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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

true ribs

ribs 1-7

false ribs

ribs 8-10(12)

floating ribs

ribs 11 and 12

costal margin

the space between costal cartilages of lower ribs

intercostal space

the space between 2 ribs


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

septum transversum

gives rise to the central tendon of the diaphragm

pleuro-peritoneal membrane

gives rise to the primordial musculature of the diaphragm

pleuro-peritoneal folds

gives rise to the posterolateral parts of the diaphragm

sidewall mesenchyme

gives rise to the peripheral part of the diaphragm

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

paradoxical breathing

one side of the diaphragm moves

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


difficulty in respiration


difficulty in expiration


chronic obstructive pulmonary disease - muscles of respiration get large

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

subcostal nerve

intercostal nerve of T12

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)


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

cervical pleura

parietal pleura at the top portion of the lungs

mediastinal pleura

parietal pleura attached to pericardium

costal pleura

parietal pleura attached to ribs

diaphragmatic pleura

parietal pleura attached to diaphragm

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

costomediastinal recess

between the costal pleura and mediastinal 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

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