Thorax Anatomy (PDF)

THORAX  The region of the thorax The thorax (or chest) is the region of the body between the neck and the abdomen. The bonny framework of the walls of the thorax, is formed by the vertebral column behind, the ribs and intercostal spaces on either side, and the sternum and cost...

THORAX  The region of the thorax The thorax (or chest) is the region of the body between the neck and the abdomen. The bonny framework of the walls of the thorax, is formed by the vertebral column behind, the ribs and intercostal spaces on either side, and the sternum and costal cartilages in front. It communicates with the neck Superiorly , and the abdomen inferiorly separated by the diaphragm. it protects the lungs and heart and affords attachment for the muscles of the thorax, upper extremity, abdomen, and back. Structure of the Thoracic cage  Structure of the Thoracic Wall 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 on the inside The thoracic wall is formed by: Posteriorly:- thoracic part of the vertebral column Anteriorly:- the sternum and costal cartilages Laterally:- the ribs and intercostal spaces superiorly:- by the suprapleural membrane; Inferiorly:- by the diaphragm, which separates the thoracic cavity from the abdominal cavity Bonny structure of the thoracic wall  Thoracic openings. apertures Thoracic cavity has two main apertures –superior and inferior Superior Thoracic Aperture It is the anatomical oblique thoracic inlet, is bounded as follows – Posteriorly:- by vertebra T1 – Laterally:- by the 1st pair of ribs and their costal cartilages. – Anteriorly:- by the superior border of the manubrium Inferior Thoracic Aperture The inferior thoracic aperture is the anatomical thoracic outlet, is bounded as follows: – Posteriorly:- by the 12th thoracic vertebra (posterior landmark). – Posterolaterally:- by the 11th and 12th pairs of ribs. – Anterolaterally:- by the joined costal cartilages of ribs 7 and 10, forming the costal margins. – Anteriorly:- by the xiphisternal joint (anterior landmark).  The sternum The sternum is a flat bone that lies in the midline of the anterior chest wall. It can be divided into three parts: manubrium sterni, body of the sternum, and xiphoid process It articulates with the 1st to 7th ribs Jugular notch lies btn 2nd and 3rd intervertebral disc Sternal angle btn 4th and 5th intervertebral disc Xiphisternal joint btn 8th and 9th intervertebral disc  The ribs RIBS are curved, flat bones that form anterolateral bones of the thoracic cage They are remarkably light in weight yet highly resilient. Each rib has a spongy interior containing bone marrow (hematopoietic tissue), which forms blood cells. There are three types of rib: 1. True (vertebrocostal) ribs (1st to 7th ribs): They attach directly to the sternum through their own costal cartilages. 2. False (vertebrochondral) ribs (8th, 9th, and usually 10th ribs): Their cartilages are connected to the cartilage of the rib above them; thus their connection with the sternum is indirect. 3. Floating (vertebral, free) ribs (11th, 12th, and sometimes 10th ribs): The rudimentary cartilages of these ribs do not connect even indirectly with the sternum; instead they end in the posterior abdominal musculature.  Structure of a rib Morphologically ribs can be classified into two:- typical and atypical Features of Typical ribs (3rd -9th ribs) 1. Head: that is wedge-shaped and has two facets, separated by the crest of the head. 2. Neck: that connects the head with the body at the level of the tubercle. 3. Tubercle: at the junction of the neck and body and has a smooth articular part, for articulating with the corresponding transverse process of the vertebra, and a rough non-articular part, for attachment of the costotransverse ligament. 4. Body (shaft): thin, flat, and curved, most markedly at the costal angle where the rib turns anterolaterally the concave internal surface of the body has a costal groove paralleling the inferior border of the rib, which provides some protection for the intercostal nerve and vessels. Features of a typical rib  Atypical ribs (1st, 2nd, and 10th and 12th) The 1st rib: (a) is the broadest (i.e., its body is widest and nearly horizontal), (b) shortest, (c)the most sharply curved of the seven true ribs. (d) has a single facet on its head for articulation with the T1 vertebra only (e) it has two transverse grooves crossing its superior surface for the subclavian vessels;(f) the grooves are separated by a scalene tubercle and ridge, to which the anterior scalene muscle is attached. The 2nd rib: (a) it has no costal gloove (b) its has a rough area on its upper surface, the tuberosity for serratus anterior, from which part of that muscle originates. The 10th and 12th ribs:- (a) like the 1st rib, have only one facet on their heads and articulate with a single vertebra. The 11th and 12th ribs:- are short and have no neck or tubercle Sternal costal joints  Cervical ribs Cervical ribs are usually attached to the seventh cervical vertebra They are of three types 1. a bonney rib attached by a fibrous cord to the first rib 2. a thick fibrous cord attached to the seventh cervical vertebra and the first rib 3. A cartilaginous rib attached to the first rib by a fibrous cord Cervical ribs  Intercostals spaces These are spaces that separate the ribs and their costal cartilages from one another They are named according to the rib forming the superior border of the space e.g. the 4th intercostal space lies between rib 4 and rib 5. There are 11 intercostal spaces and 11 intercostal nerves. Intercostal spaces contain intercostal muscles and membranes, and two sets (main and collateral) of intercostal blood vessels and nerves, identified by the same number assigned to the space. The space below the 12th rib does not lie between ribs and thus is referred to as the subcostal space, and the anterior ramus of spinal nerve T12 is the subcostal nerve.  INTERCOSTAL MUSCLES POSTERIOR INTERCOSTAL: VEIN ARTERY EXTERNAL INTERCCOSTAL M. NERVE INTERNAL INTERCOSTAL M. INNERMOST INTERCOSTAL M. INTERCOSTAL MUUSCLES POST. INTERCOSTAL V. EXTERNAL INTERCOSTAL M. POST. INTERCOSTAL A. INTERNAL INTERCOSTAL M. INTERCOSTAL N. INNERMOST INTERCOSTAL M  Respiratory movements: In quit inspiration, the diaphragm is the principal and often the sole muscle concerned. The external intercostals and the intercartilaginous parts of the internal intercostals elevate the ribs during inspiration and thus are inspiratory in function. The interosseous portions of the internal intercostals depress the ribs performing expiratory function. At birth the ribs are horizontal, a position of full inspiration which gave no role for the ribs movements in respiration. At that age, respiration is performed by the diaphragm movements up and down (abdominal respiration). By the end of the second year the ribs became oblique and by the seventh year respiration is shared by the movements of the ribs (thoracic respiration). Respiratory cycles: Each respiratory cycle consists of an inspiratory and expiratory phase, at rest; the former is about one second and the latter about three seconds.  Intercostal nerves They are the ventral rami of the upper 11 thoracic nerves usually divided into two; typical and atypical nerves: Typical Atypical 3-6 intercostal nerves 1, 2, last 5 typical intercostal nerve are the nerve that supplies only the thoracic walls. Why they are the nerves 1,2, and 5 atypical: - The 1st thoracic nerve share in the formation of the brachial plexus which supplies the upper limb. - The lateral branch of the 2nd nerve is large and supplies the axilla and is called intercostobrachial nerve. - The lower 5 intercostal nerves supply the anterior abdominal wall as well.  Intercostal nerves  The intercostal nerves are the anterior rami of the first 11 thoracic spinal nerves.  subcostal nerve:- is the anterior ramus of the 12th thoracic nerve and runs forward in the abdominal wall.  Each intercostal nerve enters an intercostal space between the parietal pleura and the posterior intercostal membrane then runs forward between the innermost intercostal and internal intercostal muscle.  The first six nerves are distributed within their intercostal spaces.  The 7th to 9th 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  Intercostal nerves 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:- (7th to 11th intercostal nerves only) run to the parietal peritoneum. Muscles of respiration  Blood supply to the thoracic wall Blood supply to the thoracic wall is derived from two sources: 1. the anterior intercostal arteries: two in each intercostal space branches of internal thoracic artery in the 1st -6th intercostal spaces, and 7th -11th from musculophrenic artery. 2. the posterior intercostal arteries:- derived from descending thoracic aorta for 3rd -11th intercostal spaces and supreme thoracic artery from the costal cervical trunk Posterior intercostal arteries Internal thoracic artery  Branches of the internal thoracic artery 1. Two anterior intercostal arteries for the upper six intercostal spaces 2. Cutaneous branches that accompany the terminal branches of the corresponding intercostal nerves 3.The pericardiacophrenic artery that accompanies the phrenic nerve and supplies the pericardium 4. Mediastinal arteries to the contents of the anterior mediastinum (e.g., the thymus) 5. The superior epigastric artery, supplies the abdominal muscle s 6. The musculophrenic artery, tha t runs around the costal margin of the diaphragm and supplies the lower intercostal  The venous drainage a- The anterior intercostal veins: accompany their corresponding artery, the lower three join the musculophrenic vein while the upper six join the internal thoracic vein which terminates in the brachiocephalic vein. b- The posterior intercostal veins: They are 11 pairs. - The first vein joins the corresponding brachiocephalic vein. - The second and the third veins on each side join each other to form the superior intercostal vein. That on the left joins the left brachiocephalic vein and the right joins the arch of azygos vein. - On the right side from 4-11 joins the azygos vein. - On the left side, veins from 4-8 intercostal spaces form the superior hemiazygos vein and those from 9-11 spaces form the inferior hemiazygos vein; both join the azygos vein at the level of eighth thoracic vertebrae.  RT. SUPRIUM INTERCOSTAL V. LT. SUPRIUM INTERCOSTAL V. RT. SUP. INTERCOSTAL V. LT. SUP. INTERCOSTAL V. SUP. HEMIAZYGOS V. AZYGOS V. SUBCOSTAL V. INF. HEMIAZYGOS V. ASCENDING LUMBER V. LEFT RENALV. POSTERIOR I.V.C. INTERCOSTAL VEINS  Tributaries of azygos vein: - Right superior intercostal vein. - Right posterior intercostal veins from 4- 11intercostal spaces. - Right ascending lumbar vein. - Superior and inferior hemiazygos veins. - Osophageal, pleural, pericardial, mediastinal and bronchial veins. The structure of the diaphragm  Development of the Diaphragm The diaphragm is formed from the following structures: (a) the septum transversum, which forms the muscle and central tendon; (b) the two pleuroperitoneal membranes, which are largely responsible for the peripheral areas of the diaphragmatic pleura and peritoneum that cover its upper and lower surfaces, respectively; and (c) the dorsal mesentery of the esophagus, in which the crura develop Diaphragmatic Herniae Types 1. Congenital diaphramatic hearnia:- occur as the result of incomplete fusion of the septum transversum, the dorsal mesentery, and the pleuroperitoneal membranes from the body wall 1. Acquired herniae may occur in middle-aged people with weak musculature around the esophageal opening in the diaphragm. These herniae may be either sliding or paraesophageal Sliding and paraesophageal hernia Draining the pleural fluid- structure the needle pierces  Anatomic and Physiologic Changes in the Thorax with Aging 1.The rib cage becomes more rigid and loses its elasticity as the result of calcification and even ossification of the costal cartilages; this also alters their usual radiographic appearance. 2. The stooped posture (kyphosis), so often seen in the old because of degeneration of the intervertebral discs, decreases the chest capacity. 3. Disuse atrophy of the thoracic and abdominal muscles can result in poor respiratory movements. 4. Degeneration of the elastic tissue in the lungs and bronchi results in impairment of the movement of expiration.  The thoracic cavity Objectives 1. To understand the general arrangement of the thoracic viscera and their relationship to one another and to the chest wall. 2. To be able to define what is meant by the term mediastinum and to learn the arrangement of the pleura relative to the lungs. This information is fundamental to the comprehension of the function and disease of the lungs. 3. Appreciating that the structure of the heart and the lungs and that they are enveloped in serous membranes that provide a lubricating mechanism for these mobile viscera and being able to distinguish between such terms as thoracic cavity, pleural cavity (pleural space), pericardial cavity, and costodiaphragmatic recess. Bounderies of the Chest Cavity Anterolaterally : - the chest wall/thoracic wall Inferiorly/below :- the diaphragm. Superiorly:- It extends upward into the root of the neck about one fingerbreadth above the clavicle on each side (covered by supra preural membrane) NB >The diaphragm, which is a very thin muscle, is the only structure (apart from the pleura and peritoneum) that separates the chest from the abdominal viscera. The chest cavity can be divided into 1. median partition, called the mediastinum, 2. laterally placed pleurae and lungs  The mediastinum Defn:- It is a movable partition that extends superiorly to the thoracic outlet and the root of the neck and inferiorly to the diaphragm and extending anteriorly to the sternum and posteriorly to the vertebral column. It is divided into two parts : superior and inferior mediastinim by an imaginary plane extending from the the sternal angle to the lower border of 4th thoracic vertebra.  The Mediastinum Concept All of organs between the left and right mediastinal pleurae is called mediastinum. It extends from the sternum in front to the vertebral column behind, and from the thoracic inlet above to the diaphragm below.  Subdivisions of mediastinum Divided into two Superior mediastinum Inferior mediastinum – Anterior mediastinum – Middle mediastinum – Posterior mediastinum  The inferior mediastinum subdivided into 1. the anterior mediastinum:- which is a space between the pericardium and the sternum; 2. the middle mediastinum: consists of the pericardium and heart; 3. the posterior mediastinum,:- which lies between the pericardium and the vertebral column.  Left side of mediastnum Left subclavian a. Thoracic duct Left vagus n. Aortic arch Left recurrent n. Phrenic n. & Thoracic aorta pericardiacophrenic a. Sympathetic trunk Root of lung Pericardium Esophagus Greater splanchnic n  Right side of mediastnum Trachea Right vagus n. Superior vena cava Arch of azygos v. Phrenic n. & Azygos v. pericardiacophrenic a. Root of lung Sympathetic trunk Esophagus Pericardium Inferior vena cava  Content of the anterior mediastinum 1. Thymus gland- 2. Sternal pericardial ligaments( superior and inferior) 3. Pericardial branches of percardicophrenic artery 4. Loose areolar connective tissue that is embedded in the fats 5. Lymphatis and lymph nodes  Contents of the middle mediastinum 1. heart within the pericardium 2. Great vessels as they leave the heart i.e. ascending aorta, bracheocephalic trunk pulmonary trunk, trachea with its principal bronchi, broncheal arteries 3. with the phrenic nerves on each side 4. Pericardicophrenic artereis and veins  Content of the posterior mediastinum 1. The esophagus 2. Left and right vagus nerve(10th cranial nerves) 3. Greater, lesser and least spranchnic nerves 4. Azygos , hemi azygos and accessory hemi azygos 5. Thoracic ducts system 6. Sympathetic chain  Surface marking for parietal pleura - right side The cervical pleura is marked by A curved line drawn upward, from the sternoclavicular joint to a point 1 in. (2.5 cm) above the junction of the medial and intermediate thirds of the clavicle. The anterior border of the right pleura runs down behind the sternoclavicular joint, reaching the midline behind the sternal angle then continues downward until it reaches the xiphisternal joint. The lower border of the pleura on both sides follows a curved line, which crosses the 8th rib in the midclavicular line and the 10th rib in the midaxillary line, and reaches the 12th rib adjacent to the vertebral column  Surface marking for parietal pleura - left side The anterior border of the left pleura has a similar course, but at the level of the fourth costal cartilage it deviates laterally and extends to the lateral margin of the sternum to form the cardiac notch. It then turns sharply downward to the xiphisternal joint. the lower margins of the lungs cross the 6th, 8th, and 10th ribs at the midclavicular lines, the midaxillary lines, and the sides of the vertebral column, respectively; the lower margins of the pleura cross, at the same points, the 8th, 10th, and 12th ribs, respectively. The distance between the two borders corresponds to the costodiaphragmatic recess  The pleura There are two types of pleura 1. the visceral pleura –that covers the lungs and heart 2. the parietal pleura:- covers the wall of the thorax >>The parietal pleura is named according to the surfaces it covers including:- 1. The costal pleura- covering the inner chest wall 2. The diaphragmatic pleura:- covering the diapragm 3. Mediastinal pleura:- covering the inner aspects of the mediastinum 4. Suprasternal pleura- covering the inner aspects of the supra pleural membrane  costodiaphragmatic recess: - This is the lower space of the pleural cavity into which the lung expands on inspiration between the costal and diaphragmatic pleura costomediastinal recesses : slit like space where the costal pleura is reflected to become the mediastinal Pleural cavity/space: - is the space between the visceral and the parietal pleura. It is usually filled with pleural fluid. At the hilum of the lungs the mediastinal pleura is reflected around the stuctures going to the lungs forming the root of the lungs and becomes the visceral pleura  Nerve supply to the pleura The Parietal pleura:- it is sensitive to pain, temparature, touch and pressure The costal pleura is segmentally supplied by the intercostal nerves. The mediastinal pleura is supplied by the phrenic nerve. The diaphragmatic pleura is supplied over the domes by the phrenic nerve and around the periphery by the lower six intercostal nerves.  The visceral pleura:- it is only sensitive to stretch and pressure and insensitive to pain It receives an autonomic nerve supply from the pulmonary plexus (branches from vagus nerve and the sympathetic chain.  Clinical notes Air in the pleural cavity associated with serous fluid is known as hydropneumothorax, associated with pus as pyopneumothorax, and associated with blood as hemopneumothorax. A collection of pus (without air) in the pleural cavity is called an empyema Pleural effusion  The trachea It begins as continuation of the larynx at the lower border of the cricoid cartilage (at 6th cervical vertebra) and ends below at the carina by dividing into right and left principal (main) bronchi at the sternal angle (the disc between 4th and 5th thoracic vertebrae). The relations of the trachea in the superior mediastinum of the thorax are as follows: – Anteriorly: The sternum, the thymus, the left brachiocephalic vein, the origins of the brachiocephalic and left common carotid arteries, and the arch of the aorta – Posteriorly: The esophagus and the left recurrent laryngeal nerve – Right side: The azygos vein, the right vagus nerve, and the pleura – Left side: The arch of the aorta, the left common carotid and left subclavian arteries, the left vagus and left phrenic nerves, and the pleura.  Blood Supply of the Trachea The upper two thirds are supplied by the inferior thyroid arteries and the lower third is supplied by the bronchial arteries. Lymph Drainage of the Trachea The lymph drains into the pretracheal, paratracheal lymph nodes and the deep cervical nodes. Nerve Supply of the Trachea The sensory nerve supply is from the vagus nerve and the recurrent laryngeal nerves. Sympathetic nerves supply the trachealis muscle  The principal bronchi The right Principal Bronchi is wider, shorter, and more vertical than the left and is about 1 in. (2.5 cm) long. Before entering the hilum of the right lung, the principal bronchus gives off the superior lobar bronchus. On entering the hilum, it divides into a middle and an inferior lobar bronchus The left principal bronchi is narrower, longer, and more horizontal than the right and is about 2 in. (5 cm) long. It passes to the left below the arch of the aorta and in front of the esophagus. On entering the hilum of the left lung, the principal bronchus divides into a superior and an inferior lobar bronchus Carina seen via bronchoscopy The root of left lung seen via bronchscopy  The lung Each lung is conical, covered with visceral pleura, and suspended free in its own pleural cavity, being attached to the mediastinum only by its root. Bronchopulmonary segment They are anatomic, functional, and surgical units of the lungs formed by segmental bronchi. They are surrounded by connective tissue. the right lung has 10 segments while the left lung has 8-9 segments  The bronchopulmonary segments The main bronchopulmonary segments are as follows: Right lung Superior lobe: Apical, posterior, anterior Middle lobe: Lateral, medial Inferior lobe: Superior (apical), medial basal, anterior basal, lateral basal, posterior basal Left lung Superior lobe: Apical, posterior, anterior, superior lingular, inferior lingular Inferior lobe: Superior (apical), medial basal, anterior basal, lateral basal, posterior basal  The main characteristics of a bronchopulmonary segment are:- 1. It is the smallest functional subdivision of a lung lobe. 2. It is pyramid shaped, with its apex toward the lung root. 3. It is surrounded by connective tissue. 4. It has a segmental bronchus, a segmental artery, lymph vessels, and autonomic nerves. 5. The segmental vein lies in the connective tissue between adjacent bronchopulmonary segments. 6. Because it is a structural unit, a diseased segment can be removed surgically  pericardium Structure: It is a fibroserous sac that encloses the heart and the roots of the great vessels. Function: it restricts excessive movements of the heart as a whole and to serve as a lubricated container in which the different parts of the heart can contract. Location: It lies within the middle mediastinum posterior to the body of the sternum and the second to the sixth costal cartilages and anterior to the 5th to the 8th thoracic vertebrae. Parts: fibrous and serous pericardium that has both  Fibrous pericardium It is the strong fibrous part of the sac firmly attached below to the central tendon of the diaphragm. It fuses with the outer coats of the great blood vessels passing through it namely, the aorta, the pulmonary trunk, the superior and inferior venae cavae, and the pulmonary veins. The fibrous pericardium is attached in front to the sternum by the sternopericardial ligaments Conducting system of the heart Blood supply to the heart  Surface marking of the heart the heart has both an apex and four borders. The apex:- formed by the left ventricle, corresponds to the apex beat and is found in the fifth left intercostal space 3.5 in. (9 cm) from the midline. The superior border:- formed by the roots of the great blood vessels, extends from a point on the second left costal cartilage (remember sternal angle) 0.5 in. (1.3 cm) from the edge of the sternum to a point on the third right costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum. The right border:- formed by the right atrium, extends from a point on the third right costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum downward to a point on the sixth right costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum The left border:- formed by the left ventricle, extends from a point on the second left costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum to the apex beat of the heart. The inferior border:- formed by the right ventricle and the apical part of the left ventricle, extends from the sixth right costal cartilage 0.5 in. (1.3 cm) from the sternum to the apex beat Surface marking of the heart valves  Surface Anatomy of the Heart Valves The surface markings of the heart valves are as follows: The tricuspid valve: lies behind the right half of the sternum opposite the fourth intercostal space. The mitral valve:- lies behind the left half of the sternum opposite the fourth costal cartilage. The pulmonary valve:- lies behind the medial end of the third left costal cartilage and the adjoining part of the sternum. The aortic valve:- lies behind the left half of the sternum opposite the third intercostal space  Auscultation of the Heart Valves On listening to the heart with a stethoscope, one can hear two sounds: lÅ«b-dÅ«p. The first sound is produced by the contraction of the ventricles and the closure of the tricuspid and mitral valves. The second sound is produced by the sharp closure of the aortic and pulmonary valves. They are best heard as fololws:- The tricuspid valve is best heard over the right half of the lower end of the body of the sternum. The mitral valve is best heard over the apex beat, that is, at the level of the fifth left intercostal space, 3.5 in. (9 cm) from the midline. The pulmonary valve is heard with least interference over the medial end of the second left intercostal space The aortic valve is best heard over the medial end of the second right intercostal space. Mediastinal structures- right side Mediastinal structures- left side Referred pains from abdominal viscera Areas of esophageal constrictions