Abdominal aorta structure, segments of aorta, branches of aorta.

1. Abdominal Aorta

2. Abdominal Aorta
The abdominal aorta is the largest
artery in the abdominal cavity. As
part of the aorta, it is a direct
continuation of the descending aorta
(of the thorax).

3. Structure of Abdominal Aorta:-
The abdominal aorta begins at the level of the diaphragm, crossing it via the
aortic hiatus, technically behind the diaphragm, at the vertebral level of T12.[1] It
travels down the posterior wall of the abdomen, anterior to the vertebral column.
It thus follows the curvature of the lumbar vertebrae, that is, convex anteriorly.
The peak of this convexity is at the level of the third lumbar vertebra (L3). It runs
parallel to the inferior vena cava, which is located just to the right of the
abdominal aorta, and becomes smaller in diameter as it gives off branches. This is
thought to be due to the large size of its principal branches. At the 11th rib, the
diameter is 122mm long and 55mm wide and this is because of the constant
pressure.

4. Segments of Aorta:
The abdominal aorta is clinically divided into
2 segments:
The suprarenal abdominal or paravisceral
segment, inferior to the diaphragm but
superior to the renal arteries.
The Infrarenal segment, inferior to the renal
arteries and superior to the iliac bifurcation.

6. Branches of Abdominal Aorta:-
The abdominal aorta supplies blood to much of the
abdominal cavity. It begins at T12 and ends at L4 with
its bifurcation into the common iliac arteries and
usually has the following branches :-
● 3 single anterior visceral branches (coeliac,
superior mesenteric artery, inferior mesenteric
artery)
● 3 paired lateral visceral branches (suprarenal,
renal, gonadal)
● 5 paired lateral abdominal wall branches (inferior
phrenic and four lumbar)
● 3 terminal branches (two common iliac arteries
and the median sacral artery)

7. Branches :-
● Inferior phrenic arteries: Paired parietal arteries arising
posteriorly at the level of T12. They supply the
diaphragm.
● Coeliac artery: A large, unpaired visceral artery arising
anteriorly at the level of T12. It is also known as the
celiac trunk and supplies the liver, stomach, abdominal
oesophagus, spleen, the superior duodenum and the
superior pancreas.
● Superior mesenteric artery: A large, unpaired visceral
artery arising anteriorly, just below the celiac artery. It
supplies the distal duodenum, jejuno-ileum, ascending
colon and part of the transverse colon. It arises at the
lower level of L1.

8. Branches:-
● Middle suprarenal arteries: Small paired visceral
arteries that arise either side posteriorly at the level
of L1 to supply the adrenal glands.
● Renal arteries: Paired visceral arteries that arise
laterally at the level between L1 and L2. They
supply the kidneys.
● Gonadal arteries: Paired visceral arteries that arise
laterally at the level of L2. Note that the male
gonadal artery is referred to as the testicular artery
and in females, the ovarian artery.

9. Branches:-
● Inferior mesenteric artery:-A large, unpaired visceral
artery that arises anteriorly at the level of L3. It
supplies the large intestine from the splenic flexure to
the upper part of the rectum.
● Median sacral artery:-An unpaired parietal artery that
arises posteriorly at the level of L4 to supply the
coccyx, lumbar vertebrae and the sacrum.
● Lumbar arteries:-There are four pairs of parietal
lumbar arteries that arise posterolaterally between the
levels of L1 and L4 to supply the abdominal wall and
spinal cord.

11. Relations :-
The abdominal aorta lies slightly to the left of the midline of the body. It is covered, anteriorly, by the
lesser omentum and stomach, behind which are the branches of the celiac artery and the celiac plexus;
below these, by the lienal vein (splenic vein), the pancreas, the left renal vein, the inferior part of the
duodenum, the mesentery, and aortic plexus.
Posteriorly, it is separated from the lumbar vertebræ and intervertebral fibrocartilages by the anterior
longitudinal ligament and left lumbar veins.
On the right side it is in relation above with the azygos vein, cisterna chyli, thoracic duct, and the right
crus of the diaphragm—the last separating it from the upper part of the inferior vena cava, and from
the right celiac ganglion; the inferior vena cava is in contact with the aorta below.
On the left side are the left crus of the diaphragm, the left celiac ganglion, the ascending part of the
duodenum, and some coils of the small intestine.

12. Relationship with inferior vena cava:-
The abdominal aorta's venous counterpart, the inferior
vena cava (IVC), travels parallel to it on its right side.
Above the level of the umbilicus, the aorta is somewhat
posterior to the IVC, sending the right renal artery
travelling behind it. The IVC likewise sends its opposite
side counterpart, the left renal vein, crossing in front of the
aorta.
Below the level of the umbilicus, the situation is generally
reversed, with the aorta sending its right common iliac
artery to cross its opposite side counterpart (the left
common iliac vein) anteriorly.

14. Abdominal Aortic Aneurysm:-
Abdominal aortic aneurysm (AAA or triple A)[6] is
a localized enlargement of the abdominal aorta such
that the diameter is greater than 3 cm or more than
50% larger than normal diameter.[1] They usually
cause no symptoms except when ruptured.[1]
Occasionally, abdominal, back, or leg pain may
occur.[2] Large aneurysms can sometimes be felt by
pushing on the abdomen.[2] Rupture may result in
pain in the abdomen or back, low blood pressure, or
loss of consciousness, and often results in death.

15. Signs and symptoms of abdominal aortic
aneurysm:-
The vast majority of aneurysms are asymptomatic. However, as
abdominal aortic aneurysms expand, they may become painful
and lead to pulsating sensations in the abdomen or pain in the
chest, lower back, or scrotum.[15] The risk of rupture is high in
a symptomatic aneurysm, which is therefore considered an
indication for surgery. The complications include rupture,
peripheral embolization, acute aortic occlusion, and aortocaval
(between the aorta and inferior vena cava) or aortoduodenal
(between the aorta and the duodenum) fistulae. On physical
examination, a palpable and pulsatile abdominal mass can be
noted. Bruits can be present in case of renal or visceral arterial
stenosis.

16. Bibliography:-
1. Lech, Christie; Swaminathan, Anand (November 2017). "Abdominal aortic
emergencies". Emergency Medicine Clinics of North America. 35 (4): 847–867.
doi:10.1016/j.emc.2017.07.003. PMID 28987432.
2. Jim, Jeffrey; Thompson, Robert W. "Clinical features and diagnosis of abdominal
aortic aneurysm". UpToDate.
3. Jang, Timothy (28 August 2017). "Bedside ultrasonography evaluation of abdominal
aortic aneurysm—technique". Medscape.