ABDOMINAL VESSELS

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ABDOMINAL VESSELS
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• I. Introduction/General Information
• A. Uses for ultrasound
• 1. Screening procedure for abdominal
  abnormalities
• 2. Localize/Characterize masses
• 3. Measurement, rate, direction of
  blood flow via Doppler

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• General Information, continued
• B. Heart
• 1. CVT used on adults
• 2. Ultrasound used in utero
• C. Abdominal vessels
• 1. Abdominal aorta
• a. Ultrasound can delineate
  contour, course size

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General Information, continued b. Can
evaluate entire course c. Used to diagnose,
follow progress of aneurysms d. Can
distinguish between normal and aneurysm
aortic pulsations
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Abdominal Vessels, continued 2. Celiac axis
(trunk, artery) a. First unpaired branch off
abdominal aorta ( L-1) b.
Originates from ventral surface c. Gives rise
to splenic, common hepatic, left
gastric arteries
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Arteries of the Abdominal Aorta
Figure 19.11
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Abdominal Vessels, continued 3. Superior
Mesenteric Artery a. Second, unpaired branch
of abdominal aorta b. Originates
lower L-1 body c. 1 2 cm below celiac
axis d. Supplies small intestines, pancreas,
omentum, ascending and transverse
colon
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Arteries of the Abdominal Aorta
Figure 19.11
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Abdominal Vessels, cont

• 4. Inferior Mesenteric Artery
• a. Arises just above the bifurcation
  of the aorta (L-3/4)
• b. Last unpaired branch of aorta
• c. Supplies jejunum, descending and
  sigmoid colon, rectum

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Distribution of the Superior and Inferior
Mesenteric Arteries
Figure 19.13
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Abdominal Vessels, continued 4. Renal
arteries a. First major paired branches
from aorta b. Arise opposite each other 1-2
cm below SMA (L-2) c. Multiple renal
arteries occur in 20 of patients
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Renal Arteries
Figure 19.11
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Abdominal Vessels, continued 5. Common
Hepatic Artery a. Right branch of celiac
a. b. Continues to GDA, then 6. Proper
Hepatic Artery a. Branches within liver
b. Begin at porta hepatis
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Blood Supply to Liver
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Abdominal Vessels, continued 7. Inferior
Vena Cava a. Formed at L-5 b. by union
of Common Iliac Veins c. Largest vein in
body d. Dilation may be due to 1.
right-sided CHF 2. Portal hypertension
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Major Veins of the Abdomen
L-5
Figure 19.21
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Abdominal Vessels, continued 8. Veins of
Portal Circulation a. SMV joins with splenic
vein 1. runs parallel to SMA 2. On
right side of abdomen b. IMV terminates in
splenic vein c. Portal Vein enters liver
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Veins of the Hepatic Portal System
Figure 19.23
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Abdominal Vessels, continued d. Renal Veins
run parallel to renal arteries
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Major Veins of the Abdomen
Figure 19.21
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Veins of the Right Lower Limb and Pelvis
e. Femoral Veins - run parallel to
femoral arteries f. Popliteal Veins run
parallel to popliteal arteries
Figure 19.24a
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• II. Detailed Anatomy
• Arteries
• 1. Size
• a. 2.5 cm 0.5 mm
• b. inside diameter
• c. Arbitrary designation
• 2. Structure 3 coats or tunics

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Detailed Anatomy, cont a. Tunica
intima 1. aka tunica interna 2.
innermost layer 3. endothelium 4.
thin 1 cell layer basement membrane
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Vascular Tunics Tunica Intima
Tunica Intima
Artery
Capillary
Vein
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Structure, Arteries, continued b. Tunica
media 1. thickest layer 2. smooth muscle
connective tissue (mostly elastic) 3.
in lamina 4. fibers circularly arranged
around lumen
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Vascular Tunics Tunica Media
Tunica Media
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Structure arteries, continued c. Tunica
externa 1. thinner than media 2. thicker
than intima 3. white fibrous C. T. 4. A few
smooth muscle fibers, arranged
longitudinally
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Vascular Tunics Tunica Externa
Tunica Externa
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Arteries, continued 3.
Variability of arteries a. larger elastic
arteries 1. aorta, pulmonary,
carotids 2. have thicker tunica
intima 3. increased elastic
tissue
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Arteries, variability, continued 4.
very thick tunica media a. smooth muscle
b. obscured by elastic tissue 5.
tunica externa is a. thin but strong
b. limits stretch
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Structure, arteries, continued 6.
Serve as shock absorbers a. expand
contract b. accommodate the
pressure from pumping of the
heart c. Maintain blood flow
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Structure, arteries, continued 7.
arteriosclerosis leads to a. decreased
elasticity b. increased blood
pressure c. High B.P., aneurysm,
rupture of vessels
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Variability, Arteries,
continued b. Muscular arteries 1. farther
from the heart 2. tunica media a. more
smooth muscle b. Less elastic tissue
c. controlled by ANS
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Elastic vs. Muscular Arteries

• Elastic Artery
• Muscular Artery

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Variability, Muscular Arteries, continued
3. actively influence blood flow,
pressure 4. ANS a. triggers smooth
muscle contraction b.
Sympathetic and parasympathetic
responses
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Variability, arteries, continued 5.
have capacity to establish collateral
circulation 6. Especially coronary
arteries 7. contract when injured a. ANS
reaction b. Prevents blood loss
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Detailed anatomy, continued B. Arterioles
small arteries lt 0.5 mm 1. Lie close to
capillary beds 2. Muscular 3. Primary
function regulate capillary blood flow 4.
Allows for exchange of materials
between blood and tissues
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Detailed anatomy, continued C. Capillaries
(sinusoids) 1. Size 1 mm long x 10
micrometers diameter 2. Structure a.
Wall 1 cell layer thick (endothelium) b.
inner surface contacts blood
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Blood Vessel Anatomy Capillaries
Capillary
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Capillaries, continued c. outer surface
rests on basement membrane d. Beyond
basement membrane 1. loose connective
tissue 2. contains tissue fluid
( plasma outside of blood stream)
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Capillaries, continued 3. Organization of
capillaries a. Form vast, complex networks
b. Penetrate to reach most tissues c.
Pre-capillary sphincter 1. smooth muscle
rings 2. regulate blood flow between
arterioles capillary beds
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Capillaries, continued d. Capillary
beds ( 60,000 miles) 1. Specialized for
exchange of materials 2. each
pound of adipose tissue contains 200 miles of
capillaries
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Capillary Networks

• Capillaries connect arterioles to venules
• Blood flow is from the arterial to the venous
  vessels
• Every millimeter of tissue has capillary blood
  supply

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Blood Vessel Anatomy, cont D.
Venules 1. Vessels closest to capillary
beds 2. carry deoxygenated blood 3. Small
venules structurally similar to large
capillaries 4. Medium venules contain a few
circular muscle fibers 5. Large venules
have a tunica externa
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Blood Vessel Anatomy, cont E. Veins
1. Structure same tunics, but not
as distinct a. Tunica media may be
absent b. Tunica externa usually thickest
1. Provides strength to outer wall 2.
Lots of smooth muscle fibers 3. Less elastic
tissue
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Vascular Tunics Veins
Tunica Externa
Tunica Media
Tunica Interna
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• Veins, continued
• Valves in veins carrying blood
  against gravity
• a. Folds of tunica intima
• b. Prevent backflow
• c. Absent in venae cavae, pulmonary
  portal veins
  

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Valves in Veins
Venous Valve
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Valves, continued 2. Internal
jugular veins have valves a. are upside
down b. blood is flowing back to heart c.
when heart contracts, pushes blood up
into SVC d. valves keep -O2 blood from going
back up into brain
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Valves Assisted by Skeletal Muscles

• Skeletal muscle contraction, especially in the
  extremities, assists the flow of blood back to
  the heart
• Varicose Veins..

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Blood Vessel Anatomy, continued 3.
Vasa Vasorum a. vessels that supply
vessels b. associated with larger arteries
veins c. walls too thick for diffusion
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Pathways of Major Vessels F. Path of major
vessels 1. Abdominal aorta a.
Continuous with thoracic aorta _at_
diaphragm. b. Passes through _at_ T-12/L-1
c. Most inferior hiatus in diaphragm
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Pathway of Major Vessels, continued
d. Anterior to the left of
vertebral bodies e. Decreases in
external diameter caudally 1.
3.0 cm _at_ left ventricle 2. 1.5 cm _at_
bifurcation f. Moves toward midline distally
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Path of Aorta

• Parasagittal section through the thorax and
  abdomen showing the path of the aorta

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Pathway of Major Vessels, continued g.
Bifurcates into R/L common iliac arteries _at_
L-3/L-4 h. Courses posterior to IVC near
diaphragm i. Curves anteriorly along
lumbar curvature
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Pathway of Major Vessels, continued 2.
Celiac Artery a. First unpaired branch of
abdominal aorta (T-12) b. Gives
rise to 1. Splenic Artery a.
largest on left b. supplies spleen,
pancreas fundus of stomach
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The Celiac Trunk and its Branches
Celiac Trunk

• The celiac trunk is the first unpaired artery of
  the abdominal aorta
• It arises T-12/L-1 disc

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Major Paths of Vessels, Celiac Artery,
continued

• c. L. Gastroepiploic Artery
• 1. Largest branch of splenic artery
• 2. supplies greater curvature of stomach

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Celiac artery, continued
2. Left Gastric Artery
a. smallest of 3 branches b. Supplies
1. Cardiac region 2.
lesser curvature of stomach 3. Lower
esophagus
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Celiac artery, continued 3. Common Hepatic
Artery a. courses toward right b.
supplies pyloric region of stomach
duodenum c. gives rise to gastroduodenal
artery d. Continues as proper hepatic
artery
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Hepatic Artery

• Proper Hepatic Artery
• Common Hepatic Artery

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Path of major vessels, continued 4.
SMA a. Second unpaired branch b. Arises
1 2 cm below celiac artery c. May have
common origin d. After 6, 1. courses
parallel to aorta 2. then turns oblique
toward right iliac fossa
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SMA, continued d. Numerous branches that
sometimes anastomose e. Supplies 1.
small intestines 2. cecum 3.
appendix 4. ascending transverse colon
5. pancreas
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Superior Mesenteric Artery

• Superior mesenteric artery
• SMA gives rise to the inferior pancreaticoduodenal
  artery

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Path of major vessels, continued

5. Renal Arteries/Veins a. First major
paired branch of abdominal aorta b. Arise
L-2 c. more later
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Path of major vessels, cont 6. IVC
arises L-5 a. lies to right of lumbar
vertebrae b. Largest vein c. Occupies a
fossa on posterior surface of liver d.
Receives hepatic veins
IVC
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IVC, continued e. Penetrates diaphragm
at T-10 f. passes through
pericardium g. empties into right
atrium h. IVC receives blood from lower
extremities, lumbar v., renal v.,
adrenal v.
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IVC and its Tributaries
Pathway of IVC and its major contributing veins
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Path of major vessels, continued 7. Portal
system a. Receives blood from digestive
organs b. Is high in nutrients ?
enters portal vein ? then to liver
sinusoids c. then to hepatic veins ?
into IVC
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Portal circulation
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Portal system, continued d. Portal Vein
1. formed L-2 by union of SMV
splenic vein 2. travels superiorly
surrounded by lesser omentum 3.
Enters liver at porta hepatis
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Portal Vein Formation
L-2
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• III. Gray Scale Anatomy
• A. Abdominal aorta
• 1. Circular in T.S.
• 2. Tubular in L.S.
• 3. Differences from IVC
• a. IVC lies to the right

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Abdominal aorta, continued b. Near
diaphragm, IVC is anterior in L.S. c.
IVC changes diameter with respiration
d. Aorta pulsates 4. Slopes anteriorly to
L-3/4
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Gray scale anatomy, continued B.
SMA 1. Extends from 3 cm below
diaphragm to umbilicus 2. Horizontal
course on L.S. 3. Origin is 1 2 cm below
celiac 4. Lies anterior to aorta
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SMA, continued 4. In T.S. a.
sonolucent circular structure b.
posterior to body of pancreas 5.
Surrounding fat ? collar a. Different from
SMV b. SMV larger to the right
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Gray scale anatomy, continued C. Celiac
trunk/axis/artery 1. ID-ed on T.S. as
tubular branching structure 2. Originates
from anterior aorta 3. Short, vertical
(really anterior) course superior to lesser
curvature 4. Hepatic and splenic artery
branches produce seagull sign
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The Seagull Sign
Splenic Artery
Hepatic Artery
Celiac Trunk
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IV. Vascular Pathology A. Tortuosity of
abdominal aorta 1. Aorta becomes elongated,
dilated less elastic with age 2. Due
to plaque calcification 3. May become
tortuous 4. May lie to right of midline
5. May mimic an aneurysm
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Vascular Pathology, cont. B.
Aneurysms 1. Definitions a. circumscribed
dilation of an artery b. blood-containing
tumor connecting with lumen of
artery 2. Fusiform or saccular dilations
3. Usually appear distal to renal
arteries
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Aneurysms, continued 4. Measurements
abnormal if a. External A-P diameter
gt3.5 cm in upper abdomen b. gt 2.5 cm in
distal aorta 5. Patent vessel lumen
contains blood, is echolucent
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Aneurysms, continued 6. Thrombus-filled
lumen is echogenic 7. Ectatic (dilated) aorta
difficult to depict on single scan 8.
Associated with arteriosclerotic plaque
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Aneurysms, continued 9.
Excess plaque causes a. loss of elasticity
b. weakening in tunica media c.
Tears in tunica interna
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Aneurysms, continued 10. Fusiform
aneurysms a. usually project anterior
to the left b. path of least resistance c.
Laminar blood flow absent in dilation d.
Eddy currents increase likelihood of thrombus
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Aneurysms, continued 11. Ultrasound is gt 95
accurate in identifying AAA a.
Presence/location serial growth b. Diameter
determination c. Thrombus presence d.
Incidence of rupture of aneurysm
increases after 7.0 cm
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Aneurysms, continued 12. If dilation
extends toward SMA, renal arteries may be
involved 13. Less common to find aneurysm
above renal arteries 13. If dilation is
above renal arteries, suspect dissecting
thoracic aneurysm 14. If dilation extends
distally, survey common iliac arteries
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Aneurysms, continued B. Aortic
Dissection 1. Usually secondary to dissecting
thoracic aortic aneurysm 2. Dilation of
abdominal aorta with double lumen 3.
Characteristics a. Intimal flap b. Diffuse
dilation
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Aortic dissection, continued 4.
Pulsations of flap are visible 5. Aneurysms of
ascending aorta enlarge anterior and to the
right a. May extend to mediastinum b.
May erode sternum
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Vascular Pathology, cont D.
Atherosclerosis vs. Arteriosclerosis 1.
Atherosclerosis (reversible) a. deposits of
fatty materials b. in tunica intima of
arteries c. Genetic predisposition--
leads to ?
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Atherosclerosis vs. Arteriosclerosis,
cont 2. Arteriosclerosis (irreversible) a.
infiltration of intima by plaque b.
reduces lumen size c. Reduces blood supply
d. hardening of the arteries
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Progress of Arteriosclerosis
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Vascular Pathology, cont

• E. Types of aneurysms
• Axial involves entire circumference of
  artery
• Compound some tunics ruptured, some intact
• Dilation axial or fusiform general
  enlargement
• a. Active growing in diameter
• b. Passive wall is stretching

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Types of aneurysms, continued 4. Dissecting
splitting, tearing of intima a. Rarely
encircles entire lumen b. Usually one side
only c. May involve entire length to
bifurcation d. Usually originates from
thoracic aorta (high B.P.)
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Aneurysms
Berry Aneurysm
AAA
Dissecting Aneurysm
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Types of aneurysms, continued 5. Ectatic
axial or dilating, but unruptured 6.
Endogenous stretched tunica 7. Exogenous
due to trauma 8. Fusiform long skinny
expansion
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Types of aneurysms, continued 9. False a.
bleeding from another source b. pulsating
encapsulated hematoma c. fused with
aneurysm d. communicates with lumen of
artery
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Types of aneurysms, continued 10. Saccular
sac like bulge a. tunica externa
expanded b. tunica intima intact 11. Tubular
a. AKA axial passive dilation b.
Uniform dilation of entire vessel
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Types of aneurysms, continued
12. Varicose a. result of varicose
veins b. blood containing sac connecting
artery vein c. seen in antecubital
fossa d. due to repeated IV sticks
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Aneurysms Summary Views