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54 Cards in this Set
- Front
- Back
Where does the small intestine extend from?
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pylorus to ileocaecal junction
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What embryological origin does the SI predominantly have?
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Midgut
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Name the 3 SI regions
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- duodenum
- jejunum - ileum |
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How does the SI have a maximised surface area?
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- long 6-7m
- circular folds (valvulae conniventes or plivae circularis) - villi - microvilli |
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What classification of epithelium does the SI have?
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simple columnar epithelium
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What is a 'brush border'?
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When villi have microvilli on their surface to maximise surface area.
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What are crypts of Lieburkuhn?
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Tubular intestinal glands that extend from the muscularis mucosae, through the lamina propria, & open at the base of the villi
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Name 6 different cells of the SI
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enterocytes, goblet cells, paneth cells, enteroendocrine cells, stem cells, lymphocytes
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What is the functions of enterocytes?
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principally absorptive but also secretory
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What is the function of goblet cells?
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secrete mucous
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What is the function of enteroendocrine cells?
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produce peptide hormones e.g. secretin & cholecystokinin (CCK)
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what is the function of paneth cells & where are they found?
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Phagocytic cells which produce antibacterial lysozyme, present in the crypts of Lieberkuhn
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Where are stem cells found in the stomach & what do they allow?
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Crypts of Lieberkuhn - allow regeneration of epithelial cells every 3-4 days
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What role do lymphocytes play in the SI?
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immune surveillance & protection
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What 2 structures define the ends of the midgut?
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- entry of common bile duct into duodenum
- left colic flexure |
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What is the difference between pylorus & duodenum?
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mucous membrane changes from gastric to intestinal type, where intestinal membrane has villi
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What forms the pyloric sphincter?
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inner circular layer of muscle is thickened
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What is the main blood supply to the SI?
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superior mesenteric artery, with jejunal, ileal & ileocolic branches
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Which part of the SI has contribution from the coeliac trunk?
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duodenum
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How does nutrient-rich blood get from the SI to the liver?
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the superior mesenteric vein via the portal vein
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What marks the foregut/midgut interface?
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Major duodenal papilla
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What neutralises acidic stomach chyme in the SI?
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Duodenum submucosa contains compound tubular glands - Brunner's glands - which secrete alkaline mucous
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Where does the jejunum begin & end?
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duojejunal junction & ileum
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Are the duodenum & jejunum retro or intra peritoneal?
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duodenum - retroperitoneal
jejunum - mesentery, intraperitoneal |
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What is important about the terminal ileum?
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Important for absorption of vitamin B12 & bile salts
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Briefly describe coeliac disease, what part of the SI it affects & symptoms.
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Caused by intolerance to proteins in cereal crops, leads to inflammation & damage to proximal SI mucosa, destroying villi. This reduces surface area leading to malabsorption & diarrhoea
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briefly describe Crohn's disease, what part of the SI it affects & clinical features/symptoms.
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Patchy. chronic inflammation that can affect any of the GI tract, but common in the terminal ileum due to high conc of lymphoid follicles (Peyer's patches). Inflammation is transmural & clinical features include malabsorption, strictures, fistulae.
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Why are ulcers common in the first part of the duodenum?
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acidic chyme enters this area
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What are the 4 regions of the large intestine?
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caecum (+ appendix)
colon rectum anal canal |
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What embryological origin does the LI have?
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midgut & hindgut
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What is the key function of the LI?
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absorbs water & forms faeces
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What are 4 distinctive features of the LI?
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taenia coli
appendices apiploicae haustrations semilunar folds |
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what are taenia coli & where are they usually?
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3 thickened bands of longitudinal muscle, usually in caecum & colon
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What are appendices epiploicae?
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fatty tags found mostly on outside of colon
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What are haustrations?
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visible sacculations of the colon
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What are semilunar folds?
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incomplete folds on smooth mucosal surface of LI
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Describe LI epithelium
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simple columnar epithelium with no villi
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what is the difference between crypts of Lieberkuhn in SI & LI?
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LI only have mucous-secreting cells, no Panth cells
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What is the difference between the outer longitudinal muscle layers of the SI & LI?
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SI - continuous
LI - discontinuous, organised into 3 bands - taenia coli |
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What is intestinal venous drainage?
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small & large intestine venous drainage is via branches to the portal vein
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What is the surface marking for the base of the appendix?
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McBurney's point - 1/3 of the way along a line connecting the anterior superior iliac spine (ASIS) to the umbilicus
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Which parts of the colon are intra- & retro peritoneal?
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ascending & descending - retro
transverse & sigmoid - intra |
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Where is the transverse colon & why is it important?
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between hepatic & splenic flexures, distal to ascending & proximal to descending colon, & it is the midgut-hindgut interface
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where is the midgud-hindgut interface?
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transverse colon
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how does the rectum differ to the colon?
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no taenia coli
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What does the ampulla of the rectum have & what is their name?
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3 transverse folds - valves of Houston
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what is the internal anal sphincter formed by?
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inner circular layer of muscle
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what is the external anal sphincter formed by>
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skeletal muscle
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what happens at the anal transition zone?
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endoderm meets ectoderm, & simple columnar epithelium changes to stratified squamous
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how does the stratified squamous epithelium of the anus differ to that of the oesophagous?
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it is keratinised
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what are 2 complications of appendicitis?
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perforation & peritonitis
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describe ulcerative colitis & where it affects
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type of IBD - diffuse chronic inflammation. Affects only the mucosa of the LI & presents as malabsorption of water (diarrhoea) & ulceration (bleeding)
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Describe diverticular disease.
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Outpouchings of mucosa into the wall of colon, predominantly in the descending & sigmoid colon
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What parts of the intestine are mobile (have mesentery) & which are fixed (retroperitoneal)
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mesentery: jejunum, ileum, appendix, trans colon, sigmoid colon
retroperitoneal: duodenum, ascending & descending colon, caecum, rectum |