3/24/2015 Animal Nutrition 1 Some of the best known and fascinating adaptations of animals involve their feeding and digestion http://www.youtube.com/watch?v=vJvfjiCTvq4 Examples: • Reptile swallowing prey • Baleen whales 1 3/24/2015 Python http://www.youtube.com/watch?v=aDW5HpdFals Starfish http://www.youtube.com/watch?v=i-EJuL0ix5Q http://www.youtube.com/watch?v=rE8l-KFQlhY Animal diversity of feeding strategies and digestive physiology • Filter feeders, predators • Digestive systems: no true tissues and organs, gastrovascular cavity, true digestive system (alimentary canal) 2 3/24/2015 Simple intracellular digestion • Example paramecium • Food taken up into food vacuoles where enzymatic and chemical digestion occurs Figure 33.3 Anatomy of a sponge Intracellular digestion by phagocytosis in choanocyte 3 3/24/2015 Extracellular digestion • A. outside organism • B. gastrovascular cavities • C. alimentary canal Extracellular digestion • Secrete digestive enzymes onto food source • Absorb nutrients • Best known in fungi and bacteria, some higher animals Gastrovascular cavity: Hydra -extracellular digestion -increased surface area -disadvantage? 4 3/24/2015 Extracellular digestion • A. outside organism • B. gastrovascular cavities • C. alimentary canal Gastrovascular cavity vs. Alimentary Canal Alimentary canal: a simple view 5 3/24/2015 Basic parts of alimentary canal Mechanical digestion storage absorption mouth anus Alimentary canal: mammalian Mouth • Mechanical • Enzymatic • Salivary amylase – Digests starch • Food formed into bolus • Moistened and dissolving with saliva • Peristaltic contraction to stomach 6 3/24/2015 Stomach -muscular organ, approx. 1 liter capacity -esophageal sphincter, pyloric sphincter -rugae (ridges) Digestive mechanisms in stomach • Mechanical • Chemical • enzymatic Mechanical • Mixing and churning 7 3/24/2015 Digestive mechanisms • Mechanical mixing and churning • Chemical - pH around 2 – Also breaks food down • Enzymatic – Pepsin (protease) breaks down protein • Absorption – low surface area, water, small molecules such as ethanol, aspirin Why doesn’t pepsin digest stomach? Activation of pepsin -chief cells – pepsinogen (inactive) -parietal cells - HCl 8 3/24/2015 Small intestine • Most of the enzymatic digestion occurs here • Acid neutralized • Starch, protein, lipids digested Why doesn’t the small intestine digest itself? Fig. 37.13 9 3/24/2015 Most nutrient absorption takes place in small intestine • Structure: another example of increasing surface area Structure of small intestine Microvilli 10 3/24/2015 Large intestine (colon) • Major function is to reabsorb water • Rich in symbiotic bacteria • Bacteria digest cellulose • Some symbiotic bacteria produce vitamin K Variations of vertebrate digestive system • Herbivorous mammals – Specialized fermentation chambers 11.