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- 1. JIGJIGA UNIVERSITY ANATOMY OFthoracic wall and diaphragm FOR MEDICINE STUDENTS 1
- 2. Introduction • Thorax isthe superior part of trunk between neck and abdomen • Contains heart and great vessels, lungs, thymus, trachea and esophagus 2
- 3. 3 Structure of theThoracic Wall The thoracic wall is covered on the outside by skin and by muscles attaching the shoulder girdle to the trunk. The thoracic wall is formed: Posteriorly by the thoracic part of the vertebral column Anteriorly by the sternum and costal cartilages Laterally by the ribs and intercostal spaces Superiorly by the suprapleural membrane; and Inferiorly by the diaphragm, which separates the thoracic cavity from the abdominal cavity
- 4. Skeleton of thorax • Forms: osteocartilaginous thoraciccage • Includes: 12 pairs of ribs and costal cartilages 12 thoracic vertebrae and intervertebral discs Sternum 4
- 5.
- 6. Ribs • The ribsare curved, flat bones that form most of the thoracic cage . • They are remarkably light in weight yet highly resilient. 6
- 7. Ribs cont… • Thereare three types of ribs: 1. True (vertebrocostal) ribs (1st- 7th ribs) attach directly to the sternum through their own costal cartilages. 2. False (vertebrochondral) ribs (8th -10th ) ribs) have cartilages that are joined to the rib just superior to them; thus, their connection with the sternum is indirect. 3. Floating (free) ribs (11th- 12th ribs) have rudimentary cartilages that do not connect even indirectly with the sternum. 7
- 8. The ribs havea: Head: has two facets for articulation with the body of vertebra. Neck: is a constricted portion situated between the head and the tubercle. Tubercle: located at the junction of neck with shaft. • It has a facet for articulation with the transverse process of the numerically corresponding vertebra 8 Ribs cont…
- 9. Body (shaft): isthin and flattened and twisted on its long axis. • Has the costal groove that protects the intercostal nerve and vessels. Angle: is where the shaft of the rib bends sharply forward. 9 Ribs cont…
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- 11.
- 12. Costal cartilages • Connectthe upper seven ribs to the lateral edge of the sternum and the 8th, 9th, and 10th ribs to the cartilage immediately above (7th). • The costal cartilages contribute significantly to the elasticity and mobility of the thoracic walls. • In old age, the costal cartilages tend to lose some of their flexibility as the result of superficial calcification. 12
- 13. Intercostal spaces • Separatethe ribs and their costal cartilages from one another. • Spaces and neurovascular structures are named according to the rib forming the superior border of the space. • There are 11 intercostal spaces and 11 intercostal nerves. • The subcostal space is below the 12th rib and the anterior ramus of spinal nerve T12 is the subcostal nerve. 13
- 14. Rib Fractures • Themiddle ribs are most commonly fractured. • Rib fractures usually result from blows or crushing injuries. • Its broken end may injure internal organs such as a heart, lung and the spleen. • Rib fractures are painful because the broken parts move during respiration, coughing, laughing, and sneezing. 14
- 15. The Sternum • Flatbone • Lies in the anterior midline of the thorax • It consists of three fused bones Manubrium Body Xiphoid process 15
- 16.
- 17. Manubrium of theSternum • Located at level T3-T4, most widest & thickest • Superior surface is indented by jugular notch (superasternal notch) • Clavicular notch articulate with clavicle • First rib articulate with lateral margin • Inferior border articulate with body; forms projection – sternal angle 17
- 18. Strenal angle (angleof luois) • Lies at level of T4 & T5 Intervertebral disc • Marks level of 2nd pair of costal cartilage at manubrosternal joint. • Trachea bifurcates into the main (primary) bronchi at this angle. • Arch of aorta give 3 branch at this angle and • Thoracic aorta begin at level of sternal angle. 18
- 19. • Located atlevel of T5-T9 • Approximately 10 cm long; • Lateral wall has costal notches Xiphoid process • Cartilaginous at birth • Lies in a slight depression, epigastric fossa. • Lies at the level of T10 vertebra. 19 Body of the Sternum
- 20. Xiphoid process cont… •The costal margins form infrasternal (sub costal) angle • This angle is used in cardiopulmonary resuscitation (CPR) for locating proper hand position on inferior part of sternal body 20
- 21.
- 22. Sternal Fractures • Sternalfractures are not common. • Crush injuries can occur in automobile accidents. • Use of air bags in vehicles has reduced the number of sternal fractures. • The most common site of sternal fracture is at the sternal angle. • The concern in sternal injuries is the likelihood of heart injury (cardiac rupture, tamponade) or lung injury. 22
- 23. Thoracic Vertebrae • Thereare twelve thoracic vertebrae • Each of which is characterized by articulations with ribs. The special features of these vertebrae are: 1. They have bilateral costal facet (demifacets) on their bodies for articulation with the heads of ribs 2. They have facets on their transverse processes for articulation with the tubercles of ribs. 3. They have long spinous processes. 23
- 24. Other important featuresof thoracic vertebrae are the following: • Their bodies are shorter ventrally than dorsally • Their articular processes are more or less vertical. • The spinous process are curved downward • They contain circular vertebral foramina 24
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- 26.
- 27. Thoracic Apertures Superior thoracicaperture Also called the anatomical thoracic inlet. The superior thoracic aperture is bounded: Posteriorly by the T1 vertebra Laterally by the first pair of ribs and their costal cartilages Anteriorly by the superior border of the manubrium 27
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- 29. Inferior thoracic aperture Alsocalled the anatomical thoracic outlet. The inferior thoracic aperture is bounded: Posteriorly by the T12 vertebra. Posterolaterally by the11th and 12th pairs of ribs. Anterolaterally by the joined costal cartilages of ribs 7th -10th , forming the costal margin. Anteriorly by the xiphisternal joint. 29
- 30. Imaginary Lines: facilitateanatomical & clinical description of the body Anterior median (midsternal) line (AML) – • Indicates intersection of the median plane with the anterior thoracic wall. Posterior median line (PML) – a vertical line along tips of spinous process of the vertebrae. Mid clavicualr line (MCL) – • Passes thru mid point of clavicle, parallel to the AML. 30
- 31. Anterior axillary line(AAL) • Runs vertically along anterior axillary fold that is formed by inferolateral border of pectoralis major. Mid axillary line (MAL) – runs from apex (deepest part) of axillary fossa, parallel to AAL. Posterior axillary line (PAL) –runs vertically along posterior axillary fold that is formed by latissimus dorsi & teres major. 31
- 32. Muscles of thethoracic wall • Serratus posterior – Serratus posterior superior: elevates superior ribs – Serratus posterior inferior: depress inferior ribs • Levator costarum: elevates the ribs • Transversus thoracic: Weakly depress the ribs 32
- 33.
- 34. Muscles of thethoracic wall cont… • Intercostals – External intercostal muscles: pulls ribs upward during inspiration – Internal intercostal muscles: draws ribs together; aids in expiration – Innermost intercostal muscles: the same action with internal intercostal muscles • Subcostals: the same action with internal intercostal muscles 34
- 35.
- 36. Fascia of ThoracicWall • The thoracic cage is lined internally with endothoracic fascia. • It attaches the costal parietal pleura to the thoracic wall. • It becomes more fibrous over the apex of the lungs (suprapleural membrane). 36
- 37. Diaphragm • The diaphragmis a double-dome shaped, musculo- tendinous partition separating the thoracic and abdominal cavities. • It have convex superior surface, and concave inferior surface. • Principal muscle of inspiration • Composed of two portions: Muscular (peripheral part) Aponeurotic (central part) 37
- 38.
- 39. Major openings Aortic hiatus– at the level of T12, in muscular part Transmits descending aorta, thoracic duct, azygos vein Esophageal hiatus– in the muscular part of the right crus of the diaphragm at the level of T10 to left of the median plane Transmits esophagus, vagi (anterior & posterior), esophageal branch of left gastric artery Caval opening – at the level of T8, to the right of the median plane with in the central tendon Transmits IVC, branch of right phrenic nerve, lymph vessels from liver 39
- 40. Arteries Superior surface • Superiorphrenic artery (thoracic aorta) • Musculophrenic and pericardiacophrenic artery (internal thoracic artery) • Inferior surface: inferior phrenic artery Veins The superior surface • Pericardiacophrenic and musculophrenic veins (internal thoracic veins) • Superior phrenic vein (IVC) The inferior surface: inferior phrenic veins. The right into the IVC, the left into left supra renal vein. 40
- 41. Nerve supply – Phrenic(motor and sensory) – Lower six intercostal and subcostal for peripheral part (sensory) Lymphatic drainage – Thoracic surface to phrenic nodes – Abdominal surface to lateral aortic nodes – The two surfaces communicate freely 41
- 42. Respiratory movements • Breathingor pulmonary ventilation consists of two phases Inspiration: the period when air flows into the lungs Expiration: the period when gases exit the lungs • Lungs expand during inspiration and retract during expiration. 42
- 43. Inspiration • During inspirationthe lungs increase in volume by enlarging in all dimensions • Air flows from areas of high pressure to areas of low pressure to equalize the pressure within the lung to that outside the lung • During normal quiet inspiration, the diaphragm and external intercostal muscles produce the muscle movement 43
- 44. Action of diaphragmduring Inspiration • When the dome shaped diaphragm contracts, it moves inferiorly and flattens • As a result, the vertical dimension of the thoracic cavity increases 44
- 45. Action of Externalintercostal during Inspiration • The external intercostal muscles contract to raise the ribs • Because the ribs normally extend anterio-inferiorly from the vertebral column, lifting them enlarges both the lateral and anterior dimensions 45
- 46.
- 47. Deep inspiration • Duringdeep or forced inspiration, additional muscles contract and further increase thoracic volume • The rib cage is elevated by the scaleni and sterno- cleidomastoid muscle • Scapulae are elevated and fixed by trapezius, levator scapulae, rhomboids so that serratus anterior and pectoralis minor act on ribs 47
- 48. Expiration • As therespiratory muscles relax, the rib cage drops under the force of gravity and the relaxing diaphragm moves superiorly • At the same time, the many elastic fibers within the lungs recoil • As a result, the volume of the thorax and lungs decrease simultaneously, which pushes air from the lungs 48
- 49. Forced expiration • Quietexpiration in healthy people is a passive process • Forced expiration is an active process produced primarily by: – The external & internal oblique, – Rectus abdominis and – Transverse abdominis muscles • The internal intercostal muscles, quadratus lumborum and the latissimus dorsi also help to depress the rib cage 49
- 50. Nerves of thoracicwall • 12 pairs of thoracic spinal nerves • Leave spinal cord through corresponding intervertebral foramina and divide into 2 branches Posterior (dorsal) rami: innervate muscles, bones, joints and skin of the back Anterior (ventral) rami: innervate intercostal musculature, and skin of the thorax (dermatome) – Ventral rami of T1-T11= intercostal nerves – Ventral ramus of T12 = subcostal nerve 50
- 51. Intercostal Nerves • Eachenters an intercostal space between the parietal pleura and the posterior intercostal membrane. • It then runs forward between the innermost intercostal and internal intercostal muscle. • Supply successive segments of thoraco abdominal wall (dermatome and myotome). T1–T2 : also supply upper limb. T3 - T6: only intercostal region, typical. T7-T11: intercostal region + abdominal wall. 51
- 52.
- 53. Arteries of thoracicwall The arterial supply to the thoracic wall derives from the: • Thoracic aorta, through the posterior intercostal and subcostal arteries. • Subclavian artery, through the internal thoracic and supreme intercostal arteries. • Axillary artery, through the superior and lateral thoracic arteries. 53
- 54. Intercostal arteries • Intercostalvessels run in the costal groove 1. Posterior intercostal arteries 1st & 2nd- arise from superior intercostal artery (a branch of costocervical trunk of subclavian artery) 3rd -11th & subcostal artery- branches of the thoracic aorta Accompanies intercostal nerve 54
- 55.
- 56. Intercostal arteries… 2. Anteriorintercostal arteries 1st – 6th – from internal thoracic 7th- 9th – from musculophrenic 10th & 11th – have no anterior intercostal Anastomose with the posterior vessels in the intercostal spaces around the midclavicular line 56
- 57.
- 58. The internal thoracicartery Origin – Arise from the first parts of the subclavian arteries. • Descend into the thorax posterior to the clavicle and 1st costal cartilage. Termination - Terminate in the 6th intercostal space by dividing into the superior epigastric and the musculophrenic arteries. 58
- 59. Branches of ITA •Anterior intercostal arteries for the upper six intercostal spaces • Pericardiacophrenic artery, which accompanies the phrenic nerve and supplies the pericardium and diaphragm. • Mediastinal arteries to the contents of the anterior mediastinum (e.g., the thymus) 59
- 60.
- 61. Intercostal veins Right 1st –right brachiocephalic vein 2nd, 3rd & 4th - join to form superior intercostal which drain into azygos vein, then to SVC 5th - 11th & subcostal (12th) – drain directly to azygos vein. Left 1st – left brachiocephalic vein 2nd, 3rd & 4th – join to form superior intercostal which drain into left brachiocephalic 5th - 8th – drain into accessory hemiazygos vein 9th -11th & subcostal (12th) – drain into hemiazygos vein. 61
- 62.
- 63. The internal thoracicveins • Accompany the arteries (venae comitantes) • Drain into brachiocephalic vein • Intercostal vein, artery & nerve form a neurovascular bundle lying between internal intercostals and innermost intercostals in costal groove 63
- 64.