Vessels of the intestine

29 Vessels of the intestine



29.1 Anatomy



29.1.1 Generalities



Irrigation


At rest, intestinal irrigation represents 27% of total body irrigation. This percentage is very important considering that the heart, for example, draws on only 3–4% of total blood flow.



Intrinsic innervation of the intestine


The innervation of the intestine is monitored by local reflexes of the autonomic nervous system. About 100 million nerve fibers constantly inform the brain about the functioning of the small intestine.


The vagus nerve innervates the digestive tract from the esophagus to halfway along the transverse colon. Beyond the halfway mark, the transverse colon is supplied by the sacral sympathetic nerves. We will refer to this part of the colon where the innervation changes, as the Cannon–Böhm zone.


The vascular system itself is under the control of the sympathetic system.



Endogenous reflexes of the intestine


Peristaltic reflexes are triggered by tension receptors, chemoregulators, and mechanoreceptors of the digestive tract. There are many pacemaker cells in the transverse colon, making the organ particularly interesting to manipulate (Fig. 29.1).


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Fig. 29.1A The enteric nervous system.


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Fig. 29.1B The enteric nervous system (longitudinal view).



Hormonal control


The more that is learned about the physiology of the small intestine, the more complex it appears to be. In addition to local autonomic nervous system control, hormones regulate the organ as it adapts to the workings of the digestive tract. For example, vasoactive intestinal peptide (VIP) releases the smooth muscles and increases circulation. Acetylcholine levels rise considerably in the circulating blood after eating.



Immune defense function


Peyer’s patches provide local intestinal immune protection, as well as helping to defend the whole body. They secrete immunoglobulins A. In newborns, the mucosa of the digestive tube is protected by the immunoglobulins in the mother’s milk.



29.1.2 Vascular anatomy


The vascularization of the small intestine and colon is derived from both the superior and the inferior mesenteric arteries. The change occurs beyond the duodenojejunal junction. We will begin with a description of these two arteries.



Superior mesenteric artery


The superior mesenteric artery (Fig. 29.2) nestles against the medial surface of the duodenojejunal junction, at the level of L1. This junction projects on the mid-clavicular–umbilical line, about three fingerwidths above the umbilicus.


image

Fig. 29.2 Superior mesenteric artery.



Origin and course


The superior mesenteric artery:



• originates from the abdominal aorta opposite L1


• is about one vertebral body height lower than the celiac trunk


• runs beneath the caudal border of the pancreas, where it is easily located


• is situated higher and to the right of the inferior mesenteric artery


• is more superficial than the inferior mesenteric artery, and thus easier to palpate.



Collaterals


The superior mesenteric artery gives off these branches:



• middle colic


• right colic


• ileocolic


• jejunal and ileal.



Termination


The superior mesenteric artery terminates by innumerable arterioles that irrigate the small intestine and colon. These arterioles often run perpendicular to the various parts of the small intestine and colon they perfuse.



Comments


The superior and inferior mesenteric arteries anastomose with the middle colic and left colic arteries (Fig. 29.3).


image

Fig. 29.3 Anastomoses of the superior and inferior mesenteric arteries.


The first jejunal artery, branching from the superior mesenteric artery, anastomoses with the pancreaticoduodenal artery. This illustrates the vascular interdependence of these organs and shows that vascular manipulation of the pancreas engages the small intestine.



Aorta mesenteric clamp


In certain cases, the superior mesenteric artery can clamp the left renal vein against the aorta and produce lumbago and lumbar sciatic pain more commonly on the left (Fig. 29.4). The left kidney can also be affected by constriction of the superior mesenteric artery. In addition to local pain, lymphatic venous problems can involve the urogenital system. When the compression is severe, surgery is indicated.


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Fig. 29.4 Aortic–mesenteric arterial tree.



Inferior mesenteric artery



Origin


The inferior mesenteric artery arises from the left anterolateral aspect of the aorta, often just above and to the left of the umbilicus. In relation to the superior mesenteric artery, it is smaller and is situated lower, deeper, and to the left. It originates at the level of the third or fourth lumbar vertebra.



Course


As the inferior mesenteric artery descends from the aorta, it makes a large curve to the left. It then runs caudally and to the right, ending at the anterior surface of the sacrum, at the level of the third sacral segment.


It is covered by the peritoneum and rests in succession on the:



• aorta


• psoas muscle


• common iliac artery.



Collaterals


The principal branches of the inferior mesenteric artery are the:



• left colic artery, which by its ascendant branch anastomoses with the middle colic artery, a division of the superior mesenteric artery


• sigmoid arteries


• superior rectal arteries.



Termination


The inferior mesenteric artery terminates in numerous arterioles that irrigate the colon and rectum.



29.2 Manual approach



29.2.1 Generalities



Arterial irrigation of the jejunoileum


Unlike the caudal part of the duodenum, the jejunum and ileum are both intraperitoneal.


The loops of the jejunoileum are fixed to the body wall by a mesentery, measuring about 20 cm at its peritoneal root, and up to 4 m in length at its intestinal attachment.


Beyond the duodenojejunal flexure the small intestine becomes intraperitoneal. The jejunum comprises two-fifths of the small intestine, and the ileum accounts for three-fifths.


Remember that the muscle of Trietz, in addition to positional and suspensory roles, serves to protect the gastroesophageal junction, the celiac trunk, and the superior mesenteric artery.

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Nov 7, 2016 | Posted by in MANUAL THERAPIST | Comments Off on Vessels of the intestine

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