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25 Cards in this Set
- Front
- Back
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What are the main functions of the GIT? |
Digestion of food Absorption of nutrients/electrolytes Absorption of water Immunological function Excretory functions |
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What is the function of the mucosa? |
Absoptive and secretory Thin layer of muscle |
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What is the function of the submucosa? |
allows the absorbed materials to enter the blood/lymphatics Contains the nerve plexus |
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What is the function of the muscularis? |
mixes the food and controls motility Has inner circular and outer longitudinal layers of SM |
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What is the function of the serosa? |
binds and protects the GI tract |
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What does motility involve? |
Ingestion Mastriculation Deglutition Muscular contractions |
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What is mastriculation? |
Chewing food and mixing it with saliva |
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what is deglutition? |
swallowing food |
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What are the three types of muscle contractions in the GI tract? |
peristalsis= rhythmic contractions of both types of SM Segmentation= intense contraction of circular SM Pendular contractions= intense contractions of longitudinal SM |
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What are the steps in swallowing to get food to the stomach? |
Tongue moves bolus to back of pharynx which stimulates mechanoreceptors to send afferent signals to the swallowing centre in the medulla oblongata to initiate the swallowing reflex The soft palate elevates to prevent food entering the nasal passages The epiglotis covers the glotis opening, respiration ceases, upper oesophagal sphicter relaxes and the pharynx contracts strongly sending food into the oesophagus Peristaltic wave moves food through oesophagus Reflex opening of lower reflex sphincter before food bolus arrives Food enters stomach |
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What are the functions of the stomach? |
Storage of food, mixing and breakdown of food, inital digestion of proteins, killing bacteria with high acidity, moving chyme into intestine |
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What is the basal electrical rhythm of the stomach initiated by? |
pacemaker cells |
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What is the basal electrical rhythm of the stomach? |
spontaneous cycles of depolarisation- repolarisation which will trigger an AP when threshold is reached |
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What determines the strength of contraction of the stomach? |
The number of spikes fired and the amount of calcium ion influx |
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What can promote calcium influx? |
Neurotransmitters and hormones |
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What is gastric emptying regulated by? |
neural enterogastric reflex hormonal mechanisms and hormonal influences |
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What hormones are enterogasterones? |
CCK and secretin |
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What do CCK and secretin do? |
Potentiate each others mechanism Secretin stimulated by acid in duodenum CCK stimulated by amino acids and fatty acids in small intestine Inhibit motility of the stomach |
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What does gastrin do? |
Stimulated by peptides and amino acids in the stomach by PNS Inhibited by the acid somatostatin Stimulates motility, acid secretion, growth in stomach and pancreas and colonic mass movement |
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What is the basal electrical rhythm of the intestine? |
Slow wave oscillation in membrane potential initiated by pacemaker cells Frequency decreases distally |
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What is the force of contraction of the intestine determined by? |
neural and hormonal influences |
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What is the resting migrating myoelectric complex (MMC)? |
Starts 4-5 hours after a meal and is a peristaltic activity that spreads 60cm through SI, then the next wave starts slightly lower down until it reaches the LI then it will start again |
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What is MMC induced by? |
rise in plasma concentration of motilin in the SI which acts via both enteric and autonomic nerves |
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How does defecation occur? |
Distension of the rectum Reflex relaxation of the internal anal sphincter and peristaltic contraction of colon Contraction of external anal sphincter Voluntary relaxation of external anal sphincter |
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What are the factors that influence neural control and how? |
Smooth muscle Neural control= PNS has inhibitory and excitation effect and SNS inhibition effect Hormonal control = can be endocrine or local |
