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Digestive System Mouth Esophogus Liver Stomach Pancreas Large intestine Small intestine Rectum Anus Digestion: Accessory Organs • Liver • Gall Bladder • Pancreas Digestion • The process of PHYSICALLY (mechanically) and CHEMICALLY… Changing the composition of food into simpler substances that your cells can use for growth, repair and maintenance. Digestive System • As food is digested, it passes through a muscular tube leading from the mouth to the (GASTROINTESTINAL TRACT/ GI TRACT). • The GI tract is about 25 to 30 feet in length and each part plays very important functions! Digestion: Physical/Mechanical Changes • Grinding and mixing by teeth (MASTICATION) in the mouth and muscular actions of the stomach and small intestine and… • Liquefying by the addition of water and digestive juices in the mouth, stomach and small intestine Digestion: Chemical Changes • In Chemical Digestion, food is mixed with powerful acids and enzymes! • Complex nutrients are broken down into particles usable by cells: - Polysaccharides and disaccharides to monosaccharides (carb chains) - Proteins to amino acids - Fats to fatty acids to glycerol Chemical Environment of the GI Tract Neutral in mouth - (pH approx 7) Acid in stomach - (pH approx 2) Neutral in small intestine - (pH approx 7) Enzymes •Big food molecules can’t pass through cell walls. •ENZYMES are types of proteins used to break up big molecules into small ones (they act like chemical scissors). •These small molecules can pass through the wall of the small intestine into the blood. They then pass into cells and are used. Big food molecules can’t pass through cell walls. ENZYMES are used to break up big molecules into small ones (they act like These small scissors). molecules can pass through the wall of the small intestine into the blood. Digestion: Mouth • Physical Changes: - First step in digestion - Teeth grind food -Salivary glands add water (99%) • Chemical Changes: -Salivary amylase (digests starch…big sugars) Digestion: Esophagus • Transport tube (10 inches) • Muscular (muscular contractions move the food - peristalsis) • Enables swallowing to move bolus (food) from the mouth to the stomach • No enzymes added • Other tube in the throat region? Digestion: Stomach (3 hrs) • pH Shift • Inflow of gastric juice containing HCL (hydrochloric acid)…almost as strong as battery acid!! • pH rapidly decreases • Mucus (thick fluid) helps soften and lubricate food and protect it from the acids • Protein digestion begins in the stomach as the major gastric enzyme that begins to break down protein is PEPSIN. • The mixture of food and juices is called chyme…and it moves to the SI next!! Digestion: Small Intestine(SI) – 5-14 hours • About 95% of digestion takes place in SI • Coiled and folded • Made of 3 sections: duodenum (12 inches), jejunum (4ft) and ilium (5ft)….can stretch to over 20 feet!! • Peristalsis moves food through the SI • Another pH shift…what happens? • Site of NUTRIENT ABSORPTION!!! • Walls of intestine pleated with folds covered with villi. (increase surface area) Digestion: Large Intestine (aka: colon) – up to 3 days • The small intestine is connected to the large intestine (3-5 feet long in the body…5-6 stretched) • Chyme is very liquid when enters the LI, so main function is to ABSORB WATER!! • Solid wastes called feces leave through the rectum and then finally out the anus (mucus/bile/cells from lining of LI and water) Accessory Organs • Pancreas – gland behind stomach – secretes bicarbonate to neutralize environment of SI, produces 3 digestive enzymes to break down carbs, pro, fat. • Liver – large gland above stomach. Produces digestive juice called bile. (Helps to digest fat) • Gall Bladder – muscular sac that stores bile Match the organ to its function!! Mouth 1. This is where water is absorbed. 2. Makes bile which breaks up fats and it is alkaline to Esophogus give the right pH for the enzymes in the S. intestine. Stomach 3. Makes all 3 enzymes. 4. Mixes the food with enzymes that digest proteins Liver AND contains acid to kill bacteria. 5. Produces more enzymes AND this is where the food Pancreas is absorbed through the gut wall into the blood. Small 6. Chew and mix the food with saliva (contains intestine enzymes). Large 7. Links the mouth to the stomach. intestine 8. Here food that can’t be digested is stored as Rectum faeces and then leaves through the anus. Well Done!!
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