Thoracic cage, diaphragm Mark Kozsurek, M.D., Ph.D. ED I., 15/11/2011

Questions to be answered How are the bones of the thorax connected together? → the joints of the thoracic cage Which muscles act upon these joints? → the muscles of the thoracic cage How does the thoracic cage move? → the mechanism of breathing

How are the ribs connected to the vertebrae? How do the ribs attach to the sternum?

How are the ribs connected to the vertebrae? COSTOVERTEBRAL JOINTS: 1. COSTOTRANSVERSE JOINT - costal fovea of the transverse process articular facet of the the costal tubercle 2. JOINT OF HEAD OF RIB - costal facet of the vertebra - articular facet of the head of the rib

Articular surfaces of vertebrae „TYPICAL VERTEBRAE” TII-IX present a superior and an inferior costal demifacet. „ATYPICAL VERTEBRAE” - TI bears a complete superior costal facet for the head of the first rib and an inferior costal demifacet for the head of the second rib. TX only has a superior costal demifacet. TXI-XII express complete costal facets for the ribs with the same number. They have no costal facets on their transverse processes. TYPICAL

Articular surfaces of the ribs Rib I Ribs II-X Ribs XI-XII Ribs I, XI-XII have continuous facets on their heads, the articular surfaces of the heads of ribs II-X are divided into two by a crest, ribs XI-XII have no tubercle and do not articulate with transverse processes.

Joint of the head of the rib Costotransverse joint

Radiate ligament of the head of the rib (not shown) Joint of the head of the rib Costotransverse joint

radiate lig. of the head of the rib lateral costotransverse lig. superior costotransverse lig. radiate lig. of the head of the rib

Costotransverse ligament attaches the neck of the rib to the transverse process. Lateral costotransverse ligament connects the tip of the transverse process to the roughened nonarticular part of the tubercle of the rib. Superior costotransverse ligament attaches the neck of the rib to the transverse process of the vertebra above. Intra-articular ligament connects the crest of the head of the rib to the intervertebral disc. Radiate ligament of the head of the rib reinforces the capsule of the joint of the head of the rib.

Ribs II-VII: synovial joints How are the ribs connected to the sternum? Manubriosternal and xiphisternal joints: synchondroses, with age they become ossified. Sternocostal joints: Rib I: synchondrosis Ribs II-VII: synovial joints Intercostal joints: Ribs VI-X synovial joints

radiate sternocostal ligament

Thoracic muscles – the intercostal ones

external intercostal m. external intercostal membrane vertebra rib internal intercostal m. internal intercostal membrane innermost intercostal m. transversus thoracis m. sternum

Blood supply and innervation of the thoracic wall

Posterior intercostal arteries are direct branches of the thoracic aorta, while the anterior intercostal arteries arise from the internal thoracic artery, a branch of the subclavian artery. Supreme intercostal arteries of the two upper intercostal spaces also come from the subclavian artery. Posterior intercostal veins drain into the azygos vein (on the right) or into the hemiazygos/ accessory hemiazygos veins (on the left). Anterior intercostal veins open into the internal thoracic vein, which empties into the brachiocephalic vein. Intercostal nerves exit from the spinal cord and leave the vertebral canal through the intervertebral foramina. Intercostal vessels and nerves give off posterior, lateral and anterior branches to supply the external layers of the thoracic wall.

1. 4. 2. 3. 5. Pectoralis major (and minor) Serratus anterior Abdominal muscles Trapezius (Levator scapulae, Rhomboids, Serratus posterior) Latissimus dorsi

Central tendon with the opening for the inferior vena cava Diaphragm Central tendon with the opening for the inferior vena cava IVC a b c According to the site of origin muscle fibres constitute the: a, sternal part b, costal part c, lumbar part esophagus aorta superior aspect

inferior view

sternocostal triangle (of LARREY) sternal part costal part lumbar part lumbocostal triangle (of BOCHDALEK)

Blackboard!

lateral, medial, median arcuate ligaments medial part L1 lateral part

Caval opening: IVC, right phrenic nerve, central tendon, T8

Esophageal opening: esophagus, ant. et post. vagal trunk, T10

Aortic hiatus: aorta, thoracic duct (the greatest lymph vessel), L1

Sternocostal triangle of Larrey: internal thoracic artery and vein * * they are called superior epigastric a. et v. bellow the diaphragm

Between the medial and lateral parts (variable!!!): greater splanchnic nerve, azygos/hemiazygos veins, lesser splanchnic nerve and sympathetic trunk

Innervation, blood supply of the diaphragm

Internal thoracic artery (ITA) is one of the first branches of the subclavian artery. ITA gives off the pericardiacophrenic artery first which descends together with the phrenic nerve between the pleura and the pericardium. Before reaching the trigone of Larrey, ITA gives off the musculophrenic artery contributing to the blood supply of the diaphragm. Already from the abdominal aorta the inferior phrenic arteries ascend to the inferior surface of the diaphragm. Phrenic nerve arises mainly from the C4 segment, this is why injuries of the neck around or above this level may cause sudden death due to the palsy of the diaphragm.

Respiratory movements Ribs rotate around an axis defined by the two costovertebral joints.

During inspiration both the anteroposterior and lateral diameters of the chest increase!

while on the left it is in the 5th intercostal space. Quiet breathing Inspiration (active) Expiration (passive) Note: The position of the central tendon and the heart resting on it is not changing during quiet breathing!!! In midposition (green) the right dome of the diaphragm reaches the level of the 5th rib, while on the left it is in the 5th intercostal space.

90° External and internal intercostal muscles are perpendicular to each other!

external intercostal internal intercostal

Take a deep breath and relax! It’s over!