mechanical digestion

Examples of mechanical digestion in the following topics:

• Processes and Functions of the Digestive System

  • Digestion is necessary for absorbing nutrients from food and occurs through two processes: mechanical and chemical digestion.
  • Many different organs have essential roles in the digestion of food, from the mechanical breakdown of food by the teeth to the creation of bile (an emulsifier) by the liver.
  • This mechanical and chemical breakdown encompasses the process of digestion.
  • Mechanical digestion: Larger pieces of food get broken down into smaller pieces while being prepared for chemical digestion; this process starts in the mouth and continues into the stomach.
  • Enzymes in saliva then begin the chemical breakdown of food; teeth aid in the mechanical breakdown of larger food particles.

• Digestion in the Mouth, Pharynx, and Esophagus

  • Digestion is the mechanical and chemical breakdown of food into smaller components that are more readily absorbed into the bloodstream.
  • Digestion is the mechanical and chemical breakdown of food into smaller components so that it can be more readily absorbed into the bloodstream.
  • When food enters the mouth, digestion begins with the action of mastication, a form of mechanical digestion, and with the contact of saliva.
  • It cleans the oral cavity, moistens the food, and contains digestive enzymes.
  • The mechanism for swallowing is coordinated by the swallowing center in the medulla oblongata and pons.

• Mechanisms of Chemical Digestion

  • Proteins and polypeptides are digested by hydrolysis of the C-N bond .
  • In the absence of stomach pepsin, digestion in the small intestine proceeds with difficulty.
  • Stomach pepsin digests about 20% of the proteins, the rest is digested by pancreatic and small intestine enzymes.
  • Fats are digested by lipases which hydrolyze the glycerol-fatty acid bonds.
  • Proteins and polypeptides are digested by hydrolysis of the C-N bond.

• Mouth

  • The mouth receives and mechanically breaks down food, produces saliva, and is the first portion of the alimentary canal.
  • While its primary function is to begin the process of mechanically and chemically digesting food, the mouth is also the beginning of the alimentary canal—a larger digestive tube.
  • In the digestive process, the mouth's purpose is to prepare food for further digestion in the stomach and the small intestine.
  • This process begins with the mechanical breakdown of food by the teeth, which fit into the alveolar arches.
  • Describe the features of the mouth that play a role in digestion

• Aging and the Digestive System

  • Aging can result in changes in the digestive system due to decreased nerve sensitivity, muscle loss, and increased infection rate.
  • The changes associated with aging of the digestive system are largely caused by decreased nerve sensitivity, loss of muscle tone, and increased susceptibility to bacterial infection because of a weakened immune system.
  • Thus, changes include loss of strength and tone of muscular tissue and supporting muscular tissue, decreased secretory mechanisms, decreased motility of the digestive organs, changes in neurosensory feedback regarding enzyme and hormone release, and diminished response to internal sensations and pain.
  • Malabsorption of nutrients due to inflammatory bowel disease, radiation enteritis, digestive failure, and malnutrition.
  • Several aspects of the digestive tract are labeled in this diagram, including the mouth, large intestine (colon), rectum, anus, ileum, small intestine, stomach, and esophagus.

• Malabsorption of Nutrients

  • The main purpose of the gastrointestinal tract is to digest and absorb nutrients (fat, carbohydrate, protein, and fiber), micronutrients (vitamins and trace minerals), water, and electrolytes.
  • Digestion involves both mechanical and enzymatic breakdown of food.
  • Mechanical processes include chewing, gastric churning, and the to-and-fro mixing in the small intestine.
  • The final products of digestion are absorbed through the intestinal epithelial cells .
  • Causes of malabsorption include infective agents, structural defects, mucosal abnormality, enzyme deficiencies, digestive failure, or other systemic diseases affecting the GI tract.

• Organs of the Digestive System

  • The organs of the digestive system can be divided into upper and lower digestive tracts.
  • The human body uses a variety of mental and physiological cues to initiate the process of digestion.
  • Our digestive system is like a long tube, with different segments doing different jobs.
  • When we take a bite of food, the food material gets chewed up and processed in the mouth, where saliva begins the process of chemical and mechanical breakdown.
  • This diagram shows the relationship between the various organs of the digestive system.

• Gastrulation

  • The endoderm gives rise to the epithelium of the digestive and respiratory systems, and the organs associated with the digestive system, such as the liver and pancreas.
  • The molecular mechanism and timing of gastrulation is different in different organisms.

• Autonomic Interactions

  • Consider sympathetic as fight or flight and parasympathetic as rest and digest or feed and breed.
  • Increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for the enhanced blood flow to skeletal muscles.
  • Conversely, the PSNS promotes a rest-and-digest response, and promotes the following functions:

• Chemical Digestion of Carbohydrates, Proteins, Lipids, and Nucleic Acids

  • Chemical breakdown of macromolecules contained in food is completed by various enzymes produced in the digestive system.
  • The digestive enzymes, however, are secreted mainly as their inactive precursors, the zymogens.
  • Sucrose digestion yields the sugars fructose and glucose, which are readily absorbed by the small intestine.
  • Digestion of certain fats begins in the mouth, where lingual lipase breaks down short chain lipids into diglycerides.
  • Complete digestion of one molecule of fat (a triglyceride) results in three fatty acid molecules and one glycerol molecule.