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54 Cards in this Set

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