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Food and Your Digestive System The basics. We need food for 2 things: Nutrients  Serve as building blocks  Used to maintain and build tissues Energy.

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Presentation on theme: "Food and Your Digestive System The basics. We need food for 2 things: Nutrients  Serve as building blocks  Used to maintain and build tissues Energy."— Presentation transcript:

1 Food and Your Digestive System The basics

2 We need food for 2 things: Nutrients  Serve as building blocks  Used to maintain and build tissues Energy  Release energy when metabolized in cells  Break down large organic molecules to make ATP

3 The chemical composition of your body is roughly equal to the proportions of the same elements and molecules in the food you eat. (You are what you eat!)

4 Nutrient  Any component of the food that we eat that our body needs to function properly.  Macro: essential elements we need in large amounts  Micro: essential elements we need in very small amounts

5 Getting to the Matter and Energy  Most foods have essential and nonessential nutrients the we use  If our diet isn’t balanced:  Get too much or too little of a particular nutrient  Get too much or too little energy

6 Key Info Carbs  Used for energy, DNA/RNA, digestion  Excess converted to glycogen and fats Lipids  Give food flavor and tenderness  Carry vitamins A, D, E & K  Used for alternate fuel, insulation, cell membranes, emulsifiers, hormones, bile salts

7 Key Info Proteins  2 kinds: animal & plant  Enzymes, fiber (collagen), active transport, salt/water balance, energy alternative, hormones, antibodies, hemoglobin Vitamins & Minerals  Vitamins: cell formation, antioxidant, calcium absorption, blood clotting, vision, growth, bone remodeling, immune system  Minerals: bones and teeth, nerve transport, muscle contractions, heart rhythm, ATP, nerve impulses

8 Some Thoughts  We take in energy continuously  We use energy periodically  Optimal: energy input = energy output  Any calories above daily need are converted and stored as fat

9 Food and Energy  Energy available in food is measured by “burning” food.  Energy in food is converted to heat and measured as a calorie  Energy stored in food called dietary Calories (capital “C”).  One Calorie = 1000 calories

10 Digestion – the Players  Mouth  Pharynx  Esophagus  Stomach  Small Intestine  Large Intestine  Function: Convert foods into simpler molecules for absorption and use by cells. Chapter 38

11 Mouth & Esophagus  Teeth – cutting, tearing, crushing food  Saliva – secreted by salivary glands;  Moisten food  Start chemical digestion of starches with enzyme called amylase.  Create chewed clump of food (“bolus”)  Bolus travels down esophagus to stomach by peristalsis Chapter 38

12 Stomach  Large, muscular sac  Chemical digestion: Needs glands!  Mucus – protects stomach lining  Hydrochloric acid – makes contents acidic  Pepsin – enzyme to digest proteins  Mechanical digestion: Needs muscle!  Muscles contract to churn and mix stomach fluids and food. Result: chyme Chapter 38

13 Small Intestine  Pyloric valve opens and chyme flows from stomach to small intestine.  Most chemical digestion and absorption happens in small intestine.  First of three parts of SI: duodenum  Where almost all digestive enzymes enter  Enzymes from pancreas, liver and lining of duodenum Chapter 38

14 Small Intestine & Accessory Structures  Other two parts of SI: jejunum and ileum  About 6 meters long!  Small intestine lined with villi (finger-like projections)  Increase surface area for absorption of nutrient molecules  Pancreas – regulate blood sugar levels  Liver – produces bile to break down fatty molecules Chapter 38

15 Accessory Structures Pancreas  Gland  Produces enzymes for carbs, proteins, lipids, and nucleic acids  Produces sodium bicarbonate – neutralizes stomach acids so enzymes can work Liver  Organ  Bile – acts like a detergent  Allows enzymes to reach smaller fat molecules Chapter 38

16 Absorption in Small Intestine  When chyme enters jejunum and ileum, it has become mix of small and medium nutrient molecules  These molecules rapidly absorbed into the cells lining the SI  Capillaries in the villi – carbs and protein  Lymph vessels – undigested fat and fatty acids  What’s left: water, cellulose, other undigestible substances Chapter 38

17 Large Intestine (Colon)  Removes water from undigested material  Bacteria in the large intestine produce vitamin K  Concentrated waste material exits through the rectum (poop) Chapter 38

18 Chewing amylase Mouth chemical mechanical Stomach Chemical Absorption Small Intestine Water Bacteria Large Intestine Chemical: acid and enzymes Mechanical: muscle contractions Chemical: enzymes Food leaves nutrient-free Pancreas & Liver play role here Amylase: breaks down starches Poop Vitamin K RECAP! Chapter 38 bolus chyme

19 Disorders  Peptic ulcers – hole in stomach wall  Vitamin K deficiency – loss of bacteria in LI  Diarrhea & Constipation – disruption in the removal of water by large intestine  Recall: enzymes are proteins  No sodium bicarbonate = enzymes can change shape and become ineffective (active site doesn’t match substrate) Chapter 38

20 Organs of Excretion  Skin – excretes excess water, salts, and small amount of urea  Lungs – excrete carbon dioxide  Liver – converts amino acids, producing nitrogen waste. Then converts nitrogen waste into urea.  Kidneys – principle organs of excretion  Remove waste products from blood  Maintain blood pH  Regulate water content of blood (blood volume) Chapter 38 - 3

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