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Anatomy of the Thorax Learning Objectives 1. Explain the roles of skeleton, muscles, pleural cavities and lungs in breathing. 2. Explain the functions, positions and relations of the structures entering and leaving the lungs. 3. Explain the anatomical principles underlying insertion of chest drains and relief of tension pneumothorax and cardiac tamponade. 4. Describe the arterial supply and venous drainage of the thoracic viscera and thoracic walls. 5. Define the mediastinum and demonstrate its subdivisions and contents. 6. Explain the principles of X-ray imaging methods and identify the features of the normal adult chest in conventional X-ray and CT images. 7. Demonstrate using correct terminology the position and relations of the pericardium and pericardial sac, heart chambers and valves in anatomical specimens, living subjects and images. 8. Explain the origins of heart sounds and demonstrate optimal auscultation of each valve. 9. Describe and recognise normal breath sounds and percussion sounds. 10. Explain the pathways through which the heart, lungs, chest wall and diaphragm obtain their sensory and motor nerve supplies and explain referred pain of thoracic origin. 11. Describe the anatomical organisation and pathways of lymphatic drainage of the breasts. 12. Explain the physiology of lymph formation, the structure and functions of lymph nodes, the importance of lymphatic drainage in the dissemination of cancers and infections and the main pathways for lymphatic drainage of the body. 13. Demonstrate the intrathoracic positions and relations of the trachea, oesophagus, thoracic duct, vagus nerves and phrenic nerves.
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Lecture 1: The Thoracic Wall: Ribs: •
TRUE: 1-7 reach sternum
•
FALSE: 8-10 reach costal cartilage above
•
FLOATING: 11-12 lack anterior attachment
Articulations/joints with vertebral column (heads)/costal cartilage(tubercles)
Most lung tissue and most capacity for lung expansion is in the lower thorax
Diaphragm: Has a flat central tendon with muscle radiating to costal margin and vertebrae. 1st – dome flattens to increase vertical diameter of chest. 2nd – pulls costal margin up to increase transverse and antero-posterior diameters
Sternum: •
MANUBRIUM
•
BODY
•
XIPHOID
a. 1st costal cartilages attach to manubrium b. 2nd to M-S joint c. 3rd – 7th to Sternum d. 8th – 10th to Cartilage above e. 11th & 12th Floating
Thoracic Inlet is a ring formed of:
pg. 2
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•
1st Thoracic Vertebra (T1)
•
1st Ribs
•
Manubrium
Intercostal Muscles Have a secondary role – stiffen chest wall to improve efficiency of breathing movements 1. External Intercostals – a. Downwards & laterally from lower border of rib above to rib below. b. Replaced by anterior intercostal membrane at costo-chondral junction. 2. Internal Intercostals – a. attachments begin anteriorly at the sternum – from lower border of rib above to rib below – fibres directed at right angles to external intercostals. b. Replaced by membrane posteriorly 3. Innermost intercostals – Relatively trivial
Intercostal neurovascular bundles
VAN = Vein, Artery & Nerve, just below rib deep to internal intercostals
Each intercostals artery joins (anastomoses) with a major artery at each end of the intercostal space
Drains into internal thoracic vein
pg. 3
S Tran Intercostal Nerves o 11 pairs T1-T11
(+ 1 Subcostal – T12)
o
Mixed (Motor & Sensory)
o
Supplies intercostals spaces
o
Lateral cutaneous branches (anterior and posterior)
o
Anterior cutaneous – medial and lateral
pg. 4
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Lecture 2: Bronchi, Lungs, Pleura and Diaphragm Bronchial Tree •
•
•
•
Trachea o
C6 to T4/5
o
Held open by C-shaped Cartilage rings
o
Lowest ring has a hook – Carina (keel of ship)
Primary (main) Bronchi (L&R) o
Formed at T4/5
o
Right Wider and more vertical than left
Lobar (Secondary) Bronchi o
Formed within the lungs
o
Supply the lobes of the lungs
o
2 LEFT 3 RIGHT
Segmental (Tertiary) Bronchi o
Supply the bronchopulmonary segment
Lungs •
Essential for Respiration
•
Separated from each other by mediastinum
•
Lie freely in its pleural cavity apart from attachment to heart and trachea at the lung root (HILUM)
Conical in shape
APEX o
Thoracic inlet oblique – apex rises 3-4cm above first costal cartilage level
pg. 5
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BASE o
Concave
o
Rests on Convex surface of diaphragm
3 Borders – ANTERIOR, POSTERIOR, INFERIOR
3 Surfaces – COSTAL, MEDIAL(MEDIASTINAL), INFERIOR (DIAPHRAGMATIC)
Diaphragm separates the right lung from right lobe of liver and the left lung from left lobe of the liver, stomach & spleen.
Mediastinial surface: POSTERIOR – in contact with thoracic vertebrae
ANTERIOR – deeply concave – accommodates heart – cardiac impression larger on L than R
ABOVE & BEHIND – cardiac impression – hilum where vessels, bronchi & nerves enter.
Left Lung • Two lobes separated by oblique fissure:
•
o
Superior
o
Inferior
Superior lies above the fissure and includes apex & most of anterior part of lung.
Right Lung • Slightly larger three lobes separated by oblique fissure & horizontal fissure: o
Superior
o
Middle
o
Inferior (Oblique fissure)
The Root (Hilum) of the Lung •
Connects mediastinal surface to heart & trachea, all enveloped in plerua:
Principal (Primary) Bronchus
Pulmonary Artery
2 Pulmonary Veins
Bronchial Arteries (oxygenated blood from descending aorta) & Veins
Pulmonary plexus of nerves (Autonomic)
Lymph vessels and nodes
pg. 6
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The Pleura •
“Thin layer of flattened cells supported by connective tissues that lines each pleural cavity and covers the exterior of the lungs.” o
Visceral Pleura– covers surface of lungs and lines fissures between the lobes
o
Partietal Pleura – lines inner surface of chest walls
•
Visceral and parietal pleura are continuous with each other around the hilum.
•
Pleural cavity is collapsed, but moist surfaces allow lungs to glide as they expand and collapse.
•
Originally pleural pleura lined the pleural cavities, lung buds grew into them within visceral pleura covering.
•
Costo-diaphragmatic recess of pleura – free of lung except in maximal inspiration.
Breathing 1. Controlled by nervous system and produced by skeletal muscle 2. Brings about inhalation and exhalation of air into/out of the lungs, to ventilate the gas exchange areas - alveolar sacs 3. capacity of thoracic cavity can be increased: •
by movements of the diaphragm
•
by movements of the ribs
Mechanism of breathing •
Pleural Cavity expanded by wall muscles
•
Elastic lungs expand with the pleural cavity, sucking air down trachea and bronchi into lungs
pg. 7
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The Diaphragm – Main Inspiratory Muscle •
Contracts increase vertical dimension of the thoracic cavity
•
Diaphragm presses on the abdominal viscera which initially descend due to abdominal wall relaxation during inspiration.
•
Further descent is stopped by abdominal viscera, so more contracts raises the costal margin.
•
Increased thoracic capacity produced by diaphragm & rib movements, reduces intrapleural pressure, with entry of air through respiratory passages & expansion of the lungs.
Costal margin (lower border of rib cage) of diaphragm o
Xiphoid process
o
Ends of ribs 11 and 12
o
Lumbar vertebrae
Ribs in breathing:
Ribs elevated – anterior ends thrust forward & upwards – increase antero-posterior dimension of thoracic cavity.
Ribs are everted, increasing transverse diameter of thoracic cavity
Internal & external intercostal muscles stiffen the rib cage to increase efficiency of diaphragm
pg. 8
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Raising the costal margin also raises drooping anterior ends ribs, tilting sternum upwards to increase antero-posterior diameter of pleural cavities (pump-handle action – blue arrow)
Breathing out •
Quiet expiration is a passive activity not requiring muscles
•
It depends on elastic recoil in the elastic tissue throughout the lungs and in the rib cage
•
In deep or forced expiration, this is assisted by the muscles of the abdominal walls that squeeze the abdominal organs against the diaphragm and pull the lower ribs downward
pg. 9
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Lecture 3: Superior Mediastinum •
Thick midline partition between two pleural cavities
•
Conduit (channel) for structures that passes through the thorax or to other body regions.
•
Extends from SUPERIOR THORACIC APERTURE (inlet) to INFERIROR THORACIC aperture
•
Between STERNUM (anterior) and the THORACIC VERTEBRAE (posterior)
Content
Trachea (Larynx to bifurcation into principle (R&L main) bronchi
Oeseophagus (Pharynx to T10 Diaphragm)
Heart & Pericardium
Thoracic Duct (Cisterna Chyli to Left brachiocephalic vein)
Nerves
Great Vessels
Divisions o
Superior: above sternal angle
o
Inferior: below sternal angle
o
Anterior: anterior to heart in pericardial sac
o
Middle: PERICARDIAL SAC & HEART
o
Posterior: posterior to pericardial sac and diaphragm
Content of Superior Mediastinum (A-P) Thymus Phrenic Nerves Great Veins Main Lymphatic Trunks Vagus Nerves Great Arteries
pg. 10
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Trachea & Main Bronchi Upper Oeseophagus ToP VaVLe GATO
Great Veins: •
Subclavian Vein + Internal Jugular Vein = Brachiocephalic Vein
•
Left Brachiocephalic Vein crosses POSTERIOR to Manubrium
•
R & L Brachiocephalic Vein (Asymmetric) = Superior Vena Cava – Enters RA from above.
•
Azygos Vein drains posterior wall of thorax & abdomen. o
•
Arches over RIGHT LUNG ROOT into SVC
IVC enters RA from below (through central tendon of diaphragm)
Arteries: •
Ascending Aorta 1. R & L Coronary Arteries
•
Arch of Aorta 1. Left Subclavian Artery 2. Left Common Carotid Artery 3. Branchiocephalic Trunk i.
Right Common Carotid
ii.
Right Subclavian Artery
•
Descending Aorta
•
Aortic Arch arises ANTERIROR to Trachea.
•
Arches OVER left main bronchus at lung root.
•
Trachea lies behind & between brachiocephalic and left common carotid arteries.
•
Common Carotids External & Internal Carotid Arteries
pg. 11
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Pulmonary Trunk •
Starts at RIGHT ventricle
•
Deoxygenated blood to Lungs
•
Divides into L & R Pulmonary Arteries
•
Ligamentum arteriosum (previously: ductus arteriosus) connects PT to aortic arch.
Phrenic Nerves •
C3, 4, 5
•
Motor to Diaphragm
•
Sensory to: o
Mediastinal Pleura
o
Pericardium
o
Peritoneum of Central Diaphragm RIGHT PHRENIC NERVE • Right Brachiocephalic Vein •
Superior Vena Cava
•
Right Side of Heart + Pericardium – In FRONT of lung root.
LEFT PHRENIC NERVE • Crosses left vagus to cross aortic arch more anteriorly •
Passes over Pericardium towards Diaphragm.
RIGHT VAGUS NERVE • Lies on Trachea •
Crosses BEHIND lung root
•
Recurrent laryngeal branch – recurs around right subclavian artery
•
Breaks into branches on the oesophagus
LEFT VAGUS NERVE • Lateral to Common Carotids •
Passes Anterior to Aortic Arch
•
Crosses BEHIND lung root to form Recurrent Laryngeal Nerve around Ligamentum artiosum.
•
Breaks into many branches around oesophagus
pg. 12
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pg. 13
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Lecture 4: Nerves in the Thorax Somatic Nerves (Body) •
Necessary for skeletal muscle & skin.
•
Sensory to body wall
•
Segmental nerves combine to form PLEXI supplying specialised area (cervical, brachial, lumbosacral)
•
Dermatome – Skin area supplied by a single spinal nerve on one side/single spinal cord
•
Myotome - Skeletal muscle supplied by a single spinal nerve on one side/single spinal cord
Intercostal Nerves: o 11 Pairs (+ 1 subcostal) o
Mixed (Motor & Sensory)
o
Spinal/Segmental Nerves (Anterior Primary Rami)
o
Supplies intercostals spaces, lateral cutaneous branch (A&P), anterior cutaneous (Medial & Lateral)
o
Autonomic/Visceral – Organs & smooth muscles and glands.
Phrenic Nerves: o Derived from Anterior Rami of C3-5 o
No autonomic function/visceral distribution
o
Motor
Sensory supply central diaphragm, mediastinal pleura and pericardium.
o
o
Supply
Autonomic o o o
supply muscle of diaphragm
peritoneum on interior surface of central diaphragm.
Nerves (Visceral) Motor to Cardiac Muscle, Smooth Muscle and Glands Sensory to Visceral organs Parasympathetic & Sympathetic
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Parasympathetic Nerves 1. Oculomotor (III) cranial nerves 2. Facial (VII) cranial nerves 3. Glossopharyngeal (IX) cranial nerves 4. Vagus (X) cranial nerves 5. Sacral (S2 – S4) spinal nerves
Visceral Sympathetic Trunks •
All autonomic pathways have preganlionic and postganlionic neurones.
•
Branches from T1-L2
•
Sympathetic nerves to smooth muscle + glands
•
Nerves to BODY WALL synapse in TRUNK GANGLIA
•
Nerves to VISCERA synapse in LOCAL GANGLIA
•
Pain Fibres back to CNS from viscera
•
T5-T12 to abdomen in SPLANCHNIC NERVE bundles.
Sympathetic to Lungs & Heart o
T2-T4 passes through cervical & upper thoracic ganglia of trunk
o
Micro-ganglia synapses in pulmonary and cardiac plexuses
Pulmonary Plexuses
•
Sympathetic nerves DILATE bronchioles
•
Parasympathetic nerves(vagus) CONSTRICT the bronchioles
Cardiac plexuses Efferent • Sympathetic efferents increase heart rate and force of contraction •
Parasympathetic efferents (vagus) heart rate via the pacemaker tissue and constrict coronary
decrease arteries.
pg. 15
S Tran Afferent • Sympathetic afferents relay pain sensations from the heart •
Parasympathetic afferents (vagus) relay blood pressure and chemistry information from the heart
Vagus Nerves •
Cranial nerve X – arise from medulla & leave skull through jugular foramina
•
Descend neck posterolateral to common carotid arteries
•
LEFT vague crosses ANTERIOR to aortic arch then posterior to left lung root
•
RIGHT vagus passes posterior to right lung root
•
Both Vagi form a plexus around the oesophagus
•
Separates to form anterior and posterior oesophageal/gastric nerves
Oesophageal plexus • Sympathetic afferents relay pain sensation from oesophagus •
Parasympathetic afferents (vagus) senses normal physiological information from the oesophagus
Vagus nerves •
To chest & abdomen are parasympathetic (smooth & cardiac muscle + glands of gut and airway)
•
Large sensory (enteroceptor) content from gut and lungs
•
No autonomic supply to body wall (e.g. arterioles & sweat glands)
•
Recurrent laryngeal branch of vagus is NOT parasympatheteic – recurs up to the neck and supplies the skeletal muscles of the larynx.
•
Oesophagus’plexus is supplied posteriorly by the right vagus.
•
Acquire many sympathetic fibres
•
Inferior continuation of the vagi takes the fibres through the diaphragm to the abdominal viscera
Intrinsic nerves of the Oesophagus •
Plexus of ganglia and axons within the wall coordinate its activity
•
Can be up or down-regulated by the autonomic nerves
•
Part of the ENTERIC NERVOUS SYSTEM
pg. 16
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Lecture 5: Lymphatic System Why? •
More fluid leaves capillaries than returns to them.
•
No fluid movement = oedema + loss of blood volume
•
Lymphatic drains excess fluid
•
Immunological significance
Pathogens
Hormones
Cell Debris
Small Intestine:
Fats absorbed into Chylomicrons (protein coated lipids)
Released into interstitial fluid
Drains into Lacteal (Lympathic capillaries)
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Returns to venous system via the neck
Opaque and Milky – Chyle. Clear + Odourless in other vessels.
Movement: Action of adjacent structures: •
Skeletal muscles + Pulses in arteries
•
Valves ensure unidirectional
Lymph Nodes •
Small (<2.5cm long)
•
Found along lymph vessels
•
Contain lymphocytes and macrophages
•
Can act upon foreign bodies in the lymph
•
Drainage from infected regions detectable in enlarged lymph nodes
•
Armpit, groin, neck
pg. 18
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Lympathic Drainage Thoracic wall o Internal thoracic arteries (PARASTERNAL)
o Bronchomediastinal Trunks o
o
Ribs (INTERCOSTAL) o
Upper –Bronchomediastinal Trunks
o
Lower – Thoracic Duct
Diaphragm (DIAPHRAGMATIC)
o Branchiocephalic o Aortic/Lumbar o
Superficial
o Axillary or Parasternal The Thoracic Duct • Main Drainage Channel
pg. 19
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Begins at Cisterna Chyli
•
Begins at L2
•
Enters behind Oesophagus through diaphragm
•
Ascends on right of midline – Between Aorta and Azygous Vein
•
Crosses to Left at T5
•
Empties into LEFT BRACHIOCEPHALIC VEIN – Between left subclavian and internal jugular vein join.
The Lungs • TRACHEOBRONCHIAL
•
Around Bronchi + Trachea
From within lung through Hilum
Unites with PARASTERNAL + BRACHIOCEPHALIC =
BRONCHIOMEDIASTIUM(L & R)
The Heart • Follows coronary arteries into
BRACHIOCEPHALIC
TRACHEOBRONCHIAL
The Posterior Mediastinum • Nodes on Aorta receive lymph from oesophagus, diaphragm, liver and pericardium and drains into i.
Thoracic duct
ii.
Posterior Mediastinal
pg. 20
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Lecture 6: Breast Anatomy Breast Development Mammary Ridge (Milk Ridges): • 4th week •
Thickened strips of ectoderm
•
Extend from axillary to inguinal region
•
Normally only persist in pectoral area
Mammary Gland • 6th week •
Solid growths of EPIDERMIS into underlying meschencyme along mammary ridges.
Primary Bud = Primordium of Mammary Gland o Gives rise to Secondanchry Bud o
Secondary Bud develops into Lactiferous Ducts & branches
Surrounding meschencyme o Gives rise to fibrous connective tissue and fat Epidermis at origin of mammary gland (Late Fetal Period) o Becomes indented/depressed = Mammary Pit = Nipple o
At Birth: Nipples poorly formed & depressed
o
Nipples arise from proliferation of surrounding connective tissue of the areola
Birth: • Rudimentary mammary glands in M&F. •
Main lactiferous ducts formed. Possible
•
“Witch’s milk” caused by transitory changes by maternal hormones
Puberty: • Fat & Connective Tissue Development •
Growth of duct system
Pregnancy: • Increase in Oestrogen & progesterone
pg. 21
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Intralobular ducts develop & form buds which become alveoli
Abnormalities: •
Athelia: Absence of Nipples
•
Amastia: Absence of Breasts
•
Polymastia: Extra breast
•
Polythelia: Extra Nipple
Extra nipples and breast form along mammary ridges from extra mammary buds. •
Gynaecomastia: Excessive development of male breasts (Pathological or Physiological)
•
Breast structures develop in both sexes
•
Hormonal stimulus to grwoth during female puberty
•
Extra nipples or pigmented skin along mammary line
•
Hormones of pregnancy stimulate gland formation
Breast Structure Breasts have an ‘Axillary Tail’
pg. 22
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Muscle Beds underlying Breasts 1. Pectoralis major 2. Serratus anterior 3. External oblique
Breasts in relation to the axillary walls 1. Clavicle 2. Anterior axillary fold – Pectoralis major 3. Posterior Axillary fold – Latissimus dorsi 4. Medial axillary wall – Serratus anterior
Summary:
12-20 lactiferous ducts open separately on each nipple
Lactiferous sinuses underlie areolae
No glandular tissue in non-pregnant or non-lactating woman
Most of non-pregnant breast is adipose tissue
pg. 23
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Breast supported by internal suspensory ligaments
Artery Supply
Lymph Draginage & Nodes
Lymph drainage parallels blood supply
Axillary and internal thoracic nodes are main normal routes
Cancer can block drainage – raised lymph pressure forces lymph through unusual drainage route
pg. 24
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Nodes 6. Medial (Central) 7. Lateral 8. Anterior (Pectoral) 9. Posterior 10. Apical
pg. 25
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Lecture 7: Posterior Mediastinum Content:
Oesophagus
Descending aorta
Thoracic duct
Azygos venous system
Posterior mediastinal lymph nodes
Thoracic sympathetic trunks
Splanchnic nerves
Oesophagus •
Begins at C7
•
T7: o
Bends Anteriorly
o
Stops being right of aorta
o
Deviates to the left
o
Gets progressively anterior to aorta
•
Diaphragm at T10
•
Ends T11
•
Four Constrictions: o
Oesophagus junction with PHARYNX
o
Crosses ARCH OF AORTA
o
Compressed by LEFT MAIN BRONCHUS
o
At the OESOPHAGEAL HIATUS
Thirds
Artery
Vein
Lymph
Length pg. 26
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Upper Middle Lower
Inferior Thyroid
Inferior Thyroid
Deep Cervical
9cm
Aortic Branches
Azygos Branches
Mediastinal
9cm
Left Gastric
Left Gastric
Gastric
9cm
Nerves within Inferior Mediastinum •
Phrenic (C3, 4, 5) – Anterior to lung roots then cross pericardium to diaphragm
•
Vagi (Carnial Nerve X) – Posterior to lung root + form plexus following oesophagus into abdomen branches to heart and lung on the way.
•
Sympathetic trunks lie each side of the posterior mediastinum Vagus • Parasympathetic (Control smooth + cardiac muscle + glands of gut and airways) •
Large sensory from Gut and Lungs
•
LEFT RECURRENT LARYNGEAL NERVE o
NOT parasympathetic
o
Arch of Aorta starts
o
runs back up neck to supple larynx’s skeletal muscles
Sympathetic Trunks • Branches from T1-L2 •
Distribute sympathetic nerves to smooth muscle + glands
•
Nerves to BODY WALL synapse in TRUNK GANGLIA
•
Nerves to VISCERA synapse in LOCAL GANGLIA
•
Pain Fibres back to CNS from viscera
•
T5-T12 to abdomen in SPLANCHNIC NERVE bundles.
Azygos Venous System o
Drains posterior wall, upper abdomen and posterior mediastinal organs
o
LEFT ACCESSORY HEMIAZYGOS VEIN (Upper) + HEMIAZYGOS VEIN (Lower) join single right Azygos Vein
pg. 27
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Azygos Vein arches over RIGHT LUNG ROOT to enter SVC above right atrium
pg. 28