system that encircles the lung. it has 2 layers: visceral pleura that adheres to the lung and parietal pleura that covers the internal surface of the thoracic wall. in between these two layers in the pleural space/cavity filled with fluid
pleural cavity
potential space between the visceral and parietal pleura that normally contents only a thin film of serous fluid
pleural recess
a potential space where 2 adjacent parietal pleura are in contact (during expiration) and fill with lungs during deep inspiration
costodiaphragmatic recess
the most inferior part of the pleural cavity that can have fluid collection. it is between the costal pleura and diaphragmatic pleura
innervation of parietal pleura
SENSITIVE TO PAIN! - supplied by the intercostal nerves (costal and cervical pleura), phrenic nerves (mediastinal and central diaphragmatic pleura), and the lower 5 or 6 intercostal nerves (peripheral diaphragmatic pleura)
any disease that causes accumulation of fluid causes pain in the ribs
innervation of the visceral pleura
INSENSITIVE TO PAIN AND TOUCH! - supplied by autonomic fibers only
superior line of pleural reflection
pleural cavity can project as much as 3-4cm above the first costal cartilage but not above the neck of rib 1 - caused by inferior slope of rib 1 to articulation with manubrium
anterior line of pleural reflection
pleural cavities approach each other posterior to the upper part of the sternum but posterior to the lower part of the sternum, the parietal pleura does not come as close to the midline of the sternum on the left side as it does on the right side because the middle mediastinum, containing the pericardium and heart, bulges to the left
inferior line of pleural reflection
costal pleura reflects onto the diaphragm above the costal margin. in the MIDCLAVICULAR line, the pleural cavity extends inferiorly to approximately RIB 8. in the MIDAXILLARY line, it extends to RIB 10. from this point, the inferior margin courses somewhat horizontally crossing RIBS 11 & 12 to reach VERTEBRA T12. from the midclavicular line, the inferior boundary of the pleura can be approximated by a line that runs between RIB 8, RIB 10, and VERTEBRA T12