Lungs/pulmones ©NotesMed.com Lungs/pulmones • Principal organs of respiration. • The two lungs (right and left) are situated in the thoracic cavity, one on either side of the mediastinum enclosed in the pleural sac. • Each lung is large conical/pyramidal shaped with its base resting on the diaphragm and its apex extending into the root of the neck. • The right lung is larger and heavier than the left lung. • The right lung weighs about 700 g and left lung 650 g. • The right lung has three lobes and the left lung has two lobes. • The lobes are separated by deep prominent fissures on the surface of the lung and are supplied by two lobar bronchi. © NotesMed.com External features • Apex. • Base. • Three borders – Anterior – Posterior – Inferior • Two surfaces – Costal – Medial ©NotesMed.com ©NotesMed.com Anatomical position and side determination • Its conical end (apex) is directed upwards and its broader end (base) is directed downwards. • Its convex surface (costal surface) is directed outwards and its flat medial surface presenting hilum is directed inwards. • Its thin margin (anterior margin) should face forwards and its rounded border (posterior border) should face backwards. ©NotesMed.com Apex • The apex is rounded/blunt superior end of the lung. • Extends into the root of the neck about 3 cm superior to the anterior end of the 1st rib and 2.5 cm above the medial 1/3rd of the clavicle. • Covered by cervical pleura and suprapleural membrane. • Covered with cervical pleura and strengthened externally by Sibson’s fascia. Relations: • Anterior: – Subclavian artery. – Internal thoracic artery. – Scalenus anterior. • Posterior: – Neck of 1st rib and structures in front of it, e.g., • Ventral ramus of first thoracic nerve, • First posterior intercostal artery, • First posterior intercostal vein • Sympathetic chain. ©NotesMed.com ©NotesMed.com Base • lower semilunar concave surface. • Rests on the dome of the diaphragm, hence it is also sometimes called diaphragmatic surface. • Relations • On the right side, – The lung is separated from the liver by the right dome of the diaphragm. • On the left side, – The left lung is separated from the spleen and fundus of stomach by the left dome of the diaphragm. ©NotesMed.com Border • Anterior border: – Thin and shorter than the posterior border. – The anterior border of right lung is vertical. – The anterior border of left lung presents a wide cardiac notch, which is occupied by the heart and pericardium. – In this region, the heart and pericardium is uncovered by the lung. Hence this region is responsible for an area of superficial cardiac dullness. Below the cardiac notch, it presents a tongue- shaped projection called lingula. • Posterior border: – Thick and rounded. – Extends from spine of C7 vertebra to the spine of T10 vertebra. • Inferior border: – Semilunar in shape and separates the costal and medial surfaces. ©NotesMed.com ©NotesMed.com Surfaces • Costal Surface – Large, smooth, and convex. – Covered by the costal pleura and endothoracic fascia. • Relations: – Related to the lateral thoracic wall. – The number of ribs related to this surface is as follows: • Upper 6 ribs in midclavicular line. • Upper 8 ribs in midaxillary line. • Upper 10 ribs in scapular line. • (In embalmed and hardened lung, the costal surface presents impressions of the ribs.) ©NotesMed.com ©NotesMed.com Medial Surface • Small posterior vertebral part. • Large anterior mediastinal part. Relations: • vertebral part: – Related to the vertebral column, – Posterior intercostal vessels, and greater and lesser splanchnic nerves. ©NotesMed.com Medial Surface • Mediastinal part presents a hilum, and it is related to mediastinal structures such as heart, great blood vessels, and nerves. ©NotesMed.com Medial surface Groove for trachea ©NotesMed.com Right Mediastinal Surface Left Mediastinal Surface ©NotesMed.com Lobes and fissures • The right lung is divided into three lobes: – Superior – Middle and – Inferior – Separated by two fissures • an oblique fissure and a horizontal fissure. • The left lung is divided into two lobes: – Superior – Inferior – Separated by an oblique fissure. ©NotesMed.com Root of the lung • A short broad pedicle connecting the medial surface of the lung with the mediastinum. • The root of lung lies opposite the bodies of T5, T6, and T7 vertebrae. • The hilum is the area on the mediastinal surface of the lung through which structures enter or leave the lung. • The root of lung is surrounded by a tubular sheath derived from the mediastinal pleura. ©NotesMed.com ©NotesMed.com Components of root of lung • Principal bronchus in the left lung, and eparterial and hyparterial bronchi in the right lung. • Pulmonary artery. • Pulmonary veins (two in number). • Bronchial arteries (one on the right side and two on the left side). • Bronchial veins. • Lymphatics of the lung. • Anterior and posterior pulmonary plexuses of the nerves. ©NotesMed.com Arrangement of structures in the root • From before backwards (it is more or less similar on two sides): – Pulmonary vein (superior) – Pulmonary artery – Bronchus (left principal bronchus on the left side, and eparterial, and hyparterial bronchus on the right side). • From above downwards (it differs on two sides): Right side Left side Eparterial bronchus Pulmonary artery Pulmonary artery Left principal bronchus Hyparterial bronchus Inferior pulmonary vein Inferior pulmonary vein ©NotesMed.com From anterior to posterior Lower Left P ©NotesMed.com Right side BABV Upper Right PV ©NotesMed.com Left side ABV Lower Left ©NotesMed.com Relations of the root of the lung • Anterior: – Phrenic nerve. – Anterior pulmonary plexus. – Superior vena cava (on right side only). • Posterior: – Vagus nerve. – Posterior pulmonary plexus. – Descending thoracic aorta (on left side only). • Superior: – Arch of azygos vein (on right side only). – Arch of aorta (on left side only). • Inferior: – Pulmonary ligament. ©NotesMed.com Bronchopulmonary segments The bronchopulmonary segments are well-defined, wedge- shaped sectors of the lung, which are aerated by tertiary (segmental) bronchi. Right lung Left lung • Superior: • Superior: – Apical – Apical – Posterior – Posterior – Anterior – Anterior • Middle: – Superior lingular – Lateral – Inferior lingular – Medial • Inferior • Inferior: – Superior (apical) – Superior (apical) – Medial basal – Medial basal – Anterior basal – Anterior basal – Lateral basal – Lateral basal – Posterior basal – Posterior basal ©NotesMed.com ©NotesMed.com ©NotesMed.com ©NotesMed.com Bronchopulmonary segment • Conical and apex towards the lung root. • Largest subdivision of a lobe of the lungs. • Separated by connective tissue septa. • Supplied by tertiary bronchus and tertiary branch of pulmonary artery. • Surgically resectable. ©NotesMed.com Characteristic features • It is a subdivision of the lobe of the lung. • It is pyramidal in shape with apex directed towards the hilum and base towards the surface of the lung. • It is surrounded by the connective tissue. • It is aerated by the segmental (tertiary) bronchus. • Each segment has its own artery, a segmental branch of the pulmonary artery. • Each segment has its own lymphatic drainage and autonomic supply. ©NotesMed.com Blood Supply • Functionally two distinctive circulatory pathways Pulmonary Vessels – Pulmonary artery – Pulmonary vein • Bronchial Vessels – Bronchial artery – Bronchial vein ©NotesMed.com Blood Supply Bronchial Arteries • Left – Two – From Descending Thoracic Aorta • Right – One – From right 3rd Posterior Intercostal artery or upper left BA ©NotesMed.com Venous drainage • Superficial set: – Two bronchial veins on each lung • Drains blood from visceral pleura, extra-pulmonary bronchi, hilar lymph node and terminate on the • Right lung: into Azygos vein. • Left lung: into left superior intercostal or accessory hemiazygous vein. • Deep set: – Drains blood from intrapulmonary bronchi and bronchiole. – Terminate into pulmonary vein or directly to Left Atrium. ©NotesMed.com Lymphatic drainage • Consists of superficial and deep sets • Superficial set: – Ramify beneath the visceral pleura from peripheral lung tissue. • Deep set: – Ramify around the intrapulmonary bronchi and bronchioles and around the pulmonary vessels. – Drains lymph from bronchial tree, pulmonary vessels and connective tissue septa. • Both sets – bronchopulmonary node- Superior & Inferior tracheobronchial Lymph node- Paratracheal Lymph node– bronchomediastinal lymph trunk- Junction of respective inferior jugular vein and superior vena cava through thoracic duct on the left side ad right Lymphatic duct on the right side. ©NotesMed.com Lymphatic drainage ©NotesMed.com Nerve Supply • Pulmonary plexus is formed by – Parasympathatic fibers from vagus nerve – Sympathatic fibers from upper 4 or 5 thoracic ganglia of sympathatic trunk. ©NotesMed.com Pleura • The pleura-like peritoneum is a serous membrane lined by flattened epithelium (mesothelium). • The lining epithelium secretes a watery lubricant—the serous fluid. • Layers of the pleura: – Two layers: • Visceral pleura and • Parietal pleura. • Space between the two layers is called pleural cavity (vide supra). ©NotesMed.com ©NotesMed.com Visceral Pleura (Pulmonary Pleura) • The visceral pleura completely covers the surface of the lung except at the hilum and along the attachment of the pulmonary ligament. • Extends into the depths of the fissures of the lungs. • Firmly adherent to the lung surface and cannot be separated from it. ©NotesMed.com Parietal Pleura • Thicker than the visceral