Thorax Flashcards
1
Q
Anterior Mediastinum
A
Borders:
* Anteriorly: sternum, transverse thoracic, 5th-7th costal cartilages * Inferiorly: diaphragm * Superiorly: thoracic plane * Posteriorly: pericardium * Laterally: mediastinal pleura
Contents
* Loose areolar tissue * Lymph nodes * Small mediastinal branches of the internal thoracic artery * Thymus (involuted in adults)
2
Q
Azygous
A
Description/Features:
* Azygos (venous) system is a collective term given to the H-shaped configuration of the azygos, hemiazygos, accessory hemiazygos veins and left superior intercostal vein * Responsible for draining the thoracic wall and upper lumbar region * Provides important collateral circulation between the SVC and IVC should they become obstructed
Origin/Course/Relations:
* Azygos * formed by the union of the right ascending lumbar vein and the right subcostal veins at the level of T12 * enters the thorax through the aortic hiatus in the diaphragm, and passes along the right side of the vertebral column * in the aortic hiatus, it lies with the thoracic duct on the right side of the aorta * in the thorax it lies upon the intercostal arteries * arching over the right main bronchus at T5-T6 * ends: by emptying into the SVC at T4 * Hemiazygos * formed by the confluence of the left ascending lumbar vein and the left subcostal veins (sometimes communicates with the left renal vein) * enters the thorax through the left crus of the diaphragm * receives the lower left intercostal veins * ascends on the left side of the vertebral column as high as T9 and then passes across the column, behind the aorta, esophagus, and thoracic duct, to end in the azygos vein * Accessory hemiazygos * formed by veins of 3 or 4 intercostal veins below the superior intercostal vein * descends on the left side of the vertebral column * either crosses the body of T8 to empty into the azygos or hemiazygos vein
Tributaries:
* Azygos
* right ascending lumbar vein * subcostal vein * 5th to 11th right intercostal veins * right superior intercostal vein (which drains 2nd to 4th intercostal veins) * hemiazygos vein (and sometimes accessory hemiazygos vein) * some oesophageal veins * right bronchial vein * Hemiazygos
* left ascending lumbar vein * left subcostal vein * 9th to 11th left posterior intercostal veins * some oesophageal veins * Accessory hemiazygos
* 5th to 8th left posterior intercostal veins * left bronchial vein * some oesophageal veins
Variants:
* Azygos
* absence of the azygos vein (rare) * azygos continuation of the IVC * azygos occasionally opens into the right brachiocephalic or the right subclavian veins * can groove the right lung before entering the SVC: azygos lobe/fissure * Hemiazygos
* hemiazygos continuation of the IVC (often occurs with duplicated IVC) * Accessory hemiazygos * drains via a common trunk with the hemiazygos vein into the azygos vein * forms a common trunk with the hemiazygos vein that passes anterior to the aorta called the interazygos vein * drains directly into the left brachocephalic vein (rare) * may communicate with left superior intercostal vein
3
Q
Breast
A
Description/Features:
* The breast is an apocrine gland in both males and females * In females it is responsible for the production of milk * Composed of adipose and glandular tissue * Suspensory Cooper's ligaments and connective tissue * Retromammary space directly posteriorly
* Cooper's ligament attach the breast to skin anteriorly and pectoralis fascia/serratus posterior fascia posteriorly * Adult breast has nearly multiple lactiferous lobules -> lactiferous ducts -> lactiferous sinus -> nipple-areola complex * Areola contain sebatious glands * Borders
* superior: clavicle * inferior: middle of sternum * lateral: midaxillary line * medial: sternum * axillary tail: extension of breast tissue into the axilla
Relations:
* Overlies pectoralis major, serratus anterior
Arterial supply:
* Internal thoracic perforators (through 2nd and 3rd intercostal spaces) * Lateral thoracic artery (branch of axillary artery) * Pectoral branch of the thoracoacromial artery (branch of axillary artery) * Intercostal perforators
Venous drainage:
* Internal thoracic vein * Axillary vein * Posterior intercostal veins
Lymphatic drainage:
* Three pathways: axillary, internal mammary, retromammary * 75% of lymph drainage passes to the axillary nodes (mainly anterior and posterior nodes) * Remaining drainage is mainly to the parasternal nodes along the internal thoracic artery (medial side) and to the posterior intercostal nodes
Innervation:
* Thoracic intercostal nerve T3-T5 * Supraclavicular nerve from the cervical plexus
Variants:
* Breast hypoplasia: underdevelopment of the breast * Amastia: absence of breast tissue, nipple or areola * Amazia: absence of glandular parenchyma * Polythelia: supranumerary nipple * Polymastia: accessory breast tissue * Variations with hormonal level (puberty, pregnancy, post-menopause)
4
Q
Congenital diaphragm hernias
A
Congenital diaphragmatic hernia (CDH):
* Congenital malformation of the diaphragm * Malformation of the diaphragm allows the abdominal organs to push into the chest cavity, hindering proper lung formation * CDH is a life-threatening pathology in infants, major cause of death due to two complications: pulmonary hypoplasia and pulmonary hypertension
Types:
*
Bochdalek hernia
* hole in the postero-lateral corner of the diaphragm which allows passage of the abdominal viscera into the chest cavity * most common manifestation of CDH * Morgagni hernia
* herniation through the foramina of Morgagni which are located immediately adjacent and posterior to the xiphoid process of the sternum * Agenesis of diaphragm * all or part of diaphragm fails to form * Diaphragm eventration * abnormal elevation of part or all of an otherwise intact diaphragm into the chest cavity * occurs because in the region of eventration the diaphragm is thinner * allows the abdominal viscera to protrude upwards * Central tendon defect
5
Q
Coronary Arteries
A
Description:
* The coronary arteries supply the myocardium with oxygenated blood
Origin:
* Arise just distal to the aortic valve from the coronary sinuses
Course:
* Left coronary artery * arises from left coronary sinus * short common stem (left main) before dividing into the LCx and LAD (occassionally trifurcates with third branch being ramus intermedius) * LCx runs in the left atrioventricular groove (with the great cardiac vein) * LAD passes towards the apex in the anterior interventricular groove (also alongside great cardiac vein) * in left dominant hearts, the LCx supplies the posterior descending artery (8%) * Right coronary artery * arises from the right coronary sinus * runs in the right atrioventricular groove to the inferior surface of the heart * turns anteriorly to run in the posterior interventricular groove as the posterior descending artery (92%)
Branches:
*
LAD
* diagonal branches * septal perforators * LCx
* obtuse marginal branches * left posterolateral branch * RCA
* conus artery * sinoatrial artery * atrioventricular artery * marginal arteries * posterior descending artery * posterior left ventricular branch
Supply:
* LAD: anterolateral myocardium and apex, anterior two-thirds of the interventricular septum * LCx: lateral and posterolateral walls of the left ventricle * RCA: pulmonary outflow tract (conus artery), SA node, AV node, anterior wall of the right ventricle, inferior wall of both ventricles and the inferior 1/3 of the interventricular septum
Some variants:
* Left circumflex arising from the RCA * Left circumflex and LAD having separate origins * One coronary artery arising from the aorta
* RCA branches off the LCA * LCA branches off the RCA * RCA, LCA or both coronary arteries branching off the pulmonary trunk * Left dominant circulation * Conus artery arising separately
6
Q
Coronary Veins
A
Description/Features:
* The coronary veins return blood from the myocardium back to the right atrium * Coronary venous anatomy is highly variable, but is generally comprised of: * coronary sinus: * wide venous channel situated in the posterior part of the coronary sulcus * Drains into right atrium between SVC opening and tricus valve * cardiac veins (drain into the coronary sinus) * great cardiac vein: ascends to drain along the anterior longitudinal sulcus (adjacent to LAD) * middle cardiac vein: ascends in the posterior longitudinal sulcus (with posterior interventricular artery) * small cardiac vein: runs in the coronary sulcus between the right atrium and ventricle (with RCA) * posterior left ventricular vein: runs on the diaphragmatic surface of the left ventricle * Marginal vein of the left ventricle * oblique vein of the left atrium: descends on the back of the left atrium * thebesian veins (drain directly into the right atrium) * anterior cardiac veins * venae chordis minimae arise in the muscular wall of the heart
Variant anatomy:
* Coronary sinus may act as a conduit between a persistent left SVC and the right atrium * Coronary sinus may drain into the left atrium (causing right to left shunt) * Great cardiac vein may drain into the SVC or left brachiocephalic via the oblique vein of Marshall * Great cardiac vein may drain into the azygous vein * Cardiac veins may converge to empty into a common opening or directly into the right atrium
7
Q
Diaphragm
A
Description/Features:
* Diaphragm is a dome-shaped fibromuscular septum which separates the thoracic from the abdominal cavity * Important for breathing
Origin:
*
Muscle slips can be grouped according to their origins:
* sternal: arises from two strips under the xiphoid process * costal: arise from the inner surfaces of the costal cartilages of ribs 6-12 on either side (interdigitates with transversus abdominis) * lumbar: arise from the lubocostal arches and from the crura * Two paired tendinous lumbocostal arches: * medial lumbocostal arch (medial arcuate ligament): covers psoas major, attaches to the L2 vertebral body * lateral lumbocostal arch (lateral arcuate ligament): covers quadratus lumborum, attached to the L1 transverse process tip of the 12th rib * Crura are tendinous structures the blend with the anterior longitudinal ligament of the vertebral column: * right crus arises from the vertebral bodies of L1-3 * left crus arises from the vertebral bodies of L1-2 * the crura meet in the midline to form an arch called the median arcuate ligament
Insertion:
*
Central tendon: thin, strong aponeurosis situated immediately below and is fused to the fibrous pericardium
Apertures:
* Aortic Hiatus (T12): aorta, azygos vein, thoracic duct * Oesophageal Hiatus (T10): esophagus, vagus nerves, esophageal arteries/veins from left gastric * Vena Caval Foramen (T8): IVC, right phrenic nerve * Medial arcuate ligament: the sympathetic trunk * Lateral arcuate ligament: the subcostal vessels and nerve * Left phrenic pierces the left muscle dome * Greater, lesser and least splanchnic nerves pierce each crus * Hemiazygos vein passes through the left crus
Action:
*
Contraction lowers diaphragm and increases thoracic cavity size
Nerve supply:
* Phrenic nerves (C3-5) supply the ipsilateral hemidiaphragm with motor fibres * Lower intercostal nerves supply proprioceptive fibres to the margins
Blood supply: * Inferior and superior phrenic arteries (branches of the aorta) * Intercostal arteries * Subcostal arteries * Some supply from pericardiophrenic and musculophrenic arteries (branches of the internal thoracic artery)
Variants:
* Scalloped or serrated appearance: due to abnormal insertion of individual muscle slips * Dromedary diaphragm (hump) * Accessory diaphragm * Congenital diaphragm defects: Bochdalek, Morgagni, eventration, agenesis, central tendon defect
8
Q
Diaphragmatic openings
A
Caval opening (T8): Esophageal hiatus (T10):
* IVC * branches of the right phrenic nerve * note: left phrenic nerve directly pierces the dome of the left hemidiaphragm * oesophagus * vagus nerves * left and right → form oesophageal plexus at oesophageal hiatus → then become anterior and posterior vagal trunks * anterior vagal trunk predominately comprised of left vagal fibres, posterior vagal trunk predominately right vagal fibres * small oesophageal arteries from left gastric artery
Aortic hiatus (T12): * aorta * azygous vein and hemiazygos vein * thoracic duct
9
Q
1st rib
A
Description/Features:
* Most superior of the twelve ribs * Important anatomical landmark and is one of the borders of the superior thoracic aperture * First rib is short and thick and it has single articular facet for the costovertebral joint * First rib has a head, neck and shaft but lacks a discrete angle * No costal groove on its inferior surface * It has two tubercles
* transverse tubercle: posterior and lateral to the neck, bears an articular facet for the transverse process of T1 * scalene tubercle: anteriorly between the grooves for the subclavian artery and vein, anterior scalene muscle inserts here * There is a groove on lateral aspect which contains the lowest brachial plexus trunk and the subclavian artery * Anterior to the scalene tubercle is another groove for the subclavian vein
Articulations:
* Costovertebral joint: articular facet on head of the rib with single articular facet on body of T1 vertebra * Costotransverse joint: articular facet on transverse tubercle with transverse process of T1 * Costochondral joint: distal shaft with first costal cartilage
Muscle attachments:
* Anterior scalene muscle: scalene tubercle * Middle scalene muscle * Intercostal muscles: from the outer border * Subclavius muscle: arises from distal shaft and first costal cartilage * First digitation of the serratus anterior muscle
Ligamentous attachments:
* Parietal pleura: from the inner border (Sibson's fascia) * Costoclavicular ligament: anterior to the groove for the subclavian vein
Relations:
* Superior: lower trunk of the brachial plexus, subclavian vessels, clavicle * Inferior: intercostal vessels and nerves, parietal pleura * Anterior: sympathetic trunk (over neck), superior intercostal artery, ventral T1 nerve root * Posterior: parietal pleura, lung apex
Arterial supply:
* Intercostal arteries
Variant anatomy:
* Ossesous or fibrous articulation or fusion with a cervical rib * Bifid (forked) rib * Rudimentary (hypoplastic) rib: most commonly the first rib (0.2%) * Pseudoarthrosis of the first rib (0.1%)
10
Q
Internal thoracic artery
A
Origin/Termination:
* Arises from the first portion of the subclavian (prior to anterior scalene) * Terminates by dividing into the musculophrenic and superior epigastric arteries (~6th intercostal space)
Course/Relations:
* It descends behind the cartilages of the upper six ribs lateral to the margin of the sternum * As it branches from the subclavian, it is directed downward and forward * It passes posterior to the subclavian veins * It then passes posterior to the first costal cartilage, lateral to the brachiocephalic vein * In the thorax, the phrenic nerve passes posterior to the artery moving from lateral to medial
Branches:
* Intercostal Branches * supply the upper six intercostal spaces, two in number in each space * Pericardiophrenic artery * long slender branch, which accompanies the phrenic nerve to supply the the diaphragm * Pericardial Branches * supply the upper part of the anterior surface of the pericardium * Perforating branches * supplies the Pectoralis major and the skin * second, third, and fourth spaces give branches to the breast * Musculophrenic artery (terminal branch) * intercostal branches to the seventh, eighth, and ninth intercostal spaces * also supplies the lower part of the pericardium * Superior epigastric artery (terminal branch) * descends through the interval between the costal and sternal attachments of the diaphragm * enters the rectus sheath and anastomoses with the inferior epigastric artery to supply anterior part of abdominal wall
Supply:
* Supplies the anterior body wall from clavicle to umbilicus including the sternum and the breasts * via the Pericardiophrenic Artery it supplies the mediastinum, thymus, phrenic nerves and pericardium
Variants:
* Anomalous origin in 20% * Second part of subclavian artery (uncommon ~7%) * Third part of subclavian artery (rare ~1%) * Common origin with thyrocervical trunk * Right internal thoracic artery may arise from the ascending aorta * Terminal trifucation (~12.5%) with an additional xiphoid branch
11
Q
Left ventricle
A
Description/Features:
* One of the four heart chambers * Receives oxygenated blood from the left atrium and pumps it into the systemic circulation via the aorta * Conical shape * Apex projects anteroinferiorly * Thicker walled than right ventricle * Separated from right ventricle by interventricular septum which is concave in shape (bulges into right ventricle) * Smooth inflow and outflow tracts, but rest of ventricle lined by trabeculae carnae * Blood flows in via the atrioventricular orifice lined by the mitral valve and flows out passing through the aortic valve into the aorta
* There are two papillary muscles that attach to the mitral valve: * anterolateral group which attaches to the anterolateral leaflet * posteromedial group which attaches to the posteromedial leaflet
Relations:
* Superior: carina, trachea * Posterior: oesophagus, left atrium * Lateral: left pleural cavity, left lungs * Inferior: diaphragm
Arterial supply:
* Left Anterior Descending artery - supplies free wall and most of the papillary muscles * Left Circumflex artery - supplies free wall * Marginal and Diagonal branches
Venous drainage:
* Great cardiac vein, Middle cardiac vein, Posterior vein of left ventricle, Left marginal vein * Drains into Coronary sinus
Nerve supply:
* Sympathetic and Parasympathetic (vagal) stimuli flow through the paired cardiac plexus near the base of the heart
Variants:
* Double-inlet ventricle - in-flow from both the right and left atria * Parachute valve - mitral valve chordae tendinae inserting into a single papillary muscle * VSD * Transposition of great vessels
12
Q
Lungs
A
Variant anatomy:
Description/Features:
* Lungs are the functional units of respiration * Apex extends above the sternal end of the first rib, base rests on the diaphragm * Fissures * oblique fissure divides the left lung into LUL and LLL * oblique fissure and horizontal fissure divides right lung into RUL, RML, RLL * Segments * right lung is composed of three lobes subdivided into 10 segments (APA LM PALMS) * left is composed of two lobes and 8 segments (ASIA ALPS) * Surrounded by the pleura which separated them from the chest wall * Tracheobronchial tree is a branching structure of ever-decreasing diameter air tubes * can broadly be divided into conduction (air heating) and respiratory zones (gas exchange)
Segments:
* LUL (ASIA): apicoposterior, anterior, superior lingular, inferior lingular * LLL (ALPS): superior, anteromedial, lateral, posterior * RUL (APA): apical, posterior, anterior * RML: lateral, medial * RLL (PALMS): superior, anterior, medial, lateral, posterior
Relations:
* Medial: pericardium, SVC, right brachiocephalic vein, brachiocephalic artery, aortic arch, left subclavian artery, descending aorta, oesophagus, trachea, vagus nerves, phrenic nerves, heart * Anterior: ribs, intercostal vessels and nerves * Posterior: ribs, intercostal vessels and nerves, vertebral bodies, sympathetic trunk * Azygos vein arches over the right lung hila
Arterial supply:
* Pulmonary arteries: supplies de-oxygenated blood from the right ventricle * right pulmonary artery runs posterior to ascending aorta and anterior to right main bronchus * left pulmonary artery runs anterior to left main bronchus and enters root of left lung without dividing * it is attached to the aortic arch by the ligamentum arteriosum (remnant of the ductus arteriosum) * within the lung, the pulmonary arteries divide with each bronchus division * Bronchial arteries: branches of the thoracic aorta that supply oxygenated blood * two arteries arise from the left side of the thoracic aorta: superior left bronchial artery, inferior left bronchial artery * one arises from the right: right bronchial artery * common origin with an intercostal artery and this is called the intercostobronchial trunk
Venous drainage:
* Pulmonary veins: drains to the left atrium * Bronchial veins: drains to the pulmonary veins, SVC and the azygos venous system
Innervation:
* Pulmonary plexus, which is composed of fibres from the vagus nerve (parasympathetic and visceral afferent) and sympathetic ganglia
Lymphatic drainage:
* Bronchopulmonary nodes at the hilum * Bronchopulmonary foregut malformations * pulmonary sequestration: aberrant formation of segmental lung tissue that has no connection with the bronchial tree or pulmonary arteries * foregut duplication cysts: bronchogenic cyst are abnormal development of bronchial-tree during embryogenesis resulting in a cyst that does not communicate with the bronchial tree * congenital pulmonary airway malformation: multicystic mass of segmental lung tissue with abnormal bronchial proliferation * oesophageal lung: main bronchus arises from the oesophagus * Pulmonary aplasia: unilateral or bilateral absence of lung tissue * Accessory fissures: * azygos fissure: laterally displaced azygos vein makes a deep pleural fissure into the apical segment of the right upper lobe during embryological development * inferior accessory fissure: divides the right medial basal bronchopulmonary segment from the rest of the lower lobe * superior accessory fissure: separates the right lower lobe into superior and basal segments * left minor fissure: separates the lingula from the rest of the left upper lobe
13
Q
Lymphatic drainage
A
Description:
* Lymphatic drainange of breast originate from breast lobules and flow into a sub-areolar plexus, called Sappey’s plexus * From Sappey's plexus, lymphatic drainage takes place through three main routes: * Axillary pathway * fed by Sappey’s Plexus, as well as by ducts satellite lymphatics and by most of parenchymal lymphatics * this pathway runs around the inferior edge of the pectoralis major and reach the anterior group of axillary nodes * level 1 spread is below pectoralis minor, level 2 is behind pectoralis minor, level 3 is above pectoralis minor * Internal mammary pathway
* parasternal nodes * originates from both the lateral and medial halves of the breast and passes through the pectoralis major * connections may lead across the median plane and hence to the contralateral breast * Retromammary pathway
* comes from the posterior portion of the breast * retromammary space nodes * Lymphatics may reach the sheath of the rectus abdominis and the subperitoneal and subhepatic plexuses * Usually axillary lymph nodes receive more than 75% of the lymph drained from the breast (mainly anterior nodes and posterior group)
14
Q
Middle mediastinum
A
Borders:
* Bounded by the pericardial sac
Contents
* Heart * Ascending aorta * SVC * Azygos vein opening into SVC * Tracheal bifurcation * Pulmonary artery dividing into left and right * Right and left pulmonary veins * Phrenic nerves * Lymph nodes * Pericardiocophrenic arteries and veins
15
Q
Oesophagus
A
Description/Features:
* The oesophagus is a muscular tube that conveys food and fluids from the oropharynx to the stomach * Divided into three parts: * cervical: continuous with the oropharynx, commences at the lower border of cricoid cartilage (at level of C5/6) or cricopharyngeus muscle * thoracic: from thoracic aperture (T1) to the oesophageal hiatus (T10) * abdominal: from oesophageal hiatus to the cardia of the stomach at the gastro-oesophageal junction * Three normal oesophageal constrictions * cervical constriction: due to cricoid cartilage at the level of C5/6 * thoracic constriction: due to aortic arch at the level of T4/5 * abdominal constriction: at oesophageal hiatus at T10/11 * Muscular wall: skeletal muscle in the upper part and smooth muscle in the lower part * Non-keratinised stratified squamous epithelium which is replaced by columnar epithelium at the gastro-oesophageal junction * Layers: mucosa, submucosa, muscularis (inner circular, outer longitudinal layers), serosa
Relations:
* Posteriorly: vertebral column, descending aorta, thoracic duct, accessory hemiazygos and hemiazygos veins (at T8/9), longus colli * Anteriorly: trachea (T4/5), recurrent laryngeal nerves (in tracheo-oesophageal groove), left main bronchus, left atrium, pulmonary trunk and veins * Left lateral: lung, pleura, aorta, left subclavian artery, thoracic duct * Right lateral: lung, pleura, azygos vein * Descends with the left and right vagus nerve through the oesophageal hiatus
Arterial supply:
* Upper third: inferior thyroid artery * Middle third: oesophageal branches of the thoracic aorta * Lower third: oesophageal branches of the left gastric artery (site of portal-systemic collateral pathway)
Venous drainage:
* Upper third: inferior thyroid veins to brachiocephalic veins * Middle third: azygos vein to SVC * Lower third: left gastric vein to portal vein
Lymphatic drainage:
* Follows arterial supply * Upper third: deep cervical lymph nodes * Middle third: posterior mediastinal lymph nodes * Lower third: left gastric and coeliac group lymph nodes
Innervation:
* Sympathetic trunk (sympathetic) * Vagal plexus (parasympathetic) * Enteric nervous system
Variation:
* Oesophageal bronchus: bronchus arises directly from oesophagus * Oesophageal atresia: oesophagus not continuous due to an inappropriate division of the primitive foregut into the trachea and oesophagus * Tracheo-oesophageal fistula: abnormal communication between trachea and oesophagus (congenital or acquired) * Oesophageal duplication cysts * Aberrant right subclavian artery passing anterior or posterior to the oesophagus
