A+P Chapter 23: Digestive System

-Mucosa: innermost layer, glands secrete mucos, digestive enzymes and hormones
-Submucosa: loose connective tissue contains blood vessels, nerves, lymph vessels
-Muscle layer: 2layers of muscle, moves food along tract
Serosa: outermost lining

-Enteral nervous system (ENS)
-ENS part of the parasympathetic and sympathetic nervous system and responds to vagal stimulation
-ENS regulates gut motility and secretion

-Chyme is ejected from the stomach into the small intestine
-Concerned primarily with chemical digestion and absorption of food
-3 parts: duodenum, jejunum, ileum

-Aprox 10 inches
-receives chyme from stomach, secretions from gallbladder, liver and pancreas
-Most digestion and absorption occur here!!

-Patches of lymphoid tissue that line the ileum
-Diminish the bacterial content in the digestive system

-Extends from the ileocecal valve to the anus
-Cecum, colon, rectum, and anal canal
-Absorption of water and certain lytes
-Synthesis of certain vitamins by intestinal bacteria
-Temporary storage of feces
-Eliminate wastes form the body

-Villi and microvilli on the epithelial cells increase the amount of digested food that can be absorbed
-Large network of blood and lymph capillaries which drain into the hepatic portal vein and then liver
-Cells in intestinal wall secrete several digestive enzymes including secretin and cholecystokinin

-Larges gland in the body
-2 main lobes: right (larger) and left (smaller)

-Synthesis of bile salts and secretion of bile
-Synthesis of plasma proteins
-Storage of glucose in the form of glycogen, fas-sol vitamins (A,D,E,and K)
-Detoxification
-Excretion of many substances including bilirubin, cholesterol, and drugs
-Metabolism of carbohydrates, protein and fats
-Phagocytosis

-Bile salts play an important role in fat digestion and absorption of fat-soluble vitamins

-Plasma proteins play an important role in maintaing blood volume and controlling blood coagulation

-Liver plays an important role in the detoxification of drugs and other harmful substances
-Liver changes toxic substances into substances that can be more easily eliminated from the body by the kidneys

-The liver removes glucose from the blood and concerts it to glycogen when blood glucose levels rise and stores if for further use

-The liver can make a variety of amino acids

-The liver can break down fatty acids, synthesize cholesterol and phospholipids, and convert excess dietary protein and carbohydrates to fat

-The hepatic macrophages
-Can phagocytose bacteria and other substances

-receives approximately 1.5L/min from the portal vein (from all organs of digestion) and hepatic artery (delivers O2 rich blood from aorta)
-Blood leaves the liver through the hepatic veins and empties into the vena cava

-Greenish yellow secretion produced by the liver and stored in the gallbladder
-Mainly H20, lytes, cholesterol, bile pigments and bile salts
-Play an important role in fat digestion and absorption of fat-soluble vitamins
-Made from cholesterol by the liver
-If the liver is stimulated to make additional bile salts, more cholesterol is used up: the basis of the "statins"

-Bile pigment
-Formed from the hemoglobin of worn out RBC's

-Sac attached to underside of the liver
-The cystic duct connects the gallbladder with the common bile ducts
-Bile (produced in liver) flows through the hepatic duct into the cystic duct into the gallbladder

-Secrets endocrine (digestive enzymes and an alkaline secretion) and exocrine enzymes
-THE PANCREATIC ENZYMES ARE THE MOST IMPORTANT OF ALL THE DIGESTIVE ENZYMES!!
-Secretion is controlled by vagus nerve and hormones

-1: an enzyme (amylase) breaks down the polysaccharide into disaccharides
-2: DisaccaridASEs break disaccharides into monosaccharides

-Salivary amylase (ptyalin)
-Pancreatic amylase
-'-ase' indicates enzyme

-Sucrase
-Lactase
-Maltase

-Proteins are very long peptide chains, made up of amino acids, that must be broken down in order to be absorbed
-Proteases (enzymes that digest proteins) are secreted by 3 organs: stomach, intestinal cells, and pancreas
-Hydrochloric acid also aids in protein digestion by uncoiling strands of protein and making them more sensitive to protease

-Pepsin secreted by stomach
-Enterokinase secreted by intestinal cells
-Trypsin and chymotrypsin secreted by pancreas (most important)

-Lipases digest fats (most important pancreatic lipase)
-Fat tends to clump together and lipase cannot readily digest it until bile splits the clump of fat into smaller pieces (process called emulsification)
-Bile salts prevent the fatty acids (end product of fat digestion) from reforming clumps in the intestine

-Small organic molecules that help regulate cell metabolism
-Fat soluble (A,D,E, and K) are stored in fat and can become toxic
-Water-soluble (B and C) are not stored and generally excreted in the urine

-Inorganic substances necessary for norma body function

-Necessary for skin, mucous membranes and night vision
-Night blindness, dry, scaly skin, disorders of the mucous membranes

-Necessary for the absorption of calcium and phosphors
-Rickets in children; osteomalacia in adults

-Necessary for health of cell membrane
-None defined

-Needed fro the synthesis of prothrombin and other clotting factors
-Bleeding

-Helps release energy from carbohydrates and amino acids; needed for growth
-Beriberi; alcohol-induced Wernicke's syndrome

-Essential for growth
-Skin and tongue disorders; dermatitis

-Helps release energy from nutrients
-Pellagra with dermatitis, diarrhea, mental disorders

-Participates in the metabolism of amino acids and proteins
-Nervous system and skin disorders

-Helps form red blood cells and deoxyribonucleic acid (DNA)
-Anemias esp pernicious anemia

-Participates in the formation of hemoglobin and DNA
-Anemia; neural tube defects in embryo

-Necessary for the synthesis of collagen; helps maintain capillaries; aids in absorption of iron
-Scurvy; poor bone and wound healing

-Nerve and muscle activity
-Nerve and muscle disorders

-Water balance; nerve impulse conduction
-Weakness, cramps, diarrhea, dehydration, confusion

-Component of bones and teeth, nerve conduction, muscle contraction, blood clotting
-Rickets, tetany, bone softening

-Component of bones and teeth, ATP, nucleic acids, and cell membranes
-Bone demineralization

-Component to hemoglobin (RBC's)
-Anemia, dry skin

-Necessary for synthesis of thyroid hormones
-Hypothyroidism; iodine-defecient goiter

-Component of some enzymes; important in carbohydrate metabolism
-Muscle spasm, dysrhythmias, vasodilation