Digestive System Physiology

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Digestive System Physiology
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Overall Steps

1. Ingestion
2. Secretion (of enzymes)
3. Digestion
4. Absorption
5. Elimination

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Mechanical Digestion

• Mastication- chewing
• Deglutination- swallowing
• Peristalsis Segmentation

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Chemical Digestion

• Enzymes work to digest food by hydrolysis
• The function with a negative feedback loop
• They are continually being eliminated
• The have specific pH under which they function
• Examples
• amylase, slightly acidic in saliva
• pepsin, highly acidic stomach

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Chemical Digestion Chemical Digestion Chemical Digestion
Location Digestive juices and Enzymes Substance Digested
Mouth (Saliva) Amylase Starch (polysaccharides)
Stomach (Gastric juice) Pepsin (protease) Proteins
Stomach (Gastric juice) HCL Proteins
Pancreatic juice Trypsin (protease) Proteins
Pancreatic juice Lipases Fats, lipids
Pancreatic juice Amylase Starch
Intestinal Enzymes Peptidases Peptides, proteins
Intestinal Enzymes Sucrase Sucrose
Intestinal Enzymes Lactase Lactose
Intestinal Enzymes Maltase Maltose
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Chemical Digestion Chemical Digestion Chemical Digestion
Location Digestive juices and Enzymes Substance Digested
Mouth (Saliva) Amylase Starch (polysaccharides)
Stomach (Gastric juice) Pepsin (protease) Proteins
Stomach (Gastric juice) HCL Proteins
Pancreatic juice Trypsin (protease) Proteins
Pancreatic juice Lipases Fats, lipids
Pancreatic juice Amylase Starch
Intestinal Enzymes Peptidases Peptides, proteins
Intestinal Enzymes Sucrase Sucrose
Intestinal Enzymes Lactase Lactose
Intestinal Enzymes Maltase Maltose
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Macromolecule Digestion

• Starches(carbohydrates)?monosaccharides(glucose)
• Proteins(polypeptides)? amino acids
• Lipids ? fatty acids, glycerols

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Nutrient Digestion
Nutrients
include
include
are made of
include
include
are made using
such as
such as
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Emulsification of Fats
Micelle (fat droplet in water)

• Fats are insoluble in water and must be broken
  down into small droplets, or emulsified
• Lecithin and bile salts found in bile both act as
  emulsifying agents
• Micelles, tiny fat droplets are formed with lots
  of surface area
• Lipases from pancreatic enzymes can then
  breakdown fats

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Digestive Secretions

• Saliva is mostly water but also contains
  digestive enzymes
• Mucus is a mixture of water and glycoproteins
• Chief cells in stomach secrete gastric
  enzymes(pepsin)
• Parietal cells secrete HCL (activates pepsin) and
  intrinsic factor into the stomach

Enzyme Function http//www.youtube.com/watch?vAFb
PHlhI13g
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Absorption

• Stomach
• 20 alcohol
• Aspirin
• Small Intestines
• Ca, Mg, Fe
• Glucose
• Vitamins, Na, K, B12
• 80 alcohol
• Fats
• H2O
• Colon
• Na, K
• H2O
• Rectum
• Elimination of feces

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Elimination

• Defecation is the process of eliminating feces
• Defection reflex is triggered by a filling of the
  rectum
• Constipation results of slow movement of feces
  causes a high rate of water absorption
• Diarrhea is caused by a rapid movement of stool
  that does not allow for absorption of water, can
  be fatal is severe and untreated

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• Page 788

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Disorders of the Digestive System

• Gastroenteritis- inflammation of the stomach
• Anorexia- chronic loss of appetite
• Emesis- vomiting

• Nausea- unpleasant feeling before vomiting
• Diverticulosis- saclike pouches in the intestines
  that can become inflamed and infected.

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Disorders of the Digestive System

• Ulcer- open wound or sore in the stomach or small
  intestine, Caused by H. pylori
• Irritable bowel syndrome, IBS- (spastic colon)
  stress causes diarrhea or constipation
• Cirrhosis- when the liver is damaged faster than
  it can regenerate it develops scar tissue.