Anatomy of Lungs PDF

ANATOMY OF LUNGS/ PULMONES - The lungs are principal organs of respiration - They are situated in the thoracic cavity one on each side of the mediastinum enclosed in the pleural sac...

ANATOMY OF LUNGS/ PULMONES - The lungs are principal organs of respiration - They are situated in the thoracic cavity one on each side of the mediastinum enclosed in the pleural sac - Main function is to oxygenate the blood, i.e., exchange of O2 and CO2 between inspired air and blood STRUCTURE ASSOCIATED LAB/LECTURE PHOTO LUNGS - conical or pyramidal in shape and spongy in texture - In newborn baby and people living in clean environment, the lungs are rosy pink in colour - People living in polluted areas or those who are passive or active smokers, the lungs are mottled with carbon particles and appear brown or black in colour - Right lung weighs about 675g and left is about 625g - In adults the lung crepitates on touch (due to air in the alveoli) and floats in water - In foetus or stillborn lungs are solid, do not crepitate on touch and sinks in water - Right lung is shorter and broader (because of right lobe of liver) - The left lung is longer and narrower (because the heart projects to the left side) External Features: a. Apex b. Base/ diaphragmatic surface c. Three borders I. Anterior border II. Posterior border III. Inferior border d. Two surfaces I. Costal surface II. Medial surface: vertebral part & mediastinal part APEX - Rounded /blunt superior end of the lung, extends into the root of the neck  about 2.5cm above the medial one third of the clavicle - Anteriorly it is grooved by subclavian artery, scalenus anterior muscle and subclavian vein - Posteriorly related to sympathetic chain, superior intercostal vein, superior intercostal artery and ventral ramus of T1 (all 4 structures are in front of the neck of 1st rib) - Apex is covered by cervical pleura and suprapleural membrane or Sibson’s fascia - Sibson’s fascia extends from the transverse process of C7 to inner border of the first rib Apex Relations Laterally related to: scalenus medius Medially (on the right side) related to: - Right brachiocephalic vein - Right phrenic nerve - Brachiocephalic trunk - Right vagus nerve - Trachea Medially (on the left side) related to: - Left brachiocephalic vein - Left subclavian artery - Left recurrent laryngeal nerve - Oesophagus - Thoracic duct BASE/DIAPHRAGMATIC/INFERIOR SURFACE - It is semilunar and deeply concave - Rests on diaphragm which separates the right lung from right lobe of liver, and left lung from left lobe liver, fundus of stomach and spleen BORDERS I. Anterior Border - Thin and shorter than posterior border - On the right side it is almost vertical and corresponds to costomediastinal line of pleural reflection - On the left side below the 4th costal cartilage, it shows a wide notch – cardiac notch, within which the heart and pericardium are uncovered by  lung (area of superficial cardiac dullness) II. Posterior Border - Thick and ill-defined or rounded - Extends from spine of C7 to spine of T10 III. Inferior Border - Somewhat semilunar in shape - Separates the base from the costal and medial surfaces SURFACES I. Costal Surface - It is large and convex - Covered by costal pleura and endothoracic fascia - Related to lateral thoracic wall (related to ribs and their costal cartilages and the intercostal spaces) - In hardened lung, the costal surface presents impressions of ribs  II. Medial Surface Divided into posterior small vertebral part (A) and a large anterior mediastinal part (B) a. Vertebral Part - Related to vertebral bodies of thoracic vertebrae, inter-vertebral discs, posterior intercostal vessels and splanchnic nerves of the respective sides  b. Mediastinal Part - Is related to mediastinal septum, and shows cardiac impression, the hilum and a number of other impressions which differ on the two sides Mediastinal surface of right lung is related to: - Groove for the right subclavian artery a little below the apex and a notch below this produced by the 1st rib - Large cardiac impression below and in front of the hilum produced by the right atrium and auricle - In front of the hilum and leading upwards from the cardium is the groove for superior and inferior vena cava - Above, the groove for SVC is continuous with groove for right brachiocephalic vein - Above the hilum is a deep groove for arch of azygos vein - Above the groove for azygos vein, it is related to trachea and right vagus nerve - Right phrenic nerve is related in front of the hilum throughout the length - A wide shallow groove behind the hilum for oesophagus - Short but wide groove for IVC postero- inferior to the cardiac impression Right lung – Mediastinal surface A – Groove for azygos vein B – Groove for SVC C – Groove for IVC D – Groove for oesophagus E – Eparterial bronchus F – Hyparterial bronchus Mediastinal surface of left lung is related to: - A large cardiac impression below and in front of the hilum produced mainly by left ventricle and infundibulum of right ventricle - Pulmonary trunk in front of hilum in continuation of the area for infundibulum - A deep groove above the hilum produced by the arch aorta - Groove for the descending thoracic aorta is present behind the hilum and pulmonary ligament - Leading upwards from the groove for arch of aorta are two grooves – anterior one groove for left subclavian A and posterior one is for left common carotid A - Thoracic duct and oesophagus - Left phrenic nerve - Left vagus nerve - Left recurrent laryngeal nerve - Left sympathetic trunk Left lung – Mediastinal surface relations: - Groove for arch of aorta - Cardiac impression for left ventricle - Pulmonary ligament. Medially it continues as mediastinal pleura and laterally as pulmonary pleura - Lingula – medial and lateral lingular segments. Lingula corresponds to middle lobe of right lung - Groove for arch of aorta, descending thoracic aorta and oesophagus - Above the groove for arch of aorta it is related to oesophagus, trachea, thoracic duct and left recurrent laryngeal nerve LOBES AND FISSURES Right lung is divided into three lobes - superior lobe - middle lobe - inferior lobe by two fissures – 1. oblique fissure 2. horizontal fissure Left lung is divided into two lobes - superior - inferior by an oblique fissure OBLIQUE FISSURE - runs obliquely downwards forwards crossing the posterior border about 2 inches (same distance on the left side also) below the apex and inferior border about 3 inches lateral to the midline. - It separates the superior and middle lobe from the inferior lobe HORIZONTAL FISSURE - Presents only in the right lung. - It starts from the oblique fissure at the mid-axillary line, runs horizontally to the anterior border of the lung - It separates the superior lobe from the middle and inferior lobe ROOT OF THE LUNG - It is a short and broad pedicle which connects the medial surface of the lung to the mediastinum - It is formed by structures which either enter or come out of the lung at the hilum - It lies at the level of 5th, 6th and 7th thoracic vertebrae Root of the lung is made up of following structures: - Principle bronchus on the left side, and eparterial and hyparterial bronchi on the right side - One pulmonary artery - Two pulmonary veins (superior and inferior) - Bronchial arteries (one on the right and two on the left side) - Bronchial veins - Anterior and posterior plexuses of nerves - Lymphatics of the lung - Bronchopulmonary lymph nodes - Areolar tissue Sections of the roots of the lung showing their contents: Arrangement of structures in the root from before backwards - Superior pulmonary vein - pulmonary artery - bronchus ABOVE DOWNWARDS: Right Side- - Eparterial bronchus - Pulmonary artery - Hyperaterial bronchus - Inferior pulmonary vein Left side: - Pulmonary artery - Bronchus - Inferior pulmonary vein RELATIONS OF THE ROOT OF THE LUNG: Common on both sides (anterior) 1. Phrenic nerve 2. Anterior pulmonary plexus 3. Pericardiophrenic vessels Common on both sides (posterior) 1. Vagus nerve 2. Posterior pulmonary plexus On the right side: 1. Superior vena cava 2. Part of right atrium On the left side: 1. Descending thoracic aorta Superior on the right side: 1. Terminal part of azygos vein Superior on the left side: 1. Arch of aorta Inferior on the right side: 1. Pulmonary ligament OBLIQUE FISSURE can be drawn on the surface by joining: - First point 2 cm lateral to the 3rd thoracic spine - Second point on the 5th rib in the mid- axillary line - Third point on the 6th costal cartilage 7.5 cm from the median plane HORIZONTAL FISSURE can be drawn on the surface by joining: - First point on the anterior border of the right lung at the level of 4th costal cartilage - Second point on the 5th rib in the mid- axillary line ARTERIAL SUPPLY OF LUNGS Supplied by – bronchial arteries and pulmonary arteries Bronchial arteries - Supply nutrition - Right lung is supplied by one bronchial artery coming from right 3rd posterior intercostal artery - Left lung is supplied by two bronchial arteries arising from descending aorta Pulmonary Arteries - Bring deoxygenated blood from the heart to the lungs for oxygenation VENOUS DRAINAGE Drained by bronchial (deoxygenated blood) and pulmonary veins (oxygenated blood) Bronchial Veins: - Right bronchial veins drain into azygos vein - Left bronchial veins drain into hemiazygos vein or left superior intercostal vein Pulmonary Veins: - 2 on each side, carry oxygenated blood - Drain into left atrium LYMPHATIC DRAINAGE: - superficial and deep plexus of lymphatics finally drain into bronchopulmonary lymph nodes (hilar lymph nodes). - The efferents from the hilar nodes drain into tracheobronchial and paratracheal lymph nodes. - These lymph nodes enlarge in pulmonary tuberculosis. - The enlarged nodes may sometimes obstruct a lobar bronchus causing collapse (atelectasis) of the entire lobe. BRONCHIAL TREE Consists of: - principal bronchus - lobar bronchi - terminal bronchioles - respiratory bronchioles Principal Bronchi - The trachea divides into two primary (principal) bronchi, right and left primary bronchi Right principal Bronchus - is shorter, wider and more vertical than the left bronchus. - It is about 1 inch long and lies more or less in line with the trachea. - Since it is more vertical than the left the inhaled foreign particles tend to enter the right bronchus; as a result, the lung abscess occurs more commonly in the right lung Left Principal Bronchus - is narrower, longer and more horizontal than the right. - It is about 2 inches long and does not lie in line with the trachea Lobar Bronchi - on entering the lung, the right bronchus divides into 3 lobar bronchi, one for each lobe of the right lung. - the left bronchus divides into 2 lobar bronchi, one for each lobe Tertiary (segmental) bronchi - Each lobar bronchus divides into segmental bronchi, one for each bronchopulmonary segment. - The segmental bronchi divide repeatedly to form very small bronchi called terminal bronchioles, which give off respiratory bronchioles, which lack cartilage in their walls. - Each respiratory bronchiole aerates a small portion of lung called pulmonary units, which is concerned with gaseous exchange in the lung - Pulmonary Units consists of – - alveolar ducts - atria - air saccules - alveoli Bronchopulmonary Segments Self-contained functionally independent units of the lung tissue, aerated by tertiary bronchus Bronchopulmonary segments are the anatomical, functional and surgical units of the lungs Characteristic features: - It is a subdivision of the lobe of the lung - It is pyramidal in shape, with the apex directed towards the hilum and base towards the surface of the lung - Surrounded by connective tissue - Aerated by tertiary bronchus - Each segment has its own artery and segmental branch of segmental pulmonary artery - Has its own nerve, lymphatic drainage and autonomic supply BRONCHIAL TREE The right bronchus divides into: - The eparterial bronchus (continues as right superior lobar bronchus) divides into 3 segmental bronchi namely I. Apical II. anterior III. posterior - The hyparterial bronchus divides into: I. Middle lobar bronchus II. Inferior lobar bronchus - The middle lobar bronchus divides into: I. medial segmental bronchi II. lateral segmental bronchi - The inferior bronchus divides into 5 segmental bronchi, namely: I. Superior or apical II. Medial basal III. Anterior basal IV. Posterior basal V. Lateral basal The left principal bronchus divides into two: - Superior lobar bronchi - Inferior lobar bronci The left superior lobar bronchus divides into the following segmental bronchi: I. Apico-posterior (which divides into apical and posterior) II. Anterior III. Superior lingular IV. Inferior lingular The left inferior lobar bronchus divides into the following segmental bronchi: I. Superior (first branch) II. Antero-medial stem dividing into anterior basal and medial basal III. Postero-lateral stem dividing into posterior basal and lateral basal INTRAPULMONARY AIRWAYS - Segmental bronchi divide until they progressively become smaller and narrower. - Air passages less than 1 mm in diameter are called bronchioles. - Bronchioles – devoid of cartilage. Their walls are composed of smooth muscle only. - Bronchioles divide further and form terminal bronchioles. - Terminal bronchioles enter lung lobule. - Terminal bronchioles divide and give rise to respiratory bronchioles - Respiratory bronchioles divide to give rise to alveolar ducts - Each alveolar duct expands to form atrium which sprouts a number of alveolar sacs. - The alveolar sacs are studded with alveoli. Alveolar epithelium – - lined by simple squamous epithelium - Type I and type II alveolar cells. - Type II cells are slightly larger and secrete surfactant. - Blood – air barrier consists of type I cells, capillary endothelium and the basement membrane of the two in between. CLINICAL CORRELATIONS: 1. AUSCULTATION OF THE LUNG  2. BRONCHIAL ASTHMA - Occurs due to bronchospasm (spasm of smooth muscle in the wall of bronchioles), which reduces the diameter of the bronchioles - Patient will have difficulty during expiration - Airflow is further blocked by increased mucous secretion, which cannot be cleared due to failure in producing effective cough - Patient will have difficulty in breathing (dyspnea) and wheezing - In such cases bronchodilators (epinephrine) are taken, which cause bronchodilation 3. BRONCHOSCOPY - is a procedure through which the interior of the trachea and bronchi is inspected. - Carina at tracheal bifurcation is an important landmark. - Flexible fiberoptic bronchoscope can be introduced under local anesthetia. Trans-bronchial biopsies can be obtained through this instrument  4. BRONCHIETCTASIS - is a condition in which bronchi and bronchioles are dilated. - Segmental bronchi to the basal segments of the lower lobe are prone to this condition in which smaller divisions of the bronchi become permanently dilated and filled with pus. - Postural drainage is performed to remove pus by giving appropriate position to the patient.  5. BRONCHOGENIC CARCINOMA - Cancer arising in the bronchus - Usually squamous or small cell carcinoma - Mainly caused by cigarette smoking - Arises in the mucosa - Produces persistent productive cough or hemoptysis (spitting of blood) - Malignant cells can be detected in the sputum - X-ray – enlarging mass - Metastasizes early to the hilar lymph nodes and later to other thoracic lymph nodes - Supraclavicular lymph nodes are commonly involved, called “sentinel nodes” – alerts the lymph node to the possibility of malignant disease in the thoracic and/or abdominal organs - Hematogenous spread (spread of cancer cell through the blood) occurs to brain, bones, and suprarenal glands 6. PULMONARY EMBOLISM - Obstruction of a pulmonary artery by blood clot (embolus) - Common cause of morbidity (sickness) and mortality (death) - Embolus forms when a blood clot, fat globule or air bubble travels in the blood to the lungs - Arises from a leg vein after a compound fracture - Passes through the right side of the heart to a lung through a pulmonary artery or one of its branches - Partial or complete obstruction of blood flow to the lung - Lung or a sector of lung is ventilated with air but not perfused with blood