digestive system

• The stomach is a muscular organ that churns and mixes food with digestive juices to break it down further.
• Hyperglycemia is the condition of excessively high levels of glucose in the blood, where excess glucose is stored in body cells as glycogen or converted to fat.
• Carbohydrates are composed of simple sugars (monosaccharides).
• Glycolysis, the first step of cellular respiration, occurs in the cytosol and energizes a glucose molecule so it can be split into two pyruvic acid molecules and yield ATP.
• Monosaccharides are the building blocks of carbohydrates and are broken down to glucose and released to blood.
• Cellular respiration involves the oxidation of glucose, resulting in the formation of carbon dioxide, water, and ATP.
• The pyruvic acid enters the mitochondrion, where citric acid cycle enzymes remove more hydrogen atoms and decompose it to CO2.
• Carbohydrates are the body’s preferred source to produce cellular energy (ATP).
• During glycolysis and the citric acid cycle, small amounts of ATP are formed.
• The electron transport chain, which carries out oxidative phosphorylation, accounts for most of the ATP generated by cellular respiration, and finally unites the removed hydrogen with oxygen to form water.
• Polysaccharides are composed of simple sugars and are digested to simple sugars.
• Cellular uses of carbohydrates include ATP production, glycogen and fat breakdown for ATP formation, and excess storage as glycogen or fat.
• The citric acid cycle, also known as the Krebs cycle, occurs in the mitochondrion and produces virtually all the carbon dioxide and water resulting from cellular respiration, yielding a small amount of ATP.
• Glucose is the major breakdown product of carbohydrate digestion and is used to make ATP.
• Hypoglycemia is the condition of low levels of glucose in the blood, where glycogenolysis, gluconeogenesis, and fat breakdown occur to restore normal blood glucose levels.
• During glycolysis, each glucose molecule is broken down into two molecules of pyruvic acid as hydrogen atoms containing high-energy electrons are removed.
• The peritoneal attachments of the abdominal organs include the diaphragm, falciform ligament, liver, spleen, gallbladder, stomach, and pancreas.
• The stomach is a C-shaped organ located on the left side of the abdominal cavity, where food enters at the cardioesophageal sphincter from the esophagus and empties into the small intestine at the pyloric sphincter (valve).
• The layers of tissue in the alimentary canal from innermost to outermost are mucosa, submucosa, muscularis externa, and serosa.
• The regions of the stomach include the cardia, fundus, body, greater curvature, lesser curvature, pylorus, and duodenum.
• The submucosa is just beneath the mucosa, a soft connective tissue with blood vessels, nerve endings, mucosa-associated lymphoid tissue, and lymphatic vessels.
• The muscularis externa consists of an inner circular layer and an outer longitudinal layer.
• The mesentery is the innermost layer that is continuous with the outermost layer.
• The serosa is the outermost layer of the wall, containing fluid-producing cells and is continuous with the mesentery.
• The mucosa is the innermost layer, consisting of a moist membrane consisting of surface epithelium, small amount of connective tissue (lamina propria), and a scanty smooth muscle layer that lines the cavity (lumen).
• The esophagus conducts food by peristalsis, a slow rhythmic squeezing, to the stomach.
• The esophagus is a passageway for food only, with the respiratory system branching off after the pharynx.
• The alimentary canal wall contains two intrinsic nerve plexuses that are part of the autonomic nervous system: the submucosal nerve plexus and the myenteric nerve plexus.
• The esophagus is about 10 inches long and runs from the pharynx to the stomach through the diaphragm.
• Absorption of foodstuffs involves the transport of their end products in the blood or lymph.
• Digestion and absorption of foodstuffs involve the breakdown of carbohydrates, proteins, and fats by enzymes and the transport of their end products in the blood or lymph.
• Oligosaccharides consist of a few linked monosaccharides.
• The pharynx and esophagus have no digestive function and serve as passageways to the stomach.
• Amino acids enter the capillary blood in the villi and are transported to the liver via the hepatic portal vein.
• Food propulsion involves swallowing and peristalsis.
• No food absorption occurs in the mouth.
• Defecation is the elimination of indigestible substances from the GI tract in the form of feces.
• End products of digestion are absorbed in the blood or lymph.
• Food must enter mucosal cells and then move into blood or lymph capillaries for absorption.
• The gastrointestinal tract performs essential processes such as ingestion, mechanical breakdown, digestion, absorption, and defecation.