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Warm-Up

Learn about the human digestive system, including the organs involved, their functions, and the processes of digestion, absorption, and elimination. Discover the role of accessory organs in digestion and the breakdown of different nutrients. Explore fascinating facts about the digestive system.

douglasjennings
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Warm-Up

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  1. Warm-Up • Write down in correct sequence all the organs (at least 5) through which their food passes as it travels along the digestive tract. Then try to list any glands or organs that are found along the digestive tract, but through which food does not pass.

  2. Human Digestive System

  3. Human Digestive System • Digestion is the ability to process food in the body into a form that can be absorbed and used or excreted. • Digestion involves three principle processes: • Mechanical digestion: takes place in the mouth, your teeth chew the food • Chemical digestion: using chemicals to digest/ break down food, this takes place in your mouth and stomach where acid and enzymes mix with the food. • Absorption: pulling nutrients out of the food, occurs in the small intestine

  4. Structures • The GastrointestinaI tract (GI), also called the alimentary canal is the system of organs that take in food, digest it to extract nutrients and expels the waste. These organs are the mouth, pharynx, esophagus, stomach, small intestine and large intestine. • Major Functions: • Ingestion • Digestion • Absorption • Defecation or Excretion

  5. Accessory organs: Organs that help with digestion but are not part of the digestive tract. These organs are the tongue, salivary glands, liver, gall bladder, and pancreas.

  6. Mouth Pharynx Esophagus Liver Stomach Large Intestine Small Intestine Villi Human Digestive System Diagram

  7. Following the Trail • The process begins in the mouth. • Chewing initiates mechanical breakdown of food and is followed by secretion of saliva, which moistens and lubricates food for swallowing. • Saliva also contains amylases (enzymes), which start the chemical breakdown of carbohydrates. • The swallowing reflex begins in the pharynx and initiates rhythmic waves of smooth muscle contractions called peristalsis. • Peristaltic contractions transport food to the stomach and allow a person to swallow even if he/she are upside down.

  8. Following the Trail II • The stomach contains an extra layer of muscle that aids in mechanically mixing and churning food into a semiliquid form called “chyme.” • Chemical digestion begins with proteins through the action of hydrochloric acid (HCl) and the enzyme, pepsin. • Only water and a few substances, such as aspirin and alcohol, are absorbed by the lining of the stomach.

  9. Following the Trail III • As food enters the small intestine secretions from the liver, gall bladder and pancreas are added .

  10. The small intestine completes digestion of food materials by absorbing nutrients into the blood stream • The lining of the small intestine consists of tiny folds or fingerlike projections, called villi, which, in turn, are covered by microvilli which increase surface area • The villi contain capillaries and lymphatic vessels for the absorption of nutrients • Microvilli have brush border enzymes to hydrolyze lactose and sucrose.

  11. Cross-Section of small intestine Villi Microvilli

  12. The large intestine does not contain villi and it plays no role in digestion • Only water and vitamin K are absorbed from the large intestine • Undigested or unabsorbed food is eliminated through the rectum and then anus.

  13. Nutrition • Food materials are broken down to usable nutrients and absorbed into the bloodstream. • They are used by the body for metabolism, building and repair • Some nutrients are stored within the body • Nutrients include carbohydrates, proteins, lipids, vitamins, minerals and water. • Carbohydrates • Must be broken down into monosaccharides • Body’s main source of energy.

  14. Nutrition II • Proteins • Broken down to amino acids • Supply the raw materials for growth and repair. • The body requires 20 amino acids, 10 of which it cannot make and must obtain • Lipids are reduced to fatty acids and glycerol • They are used to make steroid hormones, cell membranes • Store energy

  15. Nucleic acids are reduced to nucleotides. • DNA and RNA • The genetic material of all cells.

  16. Where does each nutrient get broken down?

  17. What enzymes break down each nutrient?

  18. Nutrition III • Vitamins are organic molecules that aid in the regulation of body processes • Vitamin C: healthy teeth, gums and blood vessels; improves iron absorption and resistance to infection • Vitamin K: for normal blood clotting and synthesis of proteins found in plasma, bone, and kidneys

  19. Water • Required for metabolism and chemical reactions within the body • Transport of substances around the body • Regulation of body temperature. Approximately two-thirds of the body weight is water.

  20. Cool Facts • Your intestines will grow to at least 25 feet as an adult. Be glad you're not a full-grown horse their coiled-up intestines are 89 feet long! • Food sloshing in the stomach can last 3-4 hours • It takes 3 hours for food to move through the intestine • Food drying up and hanging out in the large intestine can last 18 hours to 2 days! • Americans eat over 2 billion pounds of chocolate a year. • In your lifetime, your digestive system may handle about 50 tons!!

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