thoracic anatomy

Question 1

What are the anatomical relations of the medial third of the clavicle?

Answer 1

● Medial - sternoclavicular joint, manubrial notch
● Posterior - first rib, brachiocephalic vein (medial to scalenus anterior), internal
jugular vein, subclavian vein (over the anterior scalene), subclavius, phrenic
nerve. Apical pleura, thoracic duct on the left
● Anterior/superior/inferior: subcutaneous tissue and skin

Question 2

Which muscles attach to the clavicle?

Answer 2

● Deltoid - lateral third, anterior attachment
● Trapezius - lateral third, posterior attachment
● Pectoralis major - medial third, anterior/inferior
● Sternocleidomastoid - clavicular head, medial third, anterior/superior
● Subclavius - inferior, middle third

Question 3

Describe the course of the subclavian vein

Answer 3

● Becomes subclavian vein from the axillary vein, medial to the outer border of the
first rib
● Courses medially, posterior to the clavicle, superior to the flat section of the first
rib.
● Lies immediately anterior to scalenus anterior which separates it from the
subclavian artery. Becomes the brachiocephalic vein at the medial border of
scalenus anterior when it joins the IJV.

Question 4

First rib
Can you please identify the main features of this bone

Answer 4

● The first rib is the broadest, flattest, shortest rib
● Single facet on its head for articulation with T1 only
● It lies horizontally, with a wide body.
● Use the superior surface to identify the side - look for the grooves and scalene
tubercle

Features:
● Head, neck tubercle and shaft
● Name the features of the superior surface from the neck to the tip (naming in this
way helps the examiner follow you on the marking sheet)
● Groove for subclavian artery and lower trunk of brachial plexus (sits behind the
artery)
● Scalene tubercle and ridge, for attachment to anterior scalene
● Groove for subclavian vein
● Flat outer surface for attachment of the first part of serratus anterior
● Attachments to costoclavicular ligament (inner) and subclavius (outer)
● The tip articulates with the costal cartilage

Question 5

Describe the neurovascular relations of the first rib

Answer 5

Nerves
● C8 above and T1 nerve root below the neck
● These unite to form the lower trunk of the brachial plexus, which sits on top of the
rib behind the subclavian artery
● Sympathetic trunk lies in contact with the anterior border of the neck

Vessels
● Subclavian artery runs in its groove, behind the scalene tubercle, touching the
outer border of the rib.
● Subclavian vein runs anterior to scalene tubercle, in its own groove
First intercostal neurovascular bundle runs beneath the undersurface, covered by
parietal pleura

Question 6

What muscles attach to the first rib

Answer 6

● Anterior scalene
● Middle scalene (medial to the groove for the artery)
● Part of erector spinae (attaches between the tubercle and angle)
● Intercostal muscles
● Subclavius (at the costochondral joint)
● Serratus anterior (the lateral surface)

Question 7

other ribs
What are the features of this rib?

Answer 7

What are the features of this rib?
● Head: wedge shaped, has 2 facets separated by the crest of the head, one for
articulatio with the numerically corresponding vertebra and one for the vertebra
superior to it
● Neck: connects the head of the rib with the body at the level of the tubercle
● Tubercle: located at the junction of the neck and the body, the smooth articular
part articulates with the corresponding transverse process of the vertebra. The
rough part provides attachment for the costotransverse ligament
● Body: Thin, flat and curved, The costal groove runs along the inferior border

Question 8

Describe the intercostal muscles

Answer 8

● External intercostals - from the tubercles of the ribs posteriorly to the
costochondral junction. They run infero-anteriorly (like you would put your hands
in your pockets of the most external layer of clothing). Most active during
inspiration at rest or forced inspiration.
● Internal intercostals - lie deep to the external intercostals. Run from the sternum
to the angle of the ribs posteriorly. They run infero-posteriorly and are most active
during expiration
● Innermost intercostals - the deepest muscle, lie laterally. The nerves and vessels
run between the innermost and the internal intercostals
● Subcostal muscles - run in the same direction as the internals but cross 2 or 3 rib
spaces
● Transverse thoracic - run from the sternum and xiphisternum transversely to the
lower ribs
● Levator costarum - from transverse processes to the ribs

Question 9

Describe the pattern of distribution of neurovascular structures in the thoracic
wall

Answer 9

● Enter the medial most part of the posterior intercostal space
● Run between the parietal pleura and internal intercostal membrane in the middle
of the space
● Near the angle of the ribs, the bundle passes between the internal and innermost
IC muscles
● Lies in the costal groove, from top to bottom = vein, artery, nerve
● Collateral branches run along the superior border of the rib
● Vessels also have some anterior supply and drainage

Question 10

Describe the arterial supply of the intercostal spaces

Answer 10

● Posterior intercostal arteries arise from branches off the subclavian and thoracic
aorta
● Anterior intercostal arteries are branches of the internal thoracic arteries.

Question 11

What are the surface landmarks for the insertion of a chest tube

Answer 11

● 4th or 5th intercostal space anterior to the mid axillary line
● Within the triangle of safety

Question 12

What are the layers traversed when inserting a lateral chest wall

Answer 12

● Skin and subcutaneous tissue
● Layers of muscles - external, internal and innermost intercostals
● Parietal pleura

Question 13

What structures may be at risk from a lateral ICC insertion?

Answer 13

● Neurovascular bundle
● Long thoracic nerve
● Diaphragm
● Pericardium
● Heart
● Spleen on the left, Liver on the right

Question 14

What are the different parts of the diaphragm?

Answer 14

● Costal muscle portion
● Crural (lumbar) portion
● Central tendinous portion

Question 15

What are the attachments of the diaphragm?

Answer 15

● Costal portion attaches to the lower 6 ribs and costal cartilages
● Crural portion attaches to L1-L3 bodies and their discs, as well as the anterior
longitudinal ligament. The right sided fibres slope upwards and to the left,
surrounding the oesophagus
● Central tendinous part attaches to the costal portion and the inferior fibrous
pericardium and falciform ligament
● At the front, fibres pass backwards from the xiphisternum

Question 16

What are the openings of the diaphragm?

Answer 16

● Aortic opening at T12 in the midline. (AORTIC HIATUS = 12 letters) This also
transmits the azygos vein and thoracic duct. (12 = 1 big + 2 small)
● Oesophageal opening at T10 (OESOPHAGUS = 10 letters) Also transmits some
vagal trunks, left gastric artery and vein (makes sense because it’s all GIT) and
some lymphatics.
● Vena Caval foramen is at T8 (VENA CAVA = 8 letters) Goes with the right
phrenic. Makes sense because the IVC sits slightly to the right
● Other things pass through including the splanchnic nerves, sympathetic trunk, left
phrenic nerve, superior epigastric vessels

Question 17

Describe the nerve supply to the diaphragm

Answer 17

● C3/4/5 keep the diaphragm alive. - Fibres from C3/4/5 via phrenic nerves,
● Phrenic nerves are the only motor nerves to the costal and crural portion. They
also provide sensory innervation to the central tendon as well as adjacent pleura,
pericardium and peritoneum.
● Left and right sides are innervated separately, and there is separate innervation
of the costal and crural portions

Question 18

How does contraction of the diaphragm result in ventilation of the lungs?

Answer 18

● Contraction of the diaphragm causes it to move inferiorly
● Descent on inspiration causes an increase in thoracic volume
● This helps generate negative pressure that drives inspiration
● Diaphragmatic contractions are responsible for 75% of inspiratory muscle action

Question 19

Aside from the diaphragm, which other muscles are responsible for ventilation?

Answer 19

● Costal muscles - move the ribs during forced respiration. Function primarily to
support intercostal spaces, resisting negative and positive intrathoracic
pressures. Externals help with inspiration, internals help with forced expiration
● Accessory muscles - scalene, SCM, pec major and minor, serratus anterior
● Abdominal wall muscles can assist in forced expiration

Question 20

Describe the lobes of the lungs and their fissures

Answer 20

● Left lung has 2 lobes, right lung has 3 lobes
● Both lungs have oblique fissures that separate upper and lower lobes. Goes from
T2 posteriorly to the 6th costal cartilage anteriorly
● The right lung is also separated by the transverse fissure at the level of the 4th
costal cartilage
● Left lung has a cardiac notch in lower lobe

Question 21

What part of the lung forms the right heart border?

Answer 21

Right Middle Lobe

Question 22

Describe the surface anatomy of the parietal pleural reflections Mentally draw it out on your own self

Answer 22

● The right and left pleural reflections begin at the apices of the lungs in the
supraclavicular fossa, approx 3cm above the clavicle
● They descend inferomedially behind the sternum in the anterior median line
● Lie parallel to each other at the level of the 2nd to 4th costal cartilages
● Below this, they become asymmetrical
● On the left side, at the level of the 4th costal cartilage, the pleura deviates to the
left and reaches the 6th costal cartilage just lateral to the left sternal edge.
● The right side passes inferiorly until it reaches the 6th costal cartilage in the
anterior median line.
● From then on, both sides pass laterally and posteriorly through the following
points
● At the 8th costal cartilage lies in the mid clavicular line
● At the level of the 10th costal cartilage lies in the mid axillary line
● At the level of the 12th costal cartilage lies in the paravertebral line
● The diaphragmatic reflection is in close contact with the diaphragm.

Question 23

What is the clinical significance of the attachment of the pleura?

Answer 23

● Pleura in the supraclavicular space may be injured
● Deviation of pleura to the left provides a window for pericardiocentesis without
traversing the pleural space
● Attachment of pleura at a lower level than the lungs allows for a potential space
and favours fluid collection in this space
● Penetrating injuries to the upper lumbar region may cause pleural injury

Question 24

Outline the structures that make up the right and left cardiomediastinal borders on
an xray

Answer 24

Right
● Right brachiocephalic vein
● Superior vena cava
● Right pulmonary trunk
● Right atrium
● Inferior vena cava

Left
● Left subclavian artery/left brachiocephalic vein
● Aortic arch
● Left pulmonary trunk
● Left atrial appendage
● Left ventricle

Question 25

Which part of the heart lies immediately behind the sternum?

Answer 25

The right ventricle

Question 26

In the supine position, which mediastinal structures are located at the same level
as the sternal angle?

Answer 26

Lung Structures
● Carina
● Hila of the lungs
● Transverse fissure of the right lung

Big Vessels
● Pulmonary trunk
● SVC as it enters the right atrium
● Ascending aorta as it becomes the arch
● Azygous vein

Nerves
● Phrenic nerve
● Vagus nerve
● Recurrent laryngeal nerve (left)

Thoracic duct
Pleura and Pericardial reflections

Question 27

The aorta
Describe the course of the thoracic aorta

Answer 27

Ascending aorta begins at the aortic orifice
Arch of the aorta begins behind the 2nd sternocostal joint
Passes supero-posteriorly and to the left, anterior to the right pulmonary artery and the
carina
The apex of the arch lies to the let of the trachea and oesophagus and descends
posterior to the left lung root, ending bac at the level of the T4 (2nd costal joint)

Descending aorta: originates at the left side at the lefel of the T4 vertebrae, Courses
inferiorly to the level of T12. Approaches the midline as it descends alongside the
oesophagus
At the inferior border of T12 it exits through the aortic hiatus and becomes the abdominal
aorta

Question 28

What are the branches of the aortic arch?

Answer 28

● Brachiocephalic trunk, which divides into the right common carotid and the right
subclavian
● Left common carotid
● Left subclavian

Question 30

Can you name other structures which lie in the superior mediastinum?

Answer 30

● Veins
○ Left and right internal jugular and subclavian veins which unite to form the
left and right brachiocephalic veins
○ Left brachiocephalic passes anteriorly to the aortic arch and unites with
the right one to form the superior vena cava

● Thymus
● Vagus nerves
● Phrenic nerves
● Trachea
● Oesophagus

Question 30

What structures can be damaged during insertion of an internal jugular central
line?

Answer 30

● Common carotid artery
● Apex of the lung
● Vagus nerve
● Oesophagus
● Thoracic duct on the left

Question 30

Describe the course of the right subclavian artery

Answer 30

● Arises from the brachiocephalic trunk
● Runs posterior to right sternoclavicular joint as it ascends through the thoracic
inlet
● Arches superolaterally and passes posterior to anterio scalene muscle
● Descends posterior to the middle of clavicle and crosses over the first rib to
become the axillary artery

Question 30

What are the branches of the subclavian artery?

Answer 30

1st part
● Vertebral artery
● Internal thoracic artery
● Thyrocervical trunk

2nd part
● Costocervical trunk

3rd part
● Dorsal scapular artery

Question 31

Please identify the great vessels and branches which enter and exit the heart on
this model

Answer 31

SVC - from the right and left brachiocephalic veins
IVC
Ascending aorta giving the brachiocephalic trunk, left common carotid and the left
subclavian artery
Pulmonary trunk and pulmonary arteries
Pulmonary veins

Question 32

Please identify the valves and chambers of the heart

Answer 32

RA, RV, LA, LV
Tricuspid, aortic, pulmonary and mitral valves

Question 33

Identify the components of the tricuspid valve

Answer 33

● 3 cusps - anterior, posterior and septal
● Chordae tendineae
● Papillary muscles

Question 34

What are the main features of the right atrium?

Answer 34

● SVC
● IVC
● Auricle
● Coronary sinus
● Fossa ovalis

Question 35

Describe the structures of the conducting system of the heart

Answer 35

● SA node: anterior-lateral near the junction of the SVC and RA
● AV node: posterior-inferior region of the interatrial septum, near the opening of
the coronary sinus
● AV bundle of His: travels through the fibrous skeleton of the heart along the
membranous part of the interventricular septum
● Divides into right and left bundles which pass on each side of the muscular
interventricular septum

Question 36

Describe the arterial supply to the cardiac conduction system

Answer 36

● SA node is supplied by the right coronary artery 60% of the time and circumflex
40% 4of the time
● AV node is supplied by the AV nodal artery from the right coronary 80% of the
time
● Right and left bundles and purkinje fibres from the LAD

Question 37

Coronary Circulation
Demonstrate on this model the arterial supply of the heart

Answer 37

Left and right main coronary arteries arise from the aortic sinuses

Right coronary artery.
● Supplies the SA node 60% of the time
● Right marginal branch and other marginal arteries
● AV nodal branch to AV node 80% of the time
● Posterior interventricular artery in the majority of people

Left coronary artery
● Gives off the left circumflex which supplies the SA node in 40%, the Cx gives off
the left marginal artery
● Left anterior descending or anterior interventricular supplies anterior ⅔ of
septum, AV bundles, and gives off lateral diagonal branches
● Left side supplies the posterior interventricular 15% of the time

Question 38

Occlusion of which vessel would cause an anterolateral STEMI?

Answer 38

Proximal LAD

Question 39

Which areas of the heart are supplied by the left coronary artery and its branches?

Answer 39

● Most of LA
● Most of LV
● Part of the anterior wall of the RV
● Interventricular septum
● Ventricular apex
● Bundle of His
● SA node in 40% of people

Question 40

Which areas are supplied by the right coronary artery

Answer 40

● RA
● Most of RV
● Diaphragmatic portion of the LV
● Posterior ⅓ of the septum
● SA node (60%)
● AV node (80%)

Question 41

Describe the venous drainage of the heart

Answer 41

Mostly via the coronary sinus
Three main tributaries are:
● Great cardiac vein (from the left side of the heart)
● Middle cardiac vein (accompany the post interventricular)
● Small cardiac veins accompany the right marginal
● Anterior cardiac veins from the RV surface drain into RA
● Smallest cardiac veins drain directly into the chambers.