Chest Wall and Lung Anatomy and Physiology Zeyad S Alharbi, M.D.

Anatomy and Physiology of the Thorax Thoracic Skeleton 12 Pair of C-shaped Ribs Ribs 1-7: Join at sternum with cartilage end-points Ribs 8-10: Join sternum with combined cartilage at 7th rib Ribs 11-12: No anterior attachment Sternum Manubrium Joins to clavicle and 1st rib Jugular Notch Body Sternal angle (Angle of Louis) Junction of the manubrium with the sternal body Attachment of 2nd rib Xiphoid Process Distal portion of sternum

Anatomy and Physiology of the Thorax Thoracic Skeleton Topographical Thoracic Reference Lines Midclavicular line Anterior axillary line Mid-axillary line Posterior axillary line Intercostal Space Artery, Vein and Nerve on inferior margin of each rib Thoracic Inlet Superior opening of the thorax Curvature of 1st rib with associated structures Thoracic Outlet Inferior opening of the thorax 12th rib and associated structures & Xiphisternal joint

Blood Supply and Innervation

Anterior Chest Wall Deformities 1. Pectus excavatum 2. Pectus carinatum 3. Poland’s syndrome 4. Sternal defects 5. Miscellaneous

Etiology and Incidence of Pectus Excavatum It is reported 1/700 of lives birth M:F=3.4:1 37% occur in Families with Chest wall deformities It is a posterior depression of the sternum and costal cartilage due to over grow of costal cartilage The 1st and 2nd ribs, manubrium are in normal position

M-S Abnormalities with Pectus Excavatum Scoliosis Kyphosis Myopathy Marfan’s syndrome Cerebral palsy Prune-belly syndrome Tuberous sclerosis

Symptoms of Pectus Excavatum Decreased exercise tolerance Fatigability Dyspnea on exertion, and sternal pain Palpitations and multiple respiratory tract infections are reported MOST complaint : cosmetic deformity rather than symptomatology

Pectus Carinatum ( Pigeon Chest ) It refers to anterior protrusion of the sternum It is less common than pectus excavatum

Categories of Pectus Carinatum 1. Chondrogladiolar (I) It is the most common pectus carinatum (II) It consists of anterior protrusion of the body of sternum and lower costal cartilages

(2) Lateral Pectus Carinatum : a unilateral protrusion of the costal cartilages and is usually accompanied by sternal rotation to the opposite side (3) Chondromanubrial: (I) Uncommon (II) Protrusion of Manubrium, 2nd and 3rd costal cartilages with relative depression of the body and sternum

Poland’s Syndrome 1841 It refers to a congenital absence of the pectoralis major and minor muscles, ribs, breast abnormality, chest wall depression and syndactyly, brachydactyly or absence of phalanges It is present in 1/30000 The etiology is unknown

Scalenus Anterior Muscle Thoracic Outlet: The space through which the subclavian artery, vein and brachial plexus pass to the upper limb Symptoms develop when these structures are compressed at the outlet Boundaries: First rib, clavicle and Scalene muscles Clavicle Scalenus Anterior Muscle 1st Rib Patient’s arm is elevated

Thoracic Outlet Syndrome “TOS” {Definition of cervical rib: an accessory rib which is not normally present. If present it may cause compression of important structures in the thoracic outlet. } Cervical Rib: 0.5-1% population (not all are symptomatic) Neurogenic symptoms 95% Ulnar nerve C8-T1 is usually affected Vascular Symptoms 5% Subclavian artery Subclavian vein {cervical rib between the transverse process of C7 & the 1st rib. You can see the cervical rib in the other side elevating the brachial plexus.}

Vascular Symptoms of TOS Subclavian Artery: Prolonged compression & trauma Intimal injury Stenosis, Thrombosis Post-stenotic Dilatation or Aneurysm Distal Micro-embolisation Band Cervical Rib {In Unilateral Raynaud’s always suspect TOS, because usually Raynaud’s phenomenon is systemic & will cause bilateral symptoms}

Surgical Treatment of TOS Depending on the surgeon’s preference, there are 2 approaches for the surgery: Supraclavicular Approach: Scalenectomy Excision of 1st rib & fibrous bands Repair of subclavian artery if it’s injured and patient has vascular problems: Thrombectomy, patch angioplasty Excision of aneurysm & bypass graft {scalenectomy & 1st rib excision are enough in those with neurological symptoms} Transaxillary Approach: Excision of 1st rib. This causes the brachial to go down a little relieving the compression

The Respiratory Muscles

Anatomy and Physiology of the Thorax Pleura: appears between the 4th and 7th gestational weeks Visceral Pleura Cover lungs Parietal Pleura Lines inside of thoracic cavity. Pleural Space

The relationships of the pleural reflections and the lobes of the lung to the ribs that at the midclavicular line, the recess is between rib spaces 6 and 8, at the midaxillary line between 8 and 10 and at the paravertebral line between 10 and 12.

Lungs – Gross Anatomy Paired, cone-shaped organs in thoracic cavity Separated by heart and other mediastinal structures Covered by pleura Extend from diaphragm inferiorly to just above clavicles superiorly Lies against thoracic cage (pleura, muscles, ribs) anteriorly, laterally and posteriorly

Lungs – Gross Anatomy Hilum Cardiac Notch Medial ‘root’ of the lung Point at which vessels, airways and lymphatics enter and exit Cardiac Notch Lies in medial part of left lung to accommodate the heart

Lobes and Fissures

Lung – Blood Supply Dual Supply Bronchial Supply: arises from superior thoracic aorta or the aortic arch. Supply bronchi, airway airway walls and pleura Pulmonary Supply Pulmonary arteries enter at hila and branch with airways

Lymphatics Lymphatic drainage follows vessels Parabronchial (peribronchial) lymphatics and nodes  hilar nodes  mediastinal nodes  pre- and para-tracheal nodes  supraclavicular nodes

Anatomy and Physiology of the Thorax Mediastinum Central space within thoracic cavity Boundaries Lateral: Lungs Inferior: Diaphragm Superior: Thoracic inlet Structures Heart Great Vessels Esophagus Trachea Nerves Vagus Phrenic Thoracic Duct

Control of Breathing

Respiratory Center in Reticular Formation of the Brain Stem Medullary Rhythmicity Center Controls basic rhythm of respiration Inspiratory (predominantly active) and expiratory (usually inactive in quiet respiration) neurones Drives muscles of respiration Pneumotaxic Area Inhibits inspiratory area Apneustic Area Stimulates inspiratory area, prolonging inspiration

Regulation of Respiratory Center Chemical Regulation Most important Central and peripheral chemoreceptors Most important factor is CO2 (and pH)  in arterial CO2 causes  in acidity of cerebrospinal fluid (CSF)  in CSF acidity is detected by pH sensors in medulla Medulla  rate and depth of breathing

Regulation of Respiratory Center Cerebral Cortex Voluntary regulation of breathing Inflation Reflex Stretch receptors in walls of bronchi/bronchioles

Respiratory Centers and Reflex Controls Figure 23.27

Pulmonary function is affected by lung resection, extent varies: pneumonectomy: FEV1: 34~36%↓ FVC: 36~40%↓ VO2 max: 20~28%↓ lobectomy: FEV1: 9~17%↓ FVC: 7~11%↓ VO2 max: 0~13%↓ Am J of Med (2005) 118, 578–583

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