Digestive System and Nutrition

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• Digestive System and Nutrition

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Outline

• The Digestive Tract
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Accessory Organs
• Nutrition
• Eating Disorders

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The Digestive Tract

• Roof of the mouth composed of two parts.
• Anterior hard palate.
• Posterior soft palate.
• Tonsils help protect against infection.
• Three pairs of salivary glands send juices
  through ducts to the mouth.
• Saliva contains bicarbonate and salivary amylase.

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Digestive Tract
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The Digestive Tract

• Teeth used to chew food into pieces small enough
  to swallow.
• Each tooth has two main divisions.
• Crown.
• Root.
• Tongue mixes chewed food with saliva and forms a
  bolus in preparation for swallowing.

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Adult Teeth and Mouth
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The Pharynx

• The pharynx receives air from the nasal cavities
  and food from the mouth.
• Swallowing is a reflex action that occurs in the
  pharynx.
• Soft palate moves to close off nasopharynx, and
  the trachea moves under the epiglottis to cover
  the glottis.

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Swallowing
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The Esophagus

• The esophagus is a muscular tube that passes from
  the pharynx through the thoracic cavity and
  diaphragm into the abdominal cavity.
• Rhythmic peristalsis pushes food along the
  digestive tract.
• Sphincters encircle tubes and act as valves.

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The Wall of the Digestive Tract

• Layers.
• Mucosa - Mucus membrane layer.
• Submucosa - Submucosal layer.
• Muscularis - Smooth muscle layer.
• Serosa - Serous membrane layer.

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Wall of the Digestive Tract
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The Stomach

• Stomach stores food and aids in digestion.
• Columnar epithelial lining contains gastric pits
  leading into gastric glands.
• Produce gastric juice containing enzyme pepsin.
• Walls of stomach have folds which help churn and
  mix food and gastric juices.
• Chyme leaves the stomach and enters the small
  intestine.

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Stomach Anatomy
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The Small Intestine

• The small intestine is the primary site for
  nutrient absorption.
• Receives bile from liver to emulsify fat.
• Walls contain villi which increase surface area
  and thus absorptive capability.
• Nutrients are eventually transported into the
  cardiovascular system and fats are transported
  into the lymphatic system.

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Small Intestine Anatomy
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Regulation of Digestive Secretions

• Secretion of digestive juices is promoted by the
  nervous system and by hormones.
• Hormones are produced by one set of cells and
  affect a different set of cells.
• Gastrin.
• Gastric inhibitory peptide (GIP).
• Secretin.
• Cholecystokinin (CCK).

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Hormonal Control of Digestive Secretions
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The Large Intestine

• The large intestine absorbs water, salts, and
  some vitamins, and stores fecal material.
• Cecum is blind end of large intestine.
• Colon.
• Ascending.
• Transverse.
• Descending.
• Sigmoid.
• Rectum.
• Anus.

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The Large Intestine

• Polyps are small growths arising from the
  epithelial lining.
• May increase likelihood of colon cancer.
• Can be removed surgically.
• Diarrhea is caused by infection of the lower
  intestinal tract and nervous stimulation, and
  results in increased peristalysis.
• Constipation can be caused by a lack of water and
  fiber, and leads to dry, hard feces.

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Three Accessory Organs

• The pancreas secretes insulin and glucagon that
  regulate blood glucose levels.
• The liver maintains homeostasis by maintaining
  blood glucose levels, producing bile, and
  detoxifying blood.
• Disorders.
• Jaundice.
• Cirrhosis.
• The gallbaldder stores excess bile.

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Digestive Enzymes

• Digestive enzymes are hydrolytic enzymes that
  break down substances into nutrient molecules.
• Glucose and amino acids are absorbed into blood
  capillaries of the villi.
• Fatty acids and glycerol reform within epithelial
  cells and enter lacteals as lipoprotein droplets.

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Nutrition

• The body requires three major classes of
  micronutrients to supply energy and optimum
  cellular metabolism.
• Carbohydrates.
• Protein.
• Fat.

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Food Guide Pyramid
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Carbohydrates

• Carbohydrates are digested to simple sugars,
  which are, or can be converted to, glucose.
• Quickest, most readily absorbed source of energy
  for the body.
• Complex carbohydrates should make up the bulk of
  the diet.

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Proteins

• Adequate protein formation requires twenty
  different amino acids, including eight essential
  amino acids.
• Body is unable to produce essential amino acids.
• Amino acids are not stored in the body, and thus
  a daily supply is needed.

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Lipids

• Fat and cholesterol are both lipids.
• Intake of fat increases weight gain, and
  increases the risk of cardiovascular disease and
  cancer.
• Plaque deposits contain saturated fats and
  cholesterol.
• For optimal cardiovascular health, less than 30
  of calories should come from fat and less than
  10 from saturated fat.

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Vitamins and Antioxidants

• Vitamins are inorganic compounds used by the body
  for metabolic purposes, but cannot be produced in
  adequate quantities.
• Antioxidants are vitamins that defend the body
  against free radicals.
• Molecules that carry an extra electron.

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Minerals

• The body also requires minerals.
• Macrominerals are present at a minimal level of 5
  grams each.
• Calcium, Potassium, Sodium, Magnesium,
  Phosphorus, Sulfur, Chloride.
• Microminerals are present at levels under 5 grams
  each.
• Iodine, Copper, Mangenese, Zinc, Iron.

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Calcium and Sodium

• Calcium counteracts osteoporosis and generally
  strengthens bones.
• Sodium helps maintain osmotic balance, but too
  much sodium can intensify hypertension.

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Eating Disorders

• Obesity.
• Most often defined as body weight 20 or more
  above ideal weight.
• Most likely caused by a combination of hormonal,
  metabolic, and social factors.
• Increases risk of heart disease.

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Eating Disorders

• Bulimia Nervosa.
• Habit of eating to excess and then purging by
  artificial means.
• Alters blood composition leading to heart rhythm
  problems and kidney damage.
• Anorexia Nervosa.
• Morbid fear of gaining weight.
• Self-induced starvation.

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Review

• The Digestive Tract
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Accessory Organs
• Nutrition

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