Digestion, Absorption,

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Digestion, Absorption, Transport
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Digestion The Digestive System

• Digestion- the process by which food is broken
  down into absorbable units.
• Digestive system- all the organs and glands
  associated with the ingestion and digestion of
  food.
• GI tract- the gastrointestinal tract.
• Gastro- stomach.
• Intestinalis- intestine.

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Anatomy Of The Gastrointestinal Tract

• Mouth- chews and mixes food with saliva.
• Salivary glands- secrete saliva.
• Epiglottis- cartilage in the throat that guards
  the entrance to the trachea. Protects airway
  during swallowing.
• Trachea (windpipe)- allows air to pass to and
  from the lungs.

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Anatomy Of The Gastrointestinal Tract continued

• Esophagus (food pipe)- passes food from the mouth
  to the stomach.
• Cardiac sphincter (lower esophageal sphincter)-
  allows passage from the esophagus to stomach.
  Prevents backflow from the stomach.
• Sphincter- a circular muscle surrounding, and
  able to close, a body opening. They are found at
  specific points along the GI tract and regulate
  the flow of food particles.

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Anatomy Of The Gastrointestinal Tract continued

• Stomach- adds acid, enzymes, and fluid. Churns,
  mixes, and grinds food to a liquid mass.
• Pyloric sphincter- allows passage from stomach to
  small intestines. Prevents backflow from small
  intestines.
• Liver- manufactures bile salts, detergent-like
  substances to help digest fats.

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Anatomy Of The Gastrointestinal Tract Continued

• Gallbladder- stores bile until needed.
• Bile duct- conducts bile from the gallbladder to
  the small intestine.
• Ileocecal valve- allows passage from the small to
  large intestine. Prevents backflow from the
  colon.
• Appendix- stores lymph cells.

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Anatomy Of The Gastrointestinal Tract continued

• Small intestine- A 10 ft. length of small
  diameter intestine that is the major site of
  digestion of food and absorption of nutrients.
  Its segments include the duodenum, jejunum, and
  ileum.
• Pancreas- a gland that secretes digestive enzymes
  and juices into the duodenum.
• Pancreatic duct- conducts pancreatic juice from
  the pancreas to the small intestine.

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Anatomy Of The Gastrointestinal Tract continued

• Large intestine (colon)- reabsorbs water and
  minerals. Passes waste along with water to the
  rectum. Its segments include the ascending,
  transverse, descending, and sigmoid colon.
• Rectum- stores waste prior to elimination.
• Anus- the terminal sphincter of the GI tract.
  Opens to allow elimination.

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Muscular Actions Of Digestion

• Peristalsis- wavelike muscular contractions of
  the GI tract that push its contents along.
• Stomach action- contains circular, longitudinal,
  and diagonal muscles that contract and relax to
  force the chyme downward to the pylorus.

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Muscular Actions Of Digestion continued

• Segmentation- periodic squeezing or partitioning
  of the intestine at intervals along its length by
  its circular muscles.
• Sphincter contractions- four major sphincter
  muscles divide the GI tract into its principal
  divisions. Contraction of these sphincters
  allows food to pass along the entire length of
  the GI tract.

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Secretions of Digestion

• The five organs which produce secretions during
  digestion
• Salivary glands
• Stomach
• Pancreas
• Liver (via gallbladder)
• Small intestine

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The Salivary Glands

• Secrete saliva into the mouth and begin the
  digestive process
• Its principal enzyme, amylase, begins
  carbohydrate metabolism.
• Saliva contains water, salts, and enzymes.

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The Stomach

• Cells in the stomach produce gastric juice which
  is a mixture of water, enzymes, and hydrochloric
  acid.
• Gastric gland are also referred to as exocrine
  glands.
• The major digestive event of the stomach is the
  partial breakdown of proteins.
• Gastro stomach

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Pancreatic Juice And Intestinal Enzymes

• Pancreatic juice is the exocrine secretion of the
  pancreas, containing enzymes for the digestion of
  carbohydrate, fat, and protein.
• The pancreas contributes digestive juices by way
  of ducts leading to the intestines.
• In addition to enzymes, pancreatic juice also
  contains sodium bicarbonate to neutralize the
  acid chyme from the stomach.

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The Liver

• The liver produces bile which is stored in the
  gallbladder.
• Bile flows from the gallbladder to the duodenum.
• Bile emulsifies fat for absorption.
• an emulsifier is ...

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Anatomy Of The Absorptive System

• Absorption- the passage of nutrients from the GI
  tract into either the blood or lymph.
• Villi- fingerlike projections from the folds of
  the small intestines.

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Anatomy Of The Absorptive Systemcontinued

• Microvilli- tiny, hairlike projections on each
  cell of every villus that trap nutrient particles
  and transport them into the cells.
• Crypts- tubular glands that lie between the
  intestinal villi and secrete intestinal juices
  into the small intestines.

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Overview of Macronutrients And Their Digestive
Fate

• Mouth
• Carbohydrate digestion begins.

• Stomach
• Carbohydrate digestion continues.
• Protein digestion begins.

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Overview of Macronutrients And Their Digestive
Fate

• Small Intestines
• Starch digestion/absorption is completed.
• Fat is emulsified and absorbed.
• Protein digestion/ absorption is completed.

• Large Intestines
• Fluid reabsorbed.
• Some fibers continue digestion.
• Some fibers pass through the large intestine and
  get excreted.

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Hormones

• Hormones- chemical messengers secreted by a
  variety of glands in response to altered
  conditions.
• They travel to target tissues or organs where
  they elicit a specific response to maintain
  homeostasis.
• Homeostasis- the maintenance of constant internal
  conditions by the bodys control systems.
• Homeo the same.
• Stasis staying.

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Gastrointestinal Hormones

• Gastrin- the hormone secreted by the cells of the
  stomach wall. Gastrin stimulates the stomach
  glands to secrete the components of hydrochloric
  acid.
• Hydrochloric acid (HCL)- an acid composed of
  hydrogen and chloride atoms.

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Hormones Of The Small Intestines

• Secretin- produced by cells in the duodenum wall.
  Target organ is the pancreas. Response is the
  release of bicarbonate-rich pancreatic juice.
• Cholecystokinin (CCK)- produced by cells of the
  intestinal wall. Target organ is the
  gallbladder. Response is the release of bile and
  slowing of GI motility.
• Gastric-inhibitory peptide- produced by the
  intestine. Target organ is the stomach.
  Response is slowing the secretion of gastric
  juice and slowing of GI motility.

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Common Digestive Problems

• Choking- when food has slipped into the air
  passage (trachea) and breathing has been blocked.
• Vomiting- when the waves of peristalsis reverse
  direction and the stomach contents are propelled
  up the esophagus and out of the mouth. Arising
  from a variety of situations.
• Diarrhea- characterized by frequent loose, watery
  stools. Indicating that the intestinal contents
  have moved too rapidly through the intestines for
  fluid absorption to take place. This can be a
  symptom of a variety of medical conditions.

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Common Digestive Problems continued

• Constipation- longer than usual time between
  bowel movements and there is difficulty, pain, or
  discomfort when having a bowel movement. Each
  persons GI tract responds differently to food,
  digestion, absorption, and transport.
• Heartburn- a painful sensation a person feels
  when the cardiac sphincter fails to prevent the
  contents of the stomach from refluxing into the
  esophagus.

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Strategies For Prevention Of Common GI Problems

• Choking
• Diarrhea

• Take small bites.
• Chew thoroughly.
• Dont talk with food in your mouth.
• Rest.
• Drink plenty of fluids to replace losses.
• Seek medical attention if problem persists.

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Strategies For Prevention Of Common GI Problems
continued

• Constipation

• Eat a high fiber diet.
• Drink plenty of fluids.
• Exercise regularly.
• Do not delay defecation.

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Strategies For Prevention Of Common GI Problems
continued)

• Heartburn

• Eat small meals
• Follow a low fat diet
• Sit up while eating
• Drink liquids in between meals
• Wait 1 hour after eating before lying down
• Wait 2 hours before exercising
• Refrain from smoking
• Obtain a healthy weight