Thorax Flashcards
1st rib: Description
The ribs are the main structural element of the thorax.
Function: Protection, respiration
Rib: Gross Anatomy
There are 12 ribs which are separated by intercostal spaces.
The first 7 ribs increase in length the lower five decrease in length.
The 1st, 11th and 12th ribs are considered atypical ribs.
Ribs: Description
True ribs – First 7 attached to the sternum directly by their own costal cartilage
False ribs – 8th to 10th, converge anteriorly via the costal cartilage to the 7th costal cartilage thus have indirect connection to the sternum.
Floating ribs – the 11th and 12th have no anterior direct or indirect sternal attachment
The first rib is the most superior of the twelve ribs. It is an atypical rib because of number differentiating features and is an important landmark for the borders of the superior thoracic aperture.
1st Rib: Features
- Compared to a typical rib the first rib is short and thick.
- It has a singular articular facet of the costovertebral joint.
- The first rib has a head, neck and shaft but lacks a discrete angle.
- Groove for the subclavian artery – laterally
- Groove for the subclavian vein – anterior to the scalene turbicle
- Transverse tubercle – Posterior and lateral to the neck it bears a facet for the transverse process of T1
- Scalene tubercle – anterior between the grooves for the subclavian artery and vein.
1st Rib: Articulation
- Costovertebral joint
- Costotransverse joint
- Costochondral joint
1st Rib: Attachments
- Anterior and middle scalene
- Intercostal muscles
- Subclavius muscle
- Serratus anterior
- Costoclavicular ligaments
1st Rib: Neurovasculature
Blood supply:
Arterial: internal thoracic and superior intercostal arteries, venous: intercostal veins
Innervation: first intercostal nerve
1st Rib: Relations
- Anterior: Sympathetic trunk over the neck, superior intercostal artery, ventral T1 nerve root
- Superior: lower trunk of the brachial plexus, subclavian artery and vein, clavicle
- Inferior: Intercostal vessels and nerves, parietal pleura
- Medial: contents of the superior thoracic aperture
- Lateral: Axillary artery and vein, divisions and cords of the brachial plexus
1st Rib: Variants
- First cervical rib
- Bifid (forked) rib
- Hypoplastic rib
Sternum: Description
The sternum completes the anterior chest wall as the ventral breastplate.
Sternum: articulations
The sternum is composed of a manubrium, a body and the xiphoid process. These articulations are via hyaline cartilage with a fibrocartilaginous intervening disc.
Sternum: Articulations
Manubrium with:
Sternal body
Clavicles
Costal cartilage of the first rib
Body:
With manubrium superiorly and xiphoid inferiorly
Costal cartilages of ribs 2 to 7
Sternum: Muscular attachments
- sternocleidomastoid, intercostal muscles, pectoralis major, sternohyoid, sternothyroid and transversus thoracis.
- the xiphisternum attaches to linea alba
Sternum: Ligaments
sternopericardial ligaments secure the fibrous pericardium to it
interclavicular ligament
anterior and posterior sternoclavicular ligaments (thickenings of the sternoclavicular joint capsule)
Sternum: Neurovasculature
Blood supply:
Internal thoracic arteries and veins
Nerve supply:
nerve supply is via anterior intercostal nerves
Lymphatics:
chain of internal mammary lymph nodes
Sternum: Variants
- Sternal foramen
- Unfused
- Pectus
Diaphragm
The diaphragm is a domed shaped muscle in that separates the thoracic cavity frim the abdominal cavity, enclosing the interior thoracic aperture.
Diaphragm: Gross anatomy
Muscular slips originated around the inferior aspect of the thorax and converge to a common insertion point the central tendon.
Flat muscle structure composed of multiple strips of muscle joining at a central tendon
Divides the thorax and the abdominal cavity
Attaches to: xiphoid process, ribs (lower six), aponeurotic arches and lumbar vertebra (crura)
Ligamentous opening of the diaphragm
Median arcuate ligament allows the passage of the psoas and sympathetic trunk
Lateral arcuate ligament allows the passage of the quadratus lumborum and subcostal nerves and vessels
Hiatuses of the Diaphragm
The caval hiatus – level T8 allows for the passage of:
- Inferior vena cava
- Branches of the right phrenic nerve
Oesophageal hiatus – level T10 allows for the passage of:
- Oesophagus
- Vagus nerves
- Oesophageal arteries
Aortic hiatus – Level T12 allows for the passage of:
- Aorta
- Azygos vein
- Hemi-azygos vein
- Thoracic duct
Lesser apetures of the diaphragm
- Left phrenic pierces the diaphragm directly
- Right crus – Right greater and lesser splanchnic nerve
- Left crus -Left greater and lesser splanchnic nerve
- Foramen of Morgagni allows the internal thoracic vessels to pass
Lumbocostal arches of the diaphragm
Medial lumbocostal arch (medial arcuate ligament) – arch that covers psoas
Lateral lumbocostal arch (lateral arcuate ligament) – covers quadratus lumborum
Diaphragmatic hiatuses
Caval hiatus at level T 8
Oesophageal hiatus at level t10
Aortic hiatus at level T12
Lesser apertures
Sternocostal foramina (Morgagni)
Diaphragm: Relations
Superior: bases of the lungs and the heart
Inferior the suprehepatic spaces, the liver, the stomach, the spleen, the adrenal glands
Lateral: ribs
Medial: central tendon of the diaphragm
Diaphragm: Neurovasculature
Arterial supply:
- musculophrenic
- Pericardiophrenic
- intercostal arteries
- Superior and inferior phrenic arteries
Venous drainage: same named veins into the system venous system
Innervation:
Bilateral phrenic nerve C3,4,5
Intercostal nerves supply proprioceptive fibres
Lymphatics:
Coeliac nodes and perihilar nodes
Diaphragm: Variants
Congenital diaphragmatic eventration
Pec Major
Pectoralis major is a large, fan-shaped muscle.
Origin: sternum, superior six costal cartilages and medial half of the clavicle
Insertion: lateral lip of the bicipital groove of the humerus
Arterial: Perforators from the internal thoracic and the thoracoacromial arteries
Innervation: medial and lateral pectoral nerves
Action: flexion, adduction and internal rotation of the shoulder joint
Variant anatomy:
- Sternalis muscle
- Poland syndrome
Aortic Arch
The aortic arch is a large arterial trunk that connects the ascending aorta the descending aorta
Function: Carries and initial distribution of the majority of the body’s arteries blood supply
Pec Minor
Pectoralis minor is a muscle of the anterior chest wall that inserts into the pectoral girdle. It lies deep to and is completely covered by pectoralis major. It divides the axillary artery into 3 parts.
Origin: anterior ribs 3-5 near the costal cartilages
Insertion: coracoid process of the scapula
Innervation: medial and lateral pectoral nerves
Action: depresses shoulder and elevation of ribs 3-5
Arterial: Perforators from the internal thoracic and the thoracoacromial arteries
Variant anatomy:
- pre-fixed origin: ribs 2-4
- post-fixed: ribs 4-6
- Poland’s syndrome also
Trapezius
origin: superior nuchal line, inion, nuchal ligament and spinous processes of C7-T12 vertebrae
insertion: clavicle and scapula
innervation: accessory nerve (CN XI)
action: complex movements of the scapula and neck
Arterial: Thoracodorsal artery
Latissimus Dorsi
origin: spinous processes of T7-T12 and thoracolumbar fascia; posterior third of the iliac crest; 9th-12th ribs, inferior angle of the scapula
insertion: floor of the bicipital groove of the humerus
innervation: thoracodorsal nerve
arterial supply: thoracodorsal artery (a branch of the subscapular artery)
action: adduction, internal rotation and extension of the shoulder joint
Aortic Arch: Gross anatomy
Layers: adventitia, media and intima
Origin: T4 plane continuation of the ascending aorta
Course: posterior and to the left in the superior mediastinum
Termination: continuation as the descending aorta pass the level T4
Branches: brachiocephalic trunk, Left common carotid artery, left subclavian artery
Aortic arch: Relations
Superior: Large vessels of the superior mediastinum
Inferior: recurrent laryngeal (which one), ligament arteriosum, the bifurcation of the pulmonary trunk
Anterior: thymus or thymic reminant, fat
Posterior: trachea, oesophagus, thoric duct crosses from right to left
Lateral: right superior vena cava, terminination of the azygos, right upper lobe left: left upper lobe lung
Variants of the Aortic arch
- Double arch
- Bovine arch common origin of the left common carotid and brachiocephalic trunk
- Left common carotid from the brachiocephalic trunk
Branches directly from the aorta:
- Thyroid Ima
- Vertebral artery (most commonly the left)
- Right subclavian and right common carotid
Right sided arch:
- Type 1 - mirror
- Type 2 – absent left subclavian
- Type 3 – isolated left subclavian
Coronary circulation: Description
The coronary arterial circulation is the system that supplies oxygenated blood the myocardium during diastole
Location: wrapped around the surface of the heart, looks like and inverted crown, located beneath the visceral layer of serous peroicardium
Right coronary artery: Gross anatomy
Origin: Right coronary cusp
Course: following the right atrioventricular groove around to the posterior aspect of the heart
Termination: Continues as the posterior interventricular artery in right circulation dominant hearts
Right coronary artery: Branches
- Sinoatrial nodal artery
- Conus artery
- Sinotubular artery
- Acute marginal branches
- Posterior interventricular
Left coronary artery: Branches
- Obtuse marginal
- Circumflex
- LAD
Circumflex coronary artery
Continues in the left atrioventricular groove around the posterior aspect of the heart gives of the posterior interventricular in left dominant hearts
LAD
Follows the anterior interventricular groove
Terminates at the apex may anastomose with the posterior interventricular artery
Branches: Obtuse marginal, septal perforators, diagonal branches
Coronary arteries: Variants
Malignant course: artery has aberrant course and passes between the aorta and pulmonary trunk
Non-malignant course: aberrant from the above described course however does not pass between large pulsating vessels
Origin from non-similarly named aortic cusp
Right or left side dominance as described above
Coronary veins
The coronary sinus drains in the right atrium its tributaries:
- Great cardiac vein (follows circumflex and LAD)
- Middle cardiac vein (Follows the posterior interventricular)
- Small cardiac vein (follows RCA)
Anterior cardiac veins drain directly into the right ventricle
Smallest cardiac veins drain directly into all four ventricles
Internal thoracic artery
The internal thoracic artery (previously called the internal mammary artery) supplies the anterior body wall and its associated structures from the clavicles to the umbilicus.
Internal thoracic artery: Gross anatomy
Origin:
First part of the subclavian arteries bilaterally
Course:
- Enters the thorax through the superior thoracic aperture posterior to the subclavian vein
- Descends lateral to the lateral border of the sternum
- Runs between the transversus thoracus muscle posteriorly and the costal cartilages and internal intercostal muscles anteriorly
- At the sixth-to-seventh costal cartilages the internal thoracic artery bifurcates into two terminal branches - musculophrenic artery and superior epigastric artery.
Internal thoracic artery: Branches
- Superior and inferior anterior intercostal arteries within each intercostal space
- Pericardiophrenic artery (runs with the phrenic nerve)
- Perforating branches
- musculophrenic artery (terminal branch)
- superior epigastric artery (terminal branch)
Internal thoracic artery: Supply
- The internal thoracic artery 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.
Internal thoracic artery: Variants
- anomalous origin in 20%
- second part (uncommon; ~7%) and third part (rare; ~1%) of subclavian artery
- terminal trifurcation (~12.5%) with an additional xiphoid branch
Left subclavian artery
Subclavian artery is a large artery that supplies the arm, neck, anterior thorax, posterior circulation of the brain
Function: Deliver oxygenated blood
Location:
Beneath the clavicles bilaterally
Left subclavian artery: Gross anatomy
Origin: the third branch on the aortic arch (normal configuration)
Course: Ascends through the superior thoracic aperture, posterior to the brachiocephalic veins, between the anterior and middle scalene muscles
Divided into 3 parts:
1st part from origin to the medial edge of scalenus anterior
2nd part to the lateral edge of scalenus anterior
3rd part to the lateral border of the first rib
Termination: continues as the axillary artery
Left subclavian artery: Branches
1st part:
- Vertebral
- Internal thoracic
- Thyrocervical trunk
2nd part:
- Costocervical trunk
- Dorsal scapular
3rd part:
- None
Left subclavian artery: Variants
- Origin variants
- Aberrant right subclavian (between trachea and oesophagus)
- Order of branches may vary
- Origin of vertebral artery from the aorta
Azygous vein
function as an alternate venous return pathway in the setting of IVC occlusion
Azygous vein: Gross anatomy
Origin: Formed by the union of the right ascending lumbar veins and right subcostal veins at the level T12-L2
Course: Ascending in the retroperitoneal space of the abdomen, enters the chest through the aortic hiatus (however may pierce the crus), it continues to ascend in the posterior mediastinum
Termination: Arches over the right main bronchus to drain in to the superior vena cava.
Azygous vein: Tributaries
- Hemiazygos vein
- Accessory hemiazygos vein
- Right superior intercostal vein
- Posterior right intercostal veins
- Right superior phrenic vein
- Tracheal veins
- Oesophageal veins
- Pericardial veins
- Vertebral venous plexus
Hemiazygous vein: Gross anatomy
Origin: Formed by the union of the left ascending lumbar veins and left subcostal veins
Course: Also through the aortic hiatus
Termination: Crosses the midline at T8-T9 to drain in the azygos vein
Hemiazygous: Tributaries
- Left posterior intercostal veins
- Left superior phrenic vein
- Left renal vein (sometimes)
- ICV sometimes
- The left superior intrercostal vein drains directly into the SVC
Hemiazygous/azygous Variants
- Azygos continuation of the svc
- Azygos lobe and fissure
- Hemiazygos continuation of the SVC
Blood supply to lungs
The lungs have dual arterial supply and venous drainage.
Pulmonary arteries
Transport deoxygenated blood to the lungs, Receive all of the arterial output of the right ventricle
Origin: Pulmonary trunk bifurcation at the level of the transthoracic plane
Course: Enters the hilum and divides into lobar, then segmental, then subsegmental arteries, then intralobular arteries, they follow the bronchi
Termination: Capillary beds of the alveoli
Bronchial arteries
Supply 1% of the blood to lung, only high-pressure oxygenated supply to the lungs
There are usually two on the left:
- Superior left bronchial artery (arises from the arch)
- Inferior left bronchial artery (arises from the desending aorta)
There is usually one on the right arising from a posterior intercostal artery (intercostalbronchial trunk)
Pulmonary veins
drain oxygenated blood from the lungs to the left atrium. Typically 2 drain each lung:
- Right superior – Right upper and middle lobes
- Right inferior – Right lower lobe
- Left superior – Left upper lobe
- Left inferior – Left lower lobe
- The pulmonary veins course in the intersegemental septa and do not course with the bronchi like the pulmonary arteries do.
Bronchial veins
- Bronchial veins – drain the bronchi and hilar structures and the middle portion of the oesophagus.
- Divisible into deep and superficial bronchial veins:
- Deep bronchial veins – Drain the deep structures of the lung into the left atrium or pulmonary veins
- Superficial bronchial veins – drain the hilum and plura. On the right they drain into the azygos, on the left they drain into the accessory hemiazygos vein.
SVC: Description
The superior vena cava (SVC) is a large valveless venous channel formed by the union of the brachiocephalic veins. It receives blood from the upper half of the body (except the heart) and returns it to the right atrium.
SVC: Gross anatomy
Origin: Lower border of the first right costal cartilage
Course: Descends vertically behind the second and third intercostal spaces to drain into the right atrium at the level of the third costal cartilage.
Its lower half is covered by the fibrous pericardium, which it pierces at the level of the second costal cartilage.
SVC: Tributaries
- azygos vein
- small veins draining the pericardium and other mediastinal structures
SVC: Relations
- left lateral: aortic arch, trachea
- right lateral: pleura, right upper lobe, right phrenic nerve
- anteriorly: thymus, manubrium
- posteriorly: azygos vein
- superiorly: brachiocephalic veins, superior thoracic aperture
- inferiorly: pericardium, right atrium
SVC: Variants
brachiocephalic veins: drain into the right atrium separately
SVC duplication
left sided SVC
Chest wall venous drainage
The venous drainage of the thorax is the vascular system that returns deoxygenated blood from the thorax to the heart
Anterior intercostal veins
Couse inferior aspect of each rib
Drains: internal thoracic and musculophrenic veins
Posterior intercostal veins
Origin: intercostal spaces
Course: Inferior to the posterior aspect of each rib (4 to 11)
Termination: drain into azygos system
Supreme intercostal vein
Origin: 1st intercostal space
Termination: drains into the brachiocephalic veins
Superior intercostal veins
Origin 2nd and 3rd intercostal veins join to form the superior intercostal vein
Termination: drains into the ayzogos and brachiocephalic (right and left)
Chest wall venous drainge: Variants
Superior intercostal may also drain the 4th intercostal space
Posterior intercostal veins may be drained by different elements of the azygos system
Phrenic N: Description
The phrenic nerves are mixed sensory/motor nerves that course through the neck and thorax to innervate the diaphragm
Phrenic N: Gross anatomy
Origin: ventral rami of C3, C4 and C5
Course: Passes on the anterior surface of scalenus anterior, over the dome of the apical pleura, entering the superior thoracic aperture posterior to the subclavian veins
Left:
Descends lateral to the left subclavian artery, passes anterior to the hilum, pierces the diaphragm directly to enter the abdominal cavity.
Right:
Descends with the superior and inferior vena cava. Enters the abdomen with the inferior vena cava through the caval hiatus at level T8
Within the abdomen the both divide in the anterior, lateral and posterior branches. Coursing out in a radial pattern.
Supply:
Sole motor supply to each hemidiaphragm, sensation to the central tendon
- Diaphragm
- Mediastinal pleura
- Pericardium
- Central diaphragmatic pleura
Phrenic N: Variants
- Course anterior to subclavian vein
- May pierce the anterior scalene muscle
- Accessory phrenic nerve
- Contribution from C2 or C6
- May supply branch to subclavius
Thoracic duct
The thoracic duct is the main lymphatic channel for the return of chyle to the venous system.
Thoracic duct: Gross anatomy
- Origin: continuation from the cistern chyli
- Course in the retroperitneum posterior to the great vessels ascending, entering the thoracic cavity via the aortic hiatus at T12, continues to ascend in the posterior mediastinum on the right hand side initially, swapping sides at the level T4, continuing superiorly through the thoracic inlet, anterior to the subclavian artery, anterior to the anterior scalene, draining in the convergence of the left subclavian and internal jugular.
Thoracic Duct: Relations
- Anterior: oesophagus, left atrium, carina
- Posterior: vertebral column, symphathetic chain of ganglion
- Left lateral: descending aorta, left lung and pleura
- Right lateral: azygos vein, right lung and pleura
Thoracic Duct: Variants
- Variant anatomy in 40% of the population
- Duplication
- Aberrant termination
- Multiple terminal channels
Continues on the right to terminate in the right internal jugular vein
Breast: Description
Bilateral prominences of the anterior thorax
Function: Lactation
Breast: Gross anatomy
- Mixed fatty and glandular tissue comprise the bulk of the breast
- Structural support via fibrous tissue known as the ligaments of Cooper
- Typically divided into 5 sections, four quadrants centered on the nipple and an axillary tail
- Glandular tissue is comprised of lobules draining into lactiferous ducts converging on the areola to drain to the nipple
- Lactiferous lobules are modified apocrine glands, typically 14-18, draining to the nipple areola complex
Breast: Neurovasculature
Arterial supply:
- Performing branches from the internal thorax and intercostal arteries
- Thoracoacromial artery
- Lateral thoracic arteries
Venous drainage:
- Axillary vein
- Internal thoracic vein
- Posterior intercostal veins
Innervation:
Thoracic intercostal nerve T3-T5
Supraclavicular nerves
Lymphatic drainage:
Initially into Sappy’s plexus (subareolar plexus) then into one of three routes (AIR):
- Axillary pathway – runs from the inferior edge of the pec major to the pectoral group of axillary nodes
- Internal mammary pathway – passes through pec major, connect may cross the medial plane to the contralateral breast
- Retromammary pathway – from the posterior portion of the breast
75% of lymph from the breast is drained via the axillary nodes
Breast: Variants
- Hypoplasia
- Amastia
- Amazia
- Polythelia
- Polymastia
Lymphatic drainage of the breast: Description
The lymphatic drainage of the breast originates from the breast lobules and flows into a subareolar plexus, called Sappy’s plexus. From this plexus, lymphatic drainage takes place through three main routes:
Lymphatic drainage of the breast: Pathways
Axiallary or lateral pathway:
Receives 75% of the lymph this pathway runs around the inferior edge of the pectoralis major and reaches the pectoral group of axillary nodes.
Internal mammary pathway:
Originates from both the medial and lateral halves of the breast and passes through the pec. Major. Connections may lead across the median plane and hence to the contralateral breast
Retromammary pathway:
Drains the posterior portion of the breast
Lymphatic drainage of the breast: Variants
Lymphatics may reach the sheath of the rectus abdominus and the sub peritoneal and subhepatic plexuses.
Left ventricle
The left ventricle is one of four heart chambers. It receives oxygenated blood from the left atrium and pumps it into the systemic circulation via the aorta.
Left ventricle: Gross anatomy
- The left ventricle is conical in shape
- anteroinferiorly projecting apex
- longer with thicker walls than the right ventricle
- separated from the right ventricle by the interventricular septum,
- Internally, there are smooth inflow and outflow tracts and the remainder of the left ventricle (mainly apical) is lined by fine trabeculae carnae.
Left ventricle: Neurovasculature
Arterial supply:
- left anterior descending artery: supplies the free wall and most of the papillary muscles
- left circumflex artery: supplies the free wall
Venous drainage:
- great cardiac vein, middle cardiac vein and posterior vein of the left ventricle: drain into the coronary sinus
- tiny myocardial thebesian veins drain directly into the right ventricle
Innervation:
- Superior and inferior cardiac plexi
- Conduction system of the heart
Lymphatics:
Lymphatics system of the heart draining into the tracheobronchial, para-aortic nodes and superior phrenic nodes.
Left ventricle: Variants
double-inlet ventricle: inflow from both the right and left atria
parachute valve: mitral valve chordae tendineae inserting into a single papillary muscle
RIght atrium: Description
The right atrium (RA) is one of the four chambers of the human heart.
Function: the first chamber to receive deoxygenated blood returning from the body, pre-loads the right ventricle with increase it efficiency (Frank Starling law)
Right atrium: Gross anatomy
The right atrium receives deoxygenated blood from the superior vena cava (SVC), the inferior vena cava (IVC), the coronary sinus (covered by the thebesian valve), and the thebesian veins.
Grossly ellipsoid in shape except for the atrial appendage.
The right atrium is separated from the left atrium by the interatrial septum. Which has an indentiation in it called the fossa ovalis (was previously the foramen ovalis prior to birth)
The right atrium leads into the right ventricle through the tricuspid valve.
The crista terminalis is a muscular ridge on the anterior aspect of the chamber.
The atrium is lined by pectinate muscles to the left of this crest, and these extend into the right atrial appendage.
Right atrium: Neurovasculature
Blood supply:
arterial supply is primarily from the right coronary artery (RCA) and several of it’s branches:
conus artery (first branch off RCA in 55%, otherwise arises off left circumflex artery)
sinoatrial node artery (usually second branch off RCA in 60%)
acute marginal branches
Venous drainage:
variable veins drain the atrial wall
tiny myocardial thebesian veins drain directly into the right ventricle
Nerve supply:
The right atrium is the location of the sinoatrial node, the heart’s pacemaker. It is located subepicardially in the terminal groove, near the junction of the SVC and right atrium.
Although the sinoatrial node can generate conduction rhythms spontaneously, it is regulated by the vagus nerve (CN X) and the cardiac sympathetic plexus.
Right atrium: Variant
Eustachian valve of the IVC
Oesophagus: Description
The oesophagus is a muscular tube that connect the pharynx to the stomach
Function: convey food bolus to the stomach
Oesophagus: Gross anatomy
~23-37cm in length
Divided into segments:
- Cervical – hypopharynx to superior thoracic aperture
- Thoracic – Sup. Thoracic aperture to the oesophageal hiatus
- Intraabdominal – diaphragm to cardia of the stomach
Course: through the superior thoracic inlet, running in the posterior mediastinum behind the trachea, passes through the diaphragm through the oesophageal hiatus at level T10
Termination: joins the cardia via the lower oesophageal sphincter
Oesophagus: Relations
Anterior: trachea, carina, heart
Posterior: vertebral bodies from C4 to T11
Lateral: Ascending laryngeal nerve in the tracheooesophageal groove
Oesophagus: Neurovasculature
Arterial supply:
- Inferior thyroid
- Direct branches of the desending aorta
- Braches from the left gastric
Venous drainage:
- Superior: Inferior thyroid plexus
- Middle: Azygos system
- Inferior: via the left gastric to portal vein
Innervation:
Oesophageal plexus supplied by the vagus and sympathetic chain of ganglions
Lymphatics:
- Deep cervical
- Posterior mediastinal
- Coeliac
Oesophagus: Variants
- Oesophageal bronchus
- Oesophageal atresia
- Tracheo-oesophageal fistula
- Duplication cyst
- Fenestrated oesophagus
Cervical relations of oesophagus
Anterior: trachea, cricoid cartilage, the isthmus of the thyroid
Posterior: bodies and disc of vertebra C4 – C7
Lateral: Trachea oesophageal grooves, right and left recurrent laryngeal nerves, the carotid spaces
Superior: Cricopharygeus, oropharynx
Inferior: Thoracic oesophagus
Thoracic oesophageal relations
Anterior: Trachea, left recurrent laryngeal nerve, pericardium
Posterior: Thoracic vertebral bodies, thoracic duct, azygos veins, descending aorta
Lateral: Right – Pleura, terminal part of the azygos vein, Left – Left subclavian artery, aortic arch, thoracic duct, pleura
Superior: Cervical oesophagus
Inferior: Diaphragm, oesophageal hiatus, the abdominal component of the oesophagus
Abdominal oesophageal relations
Anterior: Left vagus nerve, posterior surface of the heart
Posterior: Right vagus nerve, left crus of the diaphragm
Lateral: Left – fundus of the stomach, spleen, Right - coeliac axis
Superior: Thoracic oesophagus
Inferior: Cardia of the heart
Pericardium: Description
The pericardium is a sac like covering of the heart and the root of the great vessels
Function: Reduce friction between the heart and surrounding tissue to allow for cardiac movement
Pericardium: Gross anatomy
Fibrous outer sac is referred to as the fibrous pericardium, it is fused to:
- central tendon of the diaphragm
- sternum via the superior and inferior sternopericardial ligaments
- roots of the great vessels
- pre-tracheal fascia
The serous inner sac is divided into 2 layers between which there is 15-50mls of pericardial fluid. The outer layer of parietal serous pericardium is fused to the fibrous pericardium, the inner layer is adherent to the surface of the heart and origins of the great vessels
Pericardium: Recesses/sinuses
Sinuses:
- Oblique sinus – formed behind the left atrium bounded by the origins of the superior and inferior vena cava and the pulmonary veins
- Transverse sinus – between the aorta and pulmonary trunk and the atria posteriorly
Recesses:
- Pulmonic venous recess right and left
- Pulmonary recess right and left
- Superior and inferior aortic recess
- Postcaval recess
Pericardium: Neurovasculature
Arterial supply:
Pericardiophrenic and musculophrenic arteries branches of the internal thoracic
Venous drainage:
Pericardiophrenic and musculophrenic veins into brachiocephalic and internal thoracic veins
Innervation:
- Superior and inferior cardiac plexus supplied by the vagus and the sympathetic chain of ganglion
- Phrenic nerves
Pericardium: Relations
- Inferior: central tendon of the diaphragm
- Anterior: Sternum and costal cartilages (3-7), lung and plura (thymus in children)
- Lateral: pleural and lung, phrenic nerves,
- Medial: heart and origin of the great vessels
Pericardium: Variants
- Agenesis of the pericardium
- Pericardial cysts
Pleura: Description
The pleura are serous membrane sacs that contain the lungs
Function: reduce friction between the lungs and the thoracic walls
Pleura: Gross anatomy
Divided into the parietal and visceral pleural with 15-50ml of pleural fluid between them
The visceral pleura invaginates the fissures of the lungs
The parietal pleura is named after the surface it covers:
- Cervical
- Costal
- Diaphragmatic
- Mediastinal
Pleura: Lines of reflection
- 2nd rib – both descend midline
- 4th rib – the left deviates for the heart
- 6th rib – the right and left deviate for the heart
- 8th rib – Right and left both pass the mid clavicular line
- 10th rib – right and left pass the midaxillary line
- 12th rib – right and left travel posteriorly around the chest wall
Pleura: Neurovasculature
Blood supply:
Visceral pleura:
Bronchial and pulmonary arteries
Parietal pleura:
Internal thoracic, intercostal and phrenic
Venous drainage:
Bronchial and pulmonary veins
Lymphatics:
Perihilar nodes
Innervation:
The parietal pleural is innervated by the phrenic nerves and the intercostal nerves (mediastinal and costal parts respectively)
Pleura: Relations
Anterior: Anterior thorax
Posterior: posterior thorax and thoracic vertebra
Lateral: rib intercostal muscles etc
Inferior the diaphragm
Superior the superior thoracic aperture
Pleura: Variants
- Azygos lobe
- Agenesis
- Superior and inferior accessory fissures of the right lung
- Left horizontal fissure
Segmental anatomy of lungs: Description
The segmental anatomy of the lung describes the division of the lung into segments based the the supply of segmental bronchi.
Segmental anatomy of lungs: Gross anatomy
The trachea divides at the carina (T4) forming the right and left main stem bronchi. These further divide into lobar bronchi. Which then in turn divide into segmental bronchi. The lung supplied by each segmental bronchi is defined as a lung segment.
In general each lung has 10 segments, giving 20 in total
Each segment is an independent anatomically functional unit. This allows for discrete surgical resection.
Right lung segments
Upper lobe:
- Apical (B1)
- Posterior (B2)
- Anterior (B3)
Middle lobe:
- Lateral (B4)
- Medial (B5)
Lower lobe:
- Superior (B6)
- Medial (B7)
- Anterior (B8)
- Lateral (B9)
- Posterior (B10)
Left lung segments
Upper lobe:
- Apicoposterior (B1/2)
- Superior lingular (B4)
- Inferior lingular (B5)
- Anterior (B3)
Lower lobe:
- Anteriomedial (B7/B8)
- Lateral (B9)
- Posterior (B10)
- Superior (B6)
Segmental lung anatomy: Variants
- Azygos lobe
- tracheal broncus
- cardiac bronchus
- oesophageal bronchus
Thymus: Description
The thymus is a T-cell producing lymphoid organ in the anterior mediastinum that plays a role in the development of the immune system, particular the maturation of T-cells. It typically has a retrosternal location and hence can mimic retrosternal pathology.
Thymus: Gross anatomy
It is relatively large in infancy
Grows considerably immediately after birth
maximal weight in adolescence between 12 and 19 years then gradually involuting with age with progressive fatty replacement of the cellular components.
Consist of two lateral lobes touching in the midline, situated partly in the thorax, partly in the neck.
The gland extends from as high as the lower border of the thyroid gland to the fourth costal cartilage downwards.
Thymus: Relations
Anteriorly: sternum, origins of the inferior strap muscles
Posteriorly: pericardium, aortic arch, great vessels, left brachiocephalic vein, trachea
Laterally: pleura, pretracheal fascia
Thymus: Neurovasculature
Arterial:
Inferior thyroid and internal thoracic arteries
Venous:
left brachiocephalic, internal thoracic and inferior thyroid veins
Lymphatic drainage:
parasternal, brachiocephalic and tracheobronchial lymph nodes
Innervation:
- Vagus
Thymus: Variants
- variable location: ectopic and/or accessory thymic tissue may be located anywhere along the path of descent of the thymopharyngeal ducts. e.g. retrocaval, cervical, posterior mediastinal
- variable shape: e.g. unilobed, trilobed, X-shaped, inverted V-shaped
Trachea: Description
The trachea is the primary trunk of the conductive airways
Function: transmission of gas between the larynx and the main bronchi
Location: Visceral space of the neck and posterior mediastinum
Trachea: Gross anatomy
Made up of posteriorly incomplete cartilage rings with interspaced annular ligaments
Enveloped by the trachealis muscle which is particularly prominent posteriorly
Lined with ciliated epithelium
Divided into: cervical and thoracic trachea
Origin: continuation of the airway distal to the cricoid cartilage (C6)
Termination: bifurcates at the carina level L4
Trachea: Neurovasculature
Arterial supply:
- Inferior thyroid arteries
- Bronchial arteries
Venous drainage:
- Inferior thyroid veins
- Azygos system
Lymphatics:
- Drainage into deep cervical, peri and para-tracheal nodes of the mediastinum
Innervation:
- Vagus and sympathetic trunk
Trachea: Relations
- Posterior: oesophagus and recurrent laryngeal nerve
- Anterior: Thyroid strap muscle, jugular notch, manubrium, great vessels of the superior mediastinum
- Lateral: Sternocleidomastoid, brachiocephalic veins and arteries
- Superior: larynx
- Inferior: Sub-carinal lymph nodes, main bronchi
Trachea: Variants
- Trachea oesophageal fistula
- Tracheal atresia
- Pig bronchus
- Lunate trachea
- Tracheal diverticulum
Bronchial tree: Description
Branching tree of airways beginning at the carina.
The lumen diameter decreases with each branching.
Airways down to the level of the bronchioles contain c-shaped rings of hyaline cartilage to maintain the patency of the lumen.
Function: transmission of gas between the trachea and the respiratory airways of the lungs
Branches of the Bronchial tree
Right side:
- Right main bronchus
- Bronchus intermedius
- Right Upper lobe bronchus
- Right middle lobe bronchus
- Right lower lobe bronchus
Left side:
- Left main bronchus
- Left upper lobe bronchus
- Left lower lobe bronchus
Further branches:
- Segmental bronchi
- 20 to 25 generations of bronchioles
- Terminal bronchioles
Bronchial tree: Vasculature
Arterial supply:
- Bronchial arteries
- Branches of the descending aorta
Venous drainage:
- Bronchial veins draining into the azygos system
Lymphatic drainage:
- Hilar nodes
Bronchial Tree: Variants
- Bronchial cyst
- Pig bronchus
- Oesophageal branch
- Azygos bronchus
- Cardiac bronchus
Superior mediastinum: Description
Superior mediastinum is an artificially divided wedge-shaped compartment of the mediastinum located between the thoracic plane inferiorly and the thoracic inlet superiorly. The inferior mediastinum, comprising of the anterior, middle and posterior parts, lies inferiorly.
Superior mediatstinum: Boundaries
- superiorly: thoracic inlet
- inferiorly: thoracic plane
- laterally: mediastinal pleura
- anteriorly: manubrium of the sternum
- posteriorly: bodies of upper four thoracic vertebrae
Superior mediastinum: Contents
muscles: origin of sternohyoid, sternothyroid and lower end of longus colli muscles
arteries: aortic arch and great vessels
veins: right and left brachiocephalic veins, left superior intercostal vein, upper half of superior vena cava
nerves: phrenic, vagus and cardiac nerves; cardiac plexus; left recurrent laryngeal nerve
lymph nodes: brachiocephalic; tracheobronchial; paratracheal
Organs:
- trachea
- oesophagus
- thoracic duct
- thymus
T5 level: Description
The T5 level is also known as the transthoracic plane or plane of Ludwig. It is a horizontal plane at the level of the inferior endplate of L4.
Divides the superior and inferior mediastinum
T5 level transection
- Carina
- Pulmonary trunk bifurcates
- Thoracic duct crosses from right to left at this level
- Azygos vein drains into the superior vena cava
- Inferior concavity of the aortic arch
- Ligamentum venosum
- Termination of the pre-tracheal and pre-vertebral fascia
- Cardiac plexus
- Recurrent laryngeal loops under the arch
- Superior vena cava
- Sternal angle
- Ribs 2 – 4
- Internal and external intercostal muscles
- Internal thoracic artery
- Lungs
- Muscles of the thorax and arms
- Humerus
Superior thoracic apeture: Description
The superior thoracic aperture is the superior opening into the thorax
Function: Allow the passage of a large number of structure into and out of the thorax
Location: Encircled by the first rib, the T1 vertebrae and the manubrium
Thoracic inlet: Organs
- Lung apices
- Trachea
- Oesophagus
- Thymus
- Sometimes the thyroid
Thoracic inlet: Vasculature
- Brachiocephalic veins
- Internal thoracic arteries
- Brachiocephalic truck
- The left common carotid artery
- The left subclavian artery
Lymphatics:
- Cervical lymph nodes
- Thoracic duct
Thoracic inlet: Nerves
- Vagus nerves
- Phrenic nerves
- Ascending laryngeal nerves
- The sympathethetic chain of ganglion
Thoracic inlet: Muscles
- Part of sternocleidomastoid
- Sternohyoid
- Sternothyroid
Thoracic inlet: Variants
- Right common carotid and subclavian can pass through
- Thyroid IMA artery can pass through
- Thyroid can extend through
- Cervical ribs
Intercostal space:Description
The intercostal spaces are the space between the ribs. There are 11 spaces on each side and they are numbered according to the rib which is the superior border of the space.
Intercostal space: Gross anatomy
The intercostal spaces contain three layers of muscle:
- External
- Internal
- Innermost
The neurovascular bundle is found between the internal and innermost layers.
Intercostal spaces: Muscles
The external intercostal muscle fibres run down and medial
The internal intercostal muscle fibres run down and lateral
The deepest layer of muscle in the intercostal space is made up of three muscles which are collectively known as the tranversus thoracis group. This group includes the:
- subcostal muscles posteriorly
- the innermost intercostals laterally
- the transversus thoracis / sternocostalis muscles anteriorly.
Intercostal spaces: Neurovascular bundle
The neuromuscular bundles are found between the middle and innermost layers, protected by the costal groove of the superior rib of each intercostal space. They are ordered vein, artery, nerve from superior to inferior (mnemonic VAN). The collateral neurovascular bundle runs at the lower edge of the space, just above the inferior rib and the order is reversed, i.e. nerve, artery, vein from superior to inferior.
Intercostal spaces: Neurovasculature
Blood supply:
Arterial supply:
Single large posterior intercostal artery and 2 smaller anterior intercostal arteries.
In the first and second intercostal spaces a large posterior artery arises from the superior intercostal artery (a branch from the costocervical trunk).
The arteries in the remaining spaces branch directly from the descending thoracic aorta.
The anterior intercostal arteries arise from the internal thoracic and musculophrenic (below 6th interspace).
Venous drainage:
Posterior veins drain into the azygos or hemiazygos veins. Anterior veins drain into the internal thoracic or musculophrenic veins.
Innervation:
Each intercostal space is supplied segmentally by muscular branches of anterior rami of spinal nerves T1-T11.
