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Digestive System

Explore the digestive systems of herbivores, carnivores, and omnivores, as well as invertebrates. Learn about the unique digestive systems of hydra, jellyfish medusa, nematodes, rabbits, birds, and ruminants. Understand the functions of the digestive organs and the process of digestion. Discover the essential nutrients and enzymes involved in breaking down carbohydrates, proteins, and lipids. Gain knowledge about the neural regulation of digestive processes.

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Digestive System

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  1. Digestive System Biology for Majors

  2. Different Diets Herbivores Carnivores Omnivores

  3. Invertebrate Digestive System (a) hydra and jellyfish medusa (b) nematode

  4. Monogastric Digestive Systems In the rabbit the small intestine and cecum are enlarged to allow more time to digest plant material

  5. Avian Because birds do not have teeth, their stomachs have two chambers: • the proventriculus, where gastric juices are produced to digest the food before it enters the stomach • the gizzard, where the food is stored, soaked, and mechanically ground The avian esophagus has a pouch, called a crop, which stores food

  6. Ruminant Digestion

  7. Digestion Begins (a) oral cavity. Food is masticated by teeth and moistened by saliva secreted from the (b) salivary glands. Amylase and lipase in the saliva begin to digest starches and fats

  8. Esophagus The food bolus travels through the esophagus by peristaltic movements to the stomach

  9. The Stomach The human stomach is acidic and digests most of the protein from food

  10. The Small Intestine Further digestion and absorption take place in the small intestine

  11. The Large Intestine The large intestine reabsorbs water from the undigested food and stores waste until elimination

  12. Accessory Organs Accessory organs are organs that add secretions (enzymes) that catabolize food into nutrients. Accessory organs include: • salivary glands • The liver produces bile, a digestive juice that is required for the breakdown of fatty components of the food in the duodenum. The liver also processes the vitamins and fats and synthesizes many plasma proteins • The pancreas makes juices that neutralize the acidic chime and contain enzymes needed to digest protein and carbohydrates • The gallbladder aids the liver by storing bile and concentrating bile salts

  13. Where do animals get energy? The primary source of energy for animals is carbohydrates, mainly glucose. Glucose is called the body’s fuel. The digestible carbohydrates in an animal’s diet are converted to glucose molecules through a series of catabolic chemical reactions, then cellular respiration a second catabolic process turns glucose and oxygen into ATP to fuel cell functions

  14. Essential Nutrients • Essential Amino Acids • Carbohydrates for energy • The omega-3 alpha-linolenic acid and the omega-6 linoleic acid are essential fatty acids needed to make some membrane phospholipids • Vitamins and Minerals are required in small quantities for many enzymes to function and, for this reason, are considered to be co-enzymes

  15. Enzymes break Down Carbohydrates

  16. Digestion of Carbohydrates

  17. Protein Digestion

  18. Lipids are Digested in the Small Intestine

  19. Vitamins Vitamins can be either water-soluble or lipid-soluble: • Fat soluble vitamins are absorbed in the same manner as lipids • Water-soluble vitamins can be directly absorbed into the bloodstream from the intestine

  20. Digestion Review

  21. Neural Response: Digestive Phases In the cephalic phase, the neural response to the stimulus provided by food triggers salivation and secretion of gastric juices to prepare the stomach to receive food

  22. The Gastric Phase The gastric phase begins once the food arrives in the stomach. It builds on the stimulation provided during the cephalic phase. Gastric acids and enzymes process the ingested materials. The gastric phase is stimulated by • distension of the stomach • a decrease in the pH of the gastric contents • the presence of undigested material This phase consists of local, hormonal, and neural responses. These responses stimulate secretions and powerful contractions

  23. Intestinal Phase • The intestinal phase begins when chyme enters the small intestine triggering digestive secretions • This phase controls the rate of gastric emptying • In addition to gastrin emptying, when chyme enters the small intestine, it triggers other hormonal and neural events that coordinate the activities of the intestinal tract, pancreas, liver, and gallbladder

  24. Practice Question Why is the small intestine so long and twisted up?

  25. Quick Review • How are different organisms’ digestive systems similar or different? • How is energy produced through diet and digestion? • What are the steps involved in the digestive system processes? • What is the role of neural regulation in digestive processes?

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