Small Intestine
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Digestive
- Gastrin
- Pepsin
- Amylase
- Lipase
- Trypsin
- CCK
- Secretin
- GI System
- Ingestion
- Liver
- Bile
- Exocrine Pancreas
- Endocrine Pancreas
- Small Intestine
- Large Intestine
- GI Nervous Control
- Small Intestine
- Function
- Breakdown (digestion) of macromolecules
- Proteins broken down by enzymes (trypsin) into amino acids
- Polysaccharides (starches) and complex sugars broken into simple sugars (e.g. amylase for starches, lactase for lactose, maltase for maltose, etc.)
- Fats emulsified by bile, broken down by lipases into free fatty acids
- Nucleotides broken down by nucleosidases into amino acids
- Absorption of nutrients/water
- Once everything is broken down, they are absorbed by passive diffusion or active transport
- Polar carbohydrates/proteins: secondary active transport
- Nonpolar fats: passive diffusion
- Surface area is maximized for absorption through folds and villi
- Most nutrients → portal blood → liver → bloodstream
- Fat → lymph → bloodstream
- Malabsorption = diarrhea
- Once everything is broken down, they are absorbed by passive diffusion or active transport
- Breakdown (digestion) of macromolecules
- Structure (3 parts)
- Duodenum
- First section
- Most chemical breakdown of food occurs (enzymes)
- Neutralization of stomach acid by bicarbonate
- Jejunum
- Second (middle) section
- Most absorption occurs here
- Ileum
- Third section
- Some vitamins are absorbed here
- Duodenum
- Surface
- Intestinal absorptive cells (enterocytes)
- Contain villi (finger-like cell projections) to maximize surface area for absorption
- Surface of intestine also called “brush-border” due to projections
- Intestinal absorptive cells (enterocytes)
- Function