The Digestive System-nutrition

THE DIGESTIVE SYSTEM

Dig est io n  The process whereby food is broken down into smaller parts, chemically change and moved into the gastrointestinal system.

Mechanical Digestion  Food is broken down into smaller pieces by the teeth  It is then moved along the gastrointestinal tract through the esophagus, stomach and intestines  Movement is caused by rhythmic contraction of the muscular walls of the tract PERISTALSIS

Chemical digestion  Chemical changes occurs through the addition of water and the resulting splitting, or breaking down of the food molecules. HYDROLYSIS Hydrolysis involves digestive enzymes – act on food substances, causing them to break down into simple compounds

Dig est io n in t he Mo uth  Teeth and tongue begin digestion by breaking food into smaller pieces  Salivary Glands begi chemical digestion as salivary amylase begins to change starch to Dextrin and Maltose

Dig est io n in t he st oma ch Hydrochloric acid prepares the gastric 

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area for enzyme action Pepsin, produced first as inactive precursor to pepsinogen, then activated by HCL In infants, enzyme Rennin casein to coagulated curd (breaks milk protein) Lipase acts on emulsified fats Tributyrinase

Di gesti on on the Small intesti ne produces bile stores bile and releases it into small intestine to emulsify fats Produce enzymes, then are released into the small intestine

Carbohydrates: Pancreatic Amylase – AMYLOPSIN  Converts starch to dextrin and Maltose Intestinal Juices that contain enzymes:  Lactase, Sucrase and Maltase  Converts disaccharide to monosaccharide

Fat  Pancreatic lipase – turn triglycerides to digyceride and monoglyceride to fatty acids and glycerol  Bile Salt – emulsifies fats

Protein Pancreatic Proteases:  Trypsin – converts proteins, proteases and peptones to polypeptides and peptides  Chrymotypsin – converts proteases and peptones to polypeptides and dipeptides also coagulates milk  Carboxypeptidase – converts simpler peptides, dipeptides and amino acids Amiinopeptidase – converts polypeptides to peptides and amino acids Dipeptidase – converts dipeptides to amino acids

The Large intestine  Absorbs water and some other nutrients, and collects food residue for excretion

ABS ORPTI ON Is the passage of nutrients into the blood or lymphatic system Small Intestine  Villi absorbs nutrients from the chyme, then transferred them to the bloodstream  Glucose, fructose, galactose,amino acids, minerals and some water soluble vitamins are absorb by the capillaries  Fructose and galactose are carried to the liver – converted to glucose  Lacteals absorbs glycerol and fatty acids in addition to fat soluble vitamins

Large Intestine  Absorbs water  Synthesize some B vitamins and vitamin K (essential for blood clotting)  Collect food residue – food that cannot be digested and absorb (dietary fiber)

MET ABOL IS M  Nutrients are carried by the blood to the cells of the body, within the cell, nutrients are changed into energy through a process  Governed by hormone secretions

 Thyroxine and Triiodothyronine – stimulates metabolism  Calcitonin – reduces blood calcium level  Anti-diuretic Hormone – promotes retention of water  Lipotropin – release and oxidation of fats from adipose tissue  Parathyroid hormone – raises blood calcium level  Aldosterone – promote reabsorption of Na and K in kidneys,

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Insulin – reduces blood glucose Glucagon – raises blood glucose Gastrin – stimulates glands to release HCL Secretin – increase release of bile Cholecystokenin – stimulates release of enzyme rich juice in the pancreas