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Rachel Holmes Explain the actions of the pectoral muscles and investigate the roles of intercostal muscles in respiration Examine the neurovascular contents of the intercostal space Clinical relevance: Chest drains Skin Fascia (connective tissue/fat) Nerves Vessels Muscles Cartilages Bones Protects organs Allows for respiration Supports upper limbs Pectoralis major and minor ◦ Axioappendicular muscles (connect upper arm-appendix to thorax-axis Pec major and deltoid form deltopectoral groove in which the cephalic vein runs ◦ More on this when you cover the upper limb Pec major forms the anterior axillary fold (axilla=armpit) Pectoralis major ◦ Fan shaped muscle, covers superior part of thorax Pectoralis minor ◦ Located deep to pec. major ◦ Anterior wall of axilla (armpit) useful anatomical landmark (will be discussed in more detail later) ◦ Receive their blood supply from a branch of acromiothoracic aa (will cover in more detail later in course) Muscle Attachments Innervation Main Actions Pec. major Two heads: Clavicular head: anterior surface of medial half of clavicle Sternocostal: anterior of sternum, upper 6 costalcartilages To lateral lip of bicipital groove of humerus Medial and lateral pectoral nerves C5-8, T1 Adducts and medially rotates arm at shoulder joint. Clavicular head alone flexes the humerus Sternocostal head extends it from flexed position Pec. minor 3rd-5th ribs, near their costal cartilage to coracoid process of scapula Medial pectoral nerve C8,T1 Stabilises scapula (draws it anteriorly and inferiorly against thoracic wall) 3 layers of muscles Inter-costal ‘between the ribs’ External Intercostal Internal Intercostal Innermost Intercostal Attach from inferior border of superior rib to superior border of inferior rib Innervation: intercostal nn ◦ Superficial ◦ Middle ◦ Deep Important to know the direction the fibres run! External- hands in pockets Internal-hands on chest ◦ Innermost the same as internal Also, • Anteriorly external intercostals become membranous • Posteriorly internal intercostals become membranous External intercostals ◦ Fibres inferomedial ◦ Raise ribs when contracted, during inspiration Internal and innermost intercostals ◦ Fibres superomedial ◦ Lower ribs during forced expiration Contents of a typical intercostal space ◦ VAN bundle (intercostal vein, artery, nerve from superior to inferior) ◦ Collateral bundle (branches from VAN bundle) The VAN bundle runs along the inferior border of each rib in the costal groove In between the internal and innermost intercostals Rib (cross section) VAN bundle External Internal Innermost Collateral bundle 12 pairs of thoracic spinal nerves Anterior rami of T1-T11 form the intercostal nerves T12 is not intercostal- it runs under rib 12 and is known as the ‘subcostal nerve’ Dermatome- area of skin supplied by a single spinal nerve Myotome-the muscles supplied by a single spinal nerve (including anterior and posterior rami) Thoracic aorta gives rise to posterior intercostal aa Internal thoracic arteries (branches of subclavian aa) give rise to anterior intercostal aa Veins drain in a similar way Anterior intercostal vv drain into internal thoracic veins Posterior intercostal vv drain into azygos/hemiazygos system of veins (which drains into IVC) Clinical cases to consider in tasking booklet Cover the relevant anatomy! Anatomy alone can explains many conditions/diseases/procedures you will come across in clinical practice In the Summer you will have an exam on anatomy surrounding clinical cases For draining air/liquid from the pleural cavity that shouldn’t be therepneumothorax/haemothorax Pleural cavity ◦ Between visceral and parietal pleura ◦ Usually a ‘potential space’ filled only with pleural fluid Insert needle just superior to inferior rib to avoid damaging VAN bundle, between rib 4 and 5 in the midaxillary line Visceral pleura Pleural cavity Parietal pleura An anatomy text (essential) Moore and Agur, ‘Essential Clinical Anatomy’ or Drake and Vogl, ‘Gray’s Anatomy for Students’ Others you may find useful (not essential unless you’re super keen!): Lumley’s ‘Surface Anatomy’ (the be all and end all of surface anatomy) McMinn’s ‘Clinical Atlas of Human Anatomy’ (images of dissections, useful for the spotter) Pictures ◦ ◦ ◦ ◦ Moore and Agur, ‘Essential Clinical Anatomy’ 4th edition Drake and Vogl, ‘Gray’s Atlas of Anatomy’ Drake and Vogl, ‘Gray’s Anatomy for Students’ 1st edition http://alfa.saddleback.edu/N172/maintainChestTube.aspx Support reading ◦ Moore and Agur, ‘Essential Clinical Anatomy’ 4th edition Any questions? [email protected]