Digestion is the process by which food is broken down in the intestinal lumen

Digestion is the process by which food is broken down

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Digestion is the process by which food is broken down in the intestinal lumen to its basic units Dietary polysaccharides are digested and absorbed as monosaccharides. Insulin nor glucagon play a role in the promoting digestion or absorption of glucose in the small intestine. Thyroxine, the hormone released by the thyroid, promotes increased intestinal absorption of glucose which enhances the level of blood glucose. Almost any kind of small intestine disorder may result in at least a temporary disaccharidase deficiency. Therefore, glucose metabolism is affected by any disorder affecting the synthesis, release, or activity of the enzymes responsible for the digestion of carbohydrates within the small intestine. The type and severity of glucose malabsorption is dependent on the specific enzyme defect. Liver
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The liver is the main storage site for glucose (as glycogen) It is the glycogen in the liver that is broken down to glucose and then can be transported to the bloodstream via the enzyme, glucose-6- phosphatase. This enzyme is associated with the liver hepatocyte and not with muscle. Normally as much as 25% of the blood glucose is maintained via the metabolic pathway called gluconeogenesis. The liver accounts for 90% of this production. Kidney The kidneys are also capable of providing glucose to the circulation from relatively small glycogen stores, and this is done particularly during fasting states Reabsorption of glucose which has been filtered by the glomeruli. This is one of the proximal tubular functions. There are limits to the amount of any substance that the tubules can reabsorb, and its reabsorption is obviously dependent on the concentration of that substance. This limit is called the renal threshold concentration or tubular maximum for that substance (Tm). The renal threshold for glucose for most healthy individuals is approximately 10 mmol/L. Therefore, when the blood glucose level is greater than 10 mmol/L, glucose will appear in the urine (glucosuria). The glucose molecule also exerts an osmotic effect in the kidney tubules that can result in an osmotic diuresis. Tubular defects can also result in deceased ability of the tubules to reabsorb glucose. Under these conditions, glucosuria occurs, but the blood glucose is often within the normal reference limits. Muscle Muscles contain the largest amount of stores glycogen The major fuels for metabolic activity are glucose from glycogen, free fatty acids, and ketone bodies. The glycogen in muscle is used locally and is not available as a direct supply of glucose since muscle lacks the enzyme necessary to transport glucose out of the cell into circulation. The glycogen in muscle is broken down during energy demands to lactate. This lactate is transported to the liver and can be converted to glucose by the liver in the Cori cycle.
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The Fasting State Metabolic pathways are reversed during a period of fast as compared to the well-fed state.
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