Lung, pleura

• Pleura

  • Double layer serous membrane enclosing the lungs.
  • 2 layer: parietal layer: lines thoracic wall and viceral layer: covers surface of lungs
  • The 2 layers create a potential space: pleura cavity containing serous pleural fluid

  
• Viceral pleura

  • inner layer of pleura covering surface of the lungs, including the fissures between the lobes.
  • adheres tightly to the lung tissue, providing a smooth, slippery surface that allows the lungs to expand and contract with minimal friction.
  • Continuous with parietal pleura at hilum and along attachment of pulmonary ligament.

  
• Parietal pleura

  • lines the inner surface of the chest wall, the diaphragm, and the mediastinum.
  • Divided according to region in which it lies and surfaces it covers into: cervical pleura, costal pleura, mediastinal pleura and diaphragmatic pleura
  • High sensitive to pain + Temperature due to somatic innervation by intercostal and phrenic nerves (c3,4,5)
  • Develops from somatopleuratic mesoderm
• Viceral pleura

  • Pain insensitive
  • Autonomic innervation: sympathetic (2-5th sympathetic ganglion) + parasympathetic (vagus)
  • Develops from splanchcno pleuratic mesoderm
  • Firmly adhrent to lung

  
• Parietal pleura

  • Limits lung expansion
  • Thicker than viceral layer
• Cervical pleura

  • Dome shaped, covers apex of lung
  • Covered by suprapleural membrane
  • located at the apex of the lung, extends into neck (5cm above first costal cartilage. Boundary: It rises approximately 2-3 cm above clavicle and reaches into the neck region up to the level of the C7 vertebra.

  Relations: anterior: subclavian artery; Posterior: first rib of neck, sympathetic chain, posterior intercostal vein, superior intercostal artery, first thoracic nerve.

  
• Mediastenal pleura

  • Covers mediastenum. At hilum it reflected on to vessels and bronchi that enter hilum of lungs where it becomes continuous with viceral pleura

  
• Costal pleura

  lines inner surface of:

  • Sternum.
  • Ribs.
  • Costal cartilages.
  • Intercostal spaces.
  • Sides of vertebral bodies
  • Covered by endothoracic fascia

  
• Diaphragm pleura

  • Covers thoracic (upper) surface of diaphragm
  • Covers base of lungs and gets continuous with mediastenal pleura medially and costal pleura laterally

  
• Cervical pleura

  • Dome shaped, covers apex of lung
  • Covered by suprapleural membrane
  • located at the apex of the lung, extends into neck (5cm above first costal cartilage + 2.5cm above medial 1/3 of clavicle

  Relations:

  • Anterior: subclavian artery + scalenus anterior
  • Posterior: neck of first rib + sympathetic chain
  • Lateral: scalenus medius
  • Medial: large vessels of neck

  
• parietal pleura

  
• Recesses of pleura

  • The recesses of the pleura refer to specific areas where the parietal and visceral layers of the pleura do not separate completely, creating potential spaces or pockets.
  • Acts as reserve spaces for lung to expand during deep inspiration
  • Costomedial + costodiaphragmatic recesses
• Costodiaphragmatic/ costovertebral recesse

  • Situated at the junction of the costal pleura and the diaphragmatic pleura
  • Vertically its 5cm in lenght
  • extends from 8-10ribs along midaxillary line

  
• Costomedial recess

  • Situated at the junction of the costal pleura and the mediastinal pleura
  • lies anteriorly behind sternum and costal cartilages
  • More obvious on cardiac notch of lung
• Nerve supply of pleura

  • Costal pleura + peripheral part of diaphragmatic pleura: intercostal nerves
  • Central part of diaphragmatic pleura + mediastenal pleura phrenic nerves
• Sympathetic innervation to pleura: dilates bronchi

  Parasympathetic: narrows bronchial tree
• Blood supply:

  • Parietal pleura: intercostal artery + internal thoracic artery+ muscolophrenic artery. veins drain into azygous and internalthoracic veins.
  • Lymphatic: intercostal, internal mammary and posterior mediastinal nodes
  • Viceral pleura: bronchial artery and bronchial vein
  • Lymphatics: bronchopulmonary nodes
• Pleural fluid is produced by mesothelial cells that cover the surface of the lungs and the inner wall of the chest cavity.
• This fluid also helps maintain negative pressure within the pleural space, which is important for proper lung function.
• Pleural fluid has a composition similar to plasma but with lower protein content (about 3 g/dL).
• Surface anatomy of pleura

  • Apex: lies 1 inch above medial 1/3 of clavicle
  • Ant margin: right pleura extends vertically from sternoclavicular join to xiphisternal joint ( 6th costal cartilage). Left pleura extends from sternoclavicular joint to 4th costal cartilage , deviates laterally and extends to lateral margin to form cardiac notch then turns downward to xiphisternal joint
  • Inf margin: passes around chest wall, on 6th rib midclavicular line, 8th rib midaxillary line reaching adjacent to vertebral column posteriorly (T12)
  • Post margin: along vertebral column from apex (C7) to margin (T12)

  
• Pleura

  pleura

  
• The parietal pleura surrounding the root of the lung extends downwards beyond the root as a fold called the pulmonary ligament .

  • THE FOLD IS FILLED WITH LOOSE AREOLAR TISSUE and lymphatics.

  Allows for the EXPANSION OF THE PULMONARY VEINS can expand during increased venous return.

  • Allows for the DESCENT OF THE ROOT OF LUNG with the descent of the diaphragm during inspiration
• Lungs

  • Paired cone-shaped organs in thoracic cavity, with a broad base resting on the diaphragm and an apex extending above the first rib
  • Location: Situated in thoracic cavity, each lung occupies its own pleural cavity and is separated by the mediastinum
  • In young lungs are brown or gray in colour

  
• Features of lung

  • Each lung is conical in shape
  • Has an apex at upper end
  • Base at lower end resting on diaphragm
  • 3borders: anterior, posterior and inferior
  • 2 surfaces: costal and medial. Medial surface is divided into mediastinal and vertebral parts
• • Apex of lung: lies above level of anterior end of 1 rib.
  • Base of lung: semilunar and concave. Rests on diaphragm which separates right lung from right lobe of liver and left lung from left love of liver, funds of stomach and spleen
• Bordes of lung

  • Anterior border: Sharp edge that overlaps the heart, more pronounced on the left lung due to the cardiac notch.
  • Posterior border: Rounded and lies adjacent to the vertebral column.
  • Inferior border:Separates the diaphragmatic surface from the costal and mediastinal surfaces.

  
• Surfaces of lung

  • Costal surface: adjacent to ribs and intercostal spaces
  • Medial surface: divided into vertebral and mediastinal parts

  Vertebral part: related to vertebral bodies, posterior intercostal vessels and splanchnic nerves

  Mediastinal part:Faces the mediastinum.. Contains hilum and impressions of adjacent structures like heart and greater vessels

  
• Fissures and lobes of lung

  • right lung is divided into 3lobes ( upper, middle and lower) by two fissures (horizontal + oblique)
  • Left lung is divided into 2 lobes by the oblique fissure. Left lung also shows cardiac notch and lingula (Tongue-like projection of the superior lobe)

  
• Root of lung

  • It is formed by collection of structures that enter and leave the lung at the hilum. Lie opposite to bodies of 5,6,7 thoracic vertebra
  • Contents: principal bronchus on left side, one pulmonary artery, 2 pulmonary veins, one bronchial artery on right side and 2 on left sides, bronchial veins, anterior and posterior pulmonary plexus, lymphatics, bronchopulmonary lymph nodes, areolar tissue

  
• Arrangement of structures in root of lung

  From anterior to posterior is similar on both sides

  1. Superior pulmonary vein
  2. Pulmonary artery
  3. bronchus

  From above downwards is different

  • Right side. Eparterial bronchus, pulmonary artery, hyparterial bronchus, inferior pulmonary vein
  • Left side: pulmonary artery, bronchus, inferior pulmonary fein

  
• Relations of root of lungs

  Anterior:

  1. common on both sides: phrenic nerve, pericardiophrenic vessels, anterior pulmonary plexus.
  2. On right side: superior vena cava + part of right atrium

  Posterior:

  1. Common on both sides: vagus n+ posterior pulmonary plexus
  2. On left side: descending thoracic aorta

  Superior:

  1. right side: terminal azygous
  2. Left side: arch of aorta

  Inferior: pulmonary ligament

  
• Hilum

  • Depression on the mediastinal surface where structures enter and exit the lung.

  Contents: Bronchi, pulmonary arteries, pulmonary veins, lymphatic vessels, and nerves.
• Bronchial arteries


  Supply bronchial tree and pulmonary tissue
• Bronchial arteries on right side


  1 bronchial artery arises from right posterior intercostal artery
• Bronchial arteries on left side

  2 bronchial arteries from descending thoracic aorta
• Pulmonary arteries


  Bring deoxygenated blood
• Pulmonary veins


  Return oxygenated blood to heart
• Pulmonary veins


  • Superior Pulmonary Veins (Drain the superior lobes of each lung)
  • Inferior Pulmonary Veins (Drain the inferior lobes of each lung. In the right lung, the middle lobe is also drained by the superior pulmonary vein.)
• Bronchial vein


  Drain deoxygenated blood from the larger airways and the supporting structures of the lungs