Lecture 1- Thorax Lecture Notes PDF

 Thorax  Is the region of the body that lies between the neck above and the abdomen below.  Its flattened in front & behind but its rounded on each sides.  Frame work of the wall of the thorax called thoracic cage and is formed by: Sternum & costal cartilage in front. Ribs & interc...

 Thorax  Is the region of the body that lies between the neck above and the abdomen below.  Its flattened in front & behind but its rounded on each sides.  Frame work of the wall of the thorax called thoracic cage and is formed by: Sternum & costal cartilage in front. Ribs & intercostal spaces on each side. Vertebral column behind. Superiorly its narrow & communicate with the neck. Inferiorly its broad and separated from the abdomen by the diaphragm.  Space inside thoracic cage called Thoracic cavity. Floor of the thoracic cavity is pushed upward by organs of the abdominal cavity so lower part of the thoracic cage surround & protect abdominal rather than the thoracic organs (e.g liver). Contain: - Primary organs of the respiratory & cardiovascular organs. - Largest portion of the cavity contain lungs & reminder of the thoracic cavity contain heart & other structure involving in the conducting of the air and blood to and from the lungs. - Nutrients (food) traverse the thoracic cavity via the esophagus, passing from the site of entry in the head to the site of digestion and absorption in the abdomen. 3 5  The thoracic cavity is divided into three major spaces: A. The median portion or mediastinum that contain the thoracic viscera except for the lungs B. on each side, the right and left pulmonary cavities that contain the lungs. Function of the thoracic cage: 1. Protect the thoracic viscera ( heart & lung) & some of the abdominal organs. 2. Provide attachment for and support the weight of the upper limbs. 3. Provide attachment sites for muscles of the thorax, upper limb, abdomen, neck, back. 4. Resist intrathoracic pressure generated by the respiratory movement. 3 6  The thoracic wall is covered on the outside by skin and by muscles attaching the shoulder girdle to the trunk. It is lined with parietal pleura.  Thoracic wall Superficial structures Skin Superficial fascia contains breast Deep structures Deep fascia Muscles of thorax Subclavius Pectoralis major Pectoralis minor Serratus anterior Intercostales externi Intercostales interni Intercostales intimi Endothoracic fascia Lined by pariatal pleura  The thoracic wall consists of skeletal elements and muscles: Posteriorly, it is made up of twelve thoracic vertebrae and their intervening intervertebral discs; Laterally, the wall is formed by ribs (twelve on each side) and three layers of flat muscles, which span the intercostal spaces between adjacent ribs, move the ribs, and provide support for the intercostal spaces; Anteriorly, the wall is made up of the sternum,  Sternum Flat bone, divide to manubrium sterni, body of the sternum, and xiphoid process. Upper part, articulates with the body of the sternum at the manubriosternal joint, and it also articulates with the clavicles and with the 1st costal cartilage and the upper part of the 2nd costal cartilages on each side. It lies opposite the 3rd and 4th thoracic vertebrae. The superior surface of the manubrium is expanded laterally and bears a distinct and palpable notch, the jugular notch (suprasternal notch), in the midline.  The body of the sternum articulates above with the manubrium at the manubriosternal joint and below with the xiphoid process at the xiphisternal joint. On each side, it articulates with the 2nd to the 7th costal cartilages. xiphoid process is a thin plate of cartilage that becomes ossified at its proximal end during adult life. On each side of its upper lateral margin is a demifacet for articulation with the inferior end of the seventh costal cartilage.  The sternal angle (angle of Louis), at the level of the 2nd costal cartilage, lies opposite the intervertebral disc between the 4th and 5th thoracic vertebrae. The xiphisternal joint lies opposite the body of the ninth thoracic vertebra.  General Characteristics of typical Vertebra  Typical vertebra consists of a rounded body anteriorly and a vertebral arch posteriorly. These enclose a space called the vertebral foramen.  The vertebral arch gives rise to seven processes: one spinous, two transverse, and four articular.  The two superior articular processes of one vertebral arch articulate with the two inferior articular processes of the arch above, forming two synovial joints.  The pedicles are notched on their superior and Inferior borders, forming the superior and inferior Vertebral notches. On each side, the superior notch of one vertebra and the inferior notch of an adjacent Vertebra together form an intervertebral foramen.  Joints of the Vertebral Column  The atlanto-occipital joints are synovial joints.  The atlantoaxial joints are synovial joints.  With the exception of the first two cervical vertebrae, the remainder of the mobile vertebrae articulates with each other by means of cartilaginous joints between their bodies and by synovial joints between their articular processes.  Thoracic vertebrae  Typical thoracic vertebra - 2-9 - Body: heart shape, sup & inf. demifacet for head of ribs - Vertebral arch consist of pedicle and lamina. - Spine: longest, pointed directed back and down - Transverse process: Thick & has complete facet for tubercle of the corresponding rib - Articular facet: sup>> up & back Inf>> down & ant - Vertebral foramen small and circular.  Atypical thoracic vertebra 1st thoracic vertebra -Complete facet on body -Complete facet on transverse process -Inferior demifacet 10 thoracic vertebra Complete facet on its body 11 thoracic vertebra -body: complete facet -Transverse process: small& no facet for tubercle of rib -Flat inferior articular facet 12 Thoracic vertebra -body: complete facet -Transverse process: small& no facet for tubercle of rib -Convex inferior articular facet  Ribs  There are 12 pair of ribs.  All attached posteriorly to the thoracic vertebrae. Sternum  Ist and last rib is difficult to True Ribs (7) palpate.  Counting of ribs begin from the 2nd False Ribs (3)  Classification. Floating Ribs (2)  In relation to sternum 1. True ribs: first 7 2. False ribs: 8,9,10, costal cartilage to the 7th rib. 3. Floating ribs: 11 and 12, no anterior attachment.  In relation to vertebral column 4. Typical ribs: 3-9 5. Atypical ribs: 1, 2, 10, 11  Typical ribs  Long, twisted, flat bone having a rounded, smooth superior border and a sharp, thin inferior border.  The inferior border overhangs and forms the costal groove.  The anterior end of each rib is attached to the corresponding costal cartilage.  A rib has a head, neck, tubercle, shaft, and angle.  Head: two facets for articulation with the numerically corresponding vertebral body and that of the vertebra immediately above.  Neck: portion situated between the head and the tubercle.  Tubercle: prominence on the outer surface of the rib at the junction of the neck with the shaft, facet for articulation with the transverse process of the numerically corresponding vertebra, and raised non- articular part is roughened by ligament attachments.  Shaft: thin and flattened and twisted on its long axis. Its inferior border has the costal groove. The angle is where the shaft of the rib bends sharply forward.  Atypical ribs  1st Rib Small and flattened, shortest, and most sharply curved of the seven true ribs. 1st rib is close to the brachial plexus and the main vessels. Anterior Scalene attached to it, subclavian vein crosses anterior and subclavian artery and the lower trunk of the brachial plexus cross posterior. It has a single facet on its head for articulation with the T1 vertebra.  Long neck Body has 2 surfaces: 1. Lower surface smooth 2. Upper surface rough  Has scalene tubercle that inserted to it scalenus anterior muscle, which separates two grooves.  Anterior to the scalenus anterior, the subclavian vein crosses the rib; posterior to the muscle attachment, the subclavian artery and the lower trunk of the brachial plexus cross the rib and lie in contact with the bone.  Atypical ribs  Rib 2nd  Atypical ribs  10, 11, and 12 Ribs  Costal cartilage  Bars of hyaline cartilages, give elasticity of the thoracic cage which decreases with age due to superficial calcification  1- 7 ribs connect with sternum  8th, 9th, 10th, connect with 7th c.c  11th, 12th c.c embedded on abdominal muscles.  Joint Between ribs and costal cartilage- synovial joint.  Openings of the Thorax  Superior Thoracic Aperture (INLET):  It is an entrance to the thorax completely surrounded by skeletal elements, which are : The body of vertebra T1 posteriorly. The medial margin of the first rib on each side The manubrium anteriorly. The superior margin of the manubrium is in approximately the same horizontal plane as the intervertebral disc between vertebrae TII and TIII.  The opening is obliquely placed facing upward and forward. Because of the obliquity of the opening, the apices of the lung and pleurae project upward into the neck.  Through it pass: Trachea, esophagus, nerves, vessels, apex of the lung and pleura.  Openings of the Thorax  Inferior Thoracic Aperture (OUTLET):  Body of vertebra T12 posteriorly,  12th rib and the distal end of 11th rib posterolaterally,  Distal cartilaginous ends of ribs 7 to 10, which unite to form the costal margin anterolaterally,  The xiphoid process anteriorly.  It’s closed by the diaphragm, and structures passing between the abdomen and thorax pass posteriorly to the diaphragm.  Through it pass: Esophagus, large vessels and nerves, all of which pierce the diaphragm.  Joints of the Chest Wall  Joint of the sternum: 1. Manubriosternal joint Small amount of angular movement is possible during respiration. Articulation between manubrium and body of sternum Secondary cartilaginous joint (symphysis). 2. Xiphisternal joint Usually fuse in middle age (about 40), symphyses type. Articulation between xiphoid process and  Joint of the costal cartilages with the Sternum: The 1st costal cartilages articulate with the manubrium, by 1st primary cartilaginous (synchondrosis) joints that permit no movement, fibrocartilaginous not synovial. The 2nd to 7th costal cartilages articulate with the lateral border of the sternum by synovial plane joints, called sternocostal joints, synovial and have thin capsules reinforced by surrounding sternocostal ligaments. In addition, the 6th, 7th, 8th, 9th, and 10th costal cartilages articulate with one another along their borders by small synovial plane joints, called Interchondral joints. The cartilages of the 11th and 12th ribs are  Joint of the Ribs: 1. Joint of the rib with the costal cartilage Articulation between lateral end of costal cartilage and sternal end of rib. Costochondral joint are primary (hyaline) cartilaginous joint. No movement is possible. 2. Joint of the head of the ribs 1st rib and the three lowest ribs have a single synovial plane joint with their corresponding vertebral body. 2nd to 9th ribs, the head articulates by means of a synovial joint with the corresponding vertebral body and that of the vertebra above it. Strong intraarticular ligament that connects the head to the intervertebral disc. 3. Joints of the Tubercles of the ribs Articulation between tubercle of rib with transverse process of vertebra of same number. Called costotransverse joint. Synovial plane joint Absent in the lower 2 ribs  Intercostal spaces  Contain three muscles of respiration: the external intercostal, the internal intercostal, and the innermost intercostal muscle.  The innermost intercostal muscle is lined internally by the endothoracic fascia, which is lined internally by the parietal pleura.  The intercostal nerves and blood vessels run between the intermediate and deepest layers of muscles.  They are arranged in the following order from above downward: intercostal vein, intercostal artery, and intercostal nerve (i.e., VAN). The nerve is the least protected.  Intercostal Muscles  External intercostal muscle Forms the most superficial layer. Its fibers are directed downward and forward from the inferior border of the rib above to the superior border of the rib below. Anteriorly forms aponeurosis called anterior (external) intercostal membrane. Innervation- Intercostal nerves; T1–T11 Action - Most active during inspiration; supports intercostal space; moves ribs superiorly  Internal intercostal muscle Forms the intermediate layer. Its fibers are directed downward and backward from the subcostal groove of the rib above to the upper border of the rib below. The muscle extends backward from the sternum in front to the angles of the ribs behind, where the muscle is replaced by an aponeurosis, the posterior (internal) intercostal membrane. Innervation- Intercostal nerves; T1– T11 Action - Most active during expiration; supports intercostal space; moves ribs inferiorly  The innermost intercostal muscle Forms the deepest layer and corresponds to the transversus abdominis muscle in the anterior abdominal wall. It is an incomplete muscle layer and crosses more than one intercostal space within the ribs. It is related internally to fascia (endothoracic fascia) and parietal pleura and externally to the intercostal nerves and vessels. The innermost intercostal muscle can be divided into three portions, which are more or less separate from one another. Innervation- Intercostal nerves; T1–T11 Action - Acts with internal intercostal muscles  Intercostal VAN  Intercostal Nerves The intercostal nerves are the anterior rami of the first 11 thoracic spinal nerves. The anterior ramus of the 12th thoracic nerve lies in the abdomen and runs forward in the abdominal wall as the subcostal nerve. Intercostal nerves can be classified: 1. Typical intercostal nerves (3- 6) 2. Atypical intercostal nerves (others) 1. Typical intercostal nerves (3-6) Enter medial part of the posterior intercostal spaces and runs in the endothoracic facia between the parietal pleura and the posterior intercostal membrane of the internal intercostal muscle. Then runs forward inferiorly to the intercostal vessels in the subcostal groove of the corresponding rib, between the innermost intercostal and internal intercostal muscle. Near angel of the rib gives off collateral branch.  Then runs forward and at the midaxillary line gives off lateral cutaneous branch to the skin on the side of the chest. Lateral to the sternum, it pierces layers and end as anterior cutaneous branch, that divides into a medial and a lateral branch. Branches  Rami communicantes connect the intercostal nerve to a ganglion of the sympathetic trunk.  Collateral branch  Lateral cutaneous branch  Anterior cutaneous branch  Muscular branch  Pleural sensory branches go to the parietal pleura.  Peritoneal sensory branches (7th to 11th intercostal nerves only) run to the parietal peritoneum. 1. Atypical intercostal nerves  The first intercostal nerve 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 nerve is small, and there is no anterior cutaneous branch.  The second intercostal nerve is joined to the medial cutaneous nerve of the arm by a branch called the intercostobrachial nerve, which is equivalent to the lateral cutaneous branch of other nerves. The 2nd intercostal nerve therefore supplies the skin of the armpit and the upper medial side of the arm.  The 7th–11th intercostal nerves, after giving rise to lateral cutaneous branches, cross the costal margin posteriorly and continue on to supply abdominal skin and muscles  1st six intercostal nerves supply the skin and the parietal pleura covering the outer and inner surfaces of each intercostal space, respectively, and the intercostal muscles of each intercostal space and the levatores costarum and serratus posterior muscles.  In the 7th to 11th intercostal nerves supply the skin and the parietal peritoneum covering the outer and inner surfaces of the abdominal wall, respectively, and the anterior abdominal muscles, which include the external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles.  Intercostal Arteries  Internal Thoracic Artery  The internal thoracic artery supplies the anterior wall of the body from the clavicle to the umbilicus.  It is a branch of the first part of the subclavian artery in the neck.  It descends vertically on the pleura behind the costal cartilages, afinger breadth lateral to the sternum.  Ends in the sixth intercostal space by dividing into the superior epigastric and musculophrenic arteries.  Branches Two anterior intercostal arteries for the upper six intercostal spaces Perforating arteries, which accompany the terminal branches of the corresponding intercostal nerves The pericardiacophrenic artery, which accompanies the phrenic nerve and supplies the pericardium Mediastinal arteries to the contents of the anterior mediastinum (e.g., the thymus) The superior epigastric artery, which enters the rectus sheath of the anterior abdominal wall and supplies the rectus muscle as far as the umbilicus The musculophrenic artery, which runs around  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 artery, a branch of the costocervical trunk of the subclavian artery. 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 artery which arises from the first part of the subclavian artery. The anterior intercostal arteries of the lower spaces are branches of the musculophrenic artery, one of the terminal branches of the internal thoracic artery.  Each intercostal artery gives off branches to the muscles, skin, and parietal pleura. In the region of the breast in the female, the branches to the superficial structures are particularly large.  Intercostal veins 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 the musculophrenic veins.  Muscles of the thoracic wall  Accessory muscle that help elevate ribs to expand thoracic cavity during deep inspiration: 1. Axio-appendicular muscles that extend from thorax to the upper limb (Pectoralis major, minor, and serratus anterior). 2. Some of the anterolateral abdominal wall muscles (External oblique, rectus abdominis). 3. Back and neck muscles (scalenus muscles).  True muscles of the thoracic wall 1. Serratus posterior muscle – superior and inferior. 2. Levatores Costarum muscle. 3. Intercostal muscles. 4. Subcostal muscle. 5. Transversus thoracis muscles (sternocostalis) 1. Levatores Costarum: 12 pairs, triangular in shape and arises by its apex from the tip of the transverse process and is inserted into the rib below. Action: Each raises the rib below and is therefore an inspiratory muscle. Nerve supply: Posterior rami of thoracic spinal nerves. 2. Serratus Posterior Superior Muscle: Thin, flat muscle that arises from the lower cervical and upper thoracic spines (Nuchal ligament and C7 to T3). Its fibers pass downward and laterally and are inserted into the upper ribs (2nd to 5th). Action: It elevates the ribs and is therefore an inspiratory muscle. Nerve Supply: Intercostal nerves. - Serratus Posterior Inferior Muscle: Thin, flat muscle that arises from the upper lumbar and lower thoracic spines (T 12 to L2). Its fibers pass upward and laterally and are inserted into the lower ribs near the angles (8th to 12th). Action: It depresses the ribs and is therefore an expiratory muscle. Nerve Supply: Intercostal nerves. 3. Subcostal muscle Superior Attachment: Internal surface of lower ribs near their angles Inferior Attachment: Superior borders of 2nd or 3rd ribs below Probably Innervation: Intercostal nerve Main Action : as internal Intercostal muscles  4.Transversus thoracis muscles (sternocostalis) The transversus thoracis muscles are found on the deep surface of the anterior thoracic wall and in the same plane as the innermost intercostals. O: from the posterior aspect of the xiphoid process, the inferior part of the body of the sternum, and the adjacent costal cartilages of the lower true ribs. I: They pass superiorly and laterally to insert into the lower borders of the costal cartilages of ribs 3 to 4. Innervation : Related costal nerves Function: Depresses costal cartilages. The transversus thoracis muscles lie deep to the internal thoracic vessels  Diaphragm  Thin muscular and tendinous septum that separates the chest cavity above from the abdominal cavity below. Most important muscle of respiration. Dome Shaped Peripheral muscles and central tendon  A sternal part arising from the posterior surface of the xiphoid process.  A costal part arising from the deep surfaces of the lower six ribs and their costal cartilages.  A vertebral part arising by vertical columns or crura and from the arcuate ligaments.  The right crus arises from the sides of the bodies of the first three lumbar vertebrae and the intervertebral discs; The left crus arises from the sides 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 ligaments.  The medial arcuate ligament extends from the side of the body of the second lumbar vertebra 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 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. Shape of the Diaphragm Right and left domes. Right upper border of the 5th rib, left lower border of the 5th rib. 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. Levels change with respiration and distention of the abdominal viscera. Arterial blood supply The arterial supply to the diaphragm is from vessels that arise superiorly and inferiorly to it. From above, pericardiacophrenic and musculophrenic arteries supply the diaphragm. These vessels are branches of the internal thoracic arteries. Superior phrenic arteries, which arise directly from lower parts of the thoracic aorta, and small branches from intercostal arteries contribute to the supply. The largest arteries supplying the diaphragm arise from below it. These arteries are the inferior phrenic arteries, which branch directly from the abdominal aorta. Venous Drainage Venous drainage of the diaphragm is by veins that generally parallel the arteries. The veins drain into:  The brachiocephalic veins in the neck  The azygos system of veins, or  Abdominal veins (left suprarenal vein and inferior vena cava). Nerve supply Motor nerve supply: The right and left phrenic nerves (C3, 4, 5). Sensory nerve supply: The parietal pleura and peritoneum covering the central surfaces of the diaphragm are from the phrenic nerve and the periphery of the diaphragm is from the lower six intercostal nerves. Openings of the Diaphragm Aortic opening: T 12 between the crura, transmits the aorta, the thoracic duct, and the azygos vein. Esophageal opening: T 10 sling of muscles, transmits the esophagus, the right and left vagus nerves, the esophageal branches of the left gastric vessels, and the lymphatics from the lower third of the esophagus. Caval opening: T 8 central tendon, transmits the inferior vena cava and terminal branches of the right phrenic nerve. Action On contraction, the diaphragm pulls down its central tendon and increases the vertical diameter of the thorax. During breathing, the dimensions of the thorax change in the vertical, lateral, and anteroposterior directions. Elevation and depression of the diaphragm significantly alter the vertical dimensions of the thorax.  Changes in the anteroposterior and lateral dimensions result from elevation and depression of the ribs. Because the anterior ends of the ribs are inferior to the posterior ends, when the ribs are elevated, they move the sternum upward and forward. Also, the angle between the body of the sternum and the manubrium may become slightly less acute. When the ribs are depressed, the sternum moves downward and backward. This “pump handle” movement changes the dimensions of the thorax in the anteroposterior direction.  As well as the anterior ends of the ribs being lower than the posterior ends, the middles of the shafts tend to be lower than the two ends. When the shafts are elevated, the middles of the shafts move laterally. This “bucket handle” movement increases the lateral dimensions of the thorax. Clinical Correlation Diaphragmatic paralysis In cases of phrenic nerve palsy, diaphragmatic paralysis ensues, which is manifested by the elevation of the diaphragm muscle on the affected side. The most important cause of the phrenic nerve palsy that should never be overlooked is malignant infiltration of the nerve by lung cancer. Other causes include postviral neuropathy (in particular, related to varicella zoster virus), trauma, iatrogenic injury during thoracic surgery, and degenerative changes in the cervical spine with compression of the C3–C5 nerve roots.  Clinical Correlation Cervical ribs Cervical ribs are present in approximately 1% of the population. A cervical rib is an accessory rib articulating with vertebra CVII; the anterior end attaches to the superior border of the anterior aspect of rib I. Plain radiographs may demonstrate cervical ribs as small horn-like structures. Clinically, “thoracic outlet syndrome” is used to describe symptoms resulting from abnormal compression of the brachial plexus of nerves as it  Clinical Collection correlation of sternal bone marrow The subcutaneous position of the sternum makes it possible to place a needle through the hard outer cortex into the internal (or medullary) cavity containing bone marrow. Once the needle is in this position, bone marrow can be aspirated. Evaluation of this material under the microscope helps clinicians diagnose certain blood diseases  Clinical Correlation Rib fractures Single rib fractures are of little consequence, though extremely painful. After severe trauma, ribs may be broken in two or more places. If enough ribs are broken, a loose segment of chest wall, a flail segment (flail chest), is produced. When the patient takes a deep inspiration, the flail segment moves in the opposite direction to the chest wall, preventing full lung expansion and creating a paradoxically moving segment. If a large enough segment of chest wall is affected, ventilation may be impaired and assisted ventilation may be required until the ribs have healed.