The digestive system part 9
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Three phases of digestion: 1. cephalic phase
the smell, sight, thought or initial taste of food activates neural centres in the cerebral cortex, hypothalamus and brain stem. which stimulate salivation. The purpose is to prepare the mouth and stomach for food
Three phases of digestion: 2. gastric phase
once food reaches the stomach. Neural and hormonal mechanisms regulate this phase of digestion to promote gastric secretion and gastric motility
neural regulation of gastric phase
food of any kind distends the stomach and stimulates stretch receptors in its walls, Chemoreceptors monitor the pH of the stomach chyme. When food enters and distends the walls or lowers the pH level these two receptors are initiated.
hormonal regulation of gastric phase
gastric secretion during the gastric phase is also regulated by the hormone gastrin.
Gastrin is released from these cells of the gastric glands in response to several stimuli. Distension, partially digested proteins, High pH, caffeine, and Acetycholine released by parasymphatic neurons.
Three phases of digestion: phase 3 intestinal phase
begins once food enters the small intestine reflexes initiated during this phase have an inhibitory effect that slow the exit of chyme from the stomach preventing the duodenum from being overloaded
neural regulation of intestinal phase
distension of the duodenum by the presence of chyme causes the enterogastric reflex. Stretch in the duodenum wall cause neuroceptors to send nerve impulses to the medulla oblongata. As a result gastric motility is inhibited and there is an increase in the contraction of the pyloric sphincter
hormonal regulation of intestinal phase
mediated by two major hormones. Cholecystokinin and secretin
or tooth decay involves a gradual demineralization of the enamel and dentin. If untreated, microorganisms may invade the pulp, causing inflammation and infection, with subsequent death of the pulp leading to a root canal
is a collective term for a variety of conditions characterized by inflammation and degeneration of the gingivae, alveolar bone, peridontal ligament and cementum
peptic ulcer disease
a crater like lesion in a membrane, ulcers that develop in areas of the GI tract exposed to acidic gastric juice are called these. The most common complication is bleeding.
an inflammation characterized by pain, either constipation or increased frequency of defecation, nausea, vomiting and low grade fever low fiber contribute to its development
an inherited predisposition contributes to acquiring this. Maybe caused by alcohol intake and diets high in animal fat and protein. Signs include, diarrhea, constipation, cramping, abdominal pain, and rectal bleeding
is an inflammation of the liver that can be caused by viruses, drugs and chemicals, including alcohol
distorted or scarred liver as a result of chronic inflammation due to hepatitis, chemicals that destroy hepatocytes, parasites that infect the liver or alcoholism. hepatocytes are replaced by fibrous or adipose connective tissue. Symptoms include jaundice, , edema in the legs, uncontrolled bleeding and increased sensitivity to drugs.
inflammation of the mucosa of the colon and rectum in which absorption of water and salts is reduced, producing watery, bloody feces.
the diversion of feces through an opening in the colon, creating a surgical stoma that is made in the exterior of the abdominal wall. This opening serves as a substitute anus
inflammatory bowl disease
inflammation of the GI tract in two forms crohn's disease or ulcerative colitis
irritable bowel syndrome
disease of the entire GI tract in which a person reacts to stress by developing symptoms associated with alternating patterns of diarrhea and constipation
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