Download Digestion, Absorption, Metabolism, and Excretion

Digestion, Absorption, Metabolism, and
Excretion
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Chapter 9
J Pistack MS/Ed
Digestion
 Food is broken down mechanically and chemically
in the gastrointestinal tract
 Takes place in the alimentary canal
 Aided by “accessory” organs
Absorption
 Occurs when ingested food is broken down during
digestion into chemicals the body can use
 Metabolism – the some of all physical and chemical
changes that take place in the body
Excretion
 The elimination of anything the body cannot use
Alimentary Canal
 Oral cavity
 Pharynx
 Esophagus
 Large intestine
 Small intestine
 Stomach
Accessory Organs
 Located outside the alimentary canal and are
considered part of the digestive system
 Liver—produces bile
 Gall bladder—stores bile
 Pancreas—secretes enzymes
Liver
 Second largest organ
 Liver—produces bile
 Bile exits the liver through the hepatic bile duct
Gall bladder
 Gall bladder – concentrates and stores bile until it is
needed in the small intestine
 Delivered to the small intestine through the common
bile duct
 2~3 cups are secreted daily
Pancreas
 Pancreas—secretes enzymes involved with digestion
of all energy nutrients
 Secretions are known as pancreatic juice
 Arrives in the small intestine through the pancreatic
and common bile duct
Digestive Action
 Mechanical—physical “breaking down” of food:
mastication, peristalsis
 Chemical—chemical “breaking down” of food:
enzymes, hydrolysis
 Digestive enzymes are present in
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Saliva
Gastric juice
Pancreatic juice
Intestinal juice
End Products
 4 to 6 hours after a meal: body has broken down the
food into some trillion molecules
 Carbohydrates = monosaccharides
 Fats = glycerol, fatty acids, monoglycerides
 Protein = amino acids and small peptides
Alimentary canal
 No digestion takes place in the pharynx or esophagus
 Food enters the stomach from the esophagus through
the cardiac sphincter
Alimentary canal
 Stomach
 Constructed with rugae for expansion
 Contains HCl, mucus, and the enzymes pepsin, rennin,
and gastric lipase
 Churning action of the stomach mixes food with
gastric juices to produce chyme
 Peristaltic motion pushes the chyme out of the
stomach through the pyloric sphincter
Alimentary canal
 Small intestine
 About 20 feet long
 Made up of the duodenum, jejunum, and ileum
 90% of the digestive action and nearly all end product
absorption occur in the small intestine
 Emulsification – a process of breaking down non
soluble fats - takes place in the small intestine
Elimination/Excretion
 Solid waste products are eliminated as feces via the
alimentary canal
 Liquid wastes are excreted in urine via the kidneys and
bladder
 Some liquid wastes are excreted via perspiration
through the skin
 Carbon dioxide is exhaled via the lungs
Illnesses
 Steatorrhea—malabsorption of fat
 Food allergies—sensitivity; some life threatening
 Celiac disease—gluten sensitivity; leads to
malabsorption
 Lactose intolerance—deficient in lactase enzyme;
leads to digestive difficulties
Reintroducing Food After Illness
 Decreased or no food intake occurs for a variety of
reasons: flu, stomach virus, etc.
 Always encourage liquids to prevent dehydration
 Can be done with clear liquids in small sips
 Patients may experience abdominal cramping and
diarrhea on reintroducing food
Surgery of the Alimentary Canal
 A variety of illnesses may warrant part of alimentary
canal resection
 This causes problems for the patient with
malabsorption of necessary nutrients
 This is also being done in some cases as a weight loss
procedure—bariatric-stomach pouching, resection
Learning Objectives
 List the anatomic structures of gastrointestinal (GI)
tract
 Describe dietary treatments: lactose intolerance, food
allergies, and gluten sensitivity
 List the ways the body eliminates waste