A. Subcostal muscles. B. Transversus thoracis muscles.
Name of Muscle Origin Insertion Nerve Supply ActionExternal intercostal Inferior border of Superior Intercostal With first rib fixed, they raise ribs duringmuscle (11) (fibers pass rib border of nerves inspiration and thus increase anteroposteriordownward and forward ) rib below and transverse diameters of thoraxInternal intercostal Inferior border of Superior Intercostal With last rib fixed by abdominal muscles,muscle (11) (fibers pass rib border of nerves they lower ribs during expirationdownward and rib belowbackward)Innermost intercostal Adjacent ribs Adjacent Intercostal Assists external and internal intercostalmuscle (incomplete ribs nerves muscleslayer)Diaphragm (most Xiphoid process; Central Phrenic nerve Very important muscle of inspiration;important muscle of lower six costal tendon increases vertical diameter of thorax byrespiration) cartilages, first pulling central tendon downward; assists in three lumbar raising lower ribs vertebrae Also used in abdominal straining and weight liftingLevatores costarum (12) Tip of transverse Rib below Posterior rami Raises ribs and therefore inspiratory muscles process of C7 and of thoracic T1–T11 vertebrae spinal nervesSerratus posterior Lower cervical and Upper ribs Intercostal Raises ribs and therefore inspiratory musclessuperior upper thoracic nerves spinesSerratus posterior Upper lumbar and Lower ribs Intercostal Depresses ribs and therefore expiratoryinferior lower thoracic nerves muscles spines
ParacentesisSection through anintercostal space .B .Structures penetrated bya needle when it passesfrom skin surface to pleuralcavity. Depending on thesite of penetration, thepectoral muscles will bepierced in addition to theserratus anterior muscle .
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.• Each intercostal nerve enters an intercostal space between the parietal pleura and the posterior intercostal membrane. It then runs forward inferiorly with the intercostal vessels in the subcostal groove of the corresponding rib, between the innermost intercostal and internal intercostal muscle. 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. The 10th and 11th nerves, since the corresponding ribs are floating, pass directly into the abdominal wall.• Branches• Rami communicantes connect the intercostal nerve to a ganglion of the sympathetic trunk .The gray ramus joins the nerve medial at the point at which the white ramus leaves it.• The collateral branch runs forward inferiorly to the main nerve on the upper border of the rib below.• The lateral cutaneous branch reaches the skin on the side of the chest. It divides into an anterior and a posterior branch.• The 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 run to the intercostal muscles.• Pleural sensory branches go to the parietal pleura.• Peritoneal sensory branches 7 th to 11th intercostal nerves only) run to the parietal peritoneum.• 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 second intercostal nerve therefore supplies the skin of the armpit and the upper medial side of the arm. In coronary artery disease, pain is referred along this nerve to the medial side of the arm.• With the exceptions noted, the first six intercostal nerves therefore 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 addition, the 7th to the 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 Nerve Block• Area of Anesthesia& motor loss• The skin and the parietal pleura cover the outer and inner surfaces of each intercostal space, respectively; the 7th to 11th intercostal nerves supply the skin and the parietal peritoneum covering the outer and inner surfaces of the abdominal wall, respectively. Therefore, an intercostal nerve block will also anesthetize these areas. In addition, the periosteum of the adjacent ribs is anesthetized. Intercostal muscles supplied by this nerve will be weak.• Indications• Intercostal nerve block is indicated for repair of lacerations of the thoracic and abdominal walls, for relief of pain in rib fractures, and to allow pain-free respiratory movements.• Procedure• To produce analgesia of the anterior and lateral thoracic and abdominal walls, the intercostal nerve should be blocked before the lateral cutaneous branch arises at the midaxillary line.. Remember that the order of structures lying in the neurovascular bundle from above downward is intercostal vein, artery, and nerve and that these structures are situated between the posterior intercostal membrane of the internal intercostal muscle and the parietal pleura. Furthermore, laterally the nerve lies between the internal intercostal muscle and the innermost intercostal muscle.
• 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, a fingerbreadth lateral to the sternum, and 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. Those of the 2 nd, 3 rd, & 4 th spaces are important in the female for they supply the mammary gland.• 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 the costal margin of the diaphragm and supplies the lower intercostal spaces and the diaphragm• Internal Thoracic Vein• The internal thoracic vein accompanies the internal thoracic artery and drains into the brachiocephalic vein on each side.
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 artery, which is 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.• 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 space.A. Anterolateral view A. Anterolateral view.
B .Details of an intercostal space and relationships
Respiratory movements• One of the principal functions of the thoracic wall and the diaphragm is to alter the volume of the thorax and thereby move air in and out of the lungs.• 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. Depression results when the muscle fibers of the diaphragm contract. Elevation occurs when the diaphragm relaxes .• Changes in the anteroposterior and lateral dimensions result from elevation and depression of the ribs . When the ribs are elevated, they move the sternum upward and forward.• . When the ribs are depressed, the sternum moves downward and backward.• This ‘Pump handle type of movement changes the dimensions of the thorax in the anteroposterior direction• ‘Bucket handle movement of the ribs increases the lateral dimensions of the thorax• Any muscles attaching to the ribs can potentially move one rib relative to another and therefore act as accessory respiratory muscles. Muscles in the neck and the abdomen can fix or alter the positions of upper and lower ribs
Movement of thoracic wall during breathing. A. Pump handle movement of ribs and sternum.
Movement of thoracic wall during breathing. B. Bucket handle movement of ribs.
Respiratory movements& Flexible thoracic wall and inferior .thoracic aperture
• Needle Thoracostomy• A needle thoracostomy is necessary in patients with tension pneumothorax (air in the pleural cavity under pressure) or to drain fluid (blood or pus) away from the pleural cavity to allow the lung to re- expand. It may also be necessary to withdraw a sample of pleural fluid for microbiologic examination.• Lateral Approach• For the lateral approach, the patient is lying on the lateral side. The second intercostal space is identified & the anterior axillary line is used.• The skin is prepared in the usual way, and a local anesthetic is introduced along the course of the needle above the upper border of the third rib. The thoracostomy needle will pierce the following structures as it passes through the chest wall (a) skin, (b) superficial fascia (c) serratus anterior muscle, (d) external intercostal muscle, (e) internal intercostal muscle, (f) innermost intercostal muscle, (g) endothoracic fascia, and (h) parietal pleura.• The needle should be kept close to the upper border of the third rib to avoid injuring the intercostal vessels and nerve in the subcostal groove.• Tube Thoracostomy• The preferred insertion site for a tube thoracostomy is the fourth or fifth intercostal space at the anterior axillary line .The tube is introduced through a small incision. The neurovascular bundle changes its relationship to the ribs as it passes forward in the intercostal space. In the most posterior part of the space, the bundle lies in the middle of the intercostal space. As the bundle passes forward to the rib angle, it becomes closely related to the lower border of the rib above and maintains that position as it courses forward.• The introduction of a thoracostomy tube or needle through the lower intercostal spaces is possible provided that the presence of the domes of the diaphragm is remembered as they curve upward into the rib cage as far as the fifth rib (higher on the right). Avoid damaging the diaphragm and entering the peritoneal cavity and injuring the liver, spleen, or stomach.
Previous slide shows• Tube thoracostomy .A .The site for insertion of the tube at the anterior axillary line. The skin incision is usually made over the intercostal space one below the space to be pierced .B .The various layers of tissue penetrated by the scalpel and later the tube as they pass through the chest wall to enter the pleural cavity (space). The incision through the intercostal space is kept close to the upper border of the rib to avoid injuring the intercostal vessels and nerve .C .The tube advancing superiorly and posteriorly in the pleural space .
Section through anintercostal space .B .Structures penetrated bya needle when it passesfrom skin surface to pleuralcavity. Depending on thesite of penetration, thepectoral muscles will bepierced in addition to theserratus anterior muscle .
Diaphragm• The diaphragm is a thin muscular and tendinous septum that separates the chest cavity above from the abdominal cavity below . It is pierced by the structures that pass between the chest and the abdomen.• The diaphragm is the most important 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:• 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• vertebral part arising by vertical columns or crura and from the arcuate ligaments• 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 slinglike 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• As seen from in front, the diaphragm curves up into right and left domes, or cupulae. The right dome reaches as high as the upper border of the fifth rib, and the left dome may reach the lower border of the fifth rib.• Nerve Supply of the Diaphragm• 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. Action of the Diaphragm• On contraction, the diaphragm pulls down its central tendon and increases the vertical diameter of the thorax.
Openings in the Diaphragm• The diaphragm has three main openings:• The aortic opening lies anterior to the body of the 12th thoracic vertebra between the crura. It transmits the aorta, the thoracic duct, and the azygos vein.• The esophageal opening 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 third of the esophagus.• The caval opening lies at the level of the eighth thoracic vertebra in the central tendon.It transmits the inferior vena cava and terminal branches of the right phrenic nerve.• In addition to these openings, the sympathetic 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 costal origins of the diaphragm on each side.
Majorstructures passing between abdomen and thorax.
Diaphragm as seen from below. The anterior portion of the right side has been removed. Note the sternal,costal, and vertebral origins of the muscle and the important structures that pass through it .
Diaphragmatic HerniaeCongenital herniae occur as the result of incomplete fusion of the septum transversum, the dorsal mesentery, and thepleuroperitoneal membranes from the body wall. The herniae occur at the following sites: (a) the pleuroperitoneal canal(more common on the left side; caused by failure of fusion of the septum transversum with the pleuroperitonealmembrane), (b) the opening between the xiphoid and costal origins of the diaphragm, and (c) the esophageal hiatus.Acquired herniae may occur in middle-aged people with weak musculature around the esophageal opening in thediaphragm. These herniae may be either sliding or paraesophageal
Lines of Orientation• Several imaginary lines are sometimes used to describe surface locations on the anterior and posterior chest walls.• Midsternal line :Lies in the median plane over the sternum• Midclavicular line :Runs vertically downward from the midpoint of the clavicle• Anterior axillary line :Runs vertically downward from the anterior axillary fold• Posterior axillary line :Runs vertically downward from the posterior axillary fold• Midaxillary line :Runs vertically downward from a point situated midway between the anterior and posterior axillary folds• Scapular line :Runs vertically downward on the posterior wall of the thorax , passing through the inferior angle of the scapula (arms at the sides(
Questions Dr. Noura El Tahawy1. Enumerate the important muscles of normal respiration. - Mention the action of each muscle & its role in changing the diameters of the chest during respiration2. Give short account on the anatomy of the internal thoracic artery (origin, course, branches & termination)3. Complete the following statements: A. ---- The Internal mammary artery arises from ………………………………..……. … Its branches include: 1. ………. 2………… 3……….. 4…………… 5……… B ----- The anterior intercostal arteries arise from: 1…………….. 2…………….. C ----- The posterior intercostal arteries arise from: 1. ………………… 2…………………. D--- . The posterior intercostal veins drain into ………….…& …… veins while the anterior intercostal veins drain into ……………. & ……………. veins E ------ A needle inserted into the pleural cavity at the anterior axillary line will pass through the following structures: 1. ……….. 2……… 3………. 4………… 5. ……. 6…….. 7…….. 8 ……..
Questions Dr. Noura El Tahawy 3. Complete the following statements: (cont.) F. Branches of the typical Intercostal nerve include: 1…….. 2……3……4….……… G----- Intercostal nerve block at the level of the second intercostal space will result in: 1. ……………. & 2 …………….. H…. The nerve supply of the diaphragm include: 1. ………………….. 2……………….. I. The vena caval opening of the diaphragm is locate at the level of ………… vertebra. The opening transmits the following structures 1….. ………2 …… J.. The aortic opening of the diaphragm is located at the level of ……….. vertebra. The opening transmits the following structures 1………… 2……….. 3……. K. The esophageal opening of the diaphragm lies opposite ………….... vertebra. It transmits 1…….. 2……….3……………. L.. The diaphragm originated from …….., ……………, ………… & inserted into …… M. The contraction of the diaphragm leads to …..………….. diameter of chest during……… while its relaxation leads to …………….diameter of the chest during ………..
References• 1- Richard Snell; Clinical Anatomy by regions; Eighth Edition; 2008• 2. Drake et al., Grays Anatomy for Students., 2005.