The Digestive System Flashcards
Name the nerves of the gut wall
myenteric plexus and submucosal plexus
What are the layers of the gut wall?
mucosa, submucosa, muscularis, externae serosa
What are the layers of the mucosa?
muscularis mucosae, lamina propria, epithelium
What are the digestive accessory organs?
liver, gallbladder, pancreas
List the salivary glands
parotid, sublingual, submandibular
What role does saliva play in digestion?
starts digestion, amylase, lipase, bacteriostatic (IgA), high Ca, alkaline, assists swallowing, protects mouth, mouth forms bolus
What stops aspiration?
Epiglottis
How can swallowing be visualised?
barium swallow = swallow liquid barium imaged by X-Ray
How does a bolus move from the mouth to the stomach?
Oesophagus (visualised by endoscopy) –> bolus enters, upper end: voluntary, lower end: involuntary, rapid peristaltic transport
How does the stomach protect itself from its acid environment?
Secreted mucus resistant to pepsin (enzymatic). Mucous sticks to walls of stomach, provide physical barrier so acid doesn’t touch stomach itself. Cells come into contact with acid, secrete bicarbonate = highly alkaline = neutralising acid
What is the role of the stomach?
food store, wall relaxes so pressure doesn’t rise (repetitive relaxation), contracts rhythmically, secretes acid + proteolytic enzymes, secretes mucus, produce hypertonic chyme from bolus (greater conc of minerals, salt proteins = draw water from vascular system)
What is hypertonic chyme?
Becomes hypertonic in stomach, hypertonic chyme from bolus (greater conc of minerals, salt proteins = draw water from vascular system)
What do parietal cells do?
Parietal cells: secrete H+ to lumen, HCO3 into capillaries – will move to surface of mucus cells
What is the role of chief cells?
Chief cells: secrete pepsinogens –> pepsins – hydrolyse proteins
What is the role of gastrin?
Enteroendocrine cells: secret gastrin = mucosa secrete HCL.
Hormone which stimulates secretion of gastric juice and is secreted into bloodstream by stomach wall in response to presence of food.
How long is the small intestine?
7 meters
What enables the small intestine to have such a large surface area?
Microvilli, villi and folding
In order list the parts of the small intestine?
Duodenum, jejunum, ileum
What happens in the duodenum?
secrete bicarbonate, water from ECF to make hypertonic chyme isotonic, bile enters small intestine here, liver & pancreas secret alkali = neutralise acidic chyme, liver pancreas and intestine secrete enzymes to complete digestion of chyme. Bile = water, alkali, bile salts (emulsify fat). Absorbs iron
Describe the role of the jejunum
absorbs sugars, AA, and fatty acids
Outline what happens in the ileum
absorbs vit b12, bile acids, remaining nutrients
Describe the location of the duodenum
proximal part of SI, C-shaped, 20-22cm long, curves around head of pancreas
List the part of the large intestine in order
caecum, ascending colon, transverse, descending, sigmoid
How long is the large intestine?
1.2 meters
Outline the role of the colon
Numerous crypts of lieberkuhn: cells produce mucus. Peyer patch (lymphoid tissue) present. Surface epithelial cells absorb water/electrolytes. Water recovery: decreased = dehydration, electrolyte imbalance. Await expulsion. Contain most of GI bacteria: involved in synthesis of vik K B12, breakdown of primary bile acid to secondary
What is the role of the rectum?
critical mass gives urge to defecate
What is the final structure of the digestive system?
anus
What are the paracrine methods of controlling the digestive system?
histamine: controls production of acid in stomach. vasoactive subs: affect blood flow in gut
List the endocrine controls of the digestive system
SECRETIN: promotes bicarbonate secretion, bile prod, inhibits acid secretion.
CHOLECYSTKININ: promotes release of pancreatic digestive enzymes, bile.
GASTRIN: promotes HCL prod
Which parts of the digestive system are under somatic control?
somatic: ingestion, excretion
List the order of the digestive system.
Mouth, saliva, epiglottis, oesophagus, stomach, duodenum, jejunum, ileum, caecum, ascending colon, transverse colon, descending colon, sigmoid, rectum, anus.
What is ghrelin and leptin?
GHRELIN = hormone prod by stomach = feeling hungry. LEPTIN = hormone prod by fat = feeling full.
What are enteroendocrine cells?
Enteroendocrine cells include G cells which secrete gastrin, gastric mucosa responds to this hormone by secreting acid.
What are crypts of lieberkuhn?
Glands that secrete intestinal juice, contain: lipase, lactase, amylase. Found in the small and large intestine
What is cholecystokinin?
Hormone synthesized/secreted by enteroendocrine cells in the duodenum. Causes release of digestive enzymes and bile from pancreas and gallbladder, respectively, also acts as a hunger suppressant
What is secretin?
Hormone released into bloodstream by duodenum promotes bicarbonate secretion, bile prod, inhibits acid secretion.
