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MEDIASTINUMMEDIASTINUM

MEDIASTINUMMEDIASTINUM

Central compartment of the Central compartment of the thoracic cavitythoracic cavity

Covered by mediastinal pleuraCovered by mediastinal pleura

Contents: all thoracic viscera Contents: all thoracic viscera EXCEPT lungsEXCEPT lungs

Extent: Extent: Superior - thoracic inletSuperior - thoracic inletInferiorInferior - diaphragm - diaphragmAnterior - sternum & costalAnterior - sternum & costal

cartilages cartilagesPosterior- bodies of thoracicPosterior- bodies of thoracic

vertebraevertebrae

MEDIASTINUMMEDIASTINUM

Surrounded by blood and lymphatic vesselsSurrounded by blood and lymphatic vesselsLymph nodes, nerves and adipose tissuesLymph nodes, nerves and adipose tissues

Looseness of structures enable mediastinum to Looseness of structures enable mediastinum to accommodate changes in movement, volume & accommodate changes in movement, volume & pressure in the thoracic cavitypressure in the thoracic cavity

Divisions of the MediastinumDivisions of the Mediastinum

SUPERIOR MEDIASTINUMSUPERIOR MEDIASTINUMSuperior - thoracic inletSuperior - thoracic inlet

Inferior - transverse thoracicInferior - transverse thoracicplaneplane

Anterior - sternal angleAnterior - sternal angle

Posterior - IV disc T4 & T5Posterior - IV disc T4 & T5

INFERIOR MEDIASTINUMINFERIOR MEDIASTINUM

Superior – transverse thoracic Superior – transverse thoracic plane plane

Inferior - diaphragmInferior - diaphragm

Divisions of the MediastinumDivisions of the Mediastinum

INFERIOR MEDIASTINUMINFERIOR MEDIASTINUMa. ANTERIOR MEDIASTINUMa. ANTERIOR MEDIASTINUM

- contains thymus remnant, lymph nodes & fats- contains thymus remnant, lymph nodes & fats

b. MIDDLE MEDIASTINUMb. MIDDLE MEDIASTINUM - contains the heart & great vessels- contains the heart & great vessels

c. POSTERIOR MEDIASTINUMc. POSTERIOR MEDIASTINUM - contains esophagus, great vessels,vagus - contains esophagus, great vessels,vagus

nervesnerves & symphathetic trunks& symphathetic trunks

Superior MediastinumSuperior Mediastinum

Contents: (Anterior – Posterior)Contents: (Anterior – Posterior)1. Thymus gland1. Thymus gland

- primary lymphoid organ located behind - primary lymphoid organ located behind manubriummanubrium

- puberty undergoes gradual involution- puberty undergoes gradual involution

2. Great Vessels2. Great VesselsBrachiocephalic VeinsBrachiocephalic VeinsSuperior Vena CavaSuperior Vena Cava

- formed at level of 1- formed at level of 1stst right costal cartilage right costal cartilage - enters right atrium at level of 3- enters right atrium at level of 3rdrd right costal right costal cartilage cartilage

Superior MediastinumSuperior Mediastinum

Contents:Contents:

Arch of the AortaArch of the Aorta- starts behind 2- starts behind 2ndnd right SC joint right SC joint- ends at 2- ends at 2ndnd left SC joint left SC joint

Branches:Branches:Brachiocephalic TrunkBrachiocephalic TrunkLeft Common Carotid ArteryLeft Common Carotid ArteryLeft Subclavian ArteryLeft Subclavian Artery

Superior MediastinumSuperior Mediastinum

Contents:Contents:3. Nerves3. Nerves

Vagus & Phrenic NervesVagus & Phrenic NervesCardiac Plexus of NervesCardiac Plexus of NervesLeft Recurrent Laryngeal NerveLeft Recurrent Laryngeal Nerve

4. Trachea4. Trachea5. Esophagus5. Esophagus6. Thoracic Duct6. Thoracic Duct7. Prevertebral Muscles7. Prevertebral Muscles

Anterior MediastinumAnterior Mediastinum

Smallest subdivision of the Inferior MediastinumSmallest subdivision of the Inferior Mediastinum

Boundaries:Boundaries:AnteriorAnterior : body of sternum & trans thoracis muscles : body of sternum & trans thoracis muscles PosteriorPosterior : pericardium : pericardium

Contents: Loose CT (Sternopericardial Ligament)Contents: Loose CT (Sternopericardial Ligament) Adipose tissueAdipose tissue Lymphatic Vessels & lymph nodesLymphatic Vessels & lymph nodes Branches of Internal Thoracic VesselsBranches of Internal Thoracic Vessels

Posterior MediastinumPosterior Mediastinum

Boundaries:Boundaries:AnteriorAnterior - Pericardium & Diaphragm- Pericardium & DiaphragmPosteriorPosterior - T5 to T12 vertebrae- T5 to T12 vertebrae

Contents:Contents:Thoracic AortaThoracic Aorta Esophagus & PlexusEsophagus & PlexusThoracic DuctThoracic Duct Thoracic Sympathetic TrunksThoracic Sympathetic TrunksPost Mediastinal LNPost Mediastinal LN Thoracic Splanchnic NerveThoracic Splanchnic NerveAzygos & Hemiazygos VeinsAzygos & Hemiazygos Veins

Thoracic AortaThoracic Aorta

Branches:Branches:1. Bronchial Arteries1. Bronchial Arteries 5. Esophageal Arteries5. Esophageal Arteries2. Pericardial Arteries2. Pericardial Arteries 6. Mediastinal Arteries6. Mediastinal Arteries3. Post. Intercostal Arteries3. Post. Intercostal Arteries7. Subcostal Arteries7. Subcostal Arteries4. Superior Phrenic Arteries4. Superior Phrenic Arteries

EsophagusEsophagus

Course: Superior to Posterior MediastinumCourse: Superior to Posterior MediastinumLocated behind: Arch of AortaLocated behind: Arch of Aorta

Pericardium & Left AtriumPericardium & Left AtriumEnters Esophageal Hiatus of the Diaphragm at level of T10Enters Esophageal Hiatus of the Diaphragm at level of T10

Anatomic Impressions or “Constrictions”:Anatomic Impressions or “Constrictions”:1. Crossing with Aortic Arch1. Crossing with Aortic Arch2. Crossing with Left Main Bronchus2. Crossing with Left Main Bronchus3. Diaphragmatic Hiatus3. Diaphragmatic Hiatus

Thoracic DuctThoracic Duct

Largest lymphatic channel in the bodyLargest lymphatic channel in the bodyOriginates from Cisterna Chyle in the abdomen & passes Originates from Cisterna Chyle in the abdomen & passes

thru aortic hiatus of diaphragm at level of T12thru aortic hiatus of diaphragm at level of T12

Relations: PosteriorRelations: Posterior : bodies of inferior 7 thoracic : bodies of inferior 7 thoracic vertebraevertebrae

Anterior Anterior : Esophagus: Esophagus LeftLeft : Thoracic Aorta: Thoracic Aorta Right Right : Azygos Vein: Azygos Vein

Conveys lymph from:Conveys lymph from:Lower extremitiesLower extremities Left side of thoraxLeft side of thoraxPelvic CavityPelvic Cavity Left side of H & NLeft side of H & NAbdominal CavityAbdominal Cavity Left upper limbLeft upper limb

Lymph Nodes of the Lymph Nodes of the Posterior MediastinumPosterior Mediastinum

Posterior Mediastinal Lymph NodesPosterior Mediastinal Lymph Nodes- receives lymph from esophagus, posterior aspect of the- receives lymph from esophagus, posterior aspect of the

pericardium & diaphragm & middle posterior ICS pericardium & diaphragm & middle posterior ICS

Azygos Venous System of the Posterior Azygos Venous System of the Posterior MediastinumMediastinum

Drains the back & thoracoabdominal walls and the Drains the back & thoracoabdominal walls and the mediastinal visceramediastinal viscera

Azygos VeinAzygos Vein- forms a collateral pathway b/w SVC & IVC- forms a collateral pathway b/w SVC & IVC- passes to the right side of inferior 8 thoracic vertebrae- passes to the right side of inferior 8 thoracic vertebrae- arches over the root of the right lung to enter the SVC- arches over the root of the right lung to enter the SVC- receives posterior intercostal veins, mediastinal,- receives posterior intercostal veins, mediastinal,

esophageal & bronchial veinsesophageal & bronchial veins

Azygos Venous System Azygos Venous System of Posterior Mediastinumof Posterior Mediastinum

Hemiazygos VeinHemiazygos Vein- arises on left side of the vertebral column to level of T9- arises on left side of the vertebral column to level of T9- receives the inferior 3 PIV, inferior esophageal veins,- receives the inferior 3 PIV, inferior esophageal veins,

small mediastinal veinssmall mediastinal veins

Accessory Hemiazygos VeinAccessory Hemiazygos Vein- starts at medial end of 4- starts at medial end of 4thth or 5 or 5thth ICS ICS - descends on left of VC from T5 thru T8 - descends on left of VC from T5 thru T8 - crosses to the right to join the Azygos Vein- crosses to the right to join the Azygos Vein- receives 4- receives 4thth thru 8 thru 8thth IC Veins IC Veins- communicates with Superior IC Vein which drains - communicates with Superior IC Vein which drains

11stst thru 3 thru 3rd rd ICSICS

Nerves of Posterior MediastinumNerves of Posterior Mediastinum

Thoracic Sympathetic TrunksThoracic Sympathetic Trunks- lie against heads of ribs in superior thorax- lie against heads of ribs in superior thorax

costovertebral joints in midthorax costovertebral joints in midthorax sides of vertebral bodies in lower thorax sides of vertebral bodies in lower thorax

Lower Thoracic Splanchnic NervesLower Thoracic Splanchnic Nerves(Greater, Lesser and Least SN)(Greater, Lesser and Least SN)- presynaptic fibers from 5- presynaptic fibers from 5thth thru 12 thru 12th th sympathetic gangliasympathetic ganglia- sympathetic innervation for most abdominal viscera- sympathetic innervation for most abdominal viscera

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