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Let’s continue our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.
Play USMLE Audio MP3 03 14 Anatomy Small Intestine 5 Below
Begin 03 14 Anatomy Small Intestine 5 Transcription
Ok, lets look at the blood supply to the small intestine.
Except for part of the duodenum supplied by a branch from the celiac trunk, what main trunk from the abdominal aorta supplies the entire small intestines?
- The superior mesenteric artery.
Let’s take a look at the abdominal aorta for just a second.
Just as the abdominal aorta comes into the abdomen below the diaphragm, what two arteries does it give off first?
- The right and left inferior phrenic arteries.
Then a main trunk comes off the anterior surface, what is this?
- The celiac trunk.
And at what vertebral level are we at for the origin of the celiac trunk?
- The lower border of the twelfth thoracic vertebrae.
Moving down the abdominal aorta, just slightly below the celiac trunk, what two arteries come off the sides of the abdominal aorta, one of the left one on the right?
- The middle suprarenal arteries.
At about this level a vein passes transversely across the front of the abdominal aorta a little bit below the celiac trunk and the middle suprarenal arteries, what is this vein?
- It is the splenic vein.
The splenic vein is passing form left to right to join to a larger vein, what is the larger veins its joining to?
- The superior mesenteric vein.
Then these two are going to lead into of course what vein?
- The portal vein.
What main trunk comes next off the anterior surface of the abdominal aorta just distal to where the splenic vein crosses?
- The superior mesenteric artery.
And what is the vertebral level for the superior mesenteric artery origin?
- The level of L1, the first lumbar.
What two large arteries are coming off the sides of the abdominal aorta, one on the left one on the right at about this same level perhaps just a tiny bit more distal to the origin of the superior mesenteric?
- The left and right renal arteries.
Now we have another vein crossing transversely across the abdominal aorta just below the superior mesenteric artery, what is this vein?
- The left renal vein.
And as it passes from the left kidney to the right what structure does it join which is to the right and parallel to the abdominal aorta?
- The inferior vena cava.
Inferior to the left renal vein where it crosses underneath the superior mesenteric artery are two small arteries coming off the anterior surface of the abdominal aorta, one slightly on each side of the midline, what do these two?
- These are the left and right ovarian or testicular arteries.
Now we said the origin of the superior mesenteric artery was at what level?
And what small arteries are coming off the back of the abdominal aorta at intervals one on each side?
- The lumbar arteries, starting with the L1 artery.
How many lumbar arteries are there coming off the back of the abdominal aorta one on each side?
- Four. L1 through L4.
Where do the lumbar arteries for L5 come from?
- They are branches from the middle sacral artery.
The middle sacral is also sometimes called?
- The median sacral artery.
In terms fo the architecture of the abdominal aorta, where does the median sacral artery arise?
- On the posterior surface of the aorta just above the level of its bifurcation into the iliac arteries.
At what vertebral level is this bifurcation of the abdominal aorta into the common iliac arteries?
- At about L4.
The median sacral then comes down over the anterior surface of the L5 giving off the L5 lumbar artery branches and then continues down to the sacrum. All right lets go back to the front of the abdominal aorta just to review, we were at the superior mesenteric artery at about L1, at about the same level where the left and right renal arteries came off the sides. And then under the superior mesenteric artery crossing from left to right was the renal vein. And then we come down a little bit and we have two braches coming off either side of midline and these are the ovarian or testicular arteries.
And then we come down much further and to one side of the midline is a smaller main trunk coming off the anterior aspect of the abdominal aorta, what is this next trunk?
- The inferior mesenteric artery.
On which side of midline does the inferior mesenteric artery originate?
- On the left side of the abdominal aorta from the midline.
At what vertebral level are we for the origin for the inferior mesenteric artery?
- At about L3.
And then we come down the front of the abdominal aorta a little more to just above the bifurcation and we see a small artery coming off on one side of midline again, what is this small artery?
- The ureteric branch from the aorta.
And on what side of midline is it?
- It’s on the left also like the inferior mesenteric.
And where is this left ureteric branch going to?
- The left ureter.
What artery that we’ve already looked at is supplying blood through a branch to the right ureter?
- The right ovarian or testicular artery.
And what other main artery is also supplying branches to the right ureter?
- The right common iliac artery.
What organ overlies the front of the abdominal aorta beginning just below the celiac trunk and overlying the superior mesenteric artery, the renal vein all the way down to the origins of the ovarian or testicular arteries?
- This is the pancreas.
What organ then would pass in front of the abdominal aorta just below the level of the origins of the ovarian or testicular arteries?
- The transition from the horizontal to the ascending section of the duodenum.
At what vertebral level is the horizontal and ascending portions fo the duodenum passing in front of the abdominal aorta?
- Pretty much about the area between L2 and L3.
What vessel passes down over the horizontal part of the duodenum where it passes over the abdominal aorta?
- The superior mesenteric artery is descending over that portion of the duodenum.
What artery on the right coming off the side of the abdominal aorta is passing down in front of the inferior vena cava and behind the horizontal portion of the duodenum to the right of the abdominal aorta?
- This is the right ovarian or testicular artery.
****END OF TRANSCRIPTION****
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