Thorax Complete 200L PDF

THE THORAX TOKUNBO O.S Department of Anatomy, Osun State University INTRODUCTION The trunk of the body is divided by the diaphragm into an upper part, called the thorax, and a lower part called the abdomen. THORACIC CAGE  Thoracic cage is an osteo- cartilagenous conical cage which has a nar...

THE THORAX TOKUNBO O.S Department of Anatomy, Osun State University INTRODUCTION The trunk of the body is divided by the diaphragm into an upper part, called the thorax, and a lower part called the abdomen. THORACIC CAGE  Thoracic cage is an osteo- cartilagenous conical cage which has a narrow inlet & a wide outlet ? Boundaries of thoracic cage. Ant: Sternum, Costal cartilages and ribs. Post: Thoracic vertebrae and ribs. Lat: Ribs. Thoracic Inlet (or outlet) Ant: Upper border of manubrium sterni. Post: 1st thoracic vertebra. On each side: 1st rib & 1st costal cartilage. It is sloping downwards & forward.  Suprapleural membrane Dense fascia closes the lateral part of the thoracic inlet. Triangular in shape Apex: attached to transverse process of C7 Base: Attached to medial border of the first rib Superiorly: Related to subclavian vessels Inferiorly: Apex of lung & cervical pleura  Thoracic vertebrae. They are 12 vertebra. From 2 to 9 they are called Typical. Character of typical thoracic vertebrae: Body: Heart shape & carries 2 demi-facet at its side. Transverse process: has a facet for rib tubercle of the same number. Spine: Long, pointed & directed downward and backward. Vertebral foramen: Small & circular. Articulation between Thoracic vertebrae and the ribs  Atypical (Non typical ) thoracic vertebrae. 1 st Thoracic Vertebra 1st, 10th,11th and 12th T1: Has a complete facet. One very small inferior demifacet. Spine nearly horizontal Has costal facet in transverse process for the tubercle of first rib. It has a small body, looks like a cervical vertebra.  T10 One complete facet tangential with the upper border Small costal facet on transverse process. T11 One complete circular facet away from upper border. No costal facet T12 Broad body & short, oblong spine. One complete facet midway between upper & lower borders. No costal facet  Ribs 12 pairs, all are attached posteriorly to thoracic vertebrae. True: upper 7 pairs. False: 8th,9th &10th pairs Floating ribs: 11th & 12th The ribs from 3rd to 9th are called Typical ribs. Atypical (Non Typical) are 1st,2nd, 10th,11th & 12th. Sho rtc ut t o F66 12 2 -0 03 -f02 5.jpg.lnk  1st rib Shortest C- Shaped Ant end: cup shape. Post end: It has Head, neck and tubercle. Head: One facet Surfaces: Sup. & Inferior Borders: Outer (lateral) & Inner (media). 2nd rib Twice the length of 1st Head has 2 facet Surfaces of shaft are in between that of 1st & typical  3 parts: Manubrium, Body * Xiphoid Sternum process. Manubrium: Lies opposite T3,4. Body: T5 toT8 Xiphoid T9  Intercostal Spaces There are 9 anterior and 11 posterior Each space contains: 1- Intercostal muscles: (External, Internal and transversus thoracicus) 2- An Intercostal nerve. 3- Intercostal vessels: a. Intercostal arteries (Anterior & Posterior) b. Intercostal veins (Anterior & Posterior).  EXTERNAL INTERCOSTAL Origin: From the lower border of the rib above Insertion: Into outer lip of upper border of rib below Fibers are directed from above downward and forwards Begins from post. end of Intercostal space close to the tubercle of the rib. Ends at the costochondral junction where it is replaced by external or anterior Intercostal membrane. It elevates the rib during inspiration  INTERNAL INTERCOSTAL Origin: Floor of costal groove Insertion: Inner lip of upper border of rib below Fibers are directed from above downwards & backward Begins from anterior end of space close to the sternum. Ends at the angle of the rib, where it is replaced by post. Or internal Intercostal membrane. Action: Depresses the rib downwards during expiration  Internal Intercostal is partly traversed by the nerve & vessels, which splits each muscle into 2 parts: Outer: Internal Intercostal (proper) Inner: Innermost Intercostal (In the middle of the space) Transversus thoracicus The most inner layer of thoracic wall It is formed of 3 muscles 1- Innermost Intercostal. 2- Sternocostalis. 3- Subcostalis  Sternocostalis 4 to 5 slips which arise from inner surface of lower part of body of sternum and costal cartilages Inserted into inner surface of costal cartilages from 2 to 6. Subcostalis muscle Thin bands of muscle fibers. Mainly in lower 6 spaces. Only in post. part of spaces. Origin: Inner surface & lower border of rib above. Insertion: Upper border of 2nd or 3rd rib below.  Anterior Intercostal arteries 2 small arteries in each of the 9 spaces. The upper 6 from internal mammary artery The lower 3 from musculo- phrenic artery NB. Internal mammary or internal thoracic artery is a branch from1st part of subclavian artery  Posterior Intercostal arteries One in each of the 11 spaces 1st & 2nd arise from superior Intercostal artery of costocervical trunk of 2nd part of subclavian artery The lower 9 arteries & subcostal artery arise from descending thoracic aorta.  In each space the posterior Intercostal artery and its collateral branch anastomose with the 2 anterior Intercostal arteries  Anterior Intercostal veins 2 in each space. 9th,8th & 7th join the venae commitantes of musculo-phrenic artery 6th,5th & 4th join venae commitantes of internal mammary artery 3rd,2nd &1st join internal mammary vein Internal mammary vein drains into innominate (Brachiocephalic vein)  Posterior Intercostal veins One in each of the 11 spaces. On the right: 1st drains into Rt. Innominate v. 2nd,3rd & sometimes the 4th unite to form Rt. Superior Intercostal vein (B) which drains into azygos vein. From 5th to 11th & subcostal veins drain into azygos vein ©. On the Left: 1st drains into Lt. innominate V. 2nd,3rd& sometimes the 4th join to form Lt. Superior Intercostal vein which drains into Lt innominate vein. 5th,6th,7th, & 8th form superior hemiazygos vein to azygos vein 9th,10th.11th &Subcostal form inferior hemiazygos vein to azygos vein. Lymphatic drainage of the chest wall Lymph drainage from the: Anterior chest wall: is to the anterior axillary nodes. Posterior chest wall: is to the posterior axillary nodes. Anterior intercostal spaces: is to the internal thoracic nodes. Posterior intercostal spaces: is to the para-aortic nodes.  Intercostal Nerves They are the anterior primary rami of spinal thoracic nerves fromT1 to T11 T3 toT6 are Typical T12 is called Subcostal The remaining nerves are called atypical (non-typical) Each nerve runs in the Intercostal space inferior to the Intercostal vessels  Typical Intercostal nerve From T3 to T6 Leaves the intervertebral foramen to reach the Intercostal space. Runs between pleura & post. Intercostal membrane Pierces Internal Intercostal muscle splitting it into Internal Intercostal (proper) and innermost Intercostal. Runs between Internal Intercostal muscle & Pleura. Pierces Internal Intercostal muscle, anterior Intercostal membrane, pectoralis major, and deep fascia to become anterior cutaenous nerve  Branches: White & grey rami (I) communicates with sympathetic ganglion Collateral branch to Intercostals (2) Lateral cutaenous branch to skin (3) Anterior cutaenous (4) Muscular branches Pleural sensory branches peritoneal branches (5) Articular branches.  1st Intercostal nerve: Joined to Brachial plexus, by a branch that is equivalent to lateral cutaenous branch. 2nd Intercostal nerve: Joined to the medial cutaenous nerve of the arm, by a branch called Intercostobrachial nerve ( corresponds to lateral cutaenous branch) In Angina pectoris & myocardial infarction pain referred to medial side of arm along this nerve. So, with previous exception the upper 6 Intercostal nerves supply skin & parietal pleura and Intercostal muscles in each space  Azygos Vein Connects IVC with SVC S V Begins in abdomen from back C of IVC at level of L2 Enters thorax through Aortic opening of diaphragm on Rt. side of thoracic duct & aorta. In post. Mediastinum it passes behind Rt. Border of esophagus & root of rt. Lung I In sup. Mediastinum (L4) it crosses V above the root of rt. lung C Enters the middle of the back of the SVC.  The Respiratory Diaphragm The diaphragm separates the thoracic and abdominal cavities. It is composed of a peripheral muscular portion which inserts into a central aponeurosis - the central tendon. The muscular part has three component origins: Vertebral part Sternal part Costal part  Nerve Supply to the Diaphragm Motor supply: the entire motor supply arises from the phrenic nerves (C3,4,5). Diaphragmatic contraction is the mainstay of inspiration. Sensory supply: the periphery of the diaphragm receives sensory fibres from the lower intercostal nerves. The sensory supply from the central part is carried by the phrenic nerves. Clinical Correlates THE LUNGS Right and Left Pleural Cavities Parietal Pleura Visceral (Pulmonary) Pleura Parietal Costal Mediastinal Diaphragmatic Cupola Connecting Pleura Pleural Cavities Pleural Cavities Pleura Pleural cavities In the thorax, two pleural cavities, one on either side of the mediastinum, surround the lungs: superiorly, they extend above rib I into the root of the neck; inferiorly, they extend to a level just above the costal margin; the medial wall of each pleural cavity is the mediastinum Each pleural cavity is the potential space enclosed between the visceral and parietal pleurae containing only a very thin layer of serous fluid. Such that, the surface of the lung, which is covered by visceral pleura, directly opposes and freely slides over the parietal pleura attached to the wall. Pleura Each pleural cavity is lined by a single layer of flat cells, called mesothelium, and an associated layer of supporting connective tissue; which together form the pleura. The pleura is divided into two major types, based on location: parietal and visceral pleura Pleura associated with the walls of a pleural cavity is parietal pleura; Whereas, pleura that reflects from the medial wall and onto the surface of the lung is visceral pleura, which adheres to and covers the lung. Parietal pleura The parietal pleura consists of four parts: The costal part covers the internal surfaces of the thoracic wall. The mediastinal part covers the lateral aspects of the mediastinum, the mass of tissues and organs separating the pulmonary cavities and their pleural sacs. The diaphragmatic part covers the superior or thoracic surface of the diaphragm on each side of the mediastinum. The cervical pleura extends through the superior thoracic aperture into the root of the neck, forming a cup-shaped pleural dome over the apex of the lung (the part extending above the 1st rib). The costal part of the parietal pleura (costovertebral or costal pleura) Is separated from the internal surface of the thoracic wall (sternum, ribs and costal cartilages, intercostal muscles and membranes, and sides of thoracic vertebrae) by endothoracic fascia. This extrapleural layer of loose connective tissue forms a natural cleavage plane for the surgical separation of the costal pleura from the thoracic wall The mediastinal part of the parietal pleura (mediastinal pleura) Covers the lateral aspects of the mediastinum, the partition between the pulmonary cavities. Continues superiorly into the root of the neck as cervical pleura. It is continuous with costal pleura anteriorly and posteriorly and with the diaphragmatic pleura inferiorly. Superior to the root of the lung, the mediastinal pleura is a continuous sheet passing anteroposteriorly between the sternum and the vertebral column. At the hilum of the lung, the mediastinal pleura reflects laterally onto the structures making up the root of the lung and becomes continuous with the visceral pleura The diaphragmatic part of the parietal pleura (diaphragmatic pleura) Covers the superior surface of the diaphragm, except along 1. its costal attachments (origins) and 2. where the diaphragm is fused to the pericardium (the fibroserous membrane surrounding the heart). A thin, more elastic layer of endothoracic fascia, the phrenicopleural fascia, connects the diaphragmatic pleura with the muscular fibers of the diaphragm The cervical pleura (pleural cupula, dome of pleura) is the dome-shaped cap of the pleural sac and is the superior continuation of the costal and mediastinal parts of the parietal pleura. It covers the apex of the lung that extends superiorly through the superior thoracic aperture into the root of the neck. The summit of the cervical pleura is 2-3 cm superior to the level of the medial third of the clavicle at the level of the neck of the 1st rib. The cervical pleura is reinforced by a fibrous extension of the endothoracic fascia, the suprapleural membrane (Sibson fascia), which attaches to the internal border of the 1st rib and the transverse process of C7 vertebra Lines of pleural reflection Are relatively abrupt lines along which the parietal pleura changes direction as it passes (reflects) from one wall of the pleural cavity to another. They are The sternal line of pleural reflection is sharp or abrupt and occurs where the costal pleura becomes continuous with the mediastinal pleura anteriorly. The costal line of pleural reflection is also sharp and occurs where the costal pleura becomes continuous with diaphragmatic pleura inferiorly. The vertebral line of pleural reflection is a much rounder, gradual reflection and occurs where the costal pleura becomes continuous with the mediastinal pleura posteriorly Innervation of parietal pleura The parietal pleural is innervated by somatic afferent fibers. The costal pleura is innervated by branches from the intercostal nerves and pain would be felt in relation to the thoracic wall. (Reffered Pain) The diaphragmatic pleura and the mediastinal pleura are innervated mainly by the phrenic nerves (originating at spinal cord levels C3, C4 and C5). Pain from these areas would refer to the C3, C4 and C5 dermatomes (lateral neck and the supraclavicular region of the shoulder). Visceral pleura Is continuous with parietal pleura at the hilum of each lung where structures enter and leave the organ. The visceral pleura is firmly attached to the surface of the lung, including both opposed surfaces of the fissures that divide the lungs into lobes. Although the visceral pleura is innervated by visceral afferent nerves that accompany bronchial vessels, pain is generally not elicited from this tissue Pleural recesses Recesses are spaces in which two layers of parietal pleura become opposed. Expansion of the lungs into these spaces usually occurs only during forced inspiration; the recesses also provide potential spaces in which fluids can collect and from which fluids can be aspirated. There are two pleura recesses; Costomediastinal recesses; Anteriorly, this recess occurs on each side where costal pleura is opposed to mediastinal pleura. The largest is on the left side in the region overlying the heart Costodiaphragmatic recesses; is the largest and clinically most important recesses which occur in each pleural cavity between the costal pleura and diaphragmatic pleura. The costodiaphragmatic recesses are the regions between the inferior margin of the lungs and inferior margin of the pleural cavities. They are deepest after forced expiration and shallowest after forced inspiration Clinical correlates Pneumothorax:Entry of air into the pleural cavity (pneumothorax), resulting from a penetrating wound of the parietal pleura from a bullet, for example, or from rupture of a pulmonary lesion into the pleural cavity (bronchopulmonary fistula), results in collapse of the lung. Fractured ribs may also tear the visceral pleura and lung, thus producing pneumothorax. Hydrothorax:The accumulation of a significant amount of fluid in the pleural cavity (hydrothorax) may result from pleural effusion (escape of fluid into the pleural cavity). With a chest wound, blood may also enter the pleural cavity (hemothorax). Hemothorax: results more commonly from injury to a major intercostal or internal thoracic vessel than from laceration of a lung. If both air and fluid (hemopneumothorax, if the fluid is blood) accumulate in the pleural cavity, an air and fluid level or interface (sharp line, horizontal regardless of the patient's position, indicating the upper surface of the fluid) will be seen on a radiograph  ANA202 Lecture The Pleurae Rain semester 2019/2020 By Dr. B.A. Falana Department of Anatomy Faculty of Basic Medical Sciences College of Health Sciences Osun State University Introduction The pleurae is a thin, smooth, glistening, delicate serous membrane which 1. Covers the lungs 2. Lines the wall of the thorax 3. This is a layer of mesothelial cells, supported by connective tissue. Layers of the pleura Two layers that are contained by the pleura: (a) Visceral pleura (b) Parietal pleura. Pleural Cavity is a potential space between the viscera and parietal pleura. Structure of the pleurae Each pleura can be divided into two parts: Parietal pleura – covers the internal surface of the thoracic cavity. Visceral Pleura Covers the lungs. The visceral pleura covers the outer surface of the lungs, and extends into the interlobar fissures. – It is continuous with the parietal pleura at the hilum of each lung (this is where structures enter and leave the lung). PARIETAL PLEURA The parietal pleura covers the internal surface of the thoracic cavity. It is thicker than the visceral pleura, and can be subdivided according to the part of the body that it is contact with: Therefore parietal pleura is split into the following four (4) parts: 1. Costal pleura. 2. Diaphragmatic pleura. 3. Mediastinal pleura. 4. Cervical pleura (CoDiMeCer) Parietal Pleura Cont’d 1. Mediastinal pleura – Covers the lateral aspect of the mediastinum (the central component of the thoracic cavity, containing a number of organ). 4. Diaphragmatic pleura – Covers the thoracic (superior) surface of the diaphragm.  2. Cervical pleura – Lines the extension of the pleural cavity into the neck. 3. Costal pleura – Covers the inner aspect of the ribs, costal cartilages, and intercostal muscles. VISCERAL PLEURA (Pulmonary pleura) The visceral pleura entirely covers the top layer of the lung with the exception of at the hilum and along the connection of the pulmonary ligament. It also extends in the depths of the fissures of the lungs. It is firmly adherent to the lung surface and can’t be divided from it. COSTAL PLEURA It lines the inner surface of the thoracic wall (being composed of ribs, costal cartilages, and intercostal spaces) to which it’s loosely connected by a thin layer of loose areolar tissue termed endothoracic fascia. In living beings, endothoracic fascia is easily separable from the thoracic wall. Relations of the costal pleura ANTERIOR RELATIONS – The internal thoracic vessels are directly located on the pleura within the first intercostal space. – Sternum – Costal cartilages – Ribs – Intercostal muscles.  POSTERIOR RELATIONS The costal pleura is related to the sympathetic chain as well as its branches. The intercostal nerve is located in the middle of the costal pleura as well as the posterior intercostal membrane at the posterior end of the intercostal space. THE DIAPHRAGMATIC PLEURA The thoracic surface of the diaphragm is covered by the diaphragmatic pleura. Below the lower border of the lung, the costal and diaphragmatic pleurae are in apposition to each other in quiet respiration. Costodiaphragmatic recess. The margins of the base of the lung decline and the costal and diaphragmatic pleurae split up in deep inspiration. On inspiration this lower zone of the pleural cavity into which the lung enlarges is called the costodiaphragmatic recess. MEDIASTINAL PLEURA It lines the corresponding outermost layer of the mediastinum and creates its lateral boundary. It is represented as a cuff over the root of the lung and becomes constant with the visceral pleura. CERVICAL PLEURA It is the dome of parietal pleura, which extends into the root of the neck about 1 inch (2.5 cm) above the medial end of clavicle and 2 inches (5 cm) above the 1st costal cartilage. It is termed cupola and covers the apex of the lung. It is covered by the suprapleural membrane. Connections of cervical pleura Arteriorly:–Subclavian artery and scalenus anterior muscle. Posteriorly: –Neck of 1st rib and structures passing in front of it. Laterally: –Scalenusmedius muscle. Medially: –Great vessels of the neck. Relations of the cervical pleura 1. The scaleus anterior envelops the anterolateral part of the dome of the pleura, parting it from the subclavian vein that terminates at the medial border of the muscle. 2. The subclavian artery traverses directly superior towards the vein the dome below its peak, and from the subclavian the vertebral artery rises above it. 3. The internal mammary artery goes downwards from the subclavian after it travels behind the innominate vein. 4. The costocervical trunk arcs towards the back from the subclavian and goes across the summit of the dome 5. Its superior intercostal branch goes downwards behind the dome, in the middle of the first intercostal nerve on the lateral side as well as the first thoracic sympathetic ganglion on the medial side. 6. The vagus nerve goes down on the right side in front of the medial part of the subclavian artery. 7. Its continuing laryngeal branch turns around the lower border of the artery. 8. The ansa subclavia is located towards the lateral side of the recurrent nerve. Pleural cavity The pleural cavity is a potential space between the parietal and visceral pleura. It contains a small volume of serous fluid, which has two major functions. It lubricates the surfaces of the pleurae, allowing them to slide over each other. The serous fluid also produces a surface tension, pulling the parietal and visceral pleura together. This ensures that when the thorax expands, the lung also expands, filling with air. Pleural recesses  Anteriorly and posteroinferiorly, the pleural cavity is not completely filled by the lungs.  This gives rise to recesses – where the opposing surfaces of the parietal pleura touch.  There are two recesses present in each pleural cavity:  Costodiaphragmatic – located between the costal pleurae and the diaphragmatic pleura.  Costomediastinal – located between the costal pleurae and the mediastinal pleurae, behind the sternum. – These recesses are of clinical importance, as they provide a location where fluid can collect (such as in a pleural effusion). Neurovascular Supply The two parts of the pleurae receive a different neurovascular supply: Parietal Pleura The parietal pleura is sensitive to pressure, pain, and temperature. It produces a well localised pain, and is innervated by the phrenic and intercostal nerves. The blood supply is derived from the intercostal arteries. Visceral Pleura The visceral pleura is not sensitive to pain, temperature or touch. Its sensory fibres only detect stretch. It also receives autonomic innervation from the pulmonary plexus (a network of nerves derived from the sympathetic trunk and vagus nerve). Arterial supply is via the bronchial arteries (branches of the descending aorta), which also supply the parenchyma of the lungs Clinical Application Pneumothorax A pneumothorax (commonly referred to a collapsed lung) occurs when air or gas is present within the pleural space. This removes the surface tension of the serous fluid present in the space, reducing lung extension. Clinical Features: Chest pain, shortness of breath, and asymmetrical chest expansion. Upon percussion, the affected side may be hyper-resonant (due to excess air within the chest). – It may require decompression to remove the extra air/gas in order for the lung to reinflate (this is achieved via the insertion of a chest drain). Spontaneous: A spontaneous pneumothorax occurs without a specific cause. It is sub-divided into primary (no underlying respiratory disease) and secondary (underlying respiratory disease present). Traumatic: A traumatic pneumothorax occurs as a result of blunt or penetrating chest trauma, such as a rib fracture (often seen in road traffic collisions. Radiographic appearance of a left pneumothorax. Summary The pleurae refer to the serous membranes that line the lungs and thoracic cavity. They permit efficient and effortless respiration There are two pleurae in the body: one associated with each lung. They consist of a serous membrane – a layer of simple squamous cells supported by connective tissue. This simple squamous epithelial layer is also known as the mesothelium. Each pleura can be divided into two parts: Visceral pleura – covers the lungs. Parietal pleura – covers the internal surface of the thoracic cavity. These two parts are continuous with each other at the hilum of each lung. There is a potential space between the viscera and parietal pleura, known as the pleural cavity Refereces Ali Sparke (2020). The Pleural, Revisions: 36 TeachMeSeries Ltd Lungs Pair of Cone-shaped organs Lie in pleural cavity Weigh approx 800g 90% air 10% tissue Left lung is narrower Right lung is shorter Right Lung Right Lung Left Lung Left Lung Left Lung Lungs Apices-extend 1-2 cm past clavicles At end-expiration 6th rib – midclavicular 8th rib – laterally Posteriorly Tops is at 1st vertebra Inferior border Rises & falls betwee 9th & 12th rib  ANA202 Lungs and respiratory movements Rain semester 2019/2020 session By Dr. B.A. Falana Department of Anatomy Faculty of Basic Medical Sciences College of Health Sciences Osun State University The Lungs and Breathing The space between the outer surface of the lungs and inner thoracic wall is known as the pleural space. This is usually filled with pleural fluid, forming a seal which holds the lungs against the thoracic wall by the force of surface tension. This seal ensures that when the thoracic cavity expands or reduces, the lungs undergo expansion or reduction in size accordingly. During breathing, the contraction and relaxation of muscles acts to change the volume of the thoracic cavity. As the thoracic cavity and lungs move together, this changes the volume of the lungs, in turn changing the pressure inside the lungs. Boyle’s law states that the volume of gas is inversely proportional to pressure (when temperature is constant). Therefore:  When the volume of the thoracic cavity increases – the volume of the lungs increases and the pressure within the lungs decreases. When the volume of the thoracic cavity decreases – the volume of the lungs decreases and the pressure within the lungs increases Demonstration of Boyle’s law: an increase in volume results in a decrease in pressure. Process of Inspiration Inspiration is the phase of ventilation in which air enters the lungs. It is initiated by contraction of the inspiratory muscles: Diaphragm – flattens, extending the superior/inferior dimension of the thoracic cavity. External intercostal muscles – elevates the ribs and sternum, extending the anterior/posterior dimension of the thoracic cavity. The action of the inspiratory muscles results in an increase in the volume of the thoracic cavity. As the lungs are held against the inner thoracic wall by the pleural seal, they also undergo an increase in volume. As per Boyle’s law, an increase in lung volume results in a decrease in the pressure within the lungs. The pressure of the environment external to the lungs is now greater than the environment within the lungs, meaning air moves into the lungs down the pressure gradient. Process of Passive Expiration Expiration is the phase of ventilation in which air is expelled from the lungs. It is initiated by relaxation of the inspiratory muscles: Diaphragm – relaxes to return to its resting position, reducing the superior/inferior dimension of the thoracic cavity. External intercostal muscles – relax to depress the ribs and sternum, reducing the anterior/posterior dimension of the thoracic cavity. The relaxation of the inspiratory muscles results in a decrease in the volume of the thoracic cavity. The elastic recoil of the previously expanded lung tissue allows them to return to their original size As per Boyle’s law, a decrease in lung volume results in an increase in the pressure within the lungs. The pressure inside the lungs is now greater than in the external environment, meaning air moves out of the lungs down the pressure gradient.  Forced Breathing Forced breathing is an active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume. It most commonly occurs during exercise. Active Inspiration Active inspiration involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals). All of these muscles act to increase the volume of the thoracic cavity: Scalenes – elevates the upper ribs. Sternocleidomastoid – elevates the sternum. Pectoralis major and minor – pulls ribs outwards. Serratus anterior – elevates the ribs (when the scapulae are fixed). Latissimus dorsi – elevates the lower ribs. Active Expiration Active expiration utilises the contraction of several thoracic and abdominal muscles. These muscles act to decrease the volume of the thoracic cavity: Anterolateral abdominal wall – increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity. Internal intercostal – depresses the ribs. Innermost intercostal – depresses the ribs. Fig 3 – The muscles of the anterolateral wall are utilised in forced expiration  Clinical Relevance: Diaphragmatic Paralysis The phrenic nerve provides motor innervation to the diaphragm. If the nerve becomes damaged, paralysis of the diaphragm can result. Causes of phrenic nerve palsy include: Mechanical trauma – ligation or damage to the nerve during surgery. Compression – due to a tumour within the chest cavity. Guillian-Barre syndrome – auto-immune induced muscle weakness, often triggered by infection. Neuromuscular disease – such as Multiple Sclerosis or Motor Neurone Disease.  Paralysis of the diaphragm produces a paradoxical movement. The affected side of the diaphragm moves upwards during inspiration, and downwards during expiration. A unilateral diaphragmatic paralysis is usually asymptomatic and is most often an incidental finding on x-ray. If both sides are paralysed (known as bilateral diaphragmatic paralysis), the patient may experience poor exercise tolerance, orthopnoea and fatigue. Lung function tests will show a restrictive deficit. Management of diaphragmatic paralysis is two-fold. Firstly, the underlying cause must be identified and treated (if possible). In a unilateral diaphragmatic paralysis, patients usually do not require ventilatory support, unless they already have significant lung disease or are symptomatic. In a bilateral paralysis, the patient may require ventilatory support such as non-invasive positive ventilation, or, in more severe cases, intubation and invasive ventilation. Chest X-Ray showing paralysis of the right hemidiaphragm.  Question 1 of 5 With regards to the expiration phase of breathing, which of the following statements is TRUE? The diaphragm and external intercostal muscles contract The ribs and sternum are elevated The thoracic cavity expands in volume The pressure inside the lungs rises  Bookmarks Recommended reading Applied DNA Sciences to Provide Coronavirus Test to Stony Brook University Hospital staff reporter, 360Dx, 2020 Bruker Invasive Fungal Disease Products CE-IVD Marked 360Dx, 2017 Genomic Health Q4 Revenues Rise 22 Percent; International Efforts Expected to Push 2019 Growth 360Dx, 2019 USPSTF Formalizes Slightly Expanded BRCA Screening Recommendations staff reporter, 360Dx, 2019 MEDIASTINUM The median septum of the thorax between the two lungs. DIVISIONS OF THE MEDIASTINUM Split into two for descriptive purposes: Superior and Inferior Mediastina CONTENTS OF THE MEDIASTINUM Superior mediastinum: Esophagus Trachea Arch of Aorta Sternal angle Big branches of Aortic arch Lower border Brachiocephalic (innominate) veins Middle mediastinum: Pericardium of T4 Upper half of superior vena cava Phrenic nerves Heart Vagi nerves Pulmonary trunk Ascending Aorta Lower half of SVC Posterior mediastinum: Upper part of IVC Bifurcation of trachea Esophagus. Descending thoracic Aorta. Azygos and hemiazygos veins. Vagi, greater, lesser and least splanchnic nerves. GROSS ANATOMY OF THE THORAX THE MEDIASTINUM Mediastinum The mediastinum is the central compartment of the thoracic cavity, located between the two pleural sacs. It contains most of the thoracic organs, and acts as a conduit for structures traversing the thorax on their way into the abdomen. Anatomically, the mediastinum is divided into two parts by an imaginary line that runs from the sternal angle to the T4 vertebrae: Superior mediastinum – extends upwards, terminating at the superior thoracic aperture. Inferior mediastinum – extends downwards, terminating at the diaphragm. It is further subdivided into the anterior mediastinum, middle mediastinum and posterior mediastinum. Divisions of the Mediastinum SUPERIOR MEDIASTINUM Superior - thoracic inlet Inferior - transverse thoracic plane Anterior - sternal angle Posterior - IV disc T4 & T5 INFERIOR MEDIASTINUM Superior – transverse thoracic plane Inferior - diaphragm Divisions of the Mediastinum INFERIOR MEDIASTINUM a. ANTERIOR MEDIASTINUM - contains thymus remnant, lymph nodes & fats b. MIDDLE MEDIASTINUM - contains the heart & great vessels c. POSTERIOR MEDIASTINUM - contains esophagus, great vessels,vagus nerves & symphathetic trunks Superior Mediastinum Contents: (Anterior – Posterior) 1. Thymus gland - primary lymphoid organ located behind manubrium - puberty undergoes gradual involution 2. Great Vessels Brachiocephalic Veins Superior Vena Cava - formed at level of 1st right costal cartilage - enters right atrium at level of 3rd right costal cartilage Superior Mediastinum Contents: Arch of the Aorta - starts behind 2nd right sternoclavicular joint - ends at 2nd left sternoclavicular joint Branches: Brachiocephalic Trunk Left Common Carotid Artery Left Subclavian Artery Ligamentum arteriosum Aortic Arch is connected inferiorly to the left pulmonary artery by the Ligamentum arteriosum” fibrous remnant of ductus arteriosus” Superior Mediastinum Contents: 3. Nerves Vagus & Phrenic Nerves Cardiac Plexus of Nerves Left Recurrent Laryngeal Nerve 4. Trachea 5. Esophagus 6. Thoracic Duct 7. Prevertebral Muscles Anterior Mediastinum Smallest subdivision of the Inferior Mediastinum Boundaries: Anterior : body of sternum & trans thoracis muscles Posterior : pericardium Contents: Loose CT (Sternopericardial Ligament) Adipose tissue Lymphatic Vessels & lymph nodes Branches of Internal Thoracic Vessels Posterior Mediastinum Boundaries: Anterior - Pericardium & Diaphragm Posterior - T5 to T12 vertebrae Contents: Thoracic Aorta Esophagus & Plexus Thoracic Duct Thoracic Sympathetic Trunks Posterior Mediastinal Lymph nodes Thoracic Splanchnic Nerve Azygos & Hemiazygos Veins Thoracic Aorta Branches: 1. Bronchial Arteries 5. Esophageal Arteries 2. Pericardial Arteries 6. Mediastinal Arteries 3. Post. Intercostal Arteries 7. Subcostal Arteries 4. Superior Phrenic Arteries Esophagus Course: Superior to Posterior Mediastinum Located behind: Arch of Aorta Pericardium & Left Atrium Enters Esophageal Hiatus of the Diaphragm at level of T10 Anatomic Impressions or “Constrictions”: 1. Crossing with Aortic Arch 2. Crossing with Left Main Bronchus 3. Diaphragmatic Hiatus Thoracic Duct Largest lymphatic channel in the body Originates from Cisterna Chyle in the abdomen & passes thru aortic hiatus of diaphragm at level of T12 Relations: Posterior : bodies of inferior 7 thoracic vertebrae Anterior : Esophagus Left : Thoracic Aorta Right : Azygos Vein Conveys lymph from: Lower extremities Left side of thorax Pelvic Cavity Abdominal Cavity Left upper limb Lymph Nodes of the Posterior Mediastinum Posterior Mediastinal Lymph Nodes - receives lymph from esophagus, posterior aspect of the pericardium & diaphragm & middle posterior Intercostal space Azygos Venous System of the Posterior Mediastinum Drains the back & thoracoabdominal walls and the mediastinal viscera Azygos Vein - forms a collateral pathway b/w SVC & IVC - passes to the right side of inferior 8 thoracic vertebrae - arches over the root of the right lung to enter the SVC - receives posterior intercostal veins, mediastinal, esophageal & bronchial veins Azygos Venous System of Posterior Mediastinum Hemiazygos Vein - arises on left side of the vertebral column to level of T9 - receives the inferior 3 PIV, inferior esophageal veins, small mediastinal veins Accessory Hemiazygos Vein - starts at medial end of 4th or 5th ICS - descends on left of VC from T5 thru T8 - crosses to the right to join the Azygos Vein - receives 4th thru 8th IC Veins - communicates with Superior IC Vein which drains 1st thru 3rd ICS Nerves of Posterior Mediastinum Thoracic Sympathetic Trunks - lie against heads of ribs in superior thorax costovertebral joints in midthorax sides of vertebral bodies in lower thorax Lower Thoracic Splanchnic Nerves (Greater, Lesser and Least SN) - presynaptic fibers from 5th thru 12th sympathetic ganglia - sympathetic innervation for most abdominal viscera APPLIED ANATOMY pain from the diaphragm felt can be felt cutaneously in the upper arms/chest because the phrenic nerves carry the pain via their sensory fibers up to their entry into the spinal cord at C3-C5. Shadow in the anterior mediastinum upon radiology can be of Thymoma, teratoma and thyroid gland tumor posibilities. Thymus is significant for myasthenia gravis  THE CARDIOVASCULAR SYSTEM “Cardio” = Heart “Vascular” = Vessels Vascular Circuits The heart is a double pump Heart arteries arterioles   Veins  venules  capillaries Vascular Circuits Pulmonary and Systemic Circulations Characteristics of Blood Vessels Arteries and arterioles carry blood away from heart Capillaries - site of exchange Venules, veins - return blood to heart SIZE, LOCATION, AND SURFACES COVERINGS OF THE HEART Pericardium Myocardium Endocardium MAJOR VESSELS OF THE HEART Anterior view Posterior view GROSS ANATOMY MYOCARDIAL THICKNESS AND FUNCTION L.A R.A L.V R.V HEART VALVES ATRIOVENTRICULAR VALVES SEMILUNAR VALVES BLOOD SUPPLY TO THE HEART VENOUS DRAINAGE THE HEART INNERVATION OF THE HEART INNERVATION OF THE HEART 1- Sympathetic innervation: Stimulates heart rate (tachycardia) coronary vasodilatation 2- Paraympathetic innervation: Slows heart rate (bradycardia) Coronary vasoconstriction 3- Pain fibers: upper thoracic segments of the spinal cord CLINICAL ANATOMY CORONARY ARTERY DISEASE Heart muscle receiving insufficient blood supply narrowing of vessels--- atherosclerosis, artery spasm or clot atherosclerosis--smooth muscle & fatty deposits in walls of arteries Treatment drugs, bypass graft, angioplasty, stent BY-PASS GRAFT MI = MYOCARDIAL INFARCTION death of area of heart muscle from lack of O2 replaced with scar tissue results depend on size & location of damage BLOOD CLOT use clot dissolving drugs streptokinase or t-PA & heparin balloon angioplasty ANGINA PECTORIS heart pain from ischemia (lack of blood flow and oxygen) of cardiac muscle PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY CONGESTIVE HEART FAILURE (CHF) Congestive heart failure (CHF) is caused by: Coronary atherosclerosis Persistent high blood pressure Multiple myocardial infarcts Dilated cardiomyopathy (DCM) – main pumping chambers of the heart are dilated and contract poorly. CONGENITAL HEART DEFECTS ATRIAL SEPTAL DEFECT ARTIFICIAL HEART THANK YOU FOR LISTENING ANA 202 Great Vessels GREAT VESSELS The pulmonary trunk, approximately 5 cm long and 3 cm wide, is the arterial continuation of the right ventricle and divides into right and left pulmonary arteries. The pulmonary trunk and arteries conduct poorly oxygenated blood to the lungs for oxygenation. The great vessels of the heart function to carry blood to and from the heart as it pumps, located largely within the middle mediastinum. This includes the structure and anatomical relationships of the aorta, pulmonary arteries and veins, and the superior and inferior vena cavae. Ligamentum arteriosum Left recurrent laryngeal n. GREAT VESSELS cotnd. The brachiocephalic veins are formed posterior to the sternoclavicular joints by the union of the internal jugular and subclavian veins. At the level of the inferior border of the 1st right costal cartilage, the brachiocephalic veins unite to form the SVC. The left brachiocephalic vein is more than twice as long as the right vein because it passes from the left to the right side, passing over the anterior aspects of the roots of the three major branches of the arch of the aorta. It shunts blood from the head, neck, and left upper limb to the right atrium. GREAT VESSELS cotnd. The superior vena cava returns blood from all structures superior to the diaphragm, except the lungs and heart. It passes inferiorly and ends at the level of the 3rd costal cartilage, where it enters the right atrium of the heart. The SVC lies in the right side of the superior mediastinum, anterolateral to the trachea and posterolateral to the ascending aorta. The right phrenic nerve lies between the SVC and the mediastinal pleura. The terminal half of the SVC is in the middle mediastinum, where it lies beside the ascending aorta and forms the posterior boundary of the transverse pericardial sinus. The ascending aorta, approximately 2.5 cm in diameter, begins at the aortic orifice. Its only branches are the coronary arteries, arising from the aortic sinuses (discussed under Semilunar Valves. The ascending aorta is intrapericardial; for this reason and because it lies inferior to the transverse thoracic plane, it is considered a content of the middle mediastinum (part of the inferior mediastinum). GREAT VESSELS cotnd. The arch of the aorta (aortic arch), the curved continuation of the ascending aorta, begins posterior to the 2nd right sternocostal (SC) joint at the level of the sternal angle and arches superiorly, posteriorly and to the left, and then inferiorly. The arch of the aorta ascends anterior to the right pulmonary artery and the bifurcation of the trachea, reaching its apex at the left side of the trachea and esophagus as it passes over the root of the left lung. The arch descends posterior to the root of the lung on the left side of the body of the T4 vertebra.  Arch of the aorta contd. The arch of the aorta ends by becoming the thoracic aorta posterior to the 2nd left sternocostal joint. The arch of the azygos vein occupies a corresponding position on the right side of the trachea over the root of the right lung, although its contents are flowing in the opposite direction. The ligamentum arteriosum, the remnant of fetal ductus arteriosus, passes from the root of the left pulmonary artery to the inferior surface of the arch of the aorta. The usual branches of the arch of the aorta are the brachiocephalic trunk, left common carotid artery, and left subclavian artery The brachiocephalic trunk, the first and largest branch of the arch of the aorta, arises posterior to the manubrium, where it is anterior to the trachea and posterior to the left brachiocephalic vein. It ascends superolaterally to reach the right side of the trachea and the right SC joint, where it divides into the right common carotid and right subclavian arteries. The left common carotid artery, the second branch of the arch of the aorta, arises posterior to the manubrium, slightly posterior and to the left of the brachiocephalic trunk. It ascends anterior to the left subclavian artery and is at first anterior to the trachea and then to its left. It enters the neck by passing posterior to the left SC joint. The left subclavian artery, the third branch of the arch, arises from the posterior part of the arch of the aorta, just posterior to the left common carotid artery. It ascends lateral to the trachea and left common carotid artery through the superior mediastinum; it has no branches in the mediastinum. As it leaves the thorax and enters the root of the neck, it passes posterior to the left SC joint. Thoracic Aorta Thoracic Aorta The thoracic aorta is the continuation of the arch of the aorta. It begins on the left side of the inferior border of the body of the T4 vertebra and descends in the posterior mediastinum on the left sides of the T5 toT12 vertebrae. As it descends, it approaches the median plane and displaces the esophagus to the right. The thoracic aortic plexus, an autonomic nerve network, surrounds it. The thoracic aorta lies posterior to the root of the left lung, pericardium, and esophagus. The thoracic aorta terminates (with a name change to abdominal aorta) anterior to the inferior border of the T12 vertebra and enters the abdomen through the aortic hiatus in the diaphragm. The thoracic duct and azygos vein ascend on its right side and accompany it through this hiatus. In a pattern that will be more evident in the abdomen, the branches of the descending aorta arise and course within three vascular planes Thoracic Aorta contd. An anterior, midline plane of unpaired visceral branches to the gut and its derivatives. Lateral planes of paired visceral branches serving viscera other than the gut and its derivatives. Posterolateral planes of paired, segmental, parietal branches to the body wall. Exceptions to this pattern include Superior phrenic arteries, paired parietal branches that pass anterolaterally to the superior surface of the diaphragm (which is actually facing posteriorly at this level owing to the convexity of the diaphragm), where they anastomose with the musculophrenic and pericardiacophrenic branches of the internal thoracic artery. Pericardial branches, unpaired branches that arise anteriorly but, instead of passing to the gut, send twigs to the pericardium. The same is true for the small mediastinal arteries that supply the lymph nodes and other tissues of the posterior mediastinum. SURFACE ANATOMY OF THE THORAX MBBS Online Lecture Series Session: 2019/2020 By Dr. Benedict Falana Department of Anatomy  Introduction A thorough knowledge of thoracic anatomy is of fundamental importance to the surgeon. Surface anatomy is an often-neglected component of traditional topographic anatomic teaching, but a proper understanding of the relationship of surface features to deeper structures is invaluable in the clinical assessment of a patient and in the interpretation of radiologic imaging. Familiarity with thoracic surgical landmarks is a prerequisite for the successful placing of a thoracic incision. Thoracic incisions are placed to provide the best access to the pulmonary hila, trachea, or great vessels based on knowledge of the surface anatomy. Similarly, knowledge of the intrathoracic anatomy and level of the diaphragm based on surface landmarks is useful for interventional procedures, such as tube thoracostomy Furthermore, knowledge of the chest wall musculature is essential in the use of muscle flaps for reconstruction  Surface anatomy of the chest and neck Muscular landmarks The sternocleidomastoid arises by two heads, from the upper part and anterior surface of the manubrium and from the medial third of the clavicle. The muscle extends diagonally upward to insert onto the mastoid process of the skull base. The medial border of the muscle is an important landmark for oblique cervical incisions used in approaches to the cervical esophagus and for cannulation of the internal jugular vein. Pectoralis major arises from the second to sixth costal cartilages and ribs, sternum, and medial half of the clavicle and passes as a fan-shaped muscle to insert into the lateral lip of the intertubercular groove of the humerus. The lower margin of the muscle forms the anterior fold of the axilla. In men, the lower border may be seen as a curved line leading out to the axilla that corresponds to the fifth rib..  Below pectoralis major lies serratus anterior on the anterolateral aspect of the chest wall. Serratus anterior arises from muscular slips from the upper eight ribs and attaches to the anterior surface and vertebral border of the scapula. The muscular slips on the lower ribs may be seen on thin, muscular patients: the highest visible digitationindicates the sixth rib. The muscular borders of the axilla define the axillary lines, imaginary vertical lines that are useful for description of thoracic anatomy. The axillary fold produced by the pectoralis major and extends downward to pass through the anterior superior iliac spine. The posterior axillary line passes through the posterior axillary fold that is formed by latissimus dorsi and teres major. The midaxillary line runs vertically between these anterior and posterior lines. In men, the nipple overlies the fourth intercostal space, near the lower border of pectoralis major, just lateral to the midclavicular line (approximately 10 cm from the midline). In women, nipple position is inconsistent but the circular base of the breast arises over the second to sixth ribs and extends from the lateral border of the sternum to the midaxillary line; the upper outer quadrant extends into the axilla along the lower border of pectoralis major.  Bony landmarks The sternum is easily palpable and is comprised of the manubrium, body, and xiphisternum. The manubrium lies superiorly with the suprasternal or jugular notch marking its upper border, which is easily palpable between the clavicular heads. The upper border of the manubrium is used as a landmark when making a mediastinoscopy or collar incision. It also corresponds to the level of the lower border of the second thoracic vertebra and first thoracic spinous process. The manubrium is 4cm long and overlies the aortic arch. The manubrium articulates with the sternal body at the (sternal) angle of Louis: this manubriosternal junction is palpable as a transverse ridge in most patients. The second costal cartilages articulate with the lateral border of the sternum at the angle of Louis: counting the ribs anteriorly is most easily started at this level because the first rib is impalpable beneath the clavicle. The angle of Louis lies at the level of the lower border of the fourth thoracic vertebra. The sternal body is 10 cm long and lies opposite the fifth to eighth vertebrae in front of the heart below the body is the cartilaginous xiphisternum, which may be palpable, and lies at the level of the ninth thoracic vertebra  The plane passing through the angle of Louis and the lower border of the fourth thoracic vertebra is an important landmark for deeper thoracic structures. The plane arbitrarily divides the superior mediastinum from the rest of the mediastinum. The tracheal carina lies at this level. The concavity of the aortic arch lies just above and the bifurcation of the pulmonary trunk just below this plane. The ligamentum arteriosum between the origin of the left pulmonary artery and the concavity of the aortic arch runs almost horizontally at this level, which marks the lowest descent of the left recurrent laryngeal nerve. The azygos vein arches forward over the right hilum to enter the back of the superior vena cava in this plane, and the thoracic the midline, crosses over to reach the left side of the chest by this level. The costal cartilages connect the anterior ends of the ribs to the sternum, increase in length from the first to seventh cartilage, and then shorten. The costochondral junctions lie in a line from a point 5 cm from the midline at the angle of Louis to a point 2.5 cm behind the lowest part of the tenth costal cartilage.  The fifth rib lies just under the lower border of pectoralis major at the level of the xiphisternal joint. The seventh costal cartilage is usually the lowest that articulates directly with the sternum. Below this, the costal margin forms the easily palpable lower boundary of the bony thorax with contributions from the seventh to tenth costal cartilages. The tenth costal cartilage marks the lowest point of the costal margin, at the level of the third lumbar vertebra in the midaxillary line. The tips of the eleventh and twelfth ribs may be palpable in the body wall behind the lowest part of the costal margin.  Trachea The trachea is easily palpable above the suprasternal notch. It runs down almost vertically fromthe cricoid cartilage at the level of the sixth cervical vertebra to enter the thoracic cavity behind the manubrium. The trachea is 15 cm long: just 5 cm is palpable above the notch with the head in a neutral position, but this length increases up to 8 cm when the neck is extended (eg, in the position for tracheostomy). Within the chest the trachea lies slightly to the right of the midline and ends at its bifurcation at the carina at the level of the lower border of the fourth thoracic vertebra. This is the level described in the cadaver: 1.the carina may travel up to 2 to 3 cm with each breath and may lie at the level of the fifth or sixth thoracic vertebra at full inspiration  Surface projections of the pleura and lungs Note the area of the triangle of auscultation formed by the lateral border of trapezius muscle, medial border of scapula, and upper border of latissimus dorsi. Because this area is free of intervening muscle masses, respiratory sounds can be easily detected.  Major airways and pulmonary hila The trachea ends at its bifurcation at the level of the angle of Louis. The right main bronchus runs more vertical than the left, arising at 25 degrees from the vertical, and running for 2.5 cm before entering the right lung hilum at the level of the fifth thoracic vertebral body. The left main bronchus runs at 45 degrees for 5 cm before entering the left hilum at the level of the sixth thoracic vertebra. The hilum lies behind the second to fourth costal cartilages parallel and 2.5 cm lateral to the sternal edge. Posteriorly, this corresponds to a vertical line 5 cm from the midline alongside the fourth to sixth thoracic spinous processes.  Pleura The parietal pleura lines the chest wall and mediastinum and bounds the pleural cavity; the surface projection of the pleura is of clinical importance in the prevention of inadvertent pneumothorax during central venous cannulation or abdominal surgery. The thoracic inlet is bounded by the oblique first rib: from the lateral aspect, the upper border of the pleura follows the line of the rib, but from the front, the apex of the pleura lies 2.5 cm above the medial third of the clavicle and behind the sternocleidomastoid muscle. From the apex, the pleura follows a curved line, convex upward, toward the sternoclavicular joint. On both sides of the chest, the pleura runs toward themidline behind the angle of Louis at the level of the second costal cartilage and continues downward in the midline to the fourth costal cartilage. Here the right and left pleura diverge. The right pleura continues downward to the right side of the xiphisternal joint. The left pleura is deflected laterally to the sternal edge at the lower border of the left sixth costochondral joint. The lower limit of the costal pleura continues laterally on both sides to cross the eighth rib in the midclavicular line, the tenth rib in the midaxillary line, and the twelfth rib at the lateral border of erector spinae.  Lungs The surface markings of the lungs closely follow those of the pleurae because only a thin film of fluid separates these structures in health. In quiet respiration, however, the lower edge of the lung is usually 5 cm or two rib-spaces above the limit of the pleura; the excursion of the lung may be up to 7.5 cm in deep respiration. Although the projection of the lung apices matches the pleural projection, the inferior border of the lung crosses the sixth rib in the midclavicular line, the eighth rib in the midaxillary line, and the tenth rib at erector spinae. On the left side, the lung displays the cardiac notch and lies 2.5 cm from the edge of the pleura and sternum at the level of the fifth costal cartilage and 4 cm from the midline at the level of the sixth cartilage. The posterior borders of the lungs follow a line down either side of the vertebral column from the level of the spine of the seventh cervical vertebra down to the spine of the tenth thoracic vertebra. The separation of visceral and parietal pleura below the base of the lung gives rise to the slit-like costodiaphragmatic recess behind the dome of the diaphragm. There is a similarly formed costomediastinal recess behind the left lower costal cartilages because of the cardiac notch of the left lung.  vertebra down to the spine of the tenth thoracic vertebra. The separation of visceral and parietal pleura below the base of the lung gives rise to the slit-like costodiaphragmatic recess behind the dome of the diaphragm. There is a similarly formed costomediastinal recess behind the left lower costal cartilages because of the cardiac notch of the left lung. vertebra down to the spine of the tenth thoracic vertebra. The separation of visceral and parietal pleura below the base of the lung gives rise to the slit-like costodiaphragmatic recess behind the dome of the diaphragm. There is a similarly formed costomediastinal recess behind the left lower costal cartilages because of the cardiac notch of the left lung.  Pulmonary fissures The left lung is separated into upper lobe and lower lobe by the oblique or major fissure. An additional transverse or minor fissure produces the middle lobe of the right lung. The right oblique fissure starts opposite the fourth thoracic spinous process and follows the line of the fifth rib, or a line just below, to end near the right sixth costochondral junction or just above in the fifth intercostal space. The transverse fissure leaves the oblique fissure in the fifth intercostal space in the midaxillary line and runs forward to end behind the right fourth costal cartilage at the anterior border of the lung. The left oblique fissure is more variable in position than the right: it starts opposite the third of fourth spinous process and runs forward and downward through the fifth intercostal space in the midaxillary line to end near the left sixth costochondral junction or just above in the fifth intercostal space.  Assignment Describe the surface projection of the heart. (Diagrams are essential)  TIPS A Upper border of right 3rd costal cartilage. B Lower border of left 2nd costal cartilage. C Apex beat at left 5th intercostal space, lateral to mid- clavicular line. D Middle of right 6th costal cartilage The surface markings of the pericardium closely follow those for the heart with the exception that the pericardium extends more superiorly around the great vessels, so that it reaches the level of the right second costal cartilage where it invests the superior vena cava.  Surface projection of the diaphragm The diaphragm has an extensive origin from its crura on the upper lumbar vertebra, muscular slips arising from the lower ribs, and the sternum. The diaphragm is dome-shaped and its apex lies at a variable position according to respiration. The right hemidiaphragm descends to the level of the tenth thoracic vertebra, opposite the anterior end of the fifth rib, with deep inspiration. The left hemidiaphragm usually lies 1 cm lower. The diaphragm transmits several important structures between thorax and abdomen. The inferior vena cava and right phrenic nerve pass through the central tendon of the diaphragm 2.5 cm to the right of the midline at the level of the eighth thoracic vertebra, behind the right sixth costal cartilage. The esophageal hiatus, though which passes the esophagus, the anterior and posterior vagal trunks, and the esophageal branches of the left gastric artery, passes through a sling of fibers from the right crus  This hiatus lies 2.5 cm to the left of the midline at the level of the tenth thoracic vertebra, behind the left seventh costal cartilage. The aortic hiatus lies just to the left of the midline behind the median arcuate ligament of the diaphragm and passes the descending aorta, thoracic duct, and azygos vein (although this may pierce the right crus separately).  Thanks for the time.  Further readings  Agur AMR, Dalley AF, Grant JCB. Grant’s atlas of anatomy. 11th edition. Philadelphia: Lippincott Williams & Wilkins; 2005.  Deslauriers J, Mehran R. Handbook of perioperative care in general thoracic surgery. Philadelphia: Elsevier Mosby; 2005  Gray H, Standring S. Gray’s anatomy: the anatomical basis of clinical practice. 39th edition. Edinburgh (UK): Elsevier Churchill Livingstone; 2005.  Kaiser LR. Atlas of general thoracic surgery. St. Louis MO): Mosby; 1997  Keogh B, Ebbs S. Normal surface anatomy. London: Heinemann Medical; 1984.  Pearson FG. Thoracic surgery. 2nd edition. New York: Churchill Livingstone; 2002  Sinnatamby CS, Last RJ. Last’s anatomy: regional and applied. 10th edition. Edinburgh (UK): Churchill Livingstone; 1999