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Nutrition • Autotrophs – plants, some protists & bacteria – producers Nutrition • Heterotrophs – animals, fungi, some protists & bacteria – consumers Animal Nutrition • Most obtain food by ingestion – take in their food whole or piece by piece Animal Nutrition • Classify based on what they eat: – Herbivores (primary consumers) • eat autotrophs – Carnivores (secondary or higher consumers) • eat heterotrophs – Omnivores • eat both Stages of Food Processing • Ingestion – eating • Digestion – breaking down food into small molecules – mechanical and chemical (enzymatic hydrolysis) • Absorption – body takes in small molecules • Elimination – undigested material exits the body Digestion • Must take place in specialized compartments • to avoid damage to body cells Food vacuoles • food enters by endocytosis & then vacuole merges with lysosome • Some protists • Sponges – only animal with only intracellular digestion Figure 41.10 Intracellular digestion in Paramecium Gastrovascular Cavities • • • • single opening serve to both digest & transport nutrients extracellular digestion, then intracellular Platyhelminthes (planaria) & Cnidarians (hydra) What is the advantage of extracellular digestion? Eat larger food Extracellular digestion in a gastrovascular cavity Alimentary canals or Complete Digestive Tracts • two openings: mouth & anus • food passes in one direction • Found in all other animals What is the advantage of oneway movement of food? • Allows for specialization of different regions of the digestive tract Figure 41.12 Alimentary canals Types of Digestive Systems Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Earthworm Nematode Salamander Anus Pharynx Intestine Mouth Stomach Intestine Cloaca Intestine Pharynx Mouth Mouth Anus Crop Gizzard Liver Anus Esophagus Pancreas Mammalian Digestive System • Four-layered wall surrounds the lumen – – – – Mucosa (epithelial tissue) Submuscosa (connective tissue) Muscularis (muscle) Serosa (connective tissue) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oral cavity Salivary glands Liver Gallbladder Salivary gland Pharynx Esophagus Stomach Pancreas Small intestine Colon Cecum Appendix Rectum Anus Human Digestive System • Mouth – teeth mechanically break down food • Similar in function to the gizzard of birds and worms – saliva is secreted from salivary glands • • • • mucous protects mouth antibacterial agents buffer to neutralize acidity salivary amylase – hydrolyzes glucose polymers Human Digestive System • Pharynx (throat) – swallowing • Esophagus – peristalsis Swallowing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pharynx Air 1. As food moves to Larynx Trachea Esophagus Hard palate Tongue Soft palate Epiglottis the back of the mouth, the soft palate seals off the nasal cavity. 2. During swallowing, the larynx rises and is sealed off by the epiglottis. This forces the bolus into the esophagus and prevents entry into the trachea. As the bolus moves into the esophagus the larynx relaxes. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Peristalic movement Esophagus Relaxation Contraction Food Bolus Relaxation Human Digestive System • Stomach • stores food (as does the crop in other organisms) • lining secretes gastric juice • Pepsinogen (inactive) becomes pepsin (active) in low pH • smooth muscles churn the food • Acid chyme The Stomach Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stomach Gastric pit Gastric pit Esophagus Serosa Duodenum Pyloric sphincter Muscularis Mucous cell Longitudinal Circular Mucosa Oblique Chief cell Mucosa Parietal cell Submucosa Oblique Muscularis Circular Longitudinal Serosa Gastric glands Human Digestive System • Small Intestine • Longest part of the canal (6 m in humans) • Duodenum (first 25 cm) – most digestion takes place • Jejunum and ileum – mainly absorption • Very large surface area (300 m2) – folds, villi & microvilli – Similar to mycelium in fungi & roots in plants The Small Intestine Small intestine Villus Epithelial cell Capillary Lacteal Villi Mucosa Submucosa Muscularis Serosa Lymphatic duct Vein Artery Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pancreatic islet (of Langerhans) cell From liver cell Common Pancreas bile duct Gallbladder Pancreatic duct Duodenum Human Digestive System • Accessory Glands: – Pancreas • digestive enzymes – Lipase-lipids; pancreatic amylase-starch; trypsin - proteins • Bicarbonate- buffer Human Digestive System • Accessory Glands: – Liver • produces bile salts which are stored in the gallbladder until needed • aid in the digestion of fats by emulsification – Gallbladder Human Digestive System • Large Intestine or Colon – main function is concentration & storage of wastes • absorption of water, sodium, vitamin K – Feces are moved along by peristalsis and exit the body through the anus Hormonal Control of Digestion • Gastrin – released by the stomach – feeds back to cause the secretion of gastric juices – Low pH inhibits its production – negative feedback Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stomach Liver pH Proteins Gastrin (+) (+) ( – ) Chief cells Parietal cells GIP Pepsin (+) Bile Pancreas Enzymes Bicarbonate Gallbladder (+) CCK Secretin Duodenum Acinar cells (+) HCl Hormonal Control of Digestion • Enterogastrones – Released by duodenum of small intestine – inhibit peristalsis & secretions in the stomach – Secretin • Stimulated by low pH • causes pancreas to release bicarbonate – CCK (cholecystokinin) • Stimulated by high fat content • Stimulates gall bladder to release bile – GIP (gastric inhibitory peptide) • Inhibits emptying of the stomach Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stomach Liver pH Proteins Gastrin (+) (+) ( – ) Chief cells Parietal cells GIP Pepsin (+) Bile Pancreas Enzymes Bicarbonate Gallbladder (+) CCK Secretin Duodenum Acinar cells (+) HCl Evolutionary Adaptations to Diet • Teeth – pointed in carnivores, flat in herbivores Mouth and Teeth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Herbivore Carnivore Omnivore Horse Lion Human Incisors Canines Premolars Molars Evolutionary Adaptations to Diet • Length of gut – longer in herbivores than carnivores • Cecum – houses bacteria that aid in digestion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nonruminant Herbivore Ruminant Herbivore Simple stomach, large cecum Four-chambered stomach with large rumen; long small and large intestine Esophagus Stomach Small intestine Esophagus Reticulum Rumen Abomasum Omasum Cecum Small intestine Large intestine Anus Cecum Spiral loop Large intestine Anus Insectivore Carnivore Short intestine, no cecum Short intestine and colon, small cecum Esophagus Small intestine Stomach Esophagus Stomach Small intestine Large intestine Anus Anus Cecum Large intestine Evolutionary Adaptations to Diet • Ruminant Stomach- cows, deer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rumen Small intestine Esophagus Reticulum Abomasum Omasum Evolutionary Adaptations to Diet • Coprophagy – rodents, rabbits