Figure 37.2 from Notes page 613 of your text Emma’s lower heart rate Question: Why do fit athletes have lower heart Functional Connections rates? food, water intake oxygen intake • Conditioned athletes build a stronger, more efficient heart with greater capacity. To maintain the required oxygen supply the heart does not need to pump as often to distribute the same amount of oxygen as a DIGESTIVE RESPIRATORY elimination SYSTEM SYSTEM of carbon normal heart. dioxide nutrients, Liz’s question about cholesterol and Sam’s comment about avocados: water, oxygen carbon salts dioxide • Cholesterol in the diet comes exclusively from animal sources, CIRCULATORY URINARY particularly meats and dairy products. Eggs are probably the best-known SYSTEM SYSTEM source, containing a whopping 213 milligrams of cholesterol per yolk water, (more than two-thirds of the recommended daily allowance of solutes cholesterol). In contrast, foods of plant origin contain no cholesterol, elimination rapid transport elimination of including avocados. In fact, there are several studies that have shown a of food to and from all excess water, steady diet of avocados actually reduces LDL cholesterol. residues living cells salts, wastes Digestion and Human Nutrition Types of Guts Sac-like Gut Tube-like Gut Mouth Anus Single opening for Complete gut with mouth ingesting food and and anus. Food travels one- excreting wastes. way through the organism. 5 Tasks for a Digestive System Two Types of Systems 1. Mechanical processing and motility – break-up, mixing, and propelling food 1. Incomplete digestive system • One-way, saclike 2. Secretion – release of digestive enzymes digestive cavity 3. Digestion – breakdown of food into particles 2. Complete digestive system small enough (soluble) for absorption • A tube with an opening at 4. Absorption – passage of digested nutrients and each end fluid across tube wall and into body fluids 5. Elimination – expulsion of undigested, unabsorbed residues from the end of gut Digestive Specialization 1. Digestive system is often subdivided into crop functional regions 2. Specialization reflects gizzard feeding behavior cloaca Digestive Tract Structures and Functions Digestive System Adaptations Adaptations of vertebrate digestive systems reflect diet 1. Teeth (or gizzard) – physical breakdown. Herbivores and omnivores 2. Crop – storage - longer alimentary canal compared 3. Stomach – chemical breakdown to body size. - more time to digest vegetation 4. Intestine – absorption and breakdown in small - more surface area for uptake of intestine; water absorption in large intestine. nutrients 5. Cecum/Rumen – fermentation ceca -very long 6. Rectum – water removal, storage - cellulose-digesting microbes 7. Various glands/organs for enzymes and Carnivores secretions which aid digestion. - short alimentary canal - high [nutrient] in meat AFig. 21.12A Herbivores, Omnivores, Carnivores Herbivore Dentition 1. Carnivores have a high protein diet and eat meat. (sheep) Herbivores eat plants. Omnivores eat both. Herbivores and Diet and omnivores have longer guts than carnivores. flat Vegetation has more time to be digested and there is a greater surface area for absorption. Herbivores have molars cellulose digesting organisms in their guts. 2. Teeth – Herbivores have large, flat teeth with lots of Carnivore surface area for grinding plant tissue. Carnivores have (dog) sharp canines for grasping and tearing flesh. Carnivore molars are pointed. 3. Examples: Carnivores – cheetah, fox, bat, lion; large Herbivores – sheep, deer, rabbit, gopher canines Omnivores – man, bear, rat, opossum Foregut and Hindgut Fermentation Specialized Teeth 1. Ruminants (foregut fermenters) – hoofed, usually horned, herbivorous mammals with a stomach divided into 4 compartments. Examples: cattle, sheep, goats, deer, and giraffes. 1. Structure of teeth ANTELOPE HUMAN reflects feeding MOLAR MOLAR First two stomach compartments contain bacterial symbionts to behavior crown breakdown cellulose. Food is regurgitated for additional chewing (cud). Food is swallowed a second time and moves to the third and 2. Antelope brush crown root fourth stomachs before passing to intestine. teeth against dirt as 2. Hindgut fermenters – bacterial symbionts in colon or cecum (after they eat; wear the stomach) breakdown cellulose. Examples: termites, elephants, down crowns root horses, zebras, manatees, guinea pigs, rats, porcupines, beaver, rabbits, iguana, red howler monkey, koala, and some birds. Digestive System Adaptations Coprophagy – eating feces Ruminant mammals have an elaborate system for cellulose digestion Two types of feces - four-chambered stomach soft & hard - prokaryotes and protists in rumen and reticulum break down cellulose fresh cecal pellets - animal periodically regurgitates meal to soften the material(cud) Extract vitamin B AFig. 21.12B both types Termite Digestion of Cellulose Silverfish digest Trichonympha unicellular protist wood with cellulase symbiont termites Longhorned beetles digest wood with cellulase Shipworms digest wood with cellulase Teredo navalis wood bored by shipworm shipworm shipworm (bivalve) Vertebrate Digestive System: Common Elements B=Urinary Bladder C=Cecum Cr=Crop E=Esophagus G=Gall Bladder Humans L=Liver LI=Large Intestine P=Pancreas PA=Pyloric Appendices SG=Spiral Valve SI=Small Intestine St=Stomach Accessory organs Human Major components Salivary glands 1. Mouth Secretes enzymes Mechanical and chemical that digest processing (chewing Human Teeth carbohydrates reduces size of food; saliva digests carbohydrates) Liver Secretes 2. Esophagus enamel molars molecules Transports food Lower jaw required for dentin 3. Stomach digestion of fats premolars Mechanical and chemical Gall bladder processing (digestion of canines Stores secretions proteins) incisors from liver; 4. Small intestine Chemical empties into processing and absorption small intestine (digestion of proteins, fats, 1. Normal adult Pancreas carbohydrates; absorption Secretes enzymes of nutrients and water) number is 32 and other 5. Large intestine materials into Water absorption small intestine and feces formation Tongue Saliva 1. Skeletal muscle 1. Produced by salivary glands at back of sensory 2. Functions in speech, receptor mouth and under tongue positioning food, 2. Saliva includes • Salivary amylase (enzyme) swallowing • Bicarbonate (buffer) 3. Taste buds contain • Mucins (bind food into bolus) sensory receptors • Water Swallowing Structure of the Stomach 1. Complex reflex 1. J-shaped organ lies below the diaphragm sphincters 2. Tongue forces food into pharynx serosa 2. Sphincters at both ends muscle 3. Epiglottis and vocal cords close off 3. Outer serosa covers smooth trachea; breathing temporarily ceases muscle layers 4. Bolus moves into esophagus, then through mucosa 4. Inner layer of glandular esophageal sphincter into stomach epithelium faces lumen Stomach Secretions Mixing Chyme 1. Secreted into lumen (gastric fluid) 1. A thick mixture of food • Hydrochloric acid (HCl) and gastric fluid • Mucus (protective) 2. High acidity kills many • Pepsinogen (inactive form of a protein- pathogens digesting enzyme) 3. Mixed and moved by 2. Stomach cells also secrete the hormone waves of stomach gastrin into the bloodstream contractions (peristalsis) Protein Digestion in Stomach Ulcer 1. High acidity of gastric fluid denatures proteins 1. An erosion of the wall of the stomach or small intestine and exposes peptide bonds 2. Can result from undersecretion of mucus and 2. Pepsinogen secreted by stomach lining is buffers, or oversecretion of pepsin activated to pepsin by HCl 3. Most ulcers involve Helicobacter pylori bacteria and can be treated with antibiotics 3. Pepsin breaks proteins into fragments Into the Small Intestine Intestinal Secretions 1. Movement into duodenum 1. Wall of the duodenum secretes controlled by pyloric • Disaccharidases - digest disaccharides to sphincter monosaccharides 2. Duodenum receives pyloric sphincter secretions from pancreas, • Peptidases - break protein fragments down to liver, and gallbladder; amino acids continues process of • Nucleases - digest nucleotides down to nucleic digestion duodenum acids and monosaccharides Pancreatic Enzymes Fat Digestion 1. Secreted into duodenum 1. Liver produces bile 2. Bile is stored in gallbladder, then secreted 2. Pancreatic amylase into duodenum 3. Trypsin and chymotrypsin 3. Bile emulsifies fats; breaks them into small 4. Carboxypeptidase droplets 4. This gives enzymes a greater surface area 5. Lipase to work on 6. Pancreatic nucleases Hormones and Digestion Small Intestines 1. Gastrin Duodenum Jejunum • Stimulation of gastric acid • absorption of secretion. carbohydrates and 2. Cholecystokinin (CCK) proteins. • the principle stimulus for delivery of pancreatic enzymes and bile into the small intestine. Ileum - larger channels Small intestines • absorption of fats, 3. Secretin water, B12, bile • pH control salts. Lymph One villus Walls of Small Intestine - microvilli vessel mucus secretion absorption (goblet cell) 1. Projections into the intestinal lumen increase One villus the surface area available for absorption hormone secretion phagocytosis blood lysozyme secretion capillaries Lymph One villus vessel mucus secretion absorption (goblet cell) Animation of Absorption starting with absorption cell surface hormone secretion phagocytosis blood lysozyme secretion absorption capillaries Absorption of Nutrients Absorption Mechanisms INTESTINAL LUMEN 1. Passage of molecules into internal 1. Monosaccharides and amino environment