Lungs Lecture Notes - RCSI Bahrain

LungsClass: Year 1 Module: RSLecturer: Dr. Vijayalakshmi S BDepartment of AnatomyOffice no. 340Email id: [email protected]: April 27th, 2023 Learning Outcomes•Outline the embryonic development of the lungs and the clinical conditions that may arise from abn...

LungsClass: Year 1 Module: RSLecturer: Dr. Vijayalakshmi S BDepartment of AnatomyOffice no. 340Email id: [email protected]: April 27th, 2023 Learning Outcomes•Outline the embryonic development of the lungs and the clinical conditions that may arise from abnormal development.•Describe the structure and function of the pleural cavities and lungs•Explain the mechanisms involved in inspiration and expiration and the musculoskeletal structures responsible•Outline the vascular supply to the lungs and how oxygenation of pulmonary blood occurs•Identify normal respiratory landmarks on clinical or radiographic examination, and recognize some common abnormal features Development of the Lungs ENDODERM Respiratory primordium•First sign of development –ØAppearance of respiratory diverticulum (lung buds) during 4thweekØAppears as an outgrowth from the ventral wall of the foregut•Appearance and location of lung buds are dependent upon the adjacent mesoderm •Epitheliumliningof the lower respiratory organs (larynx, trachea, bronchi & lungs) –endodermal origin•Cartilage, muscular and connective tissue componentsof the trachea & lungs –splanchnic mesoderm surrounding the foregut •Initially the diverticulum has open communication with the foregut•Eventually they become separated by mesodermal folds, tracheoesophageal folds•The two folds fuse in the midline to form the tracheoesophageal septum, dividing the foregut into trachea & lung buds ventrally and esophagus dorsally The respiratory primordium maintains its communication with the pharynx through the laryngeal orifice Clinical correlates•Tracheoesophageal fistulas and esophageal atresia Development of trachea, bronchi and lungs Development of pleural layers•Splanchnic mesoderm, which covers the outside of the lung, develops into the visceral pleura•Somatic mesoderm layer, covering the body wall from inside, develops into the parietal pleura•Space in between the parietal &visceral pleura –pleural cavity Development of the bronchial tree •Secondary bronchi divide repeatedly in a branching fashion, forming 10 tertiary (segmental) bronchi creating bronchopulmonary segments•Branching is regulated by epithelial-mesenchymal interactions between the endoderm of the lung buds and splanchnic mesoderm that surrounds them Maturation of the lungsPseudoglandular period(5 –16 weeks)Canalicular period(16 –26 weeks) Terminal (Saccular) period(26 week –birth)Maturation of the lungsAlveolar period(8 month –childhood) Blood –air barrier in the lungAlveolar phase after birth Maturation of the lungs Respiratory distress syndrome Tra c h e a nCommences in the neck in the midline, below lower border of cricoid cartilage (C6vertebra)C6T4CricoidSternal anglecarinanExtends down to level of sternal angle in the thorax (lower border of T4vertebra)Tr a c h e a : E x t e n t Tr a c h e a : S t r u c t u r e•Cartilage rings reinforce and provide some rigidity to the tracheal wall to ensure that the trachea remains open (patent) at all times•Cartilage rings are connected by elastic sheets called anularligaments Fibrocartilaginous tube-Anterior and lateral walls of the trachea are supported by 15 to 20 C-shaped tracheal cartilages.Cartilage deficient posteriorly, made up of involuntary trachealismuscleSignificance? Tr a c h e a : R e l a t i o n s i n t h e t h o r a xAnteriorly –left brachiocephalic vein, arch of aorta, brachiocephalic trunk, left common carotid artery Posteriorly –Esophagus, left recurrent laryngeal nerve Tr a c h e a : R e l a t i o n s i n t h e t h o r a xLeft side-arch of aorta, left common carotid & left subclavian arteries, left lungLateral RelationsRight side-arch of azygos vein, right vagus nerve & right lung Principal Bronchi (Main bronchi)In the thorax at the level of sternal angle, trachea ends below at the carinaby dividing into right & left principal (main) bronchiCARINAis the cartilaginous ridge in the sagittal plane of the trachea where it splits into the two primary bronchiClinical significance? Right main bronchusLeft main bronchusWider, shorter, more verticalNarrower, longer, more horizontalGives off 3 lobar bronchiGives off 2 lobar bronchiPrincipal Bronchi (Main bronchi)oesophagusinferior lobar bronchusarch of aortasuperior lobar bronchussuperior lobar bronchusmiddle and inferior lobar bronchiMISSI oesophagusinferior lobar bronchusarch of aortasuperior lobar bronchussuperior lobar bronchusmiddle and inferior lobar bronchiClinical RelevanceInhaled foreign bodiesn tend to enter the wider, vertical right main bronchusCarinan useful landmark in bronchoscopy n widening of carina may be seen during bronchoscopy in cases of carcinoma involving the tracheobronchial lymph nodesMISSIPrincipal Bronchi (Main bronchi) Tracheobronchial treeTrachea Primary (main) bronchi Secondary (lobar) bronchi Tertiary (segmental) bronchi (supply the bronchopulmonary segments) Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar saccule with alveoli Functional components of respiratory tractConducting portionRespiratory portionTracheaPrimary bronchiLobar bronchiTertiary bronchiTerminal bronchioleRespiratory bronchioleAlveolar ductAlveolar sacAlveoli Clinical applicationCompromised AirwayØCricothyroidotomy (Laryngostomy)–a tube is inserted in the interval between the cricoid cartilage & the thyroid cartilageØTra c h e o s t o my–a tracheal tube is inserted between 2nd& 4thtracheal rings Clinical applicationBronchoscopyProcedure to visualize inside of the airway for diagnostic & therapeutic purposes Lungs & Pleura IntroductionLungs covered by pleurae occupy the pulmonary cavities (on either side of the mediastinum) •Lubrication to avoid friction ?•Serous membrane•Two layer–Visceral–Parietal•Pleural cavity–Potential space•Pleural fluidPleurae •Pulmonary (visceral) pleura–Closely attached–Inseparable•Parietal Pleura-Subdivisions ?1) Costal pleura•Lines the thoracic wall2) Diaphragmatic pleura•Lines the diaphragmPleurae 3) Mediastinal pleura–Covers lateral aspects of the mediastinum–At the hilum of the lung, reflects & continues as visceral pleura 4) Cervical pleura-dome shaped cap abovefirst ribPulmonary ligamentEmpty double layer of pleura inferior to the root of lung Parietal and visceral pleurae •What is Pleural cavity & what does it contain?Small space between parietal & visceral layers of pleurae containing a small amount of fluid (pleural fluid)•What do you understand by pleural recesses ? Potential slit like pleural spaces which are occupied by lungs only during inspirationi. Rt. & Lt. Costodiaphragmatic recessesii. Rt. & Lt. Costomediastinal recesses A B iiiLungs along with visceral pleura slide in & out during inspiration & expirationPleural cavity and Pleural recesses Pleurae-Nerve supplyParietal pleura is sensitive to pain, temperature, touch & pressureand is supplied by:qCostal pleura –intercostal nervesqMediastinal pleura –phrenic nerveqDiaphragmatic pleura –intercostal & phrenic nervesVisceral pleura is sensitive to stretch but insensitive to general sensations like pain & touch. It is supplied by autonomic nerve supply from pulmonary plexusReferred Pain ? Clinical applicationØPleural effusion –accumulation of excess of fluid due to increase in production of fluid or impairment of drainage of the fluidØPneumothorax –air in pleural spaceØHydrothorax, hemothoraxØEmpyema Injury to the cervical pleura & apex of the lung –lead to pneumothoraxqOpen pneumothoraxqTe n s i o n p n e u m o t h o r a x Pneumothorax Clinical applicationThoracocentesisInsertion of a chest tube ØVital organs of respirationØPorous, elastic, spongyØNew-born lung-pink, sinks in waterØAdult –black, floats in water. Why? LUNGS Lungs-featuresØEach lung has •apex •base (diaphragmatic surface)•costal surface•mediastinal surface •Anterior, posterior & inferior bordersØMediastinal surface has a depression called Hilum, in which bronchi, vessels & nerves that form the root enter & leave the lungØAnterior border of the left lung has a cardiac notch •Costal surface•Mediastinal surface•Diaphragmatic surface/base•Costal surface•Mediastinal surface•Posterior border•Anterior border•Apex Cardiac notchLingula Lungs-fissures and lobesØRight lung has two fissures –Horizontal and Oblique fissures; Three lobes –Superior, middle and Inferior lobesØLeft lung has one fissure –Oblique fissure ; Two lobes –Superior and Inferior lobes Lungs-Mediastinal surfaceCardiac impressionGroove for arch of aortaGroove for descending aortaGroove for left subclavian arteryGroove for left brachiocephalic veinArea for esophagusLeft lung Groove for arch of azygos veinGroove for SVCGroove for right subclavian arteryLungs-Mediastinal surfaceArea for tracheaCardiac impressionGroove for brachiocephalic veinGroove for IVCRight lung •Connect the medial surface of the lung to the heart and trachea by pulmonary vessels and bronchi •Other structures are nerves, bronchial vessels and lymphatics Root of Lungs The arrangement (from above downwards )Lungs-HilumOn the right side•eparterial bronchus •pulmonary artery •hyparterial bronchus •pulmonary veins On the left side•pulmonary artery •bronchus•pulmonary veins Lungs-Bronchopulmonary segmentsØIndependent respiratory units; anatomical, functional & surgical unitsØArea of the lung aerated independently by a tertiary (segmental) bronchus& supplied independently a tertiary branch of the pulmonary arteryØPyramidal-shaped segments of the lung, with their apices facing the lung root & their bases at the pleural surfaceØSeparated from adjacent segments by connective tissue septaØDrained by intersegmental parts of the pulmonary veins that lie in the connective tissue between & drain adjacent segmentsØ10 on each lung Bronchopulmonary segment•Each lung is divided into lobes•Each lobe is subdivided into bronchopulmonary segments–Wedge-shaped segments–Apex points to HilumEach segment:Has its own bronchusHas its own segmental arteryPulmonary veins run between segments Bronchopulmonary segments•10 on the Right–ApicalU–PosteriorU–AnteriorU-------------------------------–LateralM–MedialM–Apical / Superior Basal–Medial Basal–Anterior Basal–Lateral Basal–Posterior Basal•Less than 10 on the Left–ApicalU–PosteriorU•may be fused as Apicoposterior–AnteriorU–Superior lingularU–Inferior lingularU----------------------------------------–Apical / Superior Basal–Medial Basal–Anterior Basal–Lateral Basal–Posterior Basal LingularRIGHTBronchopulmonar y segments Lungs-Bronchopulmonary segmentsBronchial & pulmonary disorders (tumors or abscesses) that are localized in the segment may be surgically removed without disrupting surrounding lung tissuesClinical importance Bronchial tree•Main bronchusØTo each lung•Lobar bronchusØTo each lobe•Bronchi further divide into bronchiolesØBronchi have cartilage in the wallsØBronchiole does not•AlveoliØThin-walled sacsØFunction –gas exchange Surfactant–importance?Respiratory distress syndrome (RDS)Pneumocytes (Alveolar cells) Type I & II Vascular supply to lungs•Twosets of vessels–Pulmonary & Bronchial vesselsPulmonary arteriesSupply the alveoli with deoxygenatedbloodPulmonary veinsTwo pulmonary veins exit each lungCarry oxygenatedblood to the heartBronchial arteriesSupply most of bronchial tree & visceral pleuraBronchial veinsDrain most of bronchial tree & visceral pleura Lungs-Ve n o u s d r a i n a g e & N e r v e s u p p l yBronchial veins-drain blood from conducting portionRight bronchial vein drains into azygos veinLeft bronchial vein into accessory hemiazygos vein / left superior intercostal veinLeft superior intercostal veinAzygos veinAccessory hemiazygos veinPulmonary plexus –efferent & afferent autonomic nerve fibersSympathetic fibers –T 2, 3 & 4 gangliaParasympathetic fibers –Vagus nerveActions of the nerve fibers? Lungs-Lymphatic drainageØSuperficial lymphatic plexus -bronchopulmonary (hilar) lymph nodesØDeep lymphatic plexus –pulmonary lymph nodes –hilar lymph nodes References