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Author
Dr. Sachinder Singh Hans is a vascular surgeon in Clinton Township, Michigan. He received his
medical degree from Government Medical College, Patiala, Internship (January–December 1969)
and House Officer Surgery (1970) from Rajindra Hospital, Patiala (Pb.) India. He has been in practice
for more than 45 years. Board certifications include:
• American Board of Surgery – Surgery
• American Board of Surgery – Surgical Critical Care
• American Board of Surgery – Vascular Surgery
• Education includes:
• Postgraduate Institute of Medical Education, Chandigarh, India with Master in Surgery (MS)
June 1972
• Registrar of Surgery Chandigarh, India June 1972–1973
• Government Medical College of Patiala, MI, 1969
• Internships & Residencies Ascension Macomb–Oakland Hospital, Surgery, MI, 1977
• Fellowship in Vascular Surgery, Beaumont Hospital–Royal Oak, Vascular Surgery, MI,
July 1979–June 1980
SECTION 1: ANATOMY, PHYSIOLOGY,
AND HEMODYNAMICS
MCQs 1–18
Q1. A common origin of the brachiocephalic
artery and left common carotid artery
(bovine aortic arch) is present in:
A. Under 10% of individuals
B. 11%–20% of individuals
C. 21%–30% of individuals
D. Greater than 30% of individuals
Q2. Dysphagia lusoria is caused by:
A. Aberrant aneurysmal left subclavian
artery
B. Aberrant aneurysmal right subclavian
artery
C. Double aortic arch
D. Right-sided aortic arch
Q3. The most common persistent embryo-
genic connection between the carotid
and vertebrobasilar system persists in the
form of:
A. Persistent hypoglossal artery
B. Persistent trigeminal artery
C. Persistent otic artery
D. Proatlantal intersegmental artery
Q4. The left vertebral artery may arise from
the arch of the aorta in between the origins of the left common carotid artery and
left subclavian artery in:
A. 0.4% of individuals
B. 5%–7% of individuals
C. 8%–11% of individuals
D. 12%–15% of individuals
Q5. Brachial artery variations occur in:
A. 5% of individuals
B. 6%–10% of individuals
C. 11%–15% of individuals
D. 16%–20% of individuals
Q6. The high origin of the anterior tibial
artery from the popliteal artery occurs in:
A. 1%–4% of individuals
B. 5%–7% of individuals
C. 8%–10% of individuals
D. Greater than 10% of individuals
Q7. Cerebral autoregulation is the response
of cerebral vessels to a change in arterial blood pressure. The threshold and
saturation points of systemic mean blood
pressure are approximately:
A. 60 mmHg and 150 mmHg
B. 70 mmHg and 140 mmHg
C. 80 mmHg and 130 mmHg
D. 90 mmHg and 120 mmHg
Q8. Resistance refers to the direct ratio of
decrease in pressure to flow in a given
vascular territory. The vascular territory
that is responsible for the largest contribution to resistance is the:
A. Aorta
B. Arterioles
C. Capillaries
D. Venules
Q9. The largest contributor to vascular resis-
tance is:
A. Vessel length
B. Blood viscosity
C. Radius of the vessel
D. Hematocrit
Q10. The wall shear stress for a given vessel
radius is directly related to:
A. Larger viscosity
B. Larger velocity
C. Larger viscosity and larger velocity
D. Arterial wall strengthening
DOI: 10.1201/9781003389897-1
2 Section 1: Anatomy, Physiology, and Hemodynamics
Q11. According to Laplace law, circumferential
stress is inversely proportional to:
A. Pressure load on the vessel
B. Vessel radius
C. Wall thickness
D. Viscosity
Q12. At low strains and pressures, the burden
of bearing the stress is carried out by:
A. Elastin fibers
B. Collagen fibers
C. Endothelium
D. Blood components
Q13. All of the following statements about
fibromuscular dysplasia (FMD) are true
except:
A. Result of atherosclerosis
B. Result of non-inflammatory process
C. Primarily affects midsize vessels
D. Most often asymptomatic
Q14. A typical value of the pulse wave velocity
is in the range of:
A. 0–4 m/s
B. 5–10 m/s
C. 11–15 m/s
D. Greater than 15 m/s
Q15. Fibromuscular dysplasia most often
presents as:
A. Medial hyperplasia
B. Medial fibroplasia
C. Intimal fibroplasia
D. Perimedial fibroplasia
Q16. Just superior to the right renal artery the
suprarenal aorta is separated from the
interior vena cava by the:
A. Right crus
B. Median arcuate ligament
C. Left crus
D. Cisterna chyli
Q17. Vascular stiffness is determined by the ratio
of elastin to collagen and by the thickness of
the vessel wall and is expressed as:
A. More elastin causes more stiffness, with a
thicker wall
B. More collagen and a thinner wall
C. More collagen and a thicker wall
D. Less elastin and a thinner wall
Q18. Laminar flow ceases when the Reynolds
number is:
A. Less than 1000
B. 1001–1500
C. 1501–2100
D. Greater than 2000
Section 1: Anatomy, Physiology, and Hemodynamics 3
RATIONALE 1–18
1. RATIONALE
The three main arteries of the head and neck supplying the cerebral arterial bed arise from the
most proximal segment of the arch or the distal portion of the ascending aorta. Their origins
may be quite separate or very close, as there may be a common origin of the brachiocephalic
trunk with the left common carotid artery in 10% of the population. This variation has clinical
significance, as the proximal landing zone is increased by such a variation during performance
of thoracic endovascular aortic repair (TEVAR). During transfemoral left carotid artery stenting,
access to the left common carotid artery may pose technical challenges. Occasionally, there is
“V-shaped origin” of both common carotid arteries from a single short trunk before the continuation on each side of the neck.
Correct Answer A Under 10% of individuals
Reference
Berguer, R. (2014). Anatomy and function of the carotid and vertebral systems. In R. Berguer (Ed.),
Function and surgery of the carotid and vertebral arteries (pp. 1–31). Philadelphia, PA: Lippincott,
Williams and Wilkins.
2. RATIONALE
The aberrant right subclavian artery was first described in 1725 as arising from the descending
thoracic aorta, is one of the most common congenital anomalies of the aortic arch and occurs
in 0.05%–1% of the population. Symptoms of the aberrant right subclavian artery are mostly
related to the development of aneurysmal disease, which occurs at its origin. The aneurysm can
develop in nearly 60% of cases of aberrant right subclavian artery and is known as Kommerell
diverticulum. Dysphagia may develop in early childhood or later in life due to aneurysmal
changes. The course of the artery is usually posterior to the esophagus. The ideal method of
diagnosis is barium esophagogram with confirmatory CT or MR angiography.
Correct Answer B Aberrant aneurysmal right subclavian artery
Reference
Levitt, B., & Richter, J. E. (2007). Dysphagia lusoria: a comprehensive review. Dis Esophagus, 20(6),
455–460. PMID: 17958718.
3. RATIONALE
Carotid basilar anastomoses are rare arterial anomalies in which embryonic connections between
the carotid and vertebral arterial system persist. The persistent trigeminal artery is the most common and the most cephalad-located embryological anastomosis between the developing carotid
artery and the vertebrobasilar system to persist into adult life. Its incidence ranges from 0.1% to
0.6% by MRA and CTA imaging. The persistent primitive hypoglossal artery has been reported in
0.03%–0.26% of cases undergoing cerebral arteriography. A persistent hypoglossal artery arises
from the internal carotid artery between the cervical first and cervical second vertebral body levels
and traverses through the hypoglossal canal to join the vertebrobasilar circulation.
Correct Answer B Persistent trigeminal artery
4 Section 1: Anatomy, Physiology, and Hemodynamics
Reference
Meckel, S., Spittau, B., & McAuliffe, W. (2013). The persistent t rigemina l arter y: development, imaging anat-
omy, variants, and associated vascular pathologies. Neuroradiology, 55(1), 5–16. PMID: 22170080.
4. RATIONALE
After arising from the first part of subclavian artery, the vertebral artery ascends through the
foramen in the transverse process of the sixth cervical vertebra into the first cervical vertebra
and then it courses laterally, entering the skull through the foramen magnum and joins the
opposite vertebral artery to form the basilar artery. Vertebral arteries are often (80%–85%) variable in their size. In many instances, one vertebral artery may be large and dominant with the
contralateral vertebral artery hypoplastic or in rare circumstances even absent. The origin of
the vertebral artery can be variable. They may arise from the second portion of the subclavian
artery and may have a duplicate origin. The left vertebral artery may arise from the arch of the
aorta between the left common carotid artery and left subclavian artery in 5%–7% of cases, and
the vertebral artery may enter the fourth. fifth, or seventh cervical vertebra.
Correct Answer B 5%–7% of individuals
Reference
Satti, S. R., Cerniglia, C. A., & Koenigsberg, R. A. (2007). Cervical vertebral artery variations: an ana-
tomic study. AJNR Am J Neuroradiol, 28(5), 976–980. PMID: 17494682.
5. RATIONALE
Anatomically, the axillary artery becomes the brachial artery at the lateral border of the teres major
muscle and terminates by dividing into the radial and ulnar artery about 1 cm below the elbow
joint. The brachial artery may occasionally divide proximally (in the middle of the upper arm) and
then reunite. The brachial arter y may course superficially in front of the median ner ve and then
behind the nerve (3.6%–9%). High bifurcation of the brachial artery into the radial and ulnar artery
occurs in 8% of cases. Most often in this variant, the radial artery then becomes the brachioradial
artery and courses on a superficial plane, while the ulnar artery and the common interosseous
artery continue as a common trunk. Variations in the brachial artery have implications in clinical
practice this may result in complications during vascular interventions and open reconstructions.
High bifurcation of the brachial artery is important during performance of an arteriovenous graft
for permanent hemodialysis access. Some studies have demonstrated inferior patency of arteriovenous grafts in patients with high bifurcation of the brachial artery.
Correct Answer D 16%–20% of individuals
Reference
Anbumani T. L., Anthony Ammal S. and Thamarai Selvi A. (2016). An anatomical study of variations
in terminat ion of brachial arter y, with its embryological basis and cl inical significance. Int J Med
Res Health Sci, 5(3), 85–89. https://www.ijmrhs.com/medical-research/an-anatomical-study-
on-the-variations-of-short-saphenous-vein-and-its-termination.pdf
6. RATIONALE
The popliteal artery terminates into anterior tibial artery and tibioperoneal trunk at the inferior
border of the popliteus (4–5 cm below the knee joint line). The high origin of the anterior tibial
artery or its aberrant course may increase the risk of iatrogenic arterial injury during knee
surgery. In a review of femoral arteriograms in 1,242 patients, 89.2% had a normal branching
Section 1: Anatomy, Physiology, and Hemodynamics 5
pattern of the popliteal artery, hypoplastic or aplastic posterior tibial artery in 5.1%, hypoplastic
or aplastic anterior tibial artery in 1.7%, true bifurcation in 1.4%, and high origin of the anterior tibial artery in 1.2%. When the branching pattern of the popliteal artery is normal in one
extremity, there is a 13% probability that the contralateral side will have a variable pattern.
When the branching pattern is variant in an extremity, there is a 28% probability that the opposite side will have a variant pattern.
Correct Answer A 1%–4% of individuals
Reference
Kil, S. W., & Jung, G. S. (2009). Anatomical variations of the popliteal artery and its tibial branches:
analysis in 1242 extremities. Cardiovasc Intervent Radiol, 32(2), 233–240. PMID: 18982387.
7. RATIONALE
The autoregulatory response to changes in blood pressure helps to maintain a constant and
stable cerebral blood flow despite wide fluctuations in mean blood pressure. Decrease in
blood pressure leads to cerebral vasodilation and increase in blood pressure leads to cerebral
vasoconstriction. This autoregulation is much less effective at maintaining constant blood
flow at mean pressures below 60 mmHg or mean pressure above 150 mmHg. This autoregulation is modulated by the activity of the autonomic nervous system renin-angiotensin system
in the vessel wall, via CO2, by vasoactive and morphologic changes in the vessel walls. This
autoregulatory range is shifted toward the right in patients with long-standing hypertension.
This autoregulatory response is also present in the coronary and renal vasculature, but not in
the peripheral vasculature. Cerebral blood flow can be measured noninvasively by vascular
Doppler sonography, magnetic resonance imaging, and near-infrared spectroscopy.
Correct Answer A 60 mmHg and 150 mmHg
Reference
Willie, C. K., Tzeng, Y. C., Fisher, J. A., & Ainslie, P. N. (2014). Integrative regulation of human brain
blood flow. J Physiol, 592(5), 841–859. PMID: 24396059.
8. RATIONALE
The arterioles constitute the vascular territory with the largest contribution to the resistance,
as a maximum drop in pressure occurs in them. Arterioles are also known as resistive arteries.
Mean arterial pressure is relatively constant in the aorta and the muscular, as well as elastic
6 Section 1: Anatomy, Physiology, and Hemodynamics
Q
R
8L
4
π
µ
R
8L
R
µ
π
R
ChangeinPressure
Flow
P
Q
==
∆
arteries with pulsatile flow. Pulsatility disappears greatly in the arterioles and is absent in capillaries and venules. Peripheral vascular resistance or systemic vascular resistance (SVR) is the
resistance in the circulatory system that is used to create blood pressure and the flow of blood.
When the blood vessels constrict, it leads to an increase in SVR and a decrease in SVR when
blood vessels dilate. Vascular resistance is used to maintain organ perfusion, and in shock there
is a decrease in SVR causing decreased organ perfusion. SVR is mediated by local metabolites
and neurohormonal factors.
Correct Answer B Arterioles
Reference
Delong, C., & Sharma, S. (2022). Physiology, peripheral vascular resistance. In StatPearls. Treasure
Island (FL): StatPearls Publishing.
9. RATIONALE
It is apparent that the arterioles constitute the vascular territory with the largest resistance, as
they experience the largest drop in pressure. These vessels are known as resistive arteries. The
resistance is determined by several factors, including vessel length and diameter. Poiseuille flow
is a useful concept from fluid mechanics to understand the relationship between flow, pressure,
and resistance. The pressure gradient (ΔP) drives flow through the vessel, which moves from a
point of higher pressure (pressure proximal) to a point of lower pressure (pressure distal). The
flow has a parabolic shape, with a maximum velocity (velocity max) at the center of the lumen
and zero velocity at the interface with the endothelial surface.
In the Hagen–Poiseuille flow equation, the relationship between flow (Q), pressure drop (ΔP),
and resistance are:
=
P
∆
esistance
=
4
where μ is the blood viscosity, L is the vessel length over which the given pressure drop
(ΔP) takes place, and R is the vessel radius. It is thus apparent that the vessel radius plays a
much larger role in terms of vascular resistance than the vessel length due to its power-of-4
exponent. This explains why relatively small changes in vascular tone significantly alter
vascular resistance (e.g., a 10% vasoconstriction results in an increase of 50% in vascular
resistance).
Correct Answer C Radius of the vessel
Resistance: Resistance refers to the ratio of the drop in pressure to flow in a vascular territory:
esistance
R
()
Reference
Klabunde, R. E. (2012). Cardiovascular physiology concepts. Wolters Kluwer Health.
Section 1: Anatomy, Physiology, and Hemodynamics 7
10. RATIONALE
The wall shear stress expresses the force per unit area exerted by the wall on the fluid in
a direction on the local tangent plane. The fluid in the human body is represented by the
blood. The typical value of the wall shear stress in the arterial system is 10–100 dynes/cm2.
Acting tangentially to the endoarterial surface, pressure is much larger (1000 times). Wall
shear stress (T = μ velocity divided by R). It is obvious from this equation that a larger viscosity and velocity will lead to larger wall shear stress. High wall stress is the most important
factor in the development of high-risk plaque. In a thoracic endograft, the wall shear stress
acts tangentially to the surface of the endograft, whereas the pressure is perpendicular to the
surface of the endograft.
Correct Answer C Larger viscosity and larger velocity
Reference
Figueroa, C. A., Taylor, C. A., & Chiou, A. J., et al. (2009). Magnitude and direction of pulsatile dis-
placement forces acting on thoracic aortic endografts. J Endovasc Ther, 16(3), 350–358. PMID:
19642798.
11. RATIONALE
Laplace law for the gauge pressure inside a cylindrical membrane is given by ΔP = Y divided by
r (Y/r), where Y is the surface tension and r is the radius of the cylinder. Therefore, there is an
inverse relationship between the pressure and the radius. Hoop stress is the stress that occurs
along the pipe’s circumference when pressure is applied and acts perpendicular to the axial
direction. Three principal stressors are measured when the ends are closed and the cylinder
and the pipe are subjected to internal pressure: Hoop stress, longitudinal stress (L), and radial
stress (r). In a thin-walled pipe with a wall thickness less than the diameter, radial stress is negligible. The hoop stress increases the pipe’s diameter, whereas the longitudinal stress increases
the pipe’s length. Hoop stress is usually twice the size of the longitudinal stress. Hoop stress
is also called tangential or circumferential stress. According to Laplace law, given equal end
8 Section 1: Anatomy, Physiology, and Hemodynamics
pressures and wall morphology, the wall of a larger-diameter blood vessel experiences greater
tension than that of a smaller-diameter pipe (blood vessel).
Correct Answer C Wall thickness
Reference
Schmidt-Nielsen, K. (1990). Animal physiology: adaptation and environment. Cambridge University
Press.
12. RATIONALE
The elastin matrix has a low stiffness value. At higher stress, the collagen fibers cause the vessel
to become stiffer. The shape and compliance curves as well as stiffness curves for two different blood vessels are distinct, due to the axes of stress/pressure and strain/volume varying.
Compliance is the change in the volume (Δ v) imposed on the blood vessel by a given change in
the pressure (ΔP) as the pulse pressure between the systole and diastole. The larger the pressure, the smaller the compliance. Distensibility (D) is equal to the ratio of changes in the luminal area between the systole and the diastole divided by the pulse pressure. Distensibility is
therefore a similar metric to compliance obtained via changes in the luminal area of the vessel
rather than via changes in volume. At low strains and pressures, elastin fibers bear the burden
of stress, which has low values of stiffness.
Correct Answer A Elastin fibers
Reference
Ferruzzi, J., Collins, M. J., Yeh, A. T., et al. (2011). Mechanical assessment of elasti n integrit y in fibrillin-
1-deficient carotid arteries: implications for Marfan syndrome. Cardiovasc Res, 92(2), 287–295.
PMID: 21730037.
13. RATIONALE
Most patients with cerebrovascular FMD are asymptomatic middle-aged women who are otherwise healthy. The cause of FMD is unknown. Approximately 10% of patients with FMD have an
affected family member as well. Patients may present with headaches or dizziness, and a carotid
bruit may be detectable on physical examination. The incidence of ischemic cerebral events is quite
low at long-term follow-up. Occasionally, cerebral ischemia secondary to a thromboemboli originating from a diseased arterial segment or from a low-flow state occurs. Patients may present with
arterial dissection. There is a higher incidence of intracranial aneurysms in patients with internal
carotid artery or vertebral artery FMD. Duplex ultrasound is a standard first-line modalit y in diagnosing FMD. However, Doppler velocity diagnostic criteria applicable to atherosclerotic disease
are not reliable in the diagnosis of FMD. CTA or MRA of the neck are useful techniques in diagnosing FMD. CTA is preferable, but MRA may be helpful in diagnosing concurrent arterial dissection
through simultaneously acquired T1-fat saturation images with a time-of-flight or gadoliniumenhanced imaging. Low-dose aspirin is indicated. Duplex surveillance to rule out aneurysmal
Section 1: Anatomy, Physiology, and Hemodynamics 9
degeneration should be obtained on a yearly basis. In selected cases balloon angioplasty is indicated in patients who fail medical management and in whom the lesion is progressive.
Correct Answer A Result of atherosclerosis
Reference
Kadian-Dodov, D., Gornik, H. L., & Gu, X., et al. (2016). Dissect ion and aneur ysm in patients wit h fibro-
muscular dysplasia: findings from the U.S. registry for FMD. J Am Coll Cardiol, 68(2), 176–185.
PMID: 27386771.
14. RATIONALE
Pulse wave velocity represents the velocity at which the pressure and flow waves propagate
through the circulatory system and indicates the speed at which a wave travels down an elastic
vessel with typical values in the 5–10 m/s range. The speed is faster in the stiffer vessel. Pulse wave
velocity is a biomarker of arterial stiffness, which is a known independent predictor of all-cause
cardiovascular mortality in patients with hypertension. Pulse wave velocity increases with age for
every blood pressure category, denoting an overall stiffness of the aorta with increasing age.
Correct Answer B 5–10 m/s
Reference
Xiao, N., Humphrey, J. D., & Figueroa, C. A. (2013). Multi-scale computational model of three-
dimensional hemodynamics within a deformable full-body arterial network. J Comput Phys,
244, 22–40. PMID: 23729840.
15. RATIONALE
Fibromuscular dysplasia is classified according to the affected segment of the arterial wall. The
same classification is used for all the arteries affected by fibromuscular dysplasia. Medial fibroplasia is the most common (80%–90%), with a “string-of-beads” appearance secondary to alternating
thinned and thickened medial ridges. This appearance on arteriography is secondary to stenotic
webs that cause sequential stenosis and dilatations in the arterial wall. These dilatations may lead
to aneurysmal degeneration. Intimal fibroplasia is responsible for about 10% cases of fibromuscular
dysplasia, resulting in a long concentric stenotic lesion secondary to intimal collagen deposits. The
differential diagnosis includes atherosclerosis, vasculitis, and connective tissue disorder.
Correct Answer B Medial fibroplasia
Reference
Poloskey, S. L., Olin, J. W., & Mace, P. (2012). Fibromuscular dysplasia. Circulation, 125(18), e636–e639.
PMID: 22566353.
16. RATIONALE
The right crus separates the suprarenal aorta from the inferior vena cava (IVC). During transperitoneal exposure of the juxtarenal aorta, the left renal vein may need to be divided close to the
IVC to preserve collateral venous flow from the left kidney via the gonadal and adrenal vein. After
division of the medial crus, the suprarenal aorta is carefully exposed and mobilized. The adrenal
artery often needs to be ligated and divided before application of a suprarenal aorta clamp during
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