Thorax Second Lecture PDF

Second lecture of thorax @barhoom261  Intercostal arteries and veins  Each intercostal space contains a large single posterior intercostal artery and two small anterior intercostal arteries.  The posterior intercostal arteries of the first two spaces are branches from the supe...

Second lecture of thorax @barhoom261  Intercostal arteries and veins  Each intercostal space contains a large single posterior intercostal artery and two small anterior intercostal arteries.  The posterior intercostal arteries of the first two spaces are branches from the superior intercostal a., a branch of the costocervical trunk of the subclavian a. The posterior intercostal arteries of the lower nine spaces are branches of the descending thoracic aorta.  The anterior intercostal arteries of the first six spaces are branches of the internal thoracic a. The anterior intercostal arteries of the lower spaces are branches of the musculophrenic a., one of the terminal branches of the internal thoracic a.  Each intercostal a. gives off branches to the muscles, skin, and parietal pleura.  The corresponding posterior intercostal veins drain backward into the azygos or hemiazygos veins, and the anterior intercostal veins drain forward into the internal thoracic and musculophrenic veins.  Intercostal nerves  They are the anterior rami of the first 11 thoracic spinal nerves. The anterior ramus of the twelfth thoracic n. lies in the abdomen and runs forward in the abdominal wall as the subcostal n.  Each intercostal n. enters an intercostal space between the parietal pleura and the posterior intercostal membrane. It then runs forward inferiorly to the intercostal vessels in the subcostal groove of the corresponding rib, between the innermost intercostal and internal intercostal m. The first six nerves are distributed within their intercostal spaces. The seventh to ninth intercostal nerves leave the anterior ends of their intercostal spaces by passing deep to the costal cartilages, to enter the anterior abdominal wall. In the case of the tenth and eleventh nerves, since the corresponding ribs are floating, these nerves pass directly into the abdominal subcostal n.  Branches of intercostal n.  Rami communicantes: connect the intercostal n. to a ganglionof the sympathetic trunk.  Collateral branch: which runs forward inferiorly to the main. nerve on the upper border of the rib below.  Lateral cutaneous branch: which reaches the skin on the side ofthe chest. It divides into an anterior and a posterior branch.  Anterior cutaneous branch: which is the terminal portion of the main trunk, reaches the skin near the midline. It divides into a medial and a lateral branch.  Muscular branches: are numerous branches given off by themain nerve and its collateral branch.  Pleural sensory branches: to the parietal pleura.  Peritoneal sensory branches: to the parietal peritoneum(seventh to eleventh intercostal nerves only).  The first intercostal n. is joined to the brachial plexus by a large branch that is equivalent to the lateral cutaneous branch of typical intercostal nerves. The remainder of the first intercostal n. is small, and there is no anterior cutaneous branch  The second intercostal n. is joined to the medial cutaneous n. of the arm by a branch called the intercostobrachial n., that is equivalent to the lateral cutaneous branch of other nerves. The second intercostal n. therefore supplies the skin of the axilla and the upper medial side of the arm. With the exceptions noted, the first six intercostal nerves therefore supply:  A-the skin and the parietal pleura covering the outer and inner surfaces of each intercostal space, respectively  B- the intercostal muscles of each intercostal space and the levatores costarum and serratus posterior muscles  in addition, the seventh to the eleventh intercostal nerves supply: 1-the skin and the parietal peritoneum covering the outer and inner surfaces of the abdominal wall, respectively, 2- the anterior abdominal muscles which include the external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles.  Suprapleural membrane  Superiorly, the thorax opens into the root of the neck by a narrow aperture it is bounded by the superior border of the manubrium sterni, by the medial borders of the first ribs, and by the body of the first thoracic vertebra.  the thoracic outlet transmits structures that pass between the thorax and the neck (esophagus, trachea, blood vessels, etc.) And for the most part lie close to the midline.  on either side of these structures the outlet is closed by a dense facial layer called the suprapleural membrane.  this tent-shaped fibrous sheet is attached laterally to the medial border of the first rib and costal cartilage. It is attached at its apex with the tip of the transverse process of the 7th cervical vertebra and medially to the fascia investing the structures passing from the thorax into the neck. it protects the underlying cervical pleura and resists the changes in intrathoracic pressure occurring during respiratory movements.  Endothoracic fascia: Is a thin layer of loose connective tissue that separates the parietal pleura from the thoracic wall. The suprapleural membrane is the thickening of this fascia. Diaphragm Inferiorly, the thorax opens into the abdomen by a wide opening. It is bounded by the xiphisternal joint, the costal margin and the body of the 12th thoracic vertebra. it is closed by a muscular and tendinous septum, the diaphragm, which is pierced by the structures that pass between the thorax and the abdomen.  The diaphragm is the primary muscle of respiration. it is Dome- shaped and consists of a peripheral muscular part which arises from the margins of the thoracic opening and a centrally placed tendon.  the origin of the diaphragm can be divided into three parts: 1-Sternal part: consisting of small right and left slips arising from the posterior surface off the xiphoid process. 2-Costal part: consisting of six slips that arise from the deep surfaces of the lower six ribs and their costal cartilages. 3-vertebral part: arising by means of vertical columns or crura and from the arcuate ligaments.  The right crus arise from the sides of the bodies of the first three lumbar vertebrae and the intervertebral discs; the left crus arise from the side of the bodies of the first two lumbar vertebrae and the intervertebral disc.  Lateral to the crura the diaphragm arises from the medial and lateral arcuate ligament. The medial arcuate ligament extends from the side of the body of the second lumbar vertebrae to the tip of the transverse process of the first lumbar vertebra. The lateral arcuate ligament extends from the tip of the transverse process of the first lumbar vertebra to the lower border of the 12th rib.  The fibrous medial borders of the two crura are connected by a median arcuate ligament which crosses over the anterior surface of the aorta.  The diaphragm is inserted into a central tendon which is shaped like three leaves. The superior surface of the tendon is partially fused with the inferior surface of the fibrous pericardium. Some of the muscle fibers of the right crus pass up to the left and surround the esophageal orifice in a sling-like loop. These fibers appear to act as a sphincter and possibly assist in the prevention of regurgitation of the stomach contents into the thoracic part of the esophagus.  Shape of the diaphragm  As seen in front, the diaphragm curves up into right and left domes. The right Dome reaches as high as the upper border of the 5th rib, and the left Dome may reach the lower border of the 5th rib. The right dome lies at a higher level probably because of the large size of the right lobe of the liver. The central tendon lies at the level of the xiphisternal joint. The domes support the right and left lungs, whereas the central tendon supports the heart. The levels of the diaphragm vary with the phase of respiration, the posture, and the degree of distention of the abdominal viscera. the diaphragm is lower when a person is sitting or standing; it is higher in the supine position and after a large meal.  When seen from the side the diaphragm has the appearance of an inverted J the long limb extending up from the vertebral column and the short limb extending forward to the xiphoid process.  Openings in the diaphragm:)‫(مهمين ركز عليهم دكتور‬ The diaphragm has three main openings: 1. aortic opening: which lies anterior to the body of the 12th thoracic vertebra between the crura. It transmits the aorta the thoracic duct and the azygos vein. 2. Esophageal opening: which lies at the level of the 10th thoracic vertebra in a sling of muscle fibers derived from the right crus. It transmits the esophagus the right and left vagus nerves, the esophageal branches of the left gastric vessels and the lymphatics from the lower 1/3 of the esophagus. 3. Caval opening: which lies at the level of the 8th thoracic vertebra in the the central tendon. It transmits the inferior vena cava and terminal branches of the right phrenic n. Other openings: The greater, lesser, and lowest splanchnic nerves pierce the crura; the sympathetic trunks pass posterior to the medial arcuate ligament on each side; and the superior epigastric vessels pass between the sternal and coastal origins of the diaphragm on each side. The left phrenic nerve pierces the left Dome to supply the peritoneum on its undersurface, and the neurovascular bundles of the 7th to the 11th intercostal spaces pass into the anterior abdominal wall between the muscular slips of the costal origin of the diaphragm. DONE(: any question text me @barhoom261 Lets check your knowledge  Lets check your knowledge The intercostal neurovascular bundle is located: A. Above the superior border of the ribs. B. Superficial to the ribs anteriorly. C. In the costal (subcostal) groove. D. Superficial to the anterior intercostal membrane. E. Between the external and internal intercostal muscles.  Activity Imagine a knife passing through the thoracic wall into the lung through an intercostal space. Which is the correct order of layers through which it passes (from superficial to deep)? What is intercostal neuralgia: symptoms, causes, treatment?