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Digestive System

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What are the digestive system structures and their functions? ... Lipase digests fats. Pancreatic amylase digests carbohydrates ... – PowerPoint PPT presentation

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Title: Digestive System


1
Chapter 7
  • Digestive System
  • Attempt the pattern puzzles of digestion with a
    neighbor

2
Points to Ponder
  • What are the digestive system structures and
    their functions?
  • Where does carbohydrate, protein and fat
    digestion and absorption occur?
  • What are proteins, lipids, carbohydrates,
    minerals and vitamins needed for?
  • What are the 3 accessory organs of digestion?
  • What is obesity and why is it a problem?
  • What is LDL and HDL?
  • What are the components of a healthy diet?

3
What are the 4 major layers that make up the wall
of the GI tract?
8.1 Overview of digestion
  • Mucosa innermost epithelium that produces mucus
    that protect the lining and also produce
    digestive enzymes
  • Submucosa 2nd layer of loose connective tissue
    that contains blood vessels, lymphatic vessels
    and nerves
  • Muscularis 3rd layer made of 2 layers of smooth
    muscle that move food along the GI tract
  • Serosa outer epithelium that is part of the
    peritoneum

4
Visualizing the layers of the GI tract
8.1 Overview of digestion
5
The mouth
8.2 First part of the digestive tract
  • 3 pairs of salivary glands secrete salivary
    amylase that begins carbohydrate digestion
  • Tonsils at the back of the mouth and other
    lymphatic tissues are important in fighting
    disease
  • Contains teeth that begin the mechanical
    breakdown of food
  • The tongue is covered in taste buds and also
    assists in the mechanical breakdown and movement
    of food
  • The tongue forms a bolus (mass of chewed food)
    and moves it toward the pharynx

6
The pharynx and esophagus
8.2 First part of the digestive tract
  • Pharynx is a cavity between the mouth and
    esophagus that serves as a passageway for food
    (and air)
  • Esophagus is a long, muscular tube that carries
    food to the stomach

7
How do we swallow food?
8.2 First part of the digestive tract
8
Health focus Heartburn
8.2 First part of the digestive tract
  • Occurs when acids from the stomach pass into the
    esophagus (acid reflux)
  • Burning sensation in the esophagus
  • Chronic heartburn is called gastroesophageal
    reflux disease (GERD)
  • Tips for decreasing heartburn
  • Avoid high fat meals
  • Dont overeat
  • Eat several small meals
  • Exercise

9
The stomach
8.3 The stomach and small intestine
  • Mechanical digestion continues
  • Gastric juice contains pepsin, an enzyme that
    breaks down proteins, and HCl and mucus
  • HCl gives the stomach a pH of 2 which activates
    pepsin and helps kill bacteria found in food
  • A bacterium, Helicobacter pylori, lives in the
    mucus and can cause gastric ulcers
  • The stomach empties chyme into the small
    intestine after 2-6 hrs.

10
The small intestine
8.3 The stomach and small intestine
  • Averages 6m (18 ft) in length
  • Mechanical digestion continues
  • Enzymes secreted by the pancreas into the small
    intestine digest carbohydrates, proteins and fats
  • Bile is secreted by the gallbladder into the
    small intestine to emulsify fats
  • Digested food is absorbed through large surface
    area created by numerous villi (finger-like
    projections) and microvilli

11
How are nutrients digested and transported out of
the small intestine?
8.3 The stomach and small intestine
12
The three accessory organs
8.4 Three accessory organs and regulation of
secretions
  • Pancreas
  • Liver
  • Gallbladder

13
The pancreas
8.4 Three accessory organs and regulation of
secretions
  • Functions of the pancreas
  • 1. Secretes enzymes into the small intestine
  • Trypsin
  • Lipase
  • Pancreatic amylase
  • 2. Secretes bicarbonate into the small intestine

14
The liver and gallbladder
8.4 Three accessory organs and regulation of
secretions
  • Filters blood from the GI tract thus acting to
    remove poisons and detoxify the blood
  • Makes bile that is then stored in the gallbladder
    to be secreted into the small intestine to
    emulsify fats

15
The large intestineReview your pattern puzzles
8.5 The large intestine and defecation
  • Functions to
  • Absorb water to prevent dehydration
  • Absorbs vitamins (B complex and K) produced by
    intestinal bacteria
  • Forms and rids the body of feces

16
Disorders of the colon and rectum
8.5 The large intestine and defecation
  • Diverticulosis occurrence of pouches of mucosa
    from weak spots in the muscularis layer that can
    become infected
  • Irritable bowel syndrome (IBS) muscularis layer
    contracts with power but without its normal
    coordination that is characterized by chronic
    diarrhea and abdominal pain
  • Inflammatory bowel disease/colitis (IBD) a
    group of inflammatory disorders such as
    ulcerative colitis or Crohns disease
  • Polyps and cancer small growths found in the
    epithelial lining that can be benign or cancerous

17
Carbohydrates
8.6 Nutrition and weight control
  • Digested into glucose
  • Pancreas secretes insulin
  • Insulin binds to receptors on cells
  • Glucose can now enter cells to make ATP
  • What if your insulin receptors become less
    sensitive?
  • Cells scream at pancreas to release more insulin
  • High insulin leads to higher blood pressure, high
    cholesterol and fat deposition
  • Increased risk of type 2 diabetes, heart disease
    and liver problems

18
What changes can you make today?
8.6 Nutrition and weight control
  • Exercise-helps insulin attach to receptors
  • Get lean-Fat cells sabotage muscle cells
  • Eat original, whole grain vs. refined, processed
  • Insulin receptors work best if you keep your
    blood sugar steady
  • Eat fiber
  • Slows down sugar absorption process
  • Friend to your digestive tract
  • Aim for 25-35 grams per day

19
Proteins
8.6 Nutrition and weight control
  • Made of amino acids
  • 9 essential amino acids can not be made by the
    body
  • 11 nonessential amino acids can be made by the
    body if the building blocks are there
  • Come from plant and animal sources
  • Animal sources and soy provide all 9 essential
    amino acids
  • Empties stomach slowly and leaves you feeling
    full longer
  • What if you eat more protein that what you need?
  • Deposited as body fat

20
What changes can you make today?
8.6 Nutrition and weight control
  • Eat 0.8grams of protein per kg of body weight.
  • Choose wisely
  • Fish, shellfish, skinless (white meat) poultry
  • Lean beef (gt85) with visible fat removed
  • Beans, lentils, tofu, peanut butter, seeds
  • Grill, bake, broil, roast, poach, stir fry

21
Lipids
8.6 Nutrition and weight control
  • Fats help to maintain healthy skin, hairand
    transports vitamins (ADEK)
  • Saturated vs. Unsaturated
  • Trans-fatty acids
  • reduce the ability of cells to clear cholesterol
    from the bloodstream
  • High density lipoproteins (HDL) cholesterol
  • carries cholesterol to the liver where it is
    converted to bile salts
  • Low density lipoproteins (LDL) cholesterol
  • Deposits within walls of arteries and increases
    risk of heart attacks and stroke

22
What changes can you make today?
8.6 Nutrition and weight control
  • Choose unsaturated fats
  • Found in most plants, nuts, seeds and fish
  • Choose polys and monos
  • Include omega fatty acids
  • Dont smokeit will increase your LDLs and lower
    your HDLs
  • Limit saturated fats
  • Found in animals and processed snack food
  • Avoid trans fats
  • Ingredient list will say hydrogenated
  • Limit cholesterol to 300 mg per day
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