Digestive System Disorders Flashcards
What are the five continuous layers of the gut?
Inner layer mucosa - contains mucus-producing cells
Submucosal layer - Connective tissue, including blood vessels, nerves, lymphatics and secretory glands
Circular smooth muscle fibers
Longitudinal smooth muscle fibers
Outer layer visceral peritoneum or serosa
Peritoneum
A large serous membrane in the abdominal cavity
Parietal covers the abdominal wall and superior surface of the urinary bladder and uterus
Visceral encases the organs such as the stomach and intestine
Peritoneal cavity
The potential space between the parietal and visceral peritoneum. Contains serous fluid.. Numerous lymphatic channels drain excessive fluid from the cavity.
Characteristics of serous membranes
Thin, somewhat permeable, highly vascular.
Mesentery
Double layer of peritoneum that supports the intestines and conveys blood vessels and nerves to supply the wall of the intestine
Attaches the jejunum and ileum to the posterior (dorsal) abdominal wall
Greater omentum
A layer of fatty peritoneum that hangs from the stomach like an apron over the anterior surface surface of the transverse colon and the small intestine.
Lesser omentum
Part of the peritoneum that suspends the stomach and duodenum from the liver.
Adhesions
Inflammation of the omentum and peritoneum may lead to scar tissue that causes the structures to adhere. Ex. loops of intestine, restricting mobility.
Retroperitoneal organs
The kidneys and pancreas are located posterior to the stomach against the abdominal wall and behind the parietal peritoneum, they are covered with peritoneum only on the anterior surface and are therefore retroperitoneal organs.
Where do salivary secretions come from?
Parotid, sublingual and submandibular glands.
What do salivary secretions contain?
Mucus and the enzyme amylase which begins the digestion of carbohydrate in the mouth.
Nerves responsible for swallowing?
Trigeminal and glossopharangeal nerves - relay information to the swallowing center in the medulla.
Actions required to move food or fluid into the stomach
Cranial nerves V, IX, X, and XII Soft palate is pulled upward Vocal cords are approximated Epiglottis covers the larynx Respiration ceases Bolus is seized by constricted pharynx Bollus moves into esophagus, peristalsis initiated Lower esophageal (gastroesophageal or cardiac) sphincter relaxes allowing it to move into the stomach
Salivary amylase
Parotid gland - splits starch and glycogen into disaccharides
Pepsin
Gastric chief cells - initiates splitting of proteins
Pancreatic amylase
Pancreas - Splits starch and glycogen into disaccharides
Pancreatic Lipase
Pancreas - splits triglycerides into fatty acids and monoglycerides
Trypsin, chymotrypsin, carboxypeptidase
Pancreas - Splits proteins into peptides
Pancreatic nucleases
Pancreas - splits nucleic acids into nucleotides
Intestinal peptidase
Intestinal mucosa - converts peptides into amino acids
Intestinal lipase
Intestinal mucosa - converts fats into fatty acids and glycerol
Intestinal sucrase, maltase, lactase
Intestinal muscosa - converts disaccharides into monosaccharides
How much can the stomach hold?
1L to 1.5L
Rugae
Folds of the stomach wall
Composition of stomach wall
Three smooth muscle layers, longitudinal, circular and oblique, plus mucosa (contains numerous glands) and submucosa.
Chyme
Stomach contents with added secretions.
What do the gastric glands do?
Contain parietal cells that secrete hydrochloric acid (highly acidic, ph 2) and chief cells that secrete pepsinogen (converts into active form, pepsin by activation by hydrochloric acid)
Parietal cells produce Intrinsic factor which is required for the absorption of Vit B12 in the ileum.
Gastrin - stimulates the parietal and chief cells
What secretions are added to the chyme in the duodenum?
Secretions from the liver and the exocrine pancreas through the ampulla of Vater and duodenal papilla.
Liver
Upper right quadrant under the diaphragm. Covered by fibrous capsule.
Metabolic center
Hepatocytes
Arranged in lobules, each lobule has plates of cells radiating from central veins, eventually drain blood back into the general circulation through the hepatic veins and inferior vena cava.
Sinusoids
Filled with blood from two sources pass between the plates of hepatocytes. Blood entering sinusoid comes from branches of the hepatic artery, carrying oxygen to the liver cells, venous blood from the portal vein, which transports nutrients absorbed from the stomach and intestines (hepatic portal circulation) as well as from the pancrease and spleen. Arterial and venous blood mix and flow slowly through the sinusoids, permitting the hepatocytes to do their jobs.
Kupffer cells
Line the sinusoids. Remove and phagocytose any foreign material and bacteria from the digestive tract before blood enters the general circulation.
What does the liver do?
As blood flows through sinusoids, absorbed nutrients are taken up by the hepatocytes to be stored (iron, copper, A, B6, B12, D and K and folic acid). Releases nutrients and glucose into blood as they need to be replaced.
Converts one amino acid into another as needed.
Synthesis and control of blood levels of other materials such as plasma proteins, clotting factors or lipoproteins
Synthesis of cholesterol - for use in the production of steroid hormones such as cortisol and bile salts.
Hormones such as aldosterone and estrogen are inactivated and prepared for excretion.
Ammonia ( a nitrogen waste resulting from protein metabolism) is removed from blood and converted to urea so it can be excreted by kidneys.
Drugs and alcohol are detoxified - increases solubility to facilitate excretion.
Removes damaged or old erythrocytes to facilitate recycling of iron and protein from hemoglobin.
Serves as a blood reservoir.