Digestive System

Digestive System

Physiology • 1. Ingestion • Food enters mouth • 2. Propulsion • Food moves from one organ to next • Swallowing • Peristalsis – involuntary muscle contraction

Physiology • 3. Food Breakdown • Mechanical – chewing (teeth), churning (stomach) • Chemical • Large molecules are broken into smaller building blocks • Proteins -- amino acids • Carbs  simple sugars (monosaccharides)

Physiology • 4. Absorption • Enzymes from liver and pancreas help digest food • Nutrients are absorbed into the bloodstream by active and passive transport • 5. Defecation • Elimination of feces from body

Anatomy • Tongue – swallow • Salivary glands – moisten food and begin digestions • Esophagus – brings food from mouth to stomach (uses peristalsis) • Stomach – produces acids to breakdown food, mixes and churns

Anatomy • Small Intestine – uses enzymes from liver and pancreas to digest food • Nutrients absorbed into blood • Large Intestine – absorbs water • Rectum – stores feces • Anus – releases feces

Accessory Organs • Liver • Makes bile that helps in fat digestion • Gall bladder – stores bile • Pancreas • Makes enzymes that digest proteins, carbs and fat

Flow of food • Mouthesophagusstomachsmall intestinelarge intestinerectumanus

Nutrition and Metabolism • Nutrient • A substance in food that is used by the body to promote normal growth, maintenance and repair • ATP • Chemical energy needed by cells to do their activities • Major Nutrients • Carbohydrates • Lipids • Proteins

Nutrition and Metabolism • Other nutrients • Needed in minute (small) amounts but still very important • Vitamins • Minerals

Carbohydrates – sugars and starches • Made of carbon, hydrogen and oxygen • Almost all come from plants except lactose and glycogen • Broken down to make ATP through the process of cellular respiration (in mitochondria) • Excess stored as fat or glycogen

Carbohydrates • Monosaccharides – single sugars • Examples – glucose and fructose • Disaccharides – double sugars • Examples – sucrose (table sugar), lactose, maltose • Polysaccharides – many sugars – good for storage • Examples – starch (plants store sugar this way), glycogen (animals store sugar this way)

Lipids - fats • Made of glycerol and fatty acids • Most abundant source of usable energy • Used for • Insulation, protection • Build cell membrances • Fuel to make ATP • Broken down in the liver (use bile)

Lipids - fats • Saturated fats – all single bonds – most from animals • Examples – meat, dairy, some plants (coconut) • Unsaturated fats – some double or triple bonds • Example – seeds, nuts, vegetable oils • Cholesterol – steroid – found in cell membranes • Example – animal products – meat, eggs, cheese

Proteins • Over 50% of organic material in body • Made of amino acids • Essential amino acids come only from the diet • Used for • Collagen – bones, cartilage, tendons • Keratin – hair, nails (waterproofing) • Antibodies – immunity • Hormones – growth and development • Enzymes – regulate chemical reactions

Vitamins • Organic nutrients that the body needs in small amounts • Obtained through a balanced diet • Used for many things in body (see pgs 543-544)

Vitamins • A – healthy eyes, skin and bones • D – absorption of calcium and phosphorus (bones and teeth • E – prevents cell membrane damage • K – helps make certain proteins, especially blood clotting • B1, Riboflavin, Niacin – help in metabolism • B12/Folate – help in making DNA and RNA – important for early pregnancy • C – makes collagen, helps in detoxification, helps absorb iron

Minerals • Inorganic substances that the body needs in small amounts • Calcium – strong bones, teeth, blood clotting, muscles movement, nerve signals • Phosphorus – bone and teeth • Sulfur – part of tendons, cartilage, proteins • Sodium /potassium– nerve impulses, muscle contraction • Iron – helps make hemoglobin • Iodine – helps thyroid work

Metabolism • All the chemical reactions necessary to maintain life • Catabolism – breaking down big substances into smaller substances • Anabolism – building larger molecules from smaller building blocks • Energy intake = total energy output (heat + work +storage) • If energy intake and energy outflow are balanced, weight remains stable

BMR – basal metabolic rate • Amount of energy used by the body at rest • Used for essential activities – breathing, eating, heartbeat, kidney funct. Etc • Affected by • -surface area – large surface area in relation to volume = increased BMR (thin people) • Gender – BMR is higher in males than females • Thyroxine production • Increased thyroxine = higher BMR • Age – Young growing = higher BMR • Elderly = lower BMR • Strong emotions = higher BMR

Total Metabolic Rate • TMR – total amount of kilocalories the body must consume to fuel ALL ongoing activities (including exercise, digestion, physical activities) • If calories eaten = TMR your body maintains stable weight • If you eat more than your TMR requires – excess calories are stored as fat • If you eat less than your TMR requires – break down fat

Determining your BMR/TMR • Take your weight in pounds • Divide by 2.2 to get weight in kilograms • Multiply by .9 to get calories per hour • Multiple by 24 to get calories per day • This number is your BMR

Determining your BMR/TMR • To find your TMR – it is based on activity level • If you are sedentary (little or no exercise) • Multiply your BMR by 0.15 and add this number to your BMR • If you are lightly active (light exercise like walking, most days of week) • Multiply your BMR by 0.50 and add this number to your BMR • If you are moderately active (vigorous exercise at least 30 min per day) • Multiply your BMR by 0.70 and add this number to your BMR • If you are very active (vigorous exercise at least 60 min per day) • Multiply your BMR by 0.80 and add this number to your BMR

Digestive System