Med Oradea - Anatomy II - Digestive System - Large Intestine And Rectum

The major source of blood supply is from the superior and inferior mesenteric arteries.

The upper mesenteric gives off 3 branches: ileo-colic, right colic, and middle colic. The right colic supplies the first 2/3 of the transverse colon.

Regarding the anterior and posterior cecal arteries, they are from the ileocolic artery, together with the ascending colic, apendicular, and ileal arteries.

The sigmoid trunk is a branch of the lower mesenteric. The left colic is the other branch, and it gives off its own ascending and descending branches (the ascending for the last 1/3 of the transverse colon, and the descending branch of course to the descending colon).

The sigmoidean trunk gives off upper, middle, and lower branches

B and C are wrong. The upper mesenteric plexus does receive parasympathetic nerve fibers from the celiac plexus, but the parasympathetic fibers do not synapse there- remember parasympathetics tend to synapse in the walls of the target organ. So they are just passing through the celiac on the way to the upper mesenteric (and from there will synapse in the cecum).

Regarding option C, it's kind of a trick question. The thoracic splanchnic nerves form the celiac plexus, which gives off fibers to the upper mesenteric. Think about the order of formation- the thoracic splanchnics come before the upper mesenteric, so they couldn't "join" the upper mesenteric (because without those nerves the upper mesenteric plexus doesn't exist). By the way, the superior mesenteric plexus does receive a branch from the vagus nerve.

The urinary bladder is in front of the rectum, not behind (in women, it's in front of the vagina/uterus)

C is wrong because the cowper glands are in front of the perineal part, not behind the pelvin part. These glands only exist in men.

D is wrong because the levator ani muscle is behind the perineal part, and the pudendal vessels and nerves are lateral of the pudenal part.

A is correct - the left colic and sigmoidean trunk are branches from the lower mesenteric, which supplies the left colon

B is wrong - the sigmoidean trunk branches into the upper, middle, and *lower* sigmoidean arteries

D is wrong- the duodenojejunal flexure is below

Option B is almost correct- the haustrae are actually delimited from each other by transversal grooves. The rest is OK.

Option D is also nearly correct, but the vessels and nerves are in the submucous. The mucous layer has Lieberkuhn glands and lymphoid formations

There are 3 Houston valves, the first on the left, the second on the right, and the third back on the left

The large intestine is between the ileocecal valve to the rectum region, that's true, but it's at the level of S3, not S4. It has 7-8cm in diameter, decreasing to 3-3,5cm in the distal part. It presents teniae coli, haustrae coli, and epiploic *appendages*

A is wrong - the rectum is at S3

The sigmoid has 4 divisions: fixed (iliac colon), mobile, and rectosigmoidean. The 2nd and 3rd parts form the pelvin colon

The ileocolic artery has several branches, including the anterior cecal, posterior cecal, and appendicular

The ileocolic veins drain to the upper mesenteric and from there to the portal vein

Think about the angle of the transverse colon- it's inclined upwards to the left. So the descending colon logically is longer than the ascending and B must be wrong.

A is incorrect - the 2nd and 3rd parts together are the pelvin colon
B is incorrect - the first part is fixed, the 2nd part is mobile

The cecum is from the ileocelcal valve to the *right* iliac fossa. Think about where appendicitis pain presents itself- on the right, not the left.

Option B is wrong- the cecum doesn't have any haustrae

The appendix is below the ileocecal valve (normally) and has approximately 9cm.

It should have been clear from the question that the upper mesenteric plexus supplies whatever the upper mesenteric artery vascularizes. Option D is correct because the celiac plexus innervates all of those organs - and the celiac plexus is the source of the upper mesenteric.

The Houston valves are on the inner surface

The sacral flexure is the first part - it's concavity is forwards.

A is wrong- the bladder is in front of the pelvin part

The colon has right and left colic flexures, also called the hepatic (right) and splenic (left)

E is tricky. The duodenum and pancreas are behind the transverse colon. The liver is above.

A is almost correct- the iliac part has relations behind with the iliac muscle, genital vessels, and iliac vessels, but not with the uterus (the uterus is behind the pelvin part)

The small intestine is indeed behind the pelvin part, but it's the left, not the right iliac vessel that is behind it.

A is very nearly correct, but in fact the right colon includes the first 2/3 of the transverse colon. The left colon has only the final 1/3 of the transverse

If you've done some the other quizzes before this one, then you might have thought C was wrong. But in fact the colon receives parasympathetic innervation from both the vagus and pelvic splanchnic nerves (via several nerve plexi). Ordinarily, the splanchnic nerves are sympathetic fibers, however in the case of the colon, it receives part of its innervation from pelvic splanchnic nerves - the pelvic splanchnics are unusual because they are actually parasympathetic nerves. So C is correct.

D is incorrect. The celiac plexus supplies the abdominal aortic plexus which in turn supplies the lower mesenteric plexus. The celiac plexus does supply the upper mesenteric plexus.

The vagus provides parasympathetic innervation to everything before and including the proximal 2/3 of the transverse colon. The distal 1/3 of the transverse colon and everything afterwards receives parasympathetic innervation from the pelvic splanchnic nerves.

The rectum has a pelvic and perineal part

The rectum is supplied by 3 arteries: upper, middle, and lower hemorrhoidal. The upper is from the lower mesenteric artery, the middle is from the internal iliac (hypogastric) artery, and the lower is from the internal pudendal artery (a branch of the internal iliac)

Try not to get confused here. There are 3 veins draining the rectum: upper, middle, and lower hemorrhoidal.

Two of these drain to the caval system, and one drains to the portal system. Let's take a look:

Upper hemorrhoidal -> Inferior mesenteric -> Splenic -> Portal

Middle hemorrhoidal -> internal iliac -> inferior vena cava
Lower hemorrhoidal -> internal pudendal -> internal iliac -> inferior vena cava