Large Intestine Flashcards
what 3 areas is the large intestine divided into
appendix
caecum
colon
what are the areas of the colon
ascending
transverse
descending
sigmoid
what are the three strands of longitudinal smooth muscle called in large intestine
taeniae coli
what is the gastroileal reflex
ileocaecal valve opens in response to CCK and gastrin allowing the entry of fluid from the terminal ileum
what are the 3 main functions of the large intestine
absorption of water and electrolytes
secretions of K+ and HCO3 for mucus protection and neutralisation
storage and elimination of faeces
the large intestine contains villi true/false
false but does contain microvilli, crypts and colonic folds
what are glycoaminoglycans secreted from and what is their function
secreted from goblet cells as part of mucus to provide protection between faeces and gut wall
what is haustration
non-propulsive segmentation allowing time for fluid and electrolyte absorption
what are mass movements
contraction of circular muscle driving faeces into distal regions of the large intestine - occurs 1-3 times a day
describe the defaecation reflex
mass movement of faeces into the rectum, activates rectal stretch receptors and parasympathetic efferents
what happens to internal anal sphincter when faeces moves into the rectum
it relaxes - made of smooth muscle
what nerve supplies the rectum
pudendal nerve via S2, 3, 4
what is the purpose of colonic flora
increase intestinal immunity and outcompete pathogens for nutrients
where does colonic gas arise from
swallowed air passed in the colon
reactions with bacteria which attack carbohydrates humans cant digest
what is constipation
presence of hard faeces in the colon which make passing stools difficult and painful due to enhanced absorption of H2O
what are the main causes of constipation
ignoring the urgency to defaecate
decreased colonic motility due to diet and drugs
obstruction of faecal movement
loss of defaecation reflex
water absorption in the GI tract requires energy true/false
false - passive process
what drives the absorption of H2O
absorption on Na+ occurs through 4 different transport mechanisms
what are the 4 ways sodium is absorbed in the GI tract
Na/glucose co-transport
Na/amino acid co-transport
Na/H+ exchange
Na/H and Cl/HCO3 in parallel
which mechanisms are the main post-prandial absorption of Na+
Na/glucose and Na/amino acid co-transport
how is Cl- absorbed in the large intestine
occurs passively either transcellularly or paracellularly
provides the driving force for Na+ absorption via ENaC
Cl- absorption is greater than Cl- secretion true/false
true otherwise diarrhoea would occur
Cl- is secreted via which channel
CFTR - usually remains closed
give examples how the CFTR transporter can be activated causing diarrhoea
bacterial enterotoxins
hormones and neurotransmitters eg ACh
immune cells producing histamine and prostaglandin
what is diarrhoea and how is it caused
loose watery stools due to failure to absorb water and electrolytes.
caused by infection, chronic disease and drug side-effects
describe diverticulum
outpouching of the gut wall
where does diverticulum usually occur
sigmoid colon at the sites of arteries
describe diverticulitis
inflammed irritated diverticulum causing symptoms (diverticulous)
what are the symptoms of diverticulitis
altered bowel habit
left sided abdo pain relieved by defaecation
nausea and flatulence
what is the treatment for simple and complicated diverticulitis
simple - IV fluids and antibiotics at home
complicated relates to fistula, abscess etc requiring surgery
inflammatory bowel disease covers which disease
ulcerative colitis
Crohns disease
which areas of GI tract and layers of GI tract does UC affect
rectum and colon only
mucosal and submucosal layers
which areas of the GI tract and layers of the GI tract doe Crohns affect
from mouth to anus in skip lesions (gaps) transmural inflammation (all layers affected)
UC has granulomas formed true/false
false - granulomas in Crohns
which type of T cell mediation is UC and Crohns
Crohns - TH1 mediated
UC - TH1+TH2 mediated
which inflammatory bowel disease is aggravated by smoking
Crohns disease
which inflammatory bowel disease has an increased risk of developing colorectal carcinoma
UC
what 3 factors are thought to make up the aetiology of IBD
genetic predisposition (NOD2 gene) environmental factors (smoking) mucosal immunity
what investigations are required for IBD and what would they show
raised CRP
low Hb and albumin
possible malabsorption deficiencies
endoscopy/colonoscopy inflammed
what does the mucosa look like at endoscopy in IBD
cobblestoning
name the 4 types of drugs that are used for treatment of IBD and an example of each
5ASA - mesalazine
steroids - prednisolone/budesonide
immunosuppressants - azathioprine/methotrexate
anti-TNF - infliximab
what are some routes of administration and side effects of mesalazine
oral or topical enema/suppository
side effects - diarrhoea and renal problems
what are some side effects of steroids
weight gain, neuropsychiatric problems, osteoporosis
when in IBD are steroids used for and for how long
used to induce remission
only used for 6-8 weeks and dose slowly reduces
what are the side effects of azathioprine
pancreatitis, hepatitis and increased risk of developing skin cancer
how is infliximab administered and what is it mainly used for
IV administration
mainly used as long term therapy
what is one precaution doctors must take before beginning anti-TNF treatment
can reactivate latent TB
surgery is curative of IBD true/false
only in UC, as inflammation can be anywhere in GI tract areas cannot be resected
where does Crohns disease typically present in GI tract
terminal ileum and colon
what are some of the symptoms of Crohns disease
diarrhoea abdominal pain nausea apthous ulcers anywhere joint pain anal fissures erythema nodosum uveitis
what are some complications of Crohns disease
stricture, fistula, short bowel syndrome from resections, malabsorption, anaemia
short bowel syndrome is a bowel length less than __
200 cm
what are some common surgeries for Crohn’s disease
fistula, stricture repair
resection of bowel
what are some of the symptoms of UC
bloody diarrhoea increased frequency and urgency LIF pain night rising tenesmus erythema nodosum arthritis
what criteria measures the severity of UC symptoms
Truelove and Witt criteria
for a severe episode of UC what symptom criteria must be met
>6 bloody stools per day + one of tachycardia anaemia raised CRP fever
what are some of the complications of UC
toxic megacolon
colorectal cancer
primary sclerosing cholangitis
what is toxic megacolon
condition causing dilatation of the bowel and muscle atrophy due to persistent inflammation
name some common surgeries for UC
right hemicolectomy
proctocolectomy
removal of part of bowel with ileostomy or colonostomy
what type of gut disorder is IBS
functional gut disorder - no underlying cause
who typically presents with IBS
young women
family history of IBS
mental health problems or stressful lifestyle
caffeine, menstruation can also trigger
what are the symptoms of IBS
abdominal pain, bloating or distension change in bowel habit either way change in stool appearance tenesmus NO ALARM SYMPTOMS PRESENT
what investigations are carried out for IBS
CRP, anti-TTG for coeliac, FIT all to rule out differentials
what is the treatment for IBS
antispasmodics for pain but can cause diarrhoea anti-motility/anti-diarrhoeals fybogel peppermint oil capsules FODMAP diet
