Chapter 41 Animal Nutrition PDF

Chapter 41 Animal Nutrition 04.12.2024 PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp...

Chapter 41 Animal Nutrition 04.12.2024 PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Essential Nutrients Animals need a source of organic carbon and organic nitrogen in order to construct organic molecules. Essential nutrients are required by cells and must be obtained from dietary sources. There are four classes of essential nutrients: – Essential amino acids – Essential fatty acids – Vitamins – Minerals Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Very long tongue The six-foot neck of a giraffe Essential nutrients: Minerals are simple inorganic nutrients, usually required in small amounts. Minerals serve a variety of important functions including enzymes cofactors Essential nutients: Fatty acids and Vitamins Animals can synthesize most of the fatty acids they need The essential fatty acids are certain unsaturated fatty acids that must be obtained from the diet Vitamins are organic molecules required in the diet in small amounts Many vitamins function as coenzymes 13 vitamins essential to humans have been identified. Vitamins are grouped into two categories: fat-soluble and water-soluble Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings The four stages of food processing Small molecules Pieces of food Chemical Nutrient Mechanical digestion molecules digestion (enzymatic enter body hydrolysis) cells Food Undigested material 1 Ingestion 2 Digestion 3 Absorption 4 Elimination Mechanical & Chemical Digestion human digestive system Tongue Sphincter Salivary Oral cavity glands Salivary glands Pharynx Mouth Esophagus Esophagus pyloric sphincter Liver Stomach Gall- bladder Stomach Ascending Gall- portion of bladder large intestine Duodenum of Pancreas small intestine Small Liver intestine Small Small intestine intestine Pancreas Large Large intestine intestine Rectum Rectum Anus Anus Appendix A schematic diagram of the human digestive system Cecum The Oral Cavity, Pharynx, and Esophagus The first stage of digestion is mechanical and takes place in the oral cavity. Salivary glands deliver saliva to lubricate food. Teeth chew food into smaller particles. This is mechanical digestion that increases the surface area exposed to the enzyme: salivary amylase, initiating breakdown of glucose polymers = carbohydrate digestion. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  The tongue shapes food into a bolus and provides help with swallowing. The region we call our throat is the pharynx, a junction that opens to both the esophagus and the trachea (windpipe) The trachea leads to the lungs Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  The esophagus conducts food from the pharynx down to the stomach by peristalsis. Swallowing causes the epiglottis to block entry to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract. Coughing occurs when the swallowing reflex fails and food or liquids reach the windpipe. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings From mouth to stomach: the swallowing reflex and peristalsis Food Epiglottis Tongue up Pharynx Esophageal Glottis sphincter Glottis Esophageal Larynx contracted down sphincter Trachea Esophagus and open contracted To To Relaxed lungs stomach muscles Contracted muscles Relaxed muscles Sphincter relaxed Stomach Chemical Digestion in the Stomach The stomach stores food and secretes gastric juice, which converts a meal to acid chyme. Gastric juice is made up of hydrochloric acid + pepsin Parietal cells secrete H+ and Cl- ions separately. And intrinsic factor that is necessary for transport and absorption of vit B12 Chief cells secrete inactive pepsinogen, which is activated to pepsin when mixed with HCl in the stomach. They also secrete some gastric lipase Mucus protects the stomach lining from gastric juice. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings The stomach Esophagus and its Sphincter secretions Stomach Sphincter 5 µm Small intestine Folds of epithelial tissue Interior surface Epithelium 3 of stomach 1 Pepsinogen Pepsinogen Pepsin 2 and HCl HCl are secreted. Gastric gland 2 1 HCl converts pepsinogen to H+ pepsin. Mucus cells 3. Cl– Pepsin activates 3 more pepsinogen. Chief cells (Positive feedback) Chief cell Parietal cells Parietal cell  Gastric lipases Partial Digestion: Gastric lipase is especially important for the digestion of short-chain and medium-chain triglycerides (found in dairy products and some oils), but it is less effective against long-chain triglycerides, which require pancreatic lipase for complete digestion Role in Infants: In infants, gastric lipase plays a more significant role in fat digestion, as their pancreas is not yet fully developed and may not produce enough pancreatic lipase. Gastric lipase helps newborns digest the fat in breast milk or formula effectively  Gastric ulcers, lesions in the lining, are caused mainly by the bacterium Helicobacter pylori Coordinated contraction and relaxation of stomach muscle churn (‫حرك‬ ّ ُ‫ ي‬،‫ )يخلط‬the stomach’s contents. Sphincters prevent chyme from entering the esophagus and regulate its entry into the small intestine. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Digestion in the Small Intestine The small intestine is the longest section of the alimentary canal. It is the major organ of digestion and absorption. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Enzymatic hydrolysis in the human digestive system Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Oral cavity, Polysaccharides Disaccharides pharynx, (starch, glycogen) (sucrose, lactose) esophagus Salivary amylase Smaller polysaccharides, maltose Proteins Stomach Pepsin Small polypeptides Lumen of Polysaccharides Polypeptides DNA, RNA Fat globules small intestine Pancreatic amylases Pancreatic trypsin and Pancreatic chymotrypsin nucleases Maltose and other Bile salts disaccharides Fat droplets Nucleotides Smaller polypeptides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fatty Amino acids acids, monoglycerides Epithelium Small peptides Nucleotidases of small Nucleosides intestine Disaccharidases Dipeptidases, carboxypeptidase, (brush and aminopeptidase Nucleosidases border) Such as maltase and phosphatases Monosaccharides Amino acids Nitrogenous bases, sugars, phosphates  The first portion of the small intestine is the duodenum, where acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Liver Gallbladder Bile Stomach Secretin and CCK – Gastrin + Chyme CCK + Pancreas Hormonal control of Duodenum Secretin digestion + of small intestine Key CCK + Stimulation + – Inhibition Pancreatic secretions The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum. Its solution is alkaline and neutralizes the acidic chyme. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Bile Production by the Liver In the small intestine, bile aids in digestion and absorption of fats. Bile emulsifies fat. This is physical NOT chemical digestion Fat emulsification increases the surface area for chemical digestion of fats by lipases Bile is made in the liver and stored in the gallbladder Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Secretions of the small intestine The epithelial lining of the duodenum, called the brush border, produces several digestive enzymes Enzymatic digestion is completed as peristalsis moves the chyme and digestive juices along the small intestine. Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients and water. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Absorption in the small intestine → Villi The small intestine has villi and microvilli that increase the surface area for absorption Villi and microvilli are exposed to the intestinal lumen = space / cavity The enormous microvillar surface area greatly increases the rate of nutrient absorption Sodium-glucose linked transporter 1 (SGLT1) is responsible for the active transport of glucose and galactose into enterocytes (intestinal cells) against their concentration gradient by using the sodium gradient Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Structure of the small intestine Vein carrying blood Microvilli (brush border) at apical (lumenal) surface to hepatic portal vein Lumen Blood capillaries Epithelial cells Basal Muscle layers surface Large Epithelial cells Villi circular folds Lacteal Key Lymph Nutrient vessel absorption Intestinal wall Villi Insulin is secreted in response to high blood glucose levels to promote satiety and reduce appetite  Each villus contains a network of blood vessels and a small lymphatic vessel called a lacteal After glycerol and fatty acids are absorbed by epithelial cells, they are recombined into fats within these cells. These fats are mixed with cholesterol and coated with protein, forming molecules called chylomicrons, which are transported into lacteals. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Amino acids and sugars pass through the epithelium of the small intestine and enter the bloodstream. Capillaries and veins from the lacteals converge in the hepatic portal vein and deliver blood to the liver and then on to the heart. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  Absorption in the large intestine The colon of the large intestine is connected to the small intestine by cecum The cecum aids in the fermentation of plant material and connects where the small and large intestines meet The human cecum has an extension called the appendix, which plays a very minor role in immunity Digital image of a human colon The cecum is the first part of the large intestine. It is a pouch that receives partially digested food (chyme) from the small intestine through the ileocecal valve. This valve controls the flow of material from the small intestine into the cecum and prevents backflow from the large intestine into the small intestine. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  A major function of the colon is water reabsorption, recovering water that has entered the alimentary canal. This process is critical for maintaining fluid balance in the body Wastes of the digestive tract, the feces, become more solid as they move through the colon Feces pass through the rectum and exit via the anus Appendix: Attached to the cecum is the vermiform appendix, a small, tube-like structure. The function of the appendix is still somewhat debated, but it is thought to play a role in immune function and maintaining gut flora, particularly in early life. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings  The colon (large intestine) houses strains of the Escherichia coli, some of which produce vitamins ++ ‫تعايش‬ Feces are stored in the rectum until they can be eliminated. Two sphincters between the rectum and anus control bowel movements – the internal anal sphincter and the external anal sphincter Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Appetite-regulating peptide YY is a hormone that is secreted from hormones endocrine cells called L-cells in the small intestine It inhibits gastric motility and increases water and electrolyte absorption in the colon PYY may also suppress pancreatic secretion It is secreted by the neuroendocrine cells in the ileum and colon in response to a meal, and has been shown to reduce appetite Ghrelin: Secreted primarily by the stomach, particularly in the fundus (upper portion), but also by other tissues like the pancreas and small intestine. Function: Ghrelin is often called the "hunger hormone." It stimulates appetite by signaling the brain to increase food intake. Ghrelin levels typically rise before meals, increasing feelings of hunger, and decrease after eating. This hormone also plays a role in energy metabolism and has been shown to Obese people and leptin resistance influence fat storage. Leptin works on the hypothalamus to Regulation: Ghrelin levels are low when the reduce appetite when fat stores are stomach is full and high when the stomach is empty. sufficient, signaling that the body has Chronic stress and sleep deprivation can increase enough energy reserves ghrelin levels, which may increase hunger Review Bloodstream Veins to heart Lymphatic system Hepatic portal vein Liver Lipids Absorbed food Absorbed Mouth Stomach (except lipids) water Esophagus Small intestine Anus Secretions from the gastric glands Large Rectum of the stomach intestine Secretions from the pancreas and the liver