How are the digestion products of carbohydrates, such as glucose, galactose, and fructose, absorbed through the intestine?
The three terminal products of carbohydrate digestion are transported through the enterocyte brush border membrane via facilitative transporter proteins such as the sodium-glucose cotransporter 1 (SGLT1), glucose transporter 2 (GLUT2), and glucose transporter S (GLUTS). There is evidence of overexpression of these transporters, particularly SGLTl, in diabetes and obesity, and new therapeutic approaches for these conditions are designed to inhibit these transporters.
What does the "enterohepatic circulation" refer to?
Bile acids act as detergents which increase the solubility oflipid micelles which are taken up by the brush border membrane of the jejunum, where over 90% of fat is absorbed. The bile acids themselves remain in the intestinal lumen and are reabsorbed in the distal ileum where they enter the portal venous circulation and are re-secreted in the bile.
The secretin-glucagon family of gut hormones includes all of the following structurally related peptides EXCEPT:
Peptide hormones produced by enteroendocrine cells of the intestine are grouped into families based on their amino acid structural similarity. The secretin-glucagon family of hormones includes glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), growth hormone-releasing hormone (GHRH), and pituitary adenylyl cyclase-activating peptide (PACAP).
The most common cause of small bowel obstruction is:
Intra-abdominal adhesions related to prior abdominal surgery accounts for 75% of cases of small bowel obstruction. Cancer-related small bowel obstruction is almost always due to extrinsic compression or entrapment of the bowel by a primary or metastatic tumor; primary small bowel malignancies are rare.
A closed-loop obstruction is particularly dangerous because:
A closed-loop obstruction, in which an intestinal segment is obstructed both proximally and distally, as in a volvulus, is particularly dangerous because intraluminal pressure rises quickly and can cause venous congestion and arterial obstruction which leads to necrosis of the intestinal wall and perforation. It classically presents with "pain out of proportion to the physical exam;' and is usually apparent on CT scan which frequently shows a U -shaped or C-shaped dilated bowel loop associated with a radial distribution of mesenteric vessels converging toward a torsion point.
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