Anatomy of the Thorax
LSS Year 1
Anil Chopra
Contents
Thorax 1 – Anatomy of the Chest Wall ..................................................................... 1
Thorax 2 – Lungs, Pleura and Diaphragm ................................................................ 7
Thorax 3 – Superior Mediastinum and Great Vessels ........................................... 14
Thorax 4 – Organisation of Nerves in the Thorax – Mon 26th Feb 2007 .............. 23
Thorax 5 – Lymphatic System, Breasts and Breast Cancer .................................. 33
Thorax 6 – The Posterior Mediastinum ................................................................... 37
Thorax 1 – Anatomy of the Chest Wall
Anil Chopra
1. Demonstrate the position of the pectoralis major on the chest wall.
Large Muscle that covers the anterior (front) aspect of the chest wall and has two
heads.
2. Define the attachments of the pectoralis major.
Consists of the clavicular head (originates from the clavicle) and the sternocostal head
(originates from the sternum and costal cartilages).
3. Outline the actions of the pectoralis major.
1
Contracts when pushing.
4. Name the space between adjacent ribs
Intercostal Spaces
5. Name and summarise the functions of the muscles which are found between ribs
Intercostal muscles. There are 3:

External intercostal muscles – articulates downward and laterally

Internal intercostal muscles – articulates perpendicular to external intercostals.

Innermost intercostal muscles – fairly trivial.
Their job is to move the ribs as well as stiffen the chest wall improving efficiency of
breathing movements.
Just below each rib in the Costal groove, starting from the top, there is the intercostal
vein, artery and then the nerve (VAN).
2
6. Identify a rib and be able to determine which part of the rib is placed posteriorly
and which anteriorly.
Head of rib is on posterior, then neck and angle.
Costal cartilage is anterior.
7. Name the structures with which a rib articulates.
Posteriorly the ribs articulate with the thoracic vertebra. (T1-T12)
Anteriorly

Rib 1 has costal cartilage attached to manubrium.

Rib 2 has costal cartilage attached to the manubriosternal joint.

Ribs 3 – 6 have costal cartilage attached to body of sternum.

Rib 7 has costal cartilage attached to xiphisternal joint.

Ribs 8 – 10 have costal cartilage attached to that of above rib.

Ribs 11 & 12 do not join to anything.
All the joints between the costal cartilages and the sternum are smooth synovial joints.
Ribs 1-7 are True ribs
Ribs 8-10 are False ribs
Ribs 11&12 are Floating ribs
3
8. Identify the clavicle and demonstrate how it is positioned in the body.
 Clavicle is also known as the “collarbone” and is found on the anterior side of
the body, just superior to the first rib.
 Medially, it articulates with the manubrium of the sternum (breast-bone) at the
sternoclavicular joint.
 Laterally end it articulates with the acromion of the scapula (shoulder blade) at
the acromioclavicular joint.
9. Identify the scapula and demonstrate how it is positioned in the body.
 Scapula is also known as the “shoulder blade” and is found on the posterior
side of the body.
 Together with the clavicle it makes up the pectoral girdle.
 The scapula connects the humerus (arm bone) with the clavicle (collar bone).
4
10. Identify a thoracic vertebra.
 There are 12 thoracic vertebrae T1- T12.
 Each corresponds to a rib.
11. Name the different parts of a thoracic vertebra.
12. Explain how ribs are related to the thoracic vertebrae.
 Each vertebra articulates using the inferior and superior facets (at the head of
the rib) and also the articular part of the tubercle.
 The head of the rib articulates the superior demifacet (near the body of the
vertebrae)
 The articulate part of the tubercle articulates with a facet on the transverse
process (the wing like projections)
 The articulations between the thoracic vertebrae and the ribs are called
vertebrocostal joints.
 The vertebrae also attach to each other via the facets of the superior articular
process.
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13. Explain how vertebrae articulate with each other and how they support loads and
absorb jolts.
 Vertebrae articulate with each other by thin
intervertebral discs between them (which also limits
movement)
 The disk is made of cartilage. It is therefore a
synovial joint.
 Each disc has an outer fibrous ring consisting of
fibrocatilage called annulus fibrosus and an inner soft,
pulpy, highly elastic substance called the nucleus
pulposus.
 The discs form strong joints, permit various movements of the vertebral column
and absorb vertical shock. Under compression, they flatten, broaden and bulge
from their intervertebral spaces.
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Thorax 2 – Lungs, Pleura and Diaphragm
Anil Chopra
1. Name the contents of an intercostal space.
Intercostal space contains:
 External intercostal muscles
 Internal intercostal muscles
 Innermost intercostal muscles
 Intercostal Vein (in costal groove)
 Intercostal Artery (in costal groove)
 Intercostal Nerve (in costal groove)
 Collateral branches
2. Define the pleura.
The pleura is a layer of flattened cells supported by connective tissue that lines each
pleural cavity and covers the exterior of the lungs.
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3. Name the layers of the pleura.
Pleura consist of 2 layers:
Visceral Pleura: this covers the surface of the lungs
and is the innermost layer.
Parietal Pleura: this lines the innermost surface of the
chest wall and is in contact with the ribs and
intercostal muscles. It is the outermost layer.
These 2 layers are separated by the pleural cavity
which contains serous fluid produced by the cells in
the pleura. This helps the lungs glide as they expand
and collapse.
4. Define the extent of the lungs.
The lungs are conical in shape:
 The apex (top) of the lungs reach as high as 3-4 cm above the first costal
cartilage, in the base of the neck.
 The base (bottom) of the lungs is concave and rests on the diaphragm.
5. Define the extent of the pleura
.
The parietal pleura consists of 4 parts:
 the part relating to the intercostal spaces is the costal part
 the part relating to the diaphragm is the diaphragmatic part
 the part covering the mediastinum is the mediastinal part
 the part lining the cervical extension of the cavity is the cervical pleura
In the mediastinal part, there is a space which is made for the root or hilum of the lung.
8
The visceral pleura is continuous with the parietal pleura all the way around the
lungs attached to the outside of them, including running into both opposed surfaces of
the fissures.
 Superiorly the pleural cavity projects 3-4cm above the first costal cartilage.
 Anteriorly the pleural cavities approach one another in the upper part of the
sternum. In the lower part the right side is closer to the midline than the left
side because of the space made by the pericardium etc.
 Inferiorly the pleura reflects onto the diaphragm.
o On the left side the diaphragm separates the left lobe of the liver, the
spleen and the stomach.
o On the right side the diaphragm separates the right lobe of the liver.
During quiet breathing…
o The inferior margin of the lungs comes down to as far as about rib VI in the
midclavicular line (middle of clavicle) rib VIII in the midaxillary line (runs
down side of body) and reaches the vertebral column at TX.
o The inferior margin of the pleural cavity comes down as far as rib VIII on
the midclavicular line, rib X on the midaxillary line, and reaches the
vertebral column at TXII.
o The space between the two margins is the costodiaphragmatic recess.
6. State how the right and left lungs are normally distinguishable.
The right lung:
o Has 3 lobes, the inferior lobe, the superior lobe and the middle lobe.
o Has 2 fissures, the oblique fissure, separating the inferior lobe from the
superior and middle lobes; and the horizontal fissure separating the superior
lobe from the middle lobe.
o On its mediastinal surface in contact with the heart, inferior vena cava,
superior vena cava, azygos vein oesophagus.
o Is larger than the left lung.
The left lung:
o Has only 2 lobes, the inferior lobe and the superior lobe.
o Has 1 fissure, the oblique fissure, that separates the superior and inferior
lobes.
o On its mediastinal surface is in contact with the heart, aortic arch, thoracic
aorta, and oesophagus. It contains a notch where the heart projects into the
pleural cavity from the middle mediastinum.
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7. Identify the structures present at the Hilum of the lung.
All the structures at the Hilum are enveloped in the pleura:
o Principal bronchus
o Pulmonary artery (carry deoxygenated blood from Right ventricle)
o 2 Pulmonary veins (carry oxygenated blood to left atrium)
o Bronchial arteries and veins (carry oxygenated blood from aorta to lung tissue)
o Pulmonary plexus of nerves (mainly autonomic)
o Lymph vessels.
8. Explain the term “pulmonary circulation”.
o Right atrium  Pulmonary Artery  Lung capillaries Pulmonary Vein
Left Atrium.
o Blood is oxygenated in the lungs.
o Resistance is an eighth of the systemic circulation and blood pressure is only
25/10mmHg.
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9. Demonstrate the landmarks of the chest wall on a living chest.
o Between the medial ends of the clavicles is the jugular notch.
o If you feel down from the jugular notch where the sternum changes direction
slightly, this is the sternal angle. (this marks the top of the aortic arch, the tracheal
bifurcation and the level of the 2nd costal cartilage.
o In men the nipple lies in the 4th intercostal space (between 4th and 5th ribs)
o In women, beneath the breast is the 6th rib.
10. Demonstrate the positions of the pleural cavities, lungs and lobes of the lungs in a
living chest.
o Apex of pleura is 2-3cm above clavicle.
o Anterior of pleura runs parallel with the sternum on the right, on the left, there is a
notch between costal cartilages 4 and 7.
o Inferior end runs just above costal margin.
o Posterior border runs either side of vertebral column.
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11. Demonstrate the positions of the fissures on a living chest.
12. Describe and sketch the lungs, using correctly the following terms: apex, costal
surface, mediastinal surface, diaphragmatic surface, upper middle and lower lobes,
oblique and horizontal fissures.
Mediastinal Surface
Costal Surface
Diaphragmatic
Surface
13. Explain the structural basis for breathing, including the differences between light,
deep and forced breathing.
 Breathing is controlled by the nervous system and produced by the skeletal
muscle.
 Lungs ventilate the air sacs – the site of gas exchange.
 Movements of both the diaphragm and the ribs cause an increase of the
thoracic cavity capacity
o The muscles in the wall cause expansion of the pleural cavity.
o The elastic lungs expand with the pleural cavity.
o Air is sucked down the trachea and bronchi into the lungs.
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The Ribs move up forward and upward with a bucket-handle like action. This
increases the anteroposterior, as well as the transverse dimensions of the thoracic
cavity.
The Diaphragm is the main inspiratory muscle. When it contracts the vertical
dimension of the thoracic cavity is greatly increased. This also pushes the contents of
the abdominal cavity down and out.
Inspiration is caused by the increase in thoracic cavity capacity which results in a
reduction in the intrapleural pressure. This causes expansion of the lung and therefore
entry of the air through the respiratory passages.
 Quiet inspiration uses only the diaphragm.
 Forced inspiration uses both the diaphragm and intercostal muscles.
Expiration is caused by the elastic recoil in the tissue around the lungs and rib cage.
 Quiet expiration uses only the diaphragm.
 Forced expiration uses both the diaphragm and abdominal muscles.
14. Explain the rationale for insertion of chest drains in the pleural cavity.
 Inflammation of the pleural membrane, called pleurisy or pleuritis, may in its
early stages cause pain due to friction between the parietal and visceral layers of
the pleura.
 Fluid may build up in the pleural space, a condition known as pleural effusion.
Hence why a chest drain may be inserted into the pleural cavity.
 Any site between the fourth and seventh intercostal spaces, and between the midaxillary and anterior axillary lines may be used. This avoids the risk of
traumatising the great vessels or the heart. A common location is in the fifth
intercostal space in the mid-axillary line.
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Thorax 3 – Superior Mediastinum and Great Vessels
Anil Chopra
Superior
Ant
Middle
Inferior
Post
The mediastinum is the partition that
separates the two pleural cavities. It
extends from the superior thoracic
aperture to the diaphragm vertically and
from the sternum to the vertebral column
laterally. At the level of TV, it splits into:
 Superior mediastinum
 Inferior mediastinum which
itself is split into anterior,
middle and posterior
mediastinum
1. Describe the position and relations of the aortic arch and descending aorta.
 The ascending aorta leaves the left ventricle and is continuous with the aortic arch.
Two branches come off the ascending aorta giving rise to the left & right
coronary arteries.
 Aortic arch is behind sternal angle. It arches posteriorly and to the left over the left
bronchi of the tracheal bifurcation. (Vertebral level TIV/TV.
 It then goes down behind the left main bronchus to become the descending aorta.
2. Identify the origin of the brachiocephalic artery, the subclavian arteries and the
carotid system of arteries.
At top of the aortic arch 3 branches come out:
 Brachiocephalic trunk – this goes off to the right side of the body and almost
immediately splits into the right subclavian artery which goes to the right arm,
and the right common carotid artery which goes up to the head.
 Left common carotid artery – this goes up to supply the left side of the face and
head. It arises slightly posterior (behind) the brachiocephalic trunk and extends
along the left side of the trachea.
 Left subclavian artery – this goes on to supply the left arm. It arises slightly
posterior and just left of the left common carotid artery.
The ligamentum arteriosum is important in embryonic development. In adult life it is
a ligament that passes from the pulmonary trunk to the arch of the aorta. In foetal life
it contains the ductus arteriosum which allows blood to bypass the lungs during
development.
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3. Explain how blood leaving the heart reaches (a) head and neck, (b) lungs, (c)
thoracic and abdominal cavities.
(a) Blood reaches head and neck via the left and right common carotid arteries.
These then split into external and internal common carotid high in the neck.
(b) Blood reaches lungs via the pulmonary arteries. These arise from the pulmonary
trunk (still contained within the pericardial sac) which arises from the right ventricle.
Just inferior and to the left of the sternal angle, the pulmonary trunk splits into left &
right pulmonary arteries. Once blood has been oxygenised, it passes into the
pulmonary veins which drain directly into the left atrium.
(c) Blood reaches the abdominal and thoracic cavities from a number of different
arteries.
Anterior Wall: The left and right subclavian arteries give rise to the internal
thoracic arteries. These then travel
inferiorly either side of the sternum and
branch off into the anterior intercostal
arteries which supply the anterior half
of the thoracic cage. At around the 6th
intercostal space the internal thoracic
arteries divide into the:
- superior epigastric arteries (supplies
abdominal wall) and the
- musculophrenic arteries (pass along
the costal margin to supply the diaphragm
15
Posterior Wall: the top 2
posterior intercostal
arteries arise from the
supreme intercostal
artery which is a branch
of the costocervical trunk.
The rest arise from the
aorta.
N.B Most intercostal
arteries and veins split into
a collateral branch.
Blood is drained from the thoracic cavity
in a number of different ways.
Anterior Wall: The anterior intercostal
veins drain into the internal thoracic
veins which themselves drain into the
brachiocephalic vein.
Posterior Wall: The superior part of the
posterior wall is drained by the left and
right upper posterior intercostal veins
which drain into the azygous vein.
The rest of the posterior wall is drained
by the intercostal veins draining into the
azygous vein on the right side and the
hemiazygous and accessory hemiazygous
veins on the left side. The hemiazygous
and accessory hemiazygous drain into the
azygous which drains directly into the
inferior vena cava.
4. Identify the superior vena cava.
The superior vena cava begins just
posterior to (behind) the first costal
cartilage where the left and right
brachiocephalic veins meet. It
terminates where it enters the right
atrium just posterior to the right
third costal cartilage.
16
5. Explain how blood returns from the head and neck to the heart.
The left internal jugular vein (from the neck) and the left subclavian vein (from the
upper limb) drain into the left brachiocephalic vein which begins just posterior to
(behind) the medial (middle) end of the left clavicle. It passes right and slightly
inferiorly ending up in the superior vena cava.
The right internal jugular vein (from the neck) and the right subclavian vein (from
the upper limb) drain into the right brachiocephalic vein which begins just posterior
to (behind) the medial (middle) end of the right clavicle. It passes vertically
downward ending up in the superior vena cava.
6. Outline the principles and main applications of conventional X-ray and CT imaging.
 X-Ray:
o
Radiation in the form of X-rays are passed posterior to anterior.
o
High density e.g. bone/flowing blood stops all x-ray (blood has heavy
metal ions in it therefore absorb the x-rays) and shows up white; low density
e.g. lung fields are trans-radiant and show up black. (heavy atomic nuclei are
needed to stop X-rays)
o
Image is “backwards” i.e. always refer to things from patients point of
view (left and right)
 CT imaging:
o
Shows an image as if looking through the feet at a section
o
X-ray beam traces a section at multiple angles around the body –
visualises soft tissue in much more detail than conventional X-ray.
7. Identify thoracic skeletal features, diaphragm, lungs, lung roots, pulmonary vessels
and mediastinum in normal chest X-rays.
17
8. Using CT scan images, identify features listed in 7 and in addition lung lobes and
fissures.
& 9.Relate appearances seen in CT sections of the chest to those in the living or
dissected body; recognise the approximate vertebral level of any chest CT image.
1) Right Clavicle
2) Sternum
3) Pectoralis Major Muscle
4) Pectoralis Minor Muscle
5) Axillary Vein
6) Rib
7) Subclavian Vein
8) Trachea
9) Left Brachiocephalic Vein
10) Left Common Carotid
Artery
11) Left Subclavian Artery
12) Vertebral Body
13) Scapula
14) Level of Slice
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1) Left Brachiocephalic Vein
2) Brachiocephalic Artery
3) Superior Vena Cava
4) Left Subclavian Artery
5) Trachea
6) Esophagus
7) Level of Slice
1) Superior Vena Cava
2) Aortic Arch
3) Azygous Arch
4) Trachea
5) Esophagus
6) Level of Slice
1) Internal Thoracic Artery and
Vein
2) Ascending Aorta
3) Pulmonary Trunk
4) Right Pulmonary Artery
5) Left Pulmonary Artery
6) Right and Left Main Bronchi At
Level of Carina
7) Descending Aorta
8) Level of Slice
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1) Right Ventricle
2) Interventricular Septum
3) Left Ventricle
4) Right Hemidiaphragm
5) Area of Right Atrium
6) Area of Left Atrium
7) Descending Aorta
8) AV Groove
9) Level of Slice
10. Define pneumothorax and pleural
effusion, explain how they may arise,
recognise them in appropriate
radiographs, explain the key physical
signs associated with them, explain how
they can lead to death and explain the
anatomical basis of the emergency
procedures used to regain control in such
patients.
Pneumothorax – also known as a “collapsed lung” is where gas accumulates in the
pleural cavity.
 This air increases pleural pressure (due to lung parenchymal or bronchial injury).
It can occur for various reasons including:
 A penetrating chest wound
 Barotrauma to the lungs
 Spontaneously (most commonly in tall slim young males and in Marfan
syndrome)
 Chronic and acute lung pathologies including emphysema, asthma,
tuberculosis
 Cancer
 Catamenial pneumothorax -due to endometriosis in the chest cavity (i.e. where
the endometrium incorrectly grows in parts of the body other than the uterus)
 This causes the chest wall to spring out, and the lung to collapse. As pressure in
the pleura increases, the mediastinal structures are pushed to the opposite side and
compresses the opposite lung.
 This can lead to hypoxia, and venous return decreases due to the pressure on the
vena cava and the right atrium. This causes a decrease in cardiac output and
hypotension. If left untreated, death.
 This shows up on radiographs as transparent lung fields;
 Physical signs are:
 tachypnoea (hyperventilation)
 tachycardia (increased heart rate)
 cyanosis (bluish coloration of the skin due to the presence of deoxygenated
haemoglobin in blood vessels)
 dyspnoea (laboured breathing)
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






 chest pain
Emergency
procedure is the
needle
thoracostomy
–
puncture
usually
2nd
intercostal
space, along the
mid-clavicular line.
The trachea is
displaced to the
right side
Pneumothorax
has occurred
on the left hand
side
(characterised
by transparent
lung field)
Heart is on the
wrong
side of the body,
due
to the pressure
from the
left pleural cavity
Pleural effusion –
excess fluid that
The diaphragm is
accumulates in the
much lower due
pleural cavity, the
to pressure from
the pleural cavity
fluid-filled space
that surrounds the
lungs.
Four types of fluids can accumulate in the pleural space:
 Serous fluid (hydrothorax)
 Blood (hemothorax)
 Chyle (chylothorax)
 Pus (pyothorax or empyema)
This fluid is normally removed by lymphatics in the visceral pleura, which have
the capacity to absorb 20 times more fluid than is normally formed. When this
capacity is overwhelmed, either through excess formation or decreased lymphatic
absorption, a pleural effusion develops.
It can result from the disruption of the equilibrium across the pleural membranes
caused by some pathologic process that may originate in the lungs or be another
organ system or systemic disease.
Physical signs are
 dyspnoea (breathlessness)
 chest pain
 dull percussion
 decreased
vocal
fremitus
(vibration felt on the patient's
chest during low frequency
vocalization – “nintey nite”)
 diminished or inaudible breath
sounds
In radiographs lung fields appear
hazy
Emergency
procedure
is
thoracentesis. (draining of pleural
cavity with needle or cannula)
11. Define consolidation of the lung;
recognise it and identify the lobe(s)
involved in suitable X-rays and CT scans.
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Consolidation – the process by which an aerated lung
solidifies with debris from blood vessels usually as a result of
inflammation of the tissue.
12. Using conventional X-rays and CT images demonstrate
the landmarks of the normal heart and recognise enlargement
or displacement of the heart.
Clavicle
vertebra
e
Lung
Right border of
mediastinum
Oblique border
of the
mediastinum
Right diaphragm
Left diaphragm
Diagrammatic
border of
mediastinum
13. Identify other major structures of the mediastinum in suitable radiological images.
Brochogram (airways)
Angiogram (blood vessels)
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Thorax 4 – Organisation of Nerves in the Thorax – Mon
26th Feb 2007
Anil Chopra
1. Identify the pericardium in the cadaver and describe its organisation.
The pericardium is a fibrous sac that surrounds the heart and the roots of the great
vessels. It consists of two parts:
 Fibrous pericardium - This is a cone-shaped bag containing the serous
pericardium, heart and entrance of associated vessels and phrenic nerves from
spinal cord levels C3, C4 and C5. (The phrenic nerve also innervates this layer).
Its base rests on the diaphragm, and its apex is continuous with the adventitia of
the great vessels.
 Serous pericardium – this itself is
split up into 2 layers:
o Parietal layer – which
lines the inner surface of
the fibrous pericardium, i.e.
the outermost layer.
Around the roots of the
great vessels it is
continuous with the
visceral layer.
o Visceral layer – this is
also known as the
epicardium. It forms the
outer covering of the heart.
o
2. Demonstrate the four chambers of the heart.
3. Name the vessels that enter or leave each of the
chambers of the heart.
4. Name the four valves of the heart and indicate where
they are situated
The general orientation of the heart is that of a pyramid
on its side:
The Right atrium is on the right border of the heart on
the anterior surface. Blood enters the right atrium from:
 superior vena cava
 inferior vena cava
 coronary sinus
Its walls are covered in pectinate muscles which fan out like the teeth of a comb. Just
posterior to it is the interatrial septum (the left atrium lies posterior to the right). There
is a depression in the interatrial septum known as the fossa ovalis and around it the
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limbus fossa ovalis. This is very important during foetal life
as it was the foramen ovale, a hole between the left and right
atria so blood can bypass the non-functioning lungs before birth.
The right ventricle is on the diaphragmatic border of the heart
and also faces anteriorly, blood moving from right atrium to right
ventricle therefore moves in a horizontal direction. Its outflow is
the pulmonary trunk. There are 3 papillary muscles in the right
ventricle:
 Anterior papillary muscle is the largest.
 Posterior papillary muscle arises from posterior wall
 Septal papillary muscle which arises from the septum.
Its entry point is the tricuspid valve. This is the right
atrioventricular valve
consisting of 3 cusps;
anterior, posterior and
septal. The attachment of the
cusps to the papillary muscles
by the chordae tendinae stops
the cusps from moving back
into the right atrium.
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Its exit point is the pulmonary valve through which it enters the pulmonary trunk.
The pulmonary valve consists of three semilunar cusps (left, anterior and right) each
with a thickened portion at the end known as the nodule. They prevent blood from
flowing back into the right ventricle.
The left atrium receives oxygenated blood from the 4 pulmonary veins. It forms most
of the posterior (back) surface and is not seen at all anteriorly. The valve of the
foramen ovale is also seen in the interatrial septum. Its exit point is the mitral valve.
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The Left ventricle lies slightly anterior and superior to the left atrium. It is conical in
shape and is the longest and most muscular of the
chambers of the heart. (I.e. it has the thickest layer
of myocardium). It, like the right ventricle has
traberculae carneae and papillary muscles with
attached chordae tendinae. There are only 2
papillary muscles; posterior and anterior.
This is mainly due to the fact that the mitral valve
is only bicuspid. (It has only 2 cusps, posterior
and anterior) It works in the same way as the
tricuspid valve.
Its exit point is the aortic valve through which it
flows into the aorta. This also has 3 semilunar
cusps (right, posterior and left), but in 2 of them,
there are openings for the coronary arteries. It has
a similar function to the pulmonary valve in that it
stops the backflow of blood into the left ventricle.
5. Describe the commonest patterns of distribution
of the coronary arteries and explain the function and importance of these vessels.
There are 2 main coronary arteries each arising from one of the aortic sinuses (left
and right) each giving rise to its corresponding coronary artery:

The right coronary artery emerges from the right aortic sinus and descends
down the right atrium round to the apex of the heart branching as it does so. It
supplies the right atrium, right ventricle, sino-atrial node and atrioventricular node.

The left coronary artery emerges from the left aortic sinus and passes down
posterior (behind) to the pulmonary trunk. As it emerges it splits into two:
o
Anterior descending branch which descends anteriorly round toward
the apex of the heart.
26
o
Circumflex branch which travels round the left side of the heart and
descends on the posterior left side of the heart.
The left coronary artery supplies the left atrium, left ventricle and most of the
interventricular septum.
There are 2 variations in the distribution patterns of the coronary arteries:
Right coronary dominance: is the most common and it is where the right
coronary artery supplies most of the posterior wall and the left coronary arteries
are relatively small.
Left coronary dominance: is less common and is where the circumflex
branch supplies the majority of the posterior wall and left ventricle.
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There are 4 main cardiac veins that drain into the coronary sinus which itself drains
into the right atrium.

Great cardiac vein: begins at the apex of the heart and runs up the anterior
(front) wall along the atrioventricular sulcus, when it reaches the top it goes round
the end following the path of the circumflex artery and enlarges at the posterior
end to form coronary sinus.

Middle cardiac vein: also begins at the apex but runs up the posterior side in
the atrioventricular sulcus.

Small cardiac vein: begins in the lower anterior (front) sector of the anterior
sulcus. It travels round the back of the right atrium where it finishes in the
coronary sinus.

Posterior cardiac vein: runs up the posterior surface of the left atrium.
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6. Explain the effects of coronary insufficiency and obstruction, including the
pathways and localisation of pain associated with these conditions.
Angina pectoris is the condition where chest pain is caused by ischemia (restriction
or blockage of blood vessels causing tissue damage) of the myocardium due to
coronary artery narrowing, usually by atherosclerosis. This can result in a myocardial
infarction.
7. Demonstrate the relationship of the pericardium to the heart and great vessels and
to surrounding structures.
8. Explain the signs associated with tamponade and demonstrate the anatomical basis
for relieving this condition.
Cardiac tamponade is a condition caused by fluid in the pericardial sac “crushing”
the heart. The fluid causes an increase in pressure and so the ventricles aren’t able to
contract properly. The increased pericardial pressure, causes a decrease in cardiac
output and subsequent hypotension. Symptoms include dyspnoea (shortness of
breathe) anxiety, fatigue and cyanosis (a blue/dark purple discoloration seen in the
nail beds and mucous membranes, that result from an increased concentration of
deoxygenated haemoglobin). Treatment is pericardiocentesis- to remove fluid and
reduce pressure.
9. Use chest wall landmarks to define the cardiac outline.
 The right vertical border of the heart runs from just to the right of the
sternum on the 3rd costal cartilage down to the 6th.
 The horizontal border is formed from here (6th costal cartilage just right of
sternum) to left 5th intercostal space on the mid-clavicular line.
29

The oblique border is formed by the left ventricle formed from here (left 5th
intercostal space on mid-clavicular line) to the medial end of the 3rd intercostal
space, just left of the sternum.
10. Locate the apex beat.
The apex beat is where the horizontal and oblique borders of the heart meet. It is on
the left 5th intercostal space on the mid-clavicular line. In men it is just inferior and
medial to the nipple, in women it is on the lower border of the breast.
11. Locate suitable sites for auscultation of each heart valve and demonstrate correct
stethoscope technique.
Tricuspid valve - lower end of sternum
Mitral valve - left 5th intercostal space in mid-clavicular line (apex beat)
Pulmonary valve - left 3rd intercostal space near sternum
Aortic valve - right 2nd intercostal space near sternum.
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12. Outline the electrical and
mechanical cycles of the heart
and relate these to heart sounds
and to features of the ECG
trace.
The conduction system in the
heart is divided into four basic
main components:
 Sino-atrial node (SAN)
 Atrio-ventricular node
(AVN)
 Bundle Branches
 Subendocardial plexus
of conduction cells
1) The impulse begins
at the sino-atrial node
(the cardiac
pacemaker) in the
right atrium.
Excitation spreads
across atria causing
them to contract.
2) Excitation is
then delayed for
around 120ms
when it reaches
the Atrioventricular node.
3) The AVN then spreads the excitation down
the Purkinje fibres of the bundle branches. This
in turn causes the ventricles to contract from
the base upward.
4) This is followed by both
the atria and the ventricles
relaxing in diastole.
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13. Explain the pathways by which the heart, lungs and
the chest wall receive their motor and sensory nerve
supplies.
Vagus
The vagus nerve is the 10th cranial nerve (Cranial nerve
X).
- Arises from the medulla and
Splits into the left (runs anterior to
aortic arch but posterior to left ling root) and right
(runs posterior to right lung root).
Has parasympathetic pathways to the
heart, glands, and lungs.
Also has sensory content from
enteroceptors in gut and lungs.
Both left and right vagus nerves form a
plexus round the oesophagus.
Splits into the recurrent laryngeal nerve that runs back up to supply
skeletal muscles in the larynx
Sympathetic Trunk
All sympathetic nerves run from spinal levels T1 to L2.
Supply all parts of the body.
Two chains of sympathetic ganglia run either side of the spinal cord.
Give stimulatory effect to the heart and lungs.
Recurrent Laryngeal
A branch of the vagus nerve that supplies the skeletal muscles in the larynx.
Thoracic Somatic
These usually arise from the main
branches of thoracic spinal nerves 1- 11.
Each segment supplies a
dermatome and group of muscles.
The spinal root emerging
splits into a dorsal and ventral
root. The dorsal root contains
sensory fibres and the ventral root
contains motor fibres.
Each then splits into 2
rami one of which supplies posterior
muscles and one of which supplies its
particular dermatome
Enteric Nervous System
Intrinsic nerves of the
oesophagus.
This plexus of ganglia and axons is
located in the oesophageal wall where it co-ordinates the activity of the oesophagus.
The parasympathetic supply stimulates it, sympathetic supply
inhibits it.
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Thorax 5 – Lymphatic System, Breasts and Breast Cancer
Anil Chopra
1. Summarise the main functions and anatomical organisation of the lymphatic
system.

Lymphatic drain tissue fluid from thorax viscera that has not returned to the
venous end of the blood in capillaries.

Uncompensated fluid would result in the build up of fluid in tissues (oedema)
and loss of blood
volume.

Various forces act
across capillary walls
affecting the fluid
content of the blood.

Lymph contains
fluid from tissues,
particulate matter, fat,
few cells and few
proteins.

The lymph then
flows into the blind
ended lymph vessels.

They are thinwalled and lined by
endothelial cells.

At various points they pass through lymph nodes.

At these lymph nodes they pass fixed reticular macrophages that remove
bacteria. (it cannot however remove cancerous cells)

The lymph system is split into deep and superficial lymphatics.

Lymph from lower limbs drains into cisterna chyli and then into the thoracic
duct which itself drains into the brachiocephalic vein.

Lymph from the lower limbs drains into the cervical lymph nodes in the neck.

Lymph from the upper limbs drains into the
axillary lymph nodes.
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2. Describe the lymphatic drainage of the chest viscera (particularly the lungs and
bronchi) and outline the implications of this pattern for the spread of lung cancer.

Lymphatic drainage from the lungs, bronchi and mediastinum drain into the
left and right bronchomediastinal trunks.

The parasternal nodes run up anteriorly either side of the sternum draining
the front of the thorax, intercostal nodes run up posteriorly either side of the
spinal cord and the tracheobronchial nodes run around the trachea and bronchi.

These all drain into the left brachiocephalic vein.

Cancer cells may travel in the blood or lymph and establish new tumours
where they lodge .When metastasis occurs via lymphatic vessels, secondary
tumour sites can be predicted according to the direction of lymph flow, from the
primary tumour site. Cancerous lymph nodes feel enlarged, firm, non-tender, and
fixed to underlying structures. By contrast, most lymph nodes that are enlarged
due to an infection, are not firm, are moveable and are very tender.
3. Define the roles of breast examination and imaging within the epidemiological
context of breast cancer incidence.
 Breast cancer affects one woman in eight.
 It usually develops from the ducts of the epithelium.
 Not all lumps are cancers.
 They are somewhat dependent on oestrogen.
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

Tumours may put tension on suspensory ligaments. This may cause skin
puckering (indentations) or inverted nipples.
They may attach to muscles and are very prone to spreading in the lymph or
venous drainage of the breast.
4. Describe the lymphatic and venous drainage of the breast and relate these to the
pathways of metastasis of breast cancer.

Breasts develop in both genders, in males however they are rudimentary and
consist of small ducts, composed of cords of cells which do not extend beyond the
areola.

They overlie the anterior muscles of the chest wall and lie between ribs 2 and
6.

They have an axillary tail/process leading to the axilla. This must always be
checked on examination for lumps.

They are raised structures in the thoracic wall that contain mammary glands.

Each breast contains around 12-16 lobes which contain structures known as
alveoli. Each has a small duct which opens out into the nipple surrounded by
pigmented skin – the areola.

Underneath the areola are the lactiferous sinuses which are milk-filled spaces
that the baby sucks on.

Breasts contain internal suspensory ligaments which are used in supporting
the breast. Tensing the pectoral muscles (push down on hips) causes suspensory
ligaments to lift breast.

The bulk of it is adipose tissue but when pregnant, this turns to glandular
tissue.

Lymph drainage of breast parallels arterial supply. Arterial supply to lymph
nodes mainly from the thoracic arteries and axillary artery.

Cancers can travel in the internal thoracic (parasternal) and axillary lymph
nodes.
35

Cancers can also block lymph drainage and therefore increase pressure cause
lymph to take alternative routes.
5. List the imaging techniques used in the diagnosis of breast cancer and outline their
value and limitations.

Mammogram – this is a breast x-ray.

CT scans – computerised tomography.

Bone scan – this uses radioactive isotopes.

Self examination – is increasingly popular making sure women check their
breasts and the axillary process.

Ultrasound – is also used.
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Thorax 6 – The Posterior Mediastinum
Anil Chopra
1. Define the posterior mediastinum
Everything in the thorax that is below the plain of the sternal angle and posterior to
(behind) the pericardium is the posterior mediastinum.
2. Describe the relative positions of the descending aorta, the oesophagus, the vagus
nerves and the thoracic duct as they descend through the posterior mediastinum.
Descending aorta: this begins at vertebral level T IV (4) and it is continuous wit the
arch of the aorta. It continues anteriorly down to T XII (12) there it passes through the
aortic hiatus of the diaphragm.
Oesophagus: this is a muscular tube running down from the pharynx in the neck to
the stomach in the abdomen. Throughout the top part of the thorax it is situated to the
right of the aorta until around vertebral level T VII (7) where it bends slightly anterior
and left. It then proceeds inferiorly (down) anterior to (in front of) the aorta.
Vagus nerves: cranial nerve X (10) passes posterior to the lung roots and forms the
oesophageal plexus. They run down the length of the oesophagus to the stomach
where they eventually become the posterior and anterior vagal trunks.
Thoracic Duct: is a lymph duct that returns lymph from the lower limbs, abdomen
and pelvis to the blood. It begins below the diaphragm at the cisterna chyli, comes up
between the oesophagus and the aorta and then crosses behind the oesophagus at
around vertebral level T VI (6).
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Phrenic Nerves: pass from cervical vertebra C III, IV and
V to the diaphragm anterior to the lung roots.
3. Describe the nerve supply, arterial supply, venous
drainage and lymphatic drainage of the oesophagus
Nerve Supply: the oesophagus is supplied by the enteric
nervous system. There are oesophageal branches arising
from the vagus nerve and the sympathetic chain. The
smooth muscle fibres surrounding the oesophagus are
stimulated by the parasympathetic branches of the
autonomic nervous system. The left and right vagus nerves
form the oesophageal plexus. This network of nerves runs
down the oesophagus until it eventually becomes the
anterior and posterior vagal trunks which continue on to
the stomach.
Arterial Supply: the oesophagus is mainly supplied by
branches of the descending (or thoracic) aorta.
Venous Drainage: the oesophagus is drained entirely by the azygous system of veins.
On the left side of the body, the inferior and superior (accessory) hemiazygous veins
drain into the large azygous vein running down the right side of the body. This drains
into the superior vena cava.
Lymph Drainage: lymph from cells in the oesophagus
is drained by the thoracic duct.
4 .Explain how and at which vertebral levels the inferior
vena cava, the oesophagus and the descending aorta pass
through the diaphragm.
Vessel
Crosses
Diaphragm at
Vertebral Level
Inferior Vena
Cava:
vena caval
foramen
T VIII (T8)
Oesophagus:
oesophageal
hiatus
Aortic hiatus
T X (T10)
Descending
Aorta:
T XII (T12)
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