By CRUX OF MRCS in Day 1 — 01 Nov 2025

Planes, levels and surface markings

Key anatomical landmarks and structures by vertebral level

Key anatomical landmarks and structures.pdf

The common carotid artery biFOURcates at C4 into the internal and external carotid arteries. The abdominal aorta biFOURcates into the left and right common iliac arteries, at L4. The common iliac veins join to form the inferior vena cava at which vertebral level at L5.

Cervical vertebrae

C1 (atlas) lacks a spinous process; it only has anterior and posterior arches.
C2 (axis) has a long spinous process and bears the odontoid process (dens).
C3 features a short, bifid spinous process.
C6, marked by its prominent carotid tubercle, is the level where the vertebral artery enters the transverse foramen, ascending through the cervical transverse foramina toward the skull
- At C6, the common carotid artery pulsation can be palpated, and the trachea terminates.
The C7 vertebra, known as the vertebra prominens, has a long spinous process that is the most palpable vertebral landmark at the back of the neck.

The angle of Louis

The angle of Louis (sternal angle) at level T4/T5 is a key anatomical landmark. It corresponds to the following:

Bifurcation of trachea (carina)
Arch of aorta begins and ends
Ligamentum arteriosum
Azygous vein drains into SVC
Thoracic duct crosses to left side
Left recurrent laryngeal nerve hooks around arch (near ligamentum arteriosum)
Marks the division between superior and inferior mediastinum

The pulmonary trunk bifurcates below the trachea bifurcation at around the T5 vertebral level.

The azygos vein

The azygos vein begins at the level of L1/L2 from the right ascending lumbar and subcostal veins, entering the thorax through the aortic hiatus (T12). It ascends along the right side of the vertebral column, collecting blood from posterior intercostal and mediastinal veins. At about T4, the azygos vein arches over the right main bronchus and makes contact with the T5 vertebral body as it does so, and drains into the superior vena cava, providing an important collateral pathway between the SVC and IVC.

The three major openings of the diaphragm

Caval hiatus at T8
Oesophageal hiatus at T10
Aortic hiatus at T12

Structures passing through the caval hiatus at T8:
- IVC
- Branches of right phrenic nerve

Structures passing through the oesophageal hiatus at T10:
- Oesophagus
- Anterior (mainly left vagus) and posterior (mainly right vagus) vagal trunk
- Oesophageal branches of left gastric vessels
- Lymphatics from lower oesophagus

Structures passing through the aortic hiatus at T12:
- Aorta
- Thoracic duct
- Azygos vein
- Sometimes hemiazygos

Structures at the transpyloric plane at L1

Pylorus of stomach (hence the name)
Duodenojejunal flexure - should be located to the left at the transpyloric plane. Malposition of the DJ flexure to the right is a sign of malrotation.
Fundus of gallbladder
Hila of kidneys
Origin of superior mesenteric artery SMA
Portal vein formation behind neck of pancreas
Pancreatic neck & body
Cisterna chyli
Tips of 9th costal cartilages
Conus medullaris (end of spinal cord in adults)

📚 Exam-style questions

What are the surface markings for the internal jugular vein?
- Lobule of the ear to the sternoclavicular joint

What are the surface markings for the external jugular vein?
- Angle of mandible to middle third of clavicle

What are the surface markings for femoral artery access?
- Midpoint between the ASIS and pubic symphysis

What are the surface markings of McBurney’s point?
- ⅓ from ASIS to umbilicus

At what level does the common carotid artery bifurcate?
- [[C4:: This is also where the carotid sinus and body are located.]]

The angle of Louis (sternal angle) is a key anatomical landmark. Which structure does it correspond to?
- ((Junction of ascending and arch of aorta:: Lower, behind the sternum at second right costal cartilage))
- [[Junction of arch and descending aorta:: Arch of aorta begins and ends at the angle of Louis]]
- [[Tracheal bifurcation:: Bifurcation of trachea (carina) occurs at the angle of Louis T4/T5 level]]
- ((Apex of heart:: At 5th intercostal space, midclavicular line))
- ((Diaphragm:: Corresponds to T8 to T12 levels depending on hiatus, much lower))

A person sustains a stab wound just to the right of the angle of Louis, T4/T5. Which structure is not likely to be damaged?
- Right vagus
- Right pleura
- Thoracic duct
- [[Brachiocephalic vein::The right brachiocephalic vein is higher up, formed by the fusion of the internal jugular and subclavian vein and lying behind the sternoclavicular joint to then course obliquely down to join the left brachiocephalic to form the superior vena cava]]

A structure located at the level of the T5 vertebra is:
- ((Left atrium::Lies posterior to the esophagus around T6 to T8))
- ((Tracheal bifurcation::Occurs at the inferior margin of the T4 vertebra, angle of Louis))
- [[Bifurcation of pulmonary trunk::The pulmonary trunk bifurcates at around the T5 vertebral level, below the trachea bifurcation at sternal angle T4/T5]]
- ((Bifurcation of right bronchus::Happens at the same level as tracheal bifurcation))

A child inhales a peanut. Where is it most likely to lodge?
- Left lower lobe bronchus
- [[Right lower lobe bronchus::The right main bronchus is wider, shorter, and more vertical than the left, so foreign bodies preferentially enter it, especially into the lower lobe bronchus]]

Which structure is in direct contact with the T5 vertebral body?
- [[Azygos vein::The azygos vein makes contact with the T5 vertebral body as it arches over the right main bronchus to join the superior vena cava]]
- Tracheal bifurcation
- Ascending aorta
- Descending aorta

The vertebral artery arises from the subclavian artery and ascends through the transverse foramina of the cervical vertebrae. It enters the foramen transversarium (transverse foramen) at which level?
- C6
- C7
- C8
- C9

At which vertebral level can the common carotid artery pulsation be felt, and the trachea ends?
- C5
- C6
- C7
- C8

Which cervical vertebra is most prominently felt on the back of the neck?
- C5
- C6
- [[C7::Vertebra prominens, most palpable posteriorly]]
- C8

Which cervical vertebra is characterised by a long bifid spinous process?
- ((C1 (Atlas):: Non spinous process))
- [[C2 (Axis)::Long bifid spinous process and the odontoid peg (dens)]]
- ((C3::Short bifid spine))
- ((C6::Carotid tubercle))

C1 (Atlas) ➡️ No spinous process, just anterior and posterior arches
C2 (Axis) ➡️ Long bifid spinous process and the odontoid peg (dens)
C3 ➡️ Short bifid spine
C6 ➡️ Carotid tubercle
C7 ➡️ Has a long spine, but it is not bifid (vertebra prominens)

What is the level of the oesophageal opening in the diaphragm?
- T8
- T9
- [[T10::Oesophagus has 10 letters! Vena cava (T8) has 8 letters and aortic hiatus (T12) has 12 letters!]]
- T11

Which structure passes through the oesophageal hiatus of the diaphragm?
- [[Left vagus nerve::Oesophagus, vagus CN X, esophageal branches pass through the oesophageal hiatus at T10]]
- Azygous vein
- Thoracic duct
- Phrenic nerve

Which of the following passes through the diaphragmatic opening at T12?
- [[Azygos vein and thoracic duct::The aorta, thoracic duct, azygos vein and sometimes hemiazygos pass through the aortic hiatus at T12]]
- Vagus nerve and oesophagus
- IVC and phrenic nerve
- Ureter and gonadal vessels

What is the level of the aortic hiatus of the diaphragm?
- T6
- T8
- T10
- [[T12:: Aortic hiatus has 12 letters so it occurs at T12]]

Where is the duodenojejunal (DJ) flexure located under normal anatomical conditions?
- [[On the left at the transpyloric plane::Left is normal, right would indicate malrotation]]
- On the right at the transpyloric plane

Which of the following does not occur at the transpyloric plane?
- Fundus of the gallbladder
- Neck of the pancreas
- Hilum of the kidneys
- None of the above

At what level does the aorta bifurcate?
- L2
- L3
- [[L4::The aorta bifOURcates at LFOUR]]
- L5

What is the best level for a lumbar puncture in a 2-year-old?
- L2/L3
- L3/L4
- [[L4/L5:: The spinal cord ends lower in infants (L3) than in adults (L1/L2)]]
- L5/S1

A man presents with a DVT. CT confirms the presence of a thrombus in his common iliac vein extending into the inferior vena cava. The common iliac veins join to form the inferior vena cava at which vertebral level?
- L2
- L3
- L4
- [[L5:: The common iliac veins join to form the IVC at level L5]]

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