biol226lec09_ abdominal vessels

7/31/2019 BIOL226Lec09_ Abdominal Vessels

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ABDOMINAL VESSELS


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I. Introduction/General Information

A. Uses for ultrasound

1. Screening procedure for abdominalabnormalities

2. Localize/Characterize masses

3. Measurement, rate, direction ofblood flow via Doppler


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General Information, continued

B. Heart:

1. CVT used on adults2. Ultrasound used in utero

C. Abdominal vessels1. Abdominal aorta

a. Ultrasound can delineatecontour, course & size


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General Information, continued

b. Can evaluate entire course

c. Used to diagnose, follow progressof aneurysms

d. Can distinguish between

normal and aneurysm aorticpulsations


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Abdominal Vessels, continued

2. Celiac axis (trunk, artery)

a. First unpaired branch offabdominal aorta (~ L-1)

b. Originates from ventral surface

c. Gives rise to splenic, commonhepatic, & left gastric arteries


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Arteries of the Abdominal

Aorta

Figure 19.11


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3. Superior Mesenteric Artery

a. Second, unpaired branch of

abdominal aorta

b. Originates ~ lower L-1 body

c. 1 2 cm below celiac axisd. Supplies small intestines, pancreas,

omentum, ascending and transversecolon


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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 bifurcationof the aorta (~L-3/4)

b. Last unpaired branch of aorta

c. Supplies jejunum, descendingand sigmoid colon, rectum


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Distribution of the Superior and Inferior

Mesenteric Arteries

Figure 19.13


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4. Renal arteries

a. First major paired branchesfrom 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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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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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

Figure 19.21

L-5


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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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d. Renal Veins

run parallelto renalarteries


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Major Veins of the Abdomen

Figure 19.21


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Veins of the Right Lower Limb and Pelvis

Figure 19.24a

e. Femoral Veins -

run parallel tofemoral arteries

f. Popliteal Veins

run parallel topoplitealarteries


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II. Detailed AnatomyA. Arteries

1. Size:a. ~ 2.5 cm 0.5 mmb. inside diameterc. 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 + basementmembrane


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Vascular Tunics: Tunica IntimaTunica Intima

Artery

VeinCapillary


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Structure, Arteries, continued

b. Tunica media

1. thickest layer

2. smooth muscle & connectivetissue (mostly elastic)

3. in lamina

4. fibers circularly arrangedaround lumen


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Vascular Tunics: Tunica Media

Tunica Media


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Structure arteries, continued

c. Tunica externa

1. thinner than media2. thicker than intima3. 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 tunicaintima

3. increased elastic tissue


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Arteries, variability, continued

4. very thick tunica media

a. smooth muscleb. obscured by elastictissue

5. tunica externa isa. thin but strongb. limits stretch


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Structure, arteries, continued

6. Serve as shock absorbers

a. expand & contract

b. accommodate the

pressure from pumpingof 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 tissuec. 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 bloodflow, pressure

4. ANS:

a. triggers smooth

muscle contractionb. Sympathetic and

parasympathetic

responses


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Variability, arteries, continued

5. have capacity to establishcollateral 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 < 0.5 mm

1. Lie close to capillary beds

2. Muscular

3. Primary function: regulate capillaryblood flow

4. Allows for exchange of materialsbetween 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: CapillariesFig. 13.3

Capillary


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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 betweenarterioles & capillary beds


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Capillaries, continued

d. Capillary beds: (~ 60,000 miles)

1. Specialized for exchange ofmaterials

2. each pound of adipose tissuecontains 200 miles ofcapillaries


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Capillary Networks

Capillaries connectarterioles to venules

Blood flow is from thearterial to the venousvessels

Every millimeter of

tissue has capillaryblood 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 tolarge capillaries

4. Medium venules: contain a few circularmuscle fibers

5. Large venules: have a tunica externa


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Blood Vessel Anatomy, cont

E. Veins1. Structure: same tunics, but not

as distincta. Tunica media may be absentb. Tunica externa: usually thickest

1. Provides strength to outer wall2. Lots of smooth muscle fibers3. Less elastic tissue


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Vascular Tunics: Veins

Tunica Media

Tunica Externa

Tunica Interna


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Veins, continued

1. Valves: in veins carrying bloodagainst gravity

a. Folds of tunica intimab. 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 valvesa. are upside down

b. blood is flowing back to heartc. when heart contracts, pushes

blood up into SVCd. valves keep -O2 blood from going

back up into brain


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Valves Assisted by Skeletal Muscles

Skeletal muscle

contraction, especiallyin the extremities,assists the flow of bloodback to the heart

Varicose Veins..


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Blood Vessel Anatomy, continued

3. Vasa Vasorum:

a. vessels that supply vesselsb. 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 @diaphragm.

b. Passes through @ T-12/L-1c. Most inferior hiatus in diaphragm


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Pathway of Major Vessels, continued

d. Anterior & to the left of vertebralbodies

e. Decreases in external diametercaudally

1. 3.0 cm @ left ventricle

2. 1.5 cm @ bifurcation

f. Moves toward midline distally


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Path of Aorta

Parasagittal section

through the thorax andabdomen showing thepath of the aorta


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g. Bifurcates into R/L common iliac

arteries @ L-3/L-4h. Courses posterior to IVC near

diaphragm

i. Curves anteriorly along lumbarcurvature


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2. Celiac Arterya. First unpaired branch of

abdominal aorta (~T-12)b. Gives rise to:1. Splenic Artery:

a. largest on left

b. supplies spleen, pancreasfundus of stomach


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The Celiac Trunk and its Branches

The celiactrunk is the

first unpairedartery of theabdominalaorta

It arises~T-12/L-1 disc

Celiac Trunk


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Major Paths of Vessels, Celiac Artery, continued

c. L. Gastroepiploic

Artery1. Largest branchof splenic artery

2. supplies greatercurvature of stomach


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Celiac artery, continued

2. Left Gastric Artery:

a. smallest of 3branchesb. Supplies:

1. Cardiac region2. lesser curvature

of stomach3. Lower esophagus


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Celiac artery, continued

3. Common Hepatic Artery:

a. courses toward rightb. supplies pyloric region of

stomach & duodenumc. gives rise to gastroduodenal

arteryd. 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. SMAa. Second unpaired branch

b. Arises 1 2 cm below celiac arteryc. May have common origind. After ~6,

1. courses parallel to aorta2. then turns oblique toward

right iliac fossa


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SMA, continued

d. Numerous branches that

sometimes anastomosee. Supplies:

1. small intestines

2. cecum3. appendix4. ascending & transverse colon5. pancreas


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Superior Mesenteric Artery

Superior mesentericartery

SMA gives rise to theinferiorpancreaticoduodenal

artery


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5. RenalArteries/Veins:a. First majorpaired branch ofabdominal 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 liverd. 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 lowerextremities, lumbar v., renal v.,adrenal v.


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IVC and its

Tributaries

Pathway of IVCand its majorcontributing

veins


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7. Portal system:

a. Receives blood from digestive

organs

b. Is high in nutrients entersportal 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 bylesser omentum

3. Enters liver at porta hepatis


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Portal Vein Formation

L-2


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III. Gray Scale AnatomyA. 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 isanterior in L.S.

c. IVC changes diameter withrespiration

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 belowdiaphragm to umbilicus

2. Horizontal course on L.S.

3. Origin is 1 2 cm below celiac4. 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 SMVb. 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) coursesuperior to lesser curvature

4. Hepatic and splenic arterybranches produce seagull sign


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The Seagull Sign

Celiac Trunk

Splenic ArteryHepatic Artery


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IV. Vascular PathologyA. Tortuosity of abdominal aorta

1. Aorta becomes elongated, dilated

& less elastic with age2. Due to plaque & calcification

3. May become tortuous

4. May lie to right of midline5. May mimic an aneurysm


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Vascular Pathology, cont.

B. Aneurysms

1. Definitions:

a. circumscribed dilation of an arteryb. blood-containing tumor

connecting with lumen of artery

2. Fusiform or saccular

dilations3. Usually appear distal to

renal arteries


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Aneurysms, continued

4. Measurements abnormal if:

a. External A-P diameter

>3.5 cm in upper abdomenb. > 2.5 cm in distal aorta

5. Patent vessel lumencontains blood, is

echolucent


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6. Thrombus-filled lumen is echogenic

7. Ectatic (dilated) aorta difficult todepict on single scan

8. Associated with arterioscleroticplaque


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9. Excess plaque causes:

a. loss of elasticity

b. weakening in tunica media

c. Tears in tunica interna


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10. Fusiform aneurysms

a. usually project anterior &

to the leftb. path of least resistance

c. Laminar blood flow

absent in dilationd. Eddy currents increase

likelihood of thrombus


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11. Ultrasound is > 95% accurate inidentifying AAA

a. Presence/location & serial growthb. Diameter determination

c. Thrombus presence

d. Incidence of rupture of aneurysmincreases after 7.0 cm


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12. If dilation extends toward SMA, renalarteries may be involved

13. Less common to find aneurysm aboverenal arteries

13. If dilation is above renal arteries,suspect dissecting thoracic aneurysm

14. If dilation extends distally, surveycommon iliac arteries


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B. Aortic Dissection

1. Usually secondary to

dissecting thoracicaortic aneurysm

2. Dilation of abdominalaorta with double

lumen3. Characteristics:

a. Intimal flap

b. Diffuse dilation


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Aortic dissection, continued

4. Pulsations of flap are visible

5. Aneurysms of ascending aortaenlarge 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 materialsb. 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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E. Types of aneurysms

1. Axial involves entire circumference of

artery2. Compoundsome tunics ruptured,

some intact

3. Dilation axial or fusiform; generalenlargement

a. Active growing in diameter

b. Passive wall is stretching

Vascular Pathology, cont


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Types of aneurysms, continued

4. Dissecting splitting, tearing of intima

a. Rarely encircles entire lumen

b. Usually one side onlyc. May involve entire length to

bifurcation

d. Usually originates from thoracicaorta (high B.P.)


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Aneurysms

Berry AneurysmAAA

DissectingAneurysm


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5. Ectatic axial or dilating, butunruptured

6. Endogenous stretched tunica

7. Exogenous due to trauma

8. Fusiform long skinny expansion


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9. False

a. bleeding from

another sourceb. pulsating encapsulated

hematoma

c. fused with aneurysm

d. communicates withlumen of artery


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10. Saccular sac like bulge

a. tunica externa expandedb. tunica intima intact

11. Tubular

a. AKA axial; passive dilationb. Uniform dilation of entire vessel


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12. Varicose

a. result of varicose veins

b. blood containing sac connectingartery & vein

c. seen in antecubital fossa

d. due to repeated IV sticks


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Aneurysms: Summary Views

biol226lec09_ abdominal vessels

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