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ailmentary > LI > Flashcards

LI Flashcards

1
Q

ileocaecal valve

A 
muscular sphincter 
separates distal ileum from ceacum 
tonically active and constricted 
only relax to allow chime into LI 
prevent bacteria entering ileum
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2
Q

caecum

A

blind pouch

distal to ileocaecal calve

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3
Q

appendix

A

extension from caecum
limited role
safe refuge for gut bacteria after diaorrea

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4
Q

colon

A

ascending - start at ileocaecal valve -> hepatic flexure on the R side of the body
transverse - start at hepatic flexure and run across abdomen -> splecic flexure
descending - start at splenic flexure and runs to 1st bend of igmoid
sigmoid - S shaped runs to rectum

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5
Q

rectum

A

dilated portion
act as a storage site
has transverse rectal folds in submucosa - shelves for faeces
no taeniae coli in muscularis externa

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6
Q

anal canal

A

control movement of things out of GI
2 anal sphincters
sm under central control - internal sphincter
external muscle is striated and under vol control by pudendal nerves

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7
Q

appendix epiploicae

A

fatty tags from serosa
no physiological function
perhaps protective against intraabdominal infections

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8
Q

longitudinal muscle

A

3 bands longitudinal muscle
equally spread around the circumference
thicker than typical longitudinal layers
shorter than colon - colon forms lpouches called hastra

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9
Q

circular muscle

A

segmentally thickened

bundles of muscle from taeniae coli penetrate to keep it together

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10
Q

nodules of lymphoid tissue

A

usually solitary nodules

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11
Q

components of the LI

A 
colon
cecum 
appendix 
rectum 
anal canal
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12
Q

size of the colon

A

1.5m long, 6cm diameter

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13
Q

Edit Delete

attachment of transverse colon

A

hangs off the stomach

attached by the greater omentum

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14
Q

blood supply of the colon

A

proximal transverse colon upplied with blood by middle colic artery (branch of superior mesenteric artery)
distal 1/3 - inferior mesenteric artery
reflects the embryonic division between mid and hind gut

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15
Q

consequence of colon have 2 blood supplies

A

area between is sensitive to ischemia in haemorrhage

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16
Q

gut wall

A

peritoneum has fatty tags
muscle coat has 3 thick longitudinal bands - taeniae coli
gut wall is pouched - haustra
nodules of lymphoid tissue common in walls of distal small intestine - peyer’s patches, and LI - solitary nodules for communication between gut immune system and microbiome

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17
Q

function of tenia coli

A

large intestine motility

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18
Q

Haustra

A

taenia coli shorter than in SI
cause pouched ovoid segments - haustra
not always in same place - muscle tone

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19
Q

general plan of the gut tube

A 
serosa
longitudinal muscle 
circular muscle 
muscularis 
lamina propria 
epithelium
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20
Q

comparision of the structure of the LI and SI

A

in both:
enterocytes and goblet cells
abundant crypts
stem cells in crypts

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21
Q

LI mucosal organisation

A 
appears smooth - no villi 
enterocytes (luminal side) have short irregular microvilli - reabsorption of salts and macronutrients 
crypts have goblet cells 
no Paneth cells 
fewer enteroendocrine cells than SI 
glycocalyx - no digestive enzymes
22
Q

goblet cells in LI

A

more than in SI
more distal
mucus fascilitate passage of more solid contents, covers bacteria and particulate matter
stimulated by ACh - PNS and enteric NS - plexuses in wall of gut

23
Q

why no Paneth cells in the LI

A

would kill flora
commensal is important
less bacteria than in SI - food already been digested

24
Q

muscle layers of LI

A

muscularis externa - inner circular and outer longitudinal layer
circular are segmentally thickened
longitudinal concentrated in 3 bands - taenia coli
bundles from here penetrate the circular
between taenia longitudinal is thin
longitudinal shorter than circular = haustra = contract individually

25
Q

components if the large intestine

A 
colon
caecum 
appendix
eecctum 
anal canal
26
Q

main func of the colon

A

reabsorption of water and electrolytes
elimination of waste
microenvironment for gut bacteria

27
Q

structure of the LI

A

150cm long
6cm wide
receives blood from middle colic artery - perfuses ascending and 1st 2/3 of transverse
and from inferior mesenteric artery - perfuse last 1/3 transverse, descending colon, sigmoid colon and rectum

28
Q

innervation of the LI

A

PNS - vagus innervate ascending and most of transverse
distal colon innervated by pelvic nerves
sympathetic innervation arises from lower thoracic and upper lumber spinal cord

29
Q

reabsorption

A

ions and water
in proximal colon mainly
contents become dehydrated
na and cl are exchange mechanisms - water follows
K moves passively into lumen through tight junctions
capacity to absorb 4.5L but only absorbs 1.5l - SI ddoes more

30
Q

describe the cells of the colon

A

many goblet and enterocytes
colonic crypts - stem cells at bottom
smootgh mucosa - no villi = small sa - less absorption
enterocytes have small irregular microvilli
enterocyte structure reflects resorbative function

31
Q

goblet cells

A

line the crypts
secrete mucus to help passage - abundance increase along colon
mucous also cover bacteria and particulate matter
stimulated by ACh

32
Q

Paneth cells

A

absent in LI because of commensal bacteria

33
Q

enteroendocrine cells

A

less than in SI - absorption is simpler

34
Q

glycocalyx

A

present

doesn’t contain the digestive prush border enzymes

35
Q

motility - basic contractions

A

kneading process - minimal propulsion - allow chime to stay in colon for a long time = more absorption
proximal colon has antipropulsive contractions to keep food for longer
transverses and descending - localised segmental contractions of circular muscle - haustral contractions - shuffle contents forwards and backwards
short propulsive movements every 30mins - more after eat - clear for next food

36
Q

motility - mass movement

A

1-3 times a day
propel contents 3/4 of length in a few seconds
high fibre food, coffee, smoke promotes mass movement

37
Q

faeces

A 
indigestible waste 
2/3 water 
cellulose
bacteria = smell 
cell debris- lose because cant digest them in the SI 
bile pigments/salts
38
Q

defaecation

A

suddenly after mass movement - feel the need
pressure receptors send ssignals - myenteric plexuys to initiate peristaltic waves - inhibit internal sphincter
weak signal is helped by autonomic relflex from the brain
internal anal sphincter is relaxed in defecation reflex - via sacral spinal cord - reflex and voluntary
detention of wall detected by pressure receptors
signals to myenteric plexus to initiate peristaltic waves in descending, sigmoid colon and rectum

39
Q

what determines when it is appropriate to defecate

A

last bit rectum can detect between solid, liquid and gas

difficult to distinguish between gas and oil = spotting of underwear - especially with Orlistat

40
Q

control of the colon

A

PNS - ascending and 2/3 transverse innervated by vagus 9acid from stomach and enzyme part of pancreatic juice, distal - pelvic nerve
sympathetic - lower thoracic and upper lumbar spinal chord
external anal sphincter - somatic fibres - pudendal nerves
afferent sensory detect pressure

41
Q

enteric control of the LI

A

myenteric plexus ganglia below taenia coli
prescence of food stimulate mass movement
involved in coeliac
loss of enteric = Hirschsprung’s disease

42
Q

hormonal control of LI

A

aldosterone - Na and H2O reabsorption

by synth channel and Na/K pump

43
Q

where is bile salt reabsorbed

A

terminal ileum

44
Q

physiological role of the LI microbiome

A

form a symbiotic relationship
Synthesise and excrete Vitamin K - for coag
prevent pathogens - compete
antagonise bacteria that kill/inhibit non-indigenous species
stimulate production of cross reactive Ab
stimulate development of tissues
fibre break down
produce short chain FA - receptor in gut, panc, vagus and adipose - signal molecules - regulate gut hormone release/energy source/influence food intake/insulin sensitivity
links with drug metabolism, insulin resistance, bile acid metabolism, lipid metabolism and obesity
produce short FA - regulate gut hormone release

45
Q

location of bacteria

A

few in stomach/ proximal si - harsh environment

46
Q

prevalent species

A

bacteriodetes
gram -ve
anaerobic
non-spore forming

47
Q

pathophysiology

A

gut bacteria prime immune system
inappropriate pop of commensal = predispose infection
potential value in faecal transplant to reinstate bacteria

48
Q

large intestinal flora

A

Trillions of bacteria
size of an organ
have to look phylogenetically

49
Q

flora and colitis or colon cancer

A

changes composition

50
Q

bifidobacteria

A 
gram +ve 
non-spore forming 
lactic acid bacteria 
friendly 
prevent colonisation by potential pathogens
51
Q

links between gut bacteria and other systems

A 
drug met 
insulin resistance
bile acid met - hydroxyl gp removed so it easier to be absorbed 
lipid met 
obesity 
cancer

ailmentary (15 decks)

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