Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
THE THORACIC CAGE The thoracic cage is a osseo-cartilaginous, elastic & a conical cavity. It has a inlet & a outlet. Inlet is narrowers outlet is broader. The cage is flatened anteroposteriorly & on cross-section is reniform in shape. However, in the new born , it is rounded on cross-section. Dr Sujatha 2 BOUNDARIES Behind • the bodies of 12 thoracic vertebra & their intervertebral discs. • transverse processes of the vertebrae. • Posterior parts of ribs extending upto the posterior angles Dr Sujatha 3 Dr Sujatha 4 Front • • Strenum - which consists of the manubrium, body & xiphoid process - the manubrium lies opposite the bodies of T3 & T4 - sternal body lies opposite T5 & T8 - sternal angle correspond to the lower border of T4 - xiphi-sternal joint correspond with the intervertebral disc between T8 & T9. Anterior part of the ribs & their costal cartilages. Dr Sujatha 5 Dr Sujatha 6 On each side Twelve ribs & their costal cartilages separated by intercostal spaces, front. - the last two spaces being open in - the intercostal spaces are occupied by the intercostal muscles, vessels & nerves. Dr Sujatha 7 INLET OF THORAX × it is reniform in shape. × It measures 5cms antero-posterior & 10 cms in transverse diameters. × inlet slopes downwards &forwards. The sternal end of the first rib lies 3 to 4 cms lower than the verterbral end. × × Bounded behind by the body of T1, at the sides by the first rib & its cartilage; in front by the upper border of the manubrium. 8 Dr Sujatha Dr Sujatha 9 OUTLET OF THORAX It is bounded - behind by the body of T12. - In the front by the 7,8,9 & 10th costal cartilages & the xiphoid process forming an infra sternal angle. - At the sides by the 11 & 12 th ribs. The outlet is closed by the diaphragm. Dr Sujatha 10 FUNCTIONS OF THE THORACIC CAVITY It contains & protects essential organs of respiration & circulation ( lungs & heart ) It alters the diameters of the thorax during the different phases of respiration – by the movement of the ribs & the diaphragm. Some of the sub-diaphragmatic organs like liver, stomach & spleen are placed beneath the costal margins. Dr Sujatha 11 STERNAL ANGLE It forms a important land mark for counting the ribs. – the sternal angle articulate with the 2nd costal cartilage. it is the junction between the superior & inferior mediastinum. Sternum moves at tha sterno-manubrial joint during respiration. Dr Sujatha 12 Trachea bifurcates close to this level. Beginning & ending of the arch of aorta. Thoracic duct deviates from right to the left behind the oesophagus at this level. Superior venacava pierces the fibrous pericardium. Arch of the azygos vein terminates here. Anterior margins of the lungs & the pleura approximate at the sternal angle. Dr Sujatha 13 INTERCOSTAL SPACE There are eleven intercostal spaces on each side. Last two are open in the front because the 11th & the 12th ribs are floating ribs. Those spaces intervening between the typical ribs & traversed by vessels & nerves are known as the typical inter-costal spaces. Dr Sujatha 15 The 3rd ,4th, 5th & 6th intercostal spaces are the typical inter costal spaces & possess the following boundaries : above : sharp lower margin of the rib above & its cartilage. below : blunt upper border of the rib below & its costal cartilage. in front : lateral margin of the sternum behind : body of the corresponding thoracic vertebra. Dr Sujatha 16 Posterior part of each space is placed between two ribs is called the inter-osseous part. Anterior part intervening between the two cartilages is called the inter-cartilaginous part. Dr Sujatha 17 CONTENTS 1) - INTERCOSTAL MUSCLES. 2) - INTERCOSTAL VESSELS. 3) - INTERCOSTAL NERVES. Dr Sujatha 18 INTERCOSTAL MUSCLES. The muscles are arranged in three layers from outside inwards – - Intercostalis Externus - Intercostalis Internus - Intercostalis Intimus (inner most inter-costal muscle) Dr Sujatha 19 Intercostalis externus it extends from the sternum to the tubercles of the ribs. in the inter-osseous part it is fleshy in the inter-cartilagenous part it is replaced by an aponeurosis known as the anterior intercostal membrane. The fibres are directed downwards, forwards & medially in the anterior part. Dr Sujatha 20 Dr Sujatha 21 Origin : it arises from the lower border of the upper rib . Insertion : it is inserted into the outer lip of the upper border of the lower rib. Dr Sujatha 22 Intercostalis internus It extends from the sternum to the posterior angels of the ribs. The anterior part is fleshy. Posteriorly, it is replaced by the posterior intercostal membrane. The direction of the fibres are at right angles to that of the externus muscle. Dr Sujatha 23 Dr Sujatha 24 Origin : rib. it arises from the costal groove of the upper Insertion: into the intermediate part of the upper border of the lower rib. Dr Sujatha 25 INTERCOSTALIS INTIMUS. It is a part of the transversus thoracis muscle. It occupies middle 2/4 of the intercostal space. The intercostal nerves & the vessels run in between the internus & intimus muscles – called the neurovascular plane. Dr Sujatha 26 ORIGIN : it arises from the upper lip of the costal groove of the rib above INSERTION: into the inner lip of the upper border of the rib below. Dr Sujatha 27 Dr Sujatha 28 TRANSVERSE THORACIS MUSCLE it has three components - sub costalis - intercostalis intimus - sternocostalis. Dr Sujatha 29 Dr Sujatha 30 Action of the muscles External intercostal : elevates the ribs. Helps in inspiration Internal intercostal :depress the ribs Helps in expiration. They prevent blowing out or sucking in of the intercostal spaces during respiration Dr Sujatha 31 INTERCOSTAL VESSELS. ARTERIES In each space there are TWO groups - anterior - posterior. Dr Sujatha 32 ANTERIOR INTERCOSTAL ARTERIES Present in all spaces expect in the last two spaces. In each space they are two in number. One follows the upper margin & other follows the lower margin of the intercostal space. They run in the neurovascular plane. They anastomose with the posterior intercostal arteries at the junction of the ant 1/3 & post 2/3 of the space. Dr Sujatha 33 In the upper six spaces they are the branches of the internal thoracic artery. In the lower three spaces they are derived from the musculo -phrenic artery. Dr Sujatha 34 Dr Sujatha 35 Dr Sujatha 36 POSTERIOR INTERCOSTAL ARTERIES Each space is occupied by one posterior intercostal artery In the upper two spaces they are the branches of the superior intercostal artery – from the costocervical trunk of the subclavian artery. In the lower 9 spaces they are the branches of the descending thoracic aorta. Dr Sujatha 37 Dr Sujatha 38 Neurovascular groove The intercostal nerves & the vessels run in between the internus & intimus muscles called the neurovascular plane. In the neurovascular groove, the arrangement of the structures are (from above downwards): VAN - vein - artery - nerve Dr Sujatha 39 Dr Sujatha 40 Dr Sujatha 41 INTERCOSTAL VEINS Corresponds to the arteries Arranged in two groups - anterior - posterior. Dr Sujatha 42 Anterior group – upper six spaces drain into internal thoracic vein lower spaces drain into the musculo-phrenic vein. Posterior group – Each space presents one posterior vein. They terminates in different manner on two sides Dr Sujatha 43 Dr Sujatha 44 INTERCOSTAL NERVES Eleven in number in each side. Each nerve is the ventral ramus of a thoracic nerve. 3rd to 6th nerves are typical 7th to 11th nerves appear in the anterior abdominal wall. Dr Sujatha 45 Course The nerves pass through the respective intervertebral foramen & appears in the posterior part of the space. It intervenes in the endothoracic fascia, between the costal pleura & posterior intercostal membrane. On reaching the angle of the upper rib, it gives off a collateral branch & a lateral cutaneous branch. Then, it passes along the costal groove , in the neurovascular plane. In the anterior part of the space , it passes in front of the sternocostalis muscle ,crosses internal thoracic artery, pierces intercostalis internus, anterior intercostal membrane, pectoralis major Terminates as the anterior cutaneous nerve. Dr Sujatha 46 Dr Sujatha 47 Dr Sujatha 48 Dr Sujatha 49 Branches DISTRIBUTING BRANCHES Collateral branch Lateral cutaneous branches –pierces the internus & the externus muscles in the midaxillary line. Divides in to anterior & posterior branches. COMMUNICATING BRANCHES Ganglionic branches – with the sympathetic Ganglion, via the grey & white rami communicantes. In the anterior ppart of the space , they communicate with the adjacent nerves behind the costal cartilages. 50 Dr Sujatha Dr Sujatha 51 APPLIED ANATOMY INTER COSTAL NEURALGIA A sharp burning pain in the area of the skin supplied by thoracic spinal nerves. It may be produced by the rib fractures. The important cause of neuralgia is HERPES ZOSTER which is a viral disease of the spinal ganglia.– vesicular eruptions appear along the dermatomes of the affected nerves. Dr Sujatha 52 RESPIRATORY MOVEMENTS Respiratory movements involves Inspiration: muscles of inspiration are diaphragm, intercostal muscles , erector spinae, scalene muscles &sternocledomastoid expiration: expiration is a passive movement. Dr Sujatha 53 MECHANISM OF RESPIRATION During inspiration all the three diameters of the thorax are increased The antero-posterior diameter– by the pump handle movement. The vertical diameter – by the descent of the diaphragm producing the piston movement. Dr Sujatha 54 Dr Sujatha 55 Dr Sujatha 56 The transverse diameter -- by the passive& active methods. - the passive method is found in the upper 6 ribs - the active method is seen in 7th to 11th ribs by the bucket handle movement Dr Sujatha 57 Dr Sujatha 58 Dr Sujatha 59 Dr Sujatha 60