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26 Cards in this Set
- Front
- Back
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Role of the GIT |
Absorb nutrients and excrete waste products Requirements: breakdown of large molecules, secretion of enzymes, transport mech., secretion of compounds to aid absorption |
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Structure |
Lots of layer 2 main layer of smooth muscle: circular and longitudinal Different orientation to mix and contract |
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Control of motility |
Cyclidal contraction and relaxation Nerve plexus between 2 layers of muscle
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Cyclidal contraction and relaxation |
Line tubular tissues eg peristalsis Unidirectional movement of contents Synchronised and wavelike Lumen cavity constricts and dilates alternatively |
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Nerve plexus between 2 layers of muscle |
Nerve network Co-ordinates contraction - relaxation cycle at local lv |
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Receptors involve in regulation of motility |
= enteric nervous system -> control parasympathetic and sympathetic NS ACh, 5HT, NO, NA, ATP Respond to stretch ANS -> enteric nerve -> SM -> release ACh -> act on M3 of SM -> contract Action potential change in the membrane -> Ca influx -> ACh-> M3 -> contract |
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Pre-synaptic receptor |
5HT -> 5-HT4 -> contraction Dopamine -> D2 -> inhibit contraction -> relaxation Opioid -> opioid receptor -> inhibit contraction -> relaxation |
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GIT motility can be controlled = therapeutic |
Stimulation/antagonism of MAChr Stimulation/antagonism of pre-synaptic receptors |
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Mastication and salivation |
Grind,break up food -> swallowing -> mix food with saliva -> stimulate taste buds |
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Stomach function |
Storage of food Initiation of digestion of CHO, Protein Kill bacteria Formation of chyme b4 transfer to the small intestines |
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Small intestines function |
Mechanical and chemical digestion of nutrients -> absorption of nutrients Duodenum receives chyme from the stomach, ducts empty to duodenum to delivery enzymes from acinar cell (from pancreases)
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What are the enzymes from acinar cells in the duodenum that are responsible for the digestion of nutrients? |
amylase -> sugar lipase -> fat protease -> trypsin, chymotrypsin, carboxypeptidase HCO3 -> neutralise acid nuclease -> nucleic acid |
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Pancreatic secretion depends on? |
Cl exchange |
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Jejunum and duodenum are responsible for the absorption of nutrients |
Terminal ileum: bile absorption, vit B12 Inner s.f of SI folded: increase s.f are for absorption |
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Villi |
projecting from the folds to increase s.f area of 10 times Microvilli projected on villi Line the epithelial cells interspersed with mucous cell |
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Peyer's patches |
Immune surveillance Lymphoid nodules in ileum Collection of sub-epithelial in lymphoid follicle Proliferation of cells in the centre Macrophages, dendritic cells, lymphocytes are found on the top of the follicle towards gut lumen |
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Uptake of particles from GIT by peyer's patches |
follicles are covered with M cells -> sample the particles -> transport them inside by endocytosis -> present as antigen -> introduce to underlying T and B lymphocytes -> particles transport to the systemic circulation through the lymphatic system |
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M cells |
Cover the follicles cells of epithelial origin, phagocytic activity |
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Bile |
synthesise by the liver from cholesterol -> store in the gall bladder -> secrete into the duodenum -> re-absorb into liver (enteroheptic recycling) |
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Bile salts |
from cholesterol -> 7-hydroxycholesterol -> bile salts |
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Transport of bile salts and FAs |
in form of micelles active transport to enterocyte FAs, bile salts are mixed with chylomicron -> portal circulation |
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Absorption of CHO, protein |
Protein -> a.a -> transporter -> enterocyte Na&CHO -> polysaccharide -> glucose -> symporter -> enterocyte Symporter and transpoter |
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Absorption of Vit, minerals |
Vit C: Na dependent active transport Vit B6: simple diffusion Follic acid: facilitated transport Vit B12: intrinsic factor = parietal cells in the stomach -> absorbed in the ileum Ca: passive diffusion through Cal channel -> Cal binding protein -> ATPase -> out of the cells to maintain the gradient |
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illeocal juncture |
junction between small intestine and large intestines Prevent colonic bacteria from large intestine to small intestines |
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Large intestines |
Lil. digestion Colonic bacter digest NSP -> increase faecal bulk Store and compact faecal matter Extract more H20, Na, from contents |
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Water absorption |
Osmosis with the osmotic gradient involve Na/glucose symporter |
