Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Concept 41.5: Evolutionary adaptations of vertebrate digestive
Transcript
The Small Intestine • The small intestine is the longest section of the alimentary canal • It is the major organ of digestion and absorption LE 41-19 Liver Bile Gallbladder Stomach Acid chyme Intestinal juice Pancreas Duodenum of small intestine • The pancreas produces proteases, proteindigesting enzymes that are activated after entering the duodenum LE 41-20 Pancreas Membrane-bound enteropeptidase Inactive trypsinogen Other inactive proteases Lumen of duodenum Trypsin Active proteases • The liver produces bile, which aids in digestion and absorption of fats • The epithelial lining of the duodenum, called the brush border, produces several digestive enzymes LE 41-21 Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Oral cavity, Polysaccharides Disaccharides pharynx, Salivary amylase esophagus Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intestine Polysaccharides Polypeptides Pancreatic amylases Pancreatic trypsin and chymotrypsin Maltose and other disaccharides DNA, RNA Pancreatic nucleases Nucleotides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Disaccharidases Monosaccharides Bile salts Fat droplets Smaller polypeptides Epithelium of small intestine (brush border) Fat globules Glycerol, fatty acids, glycerides Small peptides Nucleotidases Dipeptidases, carboxypeptidase, and aminopeptidase Nucleosides Amino acids Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates LE 41-22 Key Liver Stimulation Enterogastrone Inhibition Gallbladder Gastrin CCK Stomach Pancreas Secretin Duodenum CCK Absorption of Nutrients • The small intestine has a huge surface area, due to villi and microvilli that are exposed to the intestinal lumen • The enormous microvillar surface greatly increases the rate of nutrient absorption LE 41-23 Key Vein carrying blood to hepatic portal vessel Nutrient absorption Microvilli (brush border) Blood capillaries Epithelial cells Muscle layers Epithelial cells Large circular folds Villi Lacteal Villi Intestinal wall Lymph vessel Fat globule • Amino acids and sugars pass through the epithelium of the small intestine and enter the bloodstream • After glycerol and fatty acids are absorbed by epithelial cells, they are recombined into fats within these cells Bile salts Fat droplets coated with bile salts Micelles made up of fatty acids, monoglycerides, and bile salts Epithelium of small intestine Epithelium of lacteal Lacteal The Large Intestine • The large intestine, or colon, is connected to the small intestine • Its major function is to recover water that has entered the alimentary canal • The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins Concept 41.5: Evolutionary adaptations of vertebrate digestive systems are often associated with diet • Digestive systems of vertebrates are variations on a common plan • However, there are intriguing adaptations, often related to diet Some Dental Adaptations • Dentition, an animal’s assortment of teeth, is one example of structural variation reflecting diet • Mammals have specialized dentition that best enables them to ingest their usual diet LE 41-26 Incisors Molars Canines Premolars Carnivore Herbivore Omnivore Stomach and Intestinal Adaptations • Herbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation LE 41-27 Small intestine Stomach Small intestine Cecum Colon (large intestine) Carnivore Herbivore Symbiotic Adaptations • Many herbivores have fermentation chambers, where symbiotic microorganisms digest cellulose • The most elaborate adaptations for an herbivorous diet have evolved in the animals called ruminants LE 41-28 Intestine Rumen Reticulum Esophagus Abomasum Omasum
