Digestion
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Digestion

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Digestion Digestion Presentation Transcript

  •  
  • Why Do We Need to Digest?
    • Nutrients from food provides us with the energy and materials we need for work, growth and repair
    • The problem is that most of the nutrients we need cannot be used in the form they are eaten
    • Nutrients need to be broken up into their smallest components in order to diffuse into our blood stream
  • What needs to be broken up?
    • Carbohydrates  simple sugars
    • Proteins  amino acids
    • Fats  Glycerol and fatty acids
    • Enzymes
    • Type of protein that breaks food molecules into smaller units.
  • The Process of Digestion
    • Divided into 3 stages:
    • Physical Digestion
      • Taking food in – Cutting and chewing food
    • Chemical Digestion
      • Enzymes break down food even further
    • Absorption
      • Wastes are excreted
  •  
  • Mouth
    • Physical digestion starts starch digestion
    Esophagus Rapid passage of food to stomach
  • Stomach
    • Digestion of proteins
    Liver
    • Digestion of proteins
  • Pancreas
    • Production of many enzymes which digest all types of food
    Small Intestine Production of more enzymes and absorption of most end products
  • Large Intestine
    • Reabsorption of water
    Rectum Temporary storage of undigested waste
  • Elimination
    • Removal of undigested wastes
    • On your plate with a fork and knife
    • Your saliva initiates chemical digestion with an enzyme that breaks carbohydrates down into simple sugars
    • Your teeth and tongue break up food into smaller pieces and grind it up
  • Stage 1
  • Physical Digestion - Teeth
    • Adult humans have 4 different kinds of teeth (32 total)
    • Incisors at the very front (4 on top, 4 on bottom)
    • Canines (cuspids) beside the incisors and are pointed (4 total)
          • Used for tearing or shredding
    • Premolars (8 total)
    • Molars (12 total incl. wisdom teeth)
    • Premolars + molars – flattened on upper surface, used for grinding and chewing tough food
    • Children have deciduous or primary teeth (20 total)
    • 8 Incisors
    • 4 Canines
    • 8 molars
  • Parts of the Teeth
    • Crown - visible part above the gum
    • Root – Part below the gum line, holds tooth in place
    • Enamel – protective coating – hardest substance in the body, cannot be replaced.
  • Parts of the Teeth
    • Dentine – hard bone that gives teeth shape and strength. It is sensitive to temperature, sugar, touch, acids, etc.
    • Pulp Chamber – message center for sensation in the dentine
    • Gum line – help hold and protect teeth
  • Parts of the Teeth
    • Root Canal – carries blood and nerve endings
    • Cementum – connect tooth to the jaw bone
  •  
    • Carnivores – Sharp teeth for grabbing food and ripping it apart
    • Herbivores – Flat teeth for grinding food
    • Omnivores – Flat and sharp teeth
  • What causes tooth decay?
    • Bacteria called plaque live in your mouth
    • Plaque eats any food that stays on your teeth
    • Produce acid that eats away the enamel, creating pits called cavities
    • Build up of a hard crust called tartar
    • NOTE: Sugar does not cause tooth decay, it feeds the bacteria that do
  • Brushing and flossing removes plaque and keeps gums healthy Wear mouth guards in sports Regular dental checkups (clean away tartar) Diet: calcium, phosphorus, vitamins A, C & D all help maintain teeth and gums
  • Some Dental Problems
    • Sensitivity due to the removal of enamel by cavities and exposing dentine
    • Abscesses – bacteria get into the root and infect it
    • Peridontal Disease – Affect the tissue around the teeth. Includes retreating gum line, sore gums or bleeding. Usually caused by poor diet or hygiene.
    • Halitosis – bad breath caused by smoking, infections, tooth decay, sinus infections, etc.
  •  
  • Stage 2
  • Begins In the Mouth
    • Amylase
    • 1 st enzyme to act.
    • Produced by saliva
    • Helps break down starch into sugar molecules.
  • Saliva
    • Produced by 3 pairs of glands inside the mouth
    • Is slightly acidic
    • Approx 1000 mL produced per day !
    • 99% is water
  • Function of Saliva
    • Moistens dry food
    • Binds the loose crumbs together so bits do not get into the respiratory system
    • Softens food so rough edges will not scratch the walls
    • Enzyme amylase begins chemical digestion
    • Hard Palate
    • Soft Palate
    • Uvula
  • The Tongue
    • Attached to the floor of the mouth
    • Helps to move food to the molars
    • Mixes food with saliva
  • The Tongue
    • Once the food is moist and soft, the tongue rolls it into a ball called a bolus .
    • This prepares the food to pass into the pharynx to be swallowed.
  •  
  • Swallowing
    • The tongue moves the bolus of swallowed food to the back of the mouth
    • The soft palate moves upward to partially seal off the nasal passage
    • At the same time, the epiglottis closes the opening into the respiratory passage
  •  
    • Place cracker in mouth
    • Chew WITHOUT SWALLOWING!
    • Note the taste
    • Leave on tongue until you notice a taste change (can take up to 5 min)
    • What do you taste?
  • The Sense of Taste
    • Humans detect taste with taste receptor cells
    • These are clustered into taste buds
    • Taste buds are clustered into bumps called papillae
    • There are 5 primary taste sensations
      • salty
      • sour
      • sweet
      • bitter
      • Umami (Savory)
  •  
    • The movement of food from the tongue down into the pharynx is under voluntary control
    • The second stage, involving the epiglottis and the movement of the food into the esophagus, is involuntary
  • The Esophagus
    • Flexible tube – approx. 25 cm long
    • Leads from the pharynx to the stomach
    • Walls have 2 layers of muscle
    • The inner lining covered with mucus – helps food pass through easily
  • Peristalsis
    • Bolus is moved through peristaltic action
    • Peristalsis - the rhythmic contractions of muscles – like squeezing a tube of tooth paste
    • Cardiac sphincter:
      • Ring of muscle that controls the passage of bolus into stomach
      • – like pulling a drawstring
  • The Stomach
    • Large muscular bag that stretches as it fills with food
    • Can hold 1.5 L
    • Made up of many layers, including 3 layers of muscle
    • Gastric glands produce gastric juice .
      • Pepsin (an enzyme) – Breaks down protein
      • Hydrochloric Acid
    • The muscular walls of the stomach contract to mix food with gastric juice, producing a mixture called chyme .
  • Hydrochloric Acid (HCL)
      • Lowers the pH of the stomach to allow enzymes to work efficiently
      • Helps kill bacteria
      • Mucus secretions protect the stomach walls from HCl
      • BUT sometime mucus is not enough and HCL and digestive enzymes eat away at the lining, resulting in a peptic ulcer .
  • Heart Burn
    • Presence of stomach acid in the esophagus
    • Cardiac sphincter is not working properly – opens allowing acidic stomach contents into the esophagus
    • http://videos.howstuffworks.com/hsw/17648-food-into-fuel-the-process-of-digestion-video.htm
    • The pyloric sphincter is located at the lower end of the stomach
      • Controls the flow of partially digested food (Chyme) out of the stomach
  • The Small Intestine
    • 2.5 cm in diameter, and is about 7m in length
    Esophagus Stomach Small Intestine
  • Small Intestine
    • A long coiled and looped tube
    • Fills most of the abdomen
    • Held in place by a membrane called mesentery
  • 4 functions of the Small Intestine
    • Keeps the food moving by peristalsis
    • Secretes enzymes which continue the digestive process
    • The site where digestion by chemicals from the pancreas and liver take place
    • Nutrients are absorbed into the bloodstream
  • Digestive processes…
    • 3 basic food substances in the small intestine:
      • Carbohydrates
      • Fats
      • Proteins
    • They are broken down into molecules that are small enough to pass through the wall and enter the circulatory system
  • The Pancreas
    • Produce pancreatic juice – which contain about 28 enzymes and sodium bicarbonate
      • Lipase – breaks down fat
      • Amylase – completes carbohydrate digestion
      • Trypsin and peptidase – complete protein digestion
    • Sodium bicarbonate neutralizes the acidic chyme as it comes out of the stomach
  • How are our bodies built to handle the acid in our stomach?
  •  
  • The Liver
    • Produces bile that is stored in the gall bladder
    • Bile emulsifies fat – which means that it helps fat dissolve in water so it can be digested and absorbed
  •  
  • Absorption Stage 3
  • Absorption of Nutrients
    • Villi:
    • Increase surface area for absorption
    • Collect the nutrients and transport them to where they are needed in the body
      • Surface of the small intestine is folded
      • Covering the surface are projections called villi
    • Reabsorption and Elimination: The Large Intestine
  • The Large Intestine consists of:
    • Cecum
    • Appendix
    • Colon
    • Rectum
  • The Large Intestine
    • Approx. 1.5 m in length
    • 7.6 cm in diameter
    • Functions mainly to reabsorb water
    • Appendix
      • Believed to have no function
      • Can become infected –called appendicitis
    Cecum – Where the small intestine empties into the large intestine
  • Large Intestine function
    • Reabsorbs water and maintains the fluid balance of the body
    • Absorbs certain vitamins
    • Undigested food is dried into suitable consistency for defecation
    • Stores waste before it is eliminated
  • The Rectum
    • Last section of the digestive tract
    • Ends with the anal sphincter (like a drawstring)
    • When full there is a mild feeling of discomfort, which tells us that the feces is ready to be eliminated
  • What Your Feces Can tell you…
    • Feces are 75% water and 25% solids
    • Diet lacking fiber = drier, compacted feces which can result in constipation
    • Sufficient fiber = Holds more water and is much softer which allows it to pass through easily
  • Quick Recap…
    • Small Intestine:
      • Breaks down food and absorbs nutrients
      • Villi increase’s surface area = more absorption
      • Moves the rest to the large intestine (through peristalsis)
  • Quick Recap
    • Large Intestine:
      • Removes water
      • Moves undigested food (peristalsis) to be released as waste
    • http://videos.howstuffworks.com/hsw/26494-managing-your-health-the-digestive-system-video.htm