Animal nutrition Chapter 41

Function 1. Digestion 2. Absorption of nutrients/water 3. Elimination Energy Growth 3. Elimination

1 INGESTION 2 DIGESTION 3 ABSORPTION 4 ELIMINATION Mechanical digestion 1 INGESTION Chemical digestion (enzymatic hydrolysis) 2 DIGESTION Nutrient molecules enter body cells Figure 41.5 The stages of food processing 3 ABSORPTION 4 ELIMINATION Undigested material

Heterotrophs

Intracellular digestion

Extracellular digestion

Extracellular digestion

Figure 41.1 How does a crab help an otter make fur?

Figure 41.9 Variation in alimentary canals Crop Gizzard Esophagus Intestine Pharynx Anus Mouth Typhlosole Lumen of intestine (a) Earthworm Foregut Midgut Hindgut Esophagus Rectum Anus Crop Mouth Gastric cecae Figure 41.9 Variation in alimentary canals (b) Grasshopper Stomach Gizzard Intestine Mouth Esophagus Crop Anus (c) Bird

Digestive system

General structure Gastrointestinal tract (tube) Mucosa: inner layer (epithelial) Submucosa: connective Muscularis: 2 layers of muscle Serosa: outer layer (connective) Plexues: nerves located in the submucosa

Digestive organs Mouth Pharynx Esophagus Stomach Small intestine (duodenum, jejunum, ileum) Large intestine (cecum, ascending colon, transverse colon, descending colon, sigmoid, rectum, anus)

Digestive organs Accessory organs Liver Gallbladder Pancreas

Digestion Mouth Teeth Gizzard (in birds to help grind food) Salivary glands Secrete saliva Amylase (enzyme to breakdown starch)

Mouth

Salivary glands

Digestion Chew or mastication Tongue pushes food Pharynx Epiglottis closes Esophagus

Pharynx

Esophagus Esophagus Muscular tube Connects pharynx to stomach Peristalsis: Rhythmic movement of muscle contractions Moves food along Esophageal sphincter: End of esophagus keeps food in stomach

Stomach Mucosa lining (epithelial) Parietal cells Secrete H + Cl ions Chief cells Secrete pepsinogen Pepsinogen is converted to pepsin Digests proteins

Stomach Gastric juices: HCl, pepsinogen & mucus pH=2 Chyme: Mixture of partially digested food

Stomach

Stomach

Small intestine Chyme Leaves stomach via pyloric sphincter Duodenum Digestive enzymes from pancreas Bile from liver & gallbladder Most digestion occurs in the duodenum & jejunum

Intestines

Small intestine

Small intestines Villi along intestine epithelium Microvilli “brush border” Aids in absorption Secretes enzymes Break disaccharides (sucrose, lactose)

Small intestine

Accessory organs

Accessory organs Pancreas Secretes fluids via pancreatic duct Exocrine system Trypsin & chymotrypsin (proteases) Amylase (starch) Lipase (fats) Bicarbonate (neutralizes HCl) Endocrine (insulin and glucagon)

Accessory organs Liver Secretes bile Contains bile pigments & bile salts Bile pigments are waste from break down of RBC Eliminated

Accessory organs Bile salts Emulsify the fats Bile made in liver Stored in gall bladder Released when eat fatty meal Gallstones can block release

Small intestines Monosaccharides, aa are transported to the blood capillaries Hepatic portal vein Liver Heart Transported to body

Small intestines Fatty acids & monoglycerides Villi Triglycerides Chylomicrons: (triglyceride & protein coat) Lymph system

Microvilli (brush border) at apical (lumenal) surface Fig. 41-15b Microvilli (brush border) at apical (lumenal) surface Lumen Blood capillaries Epithelial cells Basal surface Epithelial cells Lacteal Figure 41.15 The structure of the small intestine Lymph vessel Villi Key Nutrient absorption

Lumen of small intestine Triglycerides Fatty acids Monoglycerides Fig. 41-16 Lumen of small intestine Triglycerides Fatty acids Monoglycerides Epithelial cell Triglycerides Phospholipids, cholesterol, and proteins Figure 41.16 Absorption of fats Chylomicron Lacteal

Essential nutrients Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Oral cavity, pharynx, esophagus Polysaccharides Disaccharides (starch, glycogen) (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Polysaccharides Polypeptides DNA, RNA Fat globules Pancreatic amylases Pancreatic trypsin and chymotrypsin Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets Nucleotides Smaller polypeptides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fatty acids, monoglycerides Amino acids Epithelium of small intestine (brush border) Small peptides Nucleotidases Nucleosides Disaccharidases Dipeptidases, carboxypeptidase, and aminopeptidase Nucleosidases and phosphatases Monosaccharides Amino acids Nitrogenous bases, sugars, phosphates

Large intestines Absorbs water Absorbs vitamin K Concentrates wastes E. coli Feces Cloaca Combines feces & urine wastes in some animals

Large intestine

Large intestine

Absorbed food (except lipids) Absorbed water Mouth Stomach Lipids Veins to heart Hepatic portal vein Lymphatic system Liver Absorbed food (except lipids) Absorbed water Mouth Stomach Lipids Esophagus Figure 41.UN04 Summary of key concepts: mammalian digestive organs Small intestine Anus Secretions from salivary glands Secretions from gastric glands Secretions from liver Large intestine Rectum Secretions from pancreas

Food BMR Basal metabolic rate Obesity Heart disease, diabetes, stroke Anorexia, Bulimia

Essential nutrients Essential aa Minerals Vitamins A, B-complex, C, D, E, K Scurvy, rickets, pernicious anemia, bleeding

Figure 41.3 Obtaining essential nutrients from an unusual source

Abnormalities Ulcers H. pylori Bacteria Treated with antibiotics Reflux: Gastric juices go backwards to esophagus

Hiatal hernia

Pyloric Stenosis

Colon Cancer

Jaundice