food

• Ingestion, the taking in of food into the body.
• Mechanical processing of food into smaller pieces and mixing it together
• Secretion of water, acids, enzymes and buffers to aid in digestion.
• Digestion, the chemical breakdown of large food molecules into smaller ones.
• Absorption of nutrients from food into the bloodstream.
• In the mouth, mastication occurs as the teeth physically

  tear the food into smaller pieces.
• The tongue produces a ball of chewed, softened food

  called a bolus, which is swallowed.
• The uvula folds back, closing off the nasopharynx

  and forcing food down the laryngopharynx.
• The flap of tissue called the epiglottis closes the opening to the lungs to prevent entrance of food and fluids to the airways
• From the oropharynx (the portion of the pharynx situated behind the oral cavity), the bolus of swallowed substances now enters the esophagus and passes down the length of the tube by alternating contraction and relaxation of the muscles called peristalsis.
• Stomach

  The opening into the stomach is guarded by the cardiac

  sphincter, which prevents the regurgitation of acidic

  chyme from the stomach.
• Stomach

  Chemical digestion of food takes place in the..
• The partially digested food, mucus, and acid mixture

  is now referred to as chyme.
• The pyloric sphincter will open and release small

  amounts (30mL) of chyme into the small intestine.
• The first segment of the small intestine is the duodenum.
• Food enters the duodenum from the stomach by the pyloric sphincter
• In the duodenum, various enzymes are released from the acinar cells of the pancreas which assist in the breakdown of carbohydrates, proteins, and fats, and which are converted into glucose, amino acids, and fatty acids, respectively
• The jejunum is the middle segment of the small

  intestine;
• the ileum is the last segment.
• • Villi increase surface area.
• The hepatic portal system is a series of blood vessels that deliver nutrients to the liver.
• Large Intestine

  In this organ, water and ions are reabsorbed and the bulk that remains is then stored for a while until mass movements occur and defecation reflex is initiated.
• The first part of the large intestine is a pouch called the

  cecum.
• A dead-end pouch called the appendix is attached here.
• • • salivary amylase initiates carbohydrate breakdown
• • • lingual lipase starts fat digestion
• hydrochloric acid (HCI) - secretions of the parietal

  cells, which maintains the level of acidity (pH 1 to 2) in

  the stomach
• • • Pepsin Protein degradation into smaller particles
• In the duodenum of the small intestine, pancreatic

  juices are secreted by the pancreas via the ampulla of

  Vater, a duct formed by the union of the pancreatic duct

  and the common bile duct.
• Liver

  Its basic structural component is the hepatocyte.
• Liver

  It synthesizes proteins such as albumin and fibrinogen.
• Liver

  It also converts highly toxic ammonia (accumulates in the body during protein breakdown) into urea, a more tolerable form.
• The liver produces bile, a fluid that contains cholesterol, bile acids, and bilirubin which aid in lipid digestion.
• Bile is not an enzyme; it is an emulsifier. It is stored and concentrated in the gallbladder
• Bile flows from the liver canaliculi to the hepatic ducts

  and then to the common hepatic duct.
• It may flow into the gall bladder via the cystic duct to be

  stored, concentrated, and used at a later time, or go directly into the CBD, to the ampulla of Vater, and then to the duodenum.
• Pancreas

  • is both an endocrine and an exocrine gland.
•  The islets of Langerhans are responsible for the secretion of insulin (in lowering blood glucose levels) and glucagon (in raising blood glucose levels), which is an endocrine function.
• For its exocrine functions, acinar glands secrete digestive enzymes such as trypsinogen, chymotrypsinogen, and carboxypeptidase into theduodenum by the pancreatic duct and the ampulla of Vater.
• trypsinogen (converted by enterokinase to its active enzyme trypsin, which is responsible for breaking down proteins into amino acids)