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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.
pg. 1
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Lecture 1: The Thoracic Wall:
Ribs:
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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:
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MANUBRIUM
BODY
XIPHOID
a.
b.
c.
d.
e.
1st costal cartilages attach to manubrium
2nd to M-S joint
3rd – 7th to Sternum
8th – 10th to Cartilage above
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
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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
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. 3
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Lecture 2: Bronchi, Lungs, Pleura and
Diaphragm
Bronchial Tree
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Trachea
o
o
o
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Primary (main) Bronchi (L&R)
o
o
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Formed at T4/5
Right Wider and more vertical than
left
Lobar (Secondary) Bronchi
o
o
o
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C6 to T4/5
Held open by C-shaped Cartilage rings
Lowest ring has a hook – Carina (keel
of ship)
Formed within the lungs
Supply the lobes of the lungs
2 LEFT 3 RIGHT
Segmental (Tertiary) Bronchi
o
Supply the bronchopulmonary segment
Lungs
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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)
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Conical in shape
APEX
o Thoracic inlet oblique – apex rises 3-4cm above first costal cartilage level
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.
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Mediastinial surface:
 POSTERIOR – in contact with thoracic vertebrae
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ANTERIOR – deeply concave – accommodates heart – cardiac impression larger on L than R
ABOVE & BEHIND – cardiac impression – hilum where vessels, bronchi & nerves enter.
pg. 4
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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
The Pleura
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“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
pg. 5
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Mechanism of breathing
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Pleural Cavity expanded by wall muscles
Elastic lungs expand with the pleural cavity, sucking air down trachea and bronchi into lungs
The Diaphragm – Main Inspiratory Muscle
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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:
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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. 6
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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
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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. 7
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Lecture 3: Superior Mediastinum
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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
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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
o
o
o
o
Superior: above sternal angle
Inferior: below sternal angle
Anterior: anterior to heart in pericardial sac
Middle: PERICARDIAL SAC & HEART
Posterior: posterior to pericardial sac and
diaphragm
Content of Superior Mediastinum (A-P)
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Thymus
Phrenic Nerves
Great Veins
Main Lymphatic Trunks
Vagus Nerves
Great Arteries
Trachea & Main Bronchi
Upper Oeseophagus
ToP VaVLe GATO
Great Veins:
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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.
pg. 8
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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
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Descending Aorta
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Aortic Arch arises ANTERIROR to Trachea.
Arches OVER left main bronchus at lung root.
Trachea lies behind & between brachiocephalic and left common carotid arteries.
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Common Carotids  External & Internal Carotid Arteries
Pulmonary Trunk
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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
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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
pg. 9
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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. 10
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Lecture 4: Nerves in the Thorax
Somatic Nerves (Body)
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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 supply muscle of diaphragm
o Sensory supply central diaphragm, mediastinal pleura and
pericardium.
o Supply peritoneum on interior surface of central diaphragm.
Autonomic Nerves (Visceral)
o
o
o
Motor to Cardiac Muscle, Smooth
Muscle and Glands
Sensory to Visceral organs
Parasympathetic & Sympathetic
Parasympathetic Nerves
1.
2.
3.
4.
Oculomotor (III) cranial nerves
Facial (VII) cranial nerves
Glossopharyngeal (IX) cranial nerves
Vagus (X) cranial nerves
pg. 11
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5. Sacral (S2 – S4) spinal nerves
Visceral Sympathetic Trunks
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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
o
T2-T4 passes through cervical & upper thoracic
ganglia of trunk
Micro-ganglia synapses in pulmonary and
cardiac plexuses
Pulmonary Plexuses
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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)
decrease heart rate via the pacemaker
tissue and constrict coronary arteries.
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
pg. 12
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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
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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
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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. 13
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Lecture 5: Lymphatic System
Why?
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More fluid leaves capillaries than returns to them.
No fluid movement = oedema + loss of blood volume
Lymphatic drains excess fluid
Immunological significance
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Pathogens
Hormones
Cell Debris
Fats
Small Intestine:
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Fats absorbed into Chylomicrons (protein coated lipids)
Released into interstitial fluid
Drains into Lacteal (Lympathic capillaries)
Returns to venous system via the neck
 Opaque and Milky – Chyle.
pg. 14
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 Clear + Odourless in other vessels.
Movement: Action of adjacent structures:
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Skeletal muscles + Pulses in arteries
Valves ensure unidirectional
Lymph Nodes
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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
Lympathic Drainage
Thoracic wall
o Internal thoracic arteries (PARASTERNAL)
o Bronchomediastinal Trunks
o
Ribs (INTERCOSTAL)
o Upper –Bronchomediastinal Trunks
o
Lower – Thoracic Duct
pg. 15
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o
Diaphragm (DIAPHRAGMATIC)
o Branchiocephalic
o Aortic/Lumbar
o
Superficial
o Axillary or Parasternal
The Thoracic Duct
 Main Drainage Channel
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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. 16
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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
 Intralobular ducts develop & form buds which become alveoli
Abnormalities:
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Athelia: Absence of Nipples
Amastia: Absence of Breasts
Polymastia: Extra breast
Polythelia: Extra Nipple
pg. 17
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Extra nipples and breast form along mammary ridges from extra
mammary buds.
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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’
Muscle Beds underlying Breasts
1. Pectoralis major
2. Serratus anterior
3. External oblique
pg. 18
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Breasts in relation to the axillary walls
1.
2.
3.
4.
Clavicle
Anterior axillary fold – Pectoralis major
Posterior Axillary fold – Latissimus dorsi
Medial axillary wall – Serratus anterior
Summary:
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12-20 lactiferous ducts open separately on
each nipple
Lactiferous sinuses underlie areolae
No glandular tissue in non-pregnant or nonlactating woman
Most of non-pregnant breast is adipose tissue
Breast supported by internal suspensory ligaments
Artery Supply
Lymph Draginage & Nodes
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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. 19
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Nodes
6.
7.
8.
9.
10.
Medial (Central)
Lateral
Anterior (Pectoral)
Posterior
Apical
pg. 20
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Lecture 7: Posterior Mediastinum
Content:
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Oesophagus
Descending aorta
Thoracic duct
Azygos venous system
Posterior mediastinal lymph nodes
Thoracic sympathetic trunks
Splanchnic nerves
Oesophagus
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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
Upper
Middle
Lower
Artery
Vein
Lymph
Length
Inferior Thyroid
Inferior Thyroid
Deep Cervical
9cm
Aortic Branches
Azygos Branches
Mediastinal
9cm
Left Gastric
Left Gastric
Gastric
9cm
Nerves within Inferior Mediastinum
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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.
pg. 21
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
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
o
o
Drains posterior wall, upper abdomen and posterior mediastinal organs
LEFT ACCESSORY HEMIAZYGOS VEIN (Upper) + HEMIAZYGOS VEIN (Lower) join single
right Azygos Vein
Azygos Vein arches over RIGHT LUNG ROOT to enter SVC above right atrium
pg. 22