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As I understand it, most substances need help to pass through the walls of the intestines.

For example, in hepatic recirculation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2781307/) bile salts are grabbed and transported across the intestinal membranes by particular polypeptides.

Is there a summary of the sorts of things that can be transported across intestinal membranes? For example, hormones, stearates, lipids, etc. What general classes of molecules can pass the membrane and what cannot?

I am not looking for an exact answer, but a general characterization of major classes of organic molecules and their ability to pass through intestinal membranes into the body.

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    $\begingroup$ Your title says abdominal wall, which to me suggests outer muscular layers and/or parietal peritoneam, but your question seems to relate more to the inner epithelial gut tube lining or maybe the visceral peritoneal layers. Could you clarify what layer(s) you specifically are interested in. $\endgroup$ – kmm Mar 9 '18 at 16:17
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Virtually all nutrients from food can be absorbed into blood through the lining of small intestine and colon.

What can be absorbed in the small intestine:

  • Water
  • Simple sugars (monosaccharides): glucose, fructose, galactose...
  • Amino acids and small peptides (dipeptides, tripeptides)
  • Free fatty acids, monoglycerides and cholesterol
  • Minerals: sodium, potassium, iron, etc.
  • Vitamins
  • Nucleic acids
  • Alcohol
  • Various other substances from food (polyphenols, sulfate, oxalate, caffeine, preservatives...)
  • Bile acids
  • Steroid hormones, such as cortisol, aldosterone and sex hormones (JCEM)
  • Drugs
  • Various toxins

What can be absorbed in the colon:

  • Water
  • Short-chain fatty acids (from bacterial fermentation of dietary fiber and sugar alcohols)
  • Sodium, potassium and some other electrolytes

What cannot be absorbed in the intestine:

  • Polysaccharides (such as starch), oligosaccharides, disaccharides
  • Dietary fiber (soluble fiber can be fermented and the resulting substances can be absorbed in the colon)
  • Whole proteins and big peptides
  • Triglycerides, diglycerides
  • Peptide hormones, such as insulin, glucagon, calcitonin, prolactin, growth hormone and parathyroid hormone (Cambridge Core)

Sources:

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This table from Ganong's medical physiology will help you get your answer.

enter image description here

I hope it helps.

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