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Bio20B_Lecture4 - Bio 20B Continue Digestion Respiratory...

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Bio 20B: April 12, 2007 Continue Digestion Respiratory and Gas Exchange Freeman Fig. 43.6 (Figure on digestive tract and digestive system) o Know the organs part that are part of tract and system Gastro-intestinal Tract o One long tube o Contraction of these muscles propels food through the tube Contraction = peristalsis (2 to 25 cm per sec) o Mouth and Esophagus Mix food with saliva Contains: (Know these) Mucin: slippery, lubricates food Lipase: Fat breakdown Salivary Amylase: carbohydrate digestion o Digestive Compartments Most animals process food in specialized compartments These compartments reduce risk of self-digestion Esophagus, Crop, Stomach, Gizzard, Intestine, Anus o Stomach: like a sack with lots of folds, can expand and contract with amount of food Food mixed with acid, mucus and pepsin Controlled release to duodenum Receptive Relaxation: stomach stretches to accommodate 2 liters of food and fluid Protein digestion occurs here Muscles of stomach contract to churn contents Stomach mucosa contains many glands to secrete: Mucus: protect stomach wall from acids (ulcers are bacterial) Hydrochloric Acid: kills bacteria and activates protein digestion by lowering pH for pepsin to work Pepsinogen: converts to pepsin (breaks down protein) with addition of HCl (lower pH) Fig. 43-10B You can’t store pepsin because it would ‘digest’ protein that is used to store it (digest your stomach)
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Cow digestive system Freeman Fig. 43.11 o
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