The Digestive System The digestive system consists of

The Digestive System • The digestive system consists of an alimentary canal and several accessory organs.

The Digestive System • The digestive system mechanically and chemically breaks down food. • Mechanical digestion includes chewing, peristalsis and the action of bile salts. • Chemical digestion includes the use of enzymes.

Digestion and Nutrients Mechanical Digestion = Chemical Digestion = Nutrients = Big food Food Small food Nutrients carbohydrates monosaccharides fatty acids + glycerol proteins amino acids

Chemical Digestion and Nutrients Carbohydrates • Uses in the Body: Glucose converted into ATP during cellular respiration in mitochondria of all cells. ATP used by cells to supply energy for cellular processes. -

Chemical Digestion and Nutrients Carbohydrates • Dietary Sources: - starch from grains and vegetables - glycogen from meats - sugar from dairy - monosaccharides from honey and fruits • Dietary Requirements: - Varies among individuals - Depends on amount of physical activity, body size and metabolic rate.

Carbohydrate Digestion (polysaccharides to monosaccharides) Mouth Mechanical digestion by mastication Chemical digestion by enzyme in saliva Esophagus and Stomach Mechanical digestion by peristalsis Small Intestine Mechanical digestion by peristalsis Monosaccharides absorbed into blood by facilitated diffusion and active transport Chemical digestion by intestinal and pancreatic enzymes Pancreas Secretes enzymes into small intestine

Chemical Digestion and Nutrients Lipids • Uses in the Body: -fatty acids and glycerol supply energy for cellular processes and materials for building cellular structures (ex. cell membranes)

Chemical Digestion and Nutrients Lipids • Dietary Sources: - saturated fats found in meats, eggs and milk - unsaturated fats found in seeds, nuts and plant oils - monosaturated fats found in olive, peanut and canola oils • Dietary Requirements: - Recommended to be less than 30% of total calories - Depends on amount of physical activity, body size and metabolic rate.

Lipids Digestion Lipid Digestion (fat to glycerol + fatty acid) Mouth Stomach and esophagus Mechanical digestion by mastication Mechanical digestion by peristalsis Small Intestine Glycerol absorbed into lymph by facilitated diffusion; fatty acids absorbed into lymph by active transport Chemical digestion by intestinal enzyme + pancreatic enzyme Mechanical digestion by peristalsis + bile salts Liver/Gall Bladder Liver secretes bile into the gall bladder, which stores it. In the gall bladder bile crystallizes into bile salts, which are secreted into the small intestine. Pancreas Secretes enzyme into the small intestine

Chemcial Digestion and Nutrients Proteins • Uses in the Body: - amino acids used by cells to synthesize proteins. For example: enzymes, clotting factors, keratin of skin and hair, collagen of connective tissue, muscle proteins (actin and myosin), hormones and antibodies.

Chemical Digestion and Nutrients Protein • Dietary Sources: - meats, fish, poultry, cheese, eggs and cereals • Dietary Requirements: - Between 60 to 150 grams per day - Depends on amount of physical activity, body size and metabolic rate.

Protein Digestion (protein to amino acids) Mouth Esophagus Mechanical digestion by mastication Mechanical digestion by peristalsis Stomach Mechanical digestion by peristalsis Chemical digestion by Pepsin in Hydrochloric Acid Small Intestine Amino acids absorbed into bloodstream by active transport Chemical digestion by intestinal enzyme + pancreatic enzymes Pancreas Secretes enzymes into the small intestine

The Digestive System • Nutrients are absorbed into the body and the unused waste material is excreted out of the body.

The Digestive System The Alimentary Canal

The Digestive System III. The Alimentary Canal A. Lumen: channel inside the alimentary canal B. Wall Layers 1. Mucosa Structure: composed of epithelial, connective, and smooth muscle tissue; mucus secreting glands present Function: protection, absorption, secretion 2. Submucosa Structure: composed of loose connective tissue; glands, blood and lymph vessels present Function: nourishment

The Digestive System III. The Alimentary Canal A. Wall Layers 3. Muscular layer Structure: composed of 2 layers of smooth muscle; circular and longitudinal shaped fibers Function: movement 4. Serosa Structure: composes the outer layer of the canal Function: secretion of fluid to lubricate so tube can slide feely

The Digestive System IV. The Oral Cavity Mechanical digestion by mastication Chemical digestion by enzymes in the saliva - Cheeks lined by stratified squamous epithelial tissue - Tongue made of skeletal muscle includes taste buds - Palate includes tonsils which are part of lymphatic system

The Digestive System V. The Teeth - Teeth increase surface area of food exposed to enzymes to accelerate chemical digestion - 20 primary - 32 secondary

The Digestive System VI. The Pharynx Tubular passageway which connects the mouth and nasal cavity to esophagus and trachea. - Epiglottis is a flap of tissue which prevents food from entering the trachea

The Digestive System VII. The Salivary Glands Secrete saliva which contains salivary amylase: enzyme that begins breakdown of carbohydrates into disaccharides.

The Digestive System VIII. The Stomach Mechanical digestion and begins chemical digestion of proteins into aminoacids. - Pepsin (enzyme) is most effective in an acidic environment (HCl). Both secreted by mucosa - Mucosa also secretes alkaline substances to avoid stomach digesting its lining - Rugae (folds on the inner lining) allow stomach to increase its capacity

The Digestive System IX. The Small Intestine Digests all foods with mechanical and chemical digestion (both with its own enzymes and enzymes from the pancreas, and bile salts from the gallbladder) Absorption of all nutrients in distal portion of the small intestine - Epithelial cells of the mucosa are replaced continuously and make up ¼ of fecal mass

The Digestive System XII. The Gall Bladder and Pancreas Gall bladder stores bile salts Pancreas secretes enzymes into the small intestine which aid in digestion of all foods into nutrients Pancreas also secretes hormones which regulate blood sugar levels (insulin and glucagon)

The Digestive System XI. The Liver Secretes bile which crystallizes into bile salts in the gallbladder which aid in mechanical digestion of lipids. § § Blood glucose regulation Lipids and protein metabolism § Removes nitrogen compounds from amino acids and converts to urea Removes and breaks down old/damaged red blood cells from blood Removes toxins from blood – including alcohol and drugs (legal and illegal) All of these products are filtered from blood by the kidneys and excreted in urine § § §

The Digestive System X. The Large Intestine Absorbs water and electrolytes, synthesizes vitamins and forms and stores feces in the distal portion. - Feces consist of undigested food (mostly fiber), water, mucus, intestinal cells and bacteria.