Small Intestine Flashcards
what are the three areas of the small intestine called
duodenum
jejunum
ileum
what substances does the small intestine receive
chyme from stomach
bile from gallbladder
pancreatic enzymes
what are some adaptions the small intestine has to allow for maximum absorption
villi
microvilli
circular folds of Kerchring
what is segmentation
mixing and churning of chyme driven by sympathetic activity
what hormones are secreted into the small intestine and from what cells
gastrin from G cells
secretin from S cells
CCK
ghrelin
what does secretin stimulate
promotes gastric secretions and biliary HCO3
what does CCK stimulate secretion of
bile through relaxing sphincter of Oddi and contracting gallbladder
what are ghrelin and leptin
ghrelin - hunger signal
leptin - decreases appetite
the basolateral membrane of enterocyte faces the
lumen/blood vessel
the apical membrane of enterocyte faces the
opposite side of the lumen
what is digestion
enzymatic conversion of complex dietary substances into smaller form that can be absorbed
what mediates luminal digestion
pancreatic enzymes - secreted into the duodenum
what enzymes are involved in membrane digestion
brush border enzymes
what is absorption
what absorbable products are transferred across apical and basolateral membranes
carbohydrates make up what % of total food intake
45%
name 2 polysacchardies and % total intake of carbohydrates
starch
glycogen
(50%)
name 2 oligosaccharides and % total intake of carbohydrates
lactose
sucrose
(30-40%)
name 3 monosaccharides and % total intake of carbohydrates
glucose
fructose
galactose
(10%)
what happens to carbohydrates to allow them to be absorbed
complex carbohydrates are all converted into monosaccharides
what is the function of alpha-amylase
breaks down polysaccharides into oligosaccharides such as maltose
why does alpha-amylase not break carbohydrates completely down into monosaccharides
it can only break internal alpha 1,4 glycosidic bonds and not terminal alpha 1,4 glycosidic bonds
name two oligosaccharidases
sucrase
lactase
sucrase breaks sucrose into
glucose
fructose
lactase breaks lactose into
glucose
galactose
what is lactose intolerance
form of lactase insufficiency with lacking enzyme
describe the three types of lactose intolerance
primary - lack of lactase persistence allele
secondary - development post infection
congenital - rare autosomal recessive condition
at the brush border membrane how are glucose, fructose and galactose absorbed
glucose and galactose - SGLT1 transporter
sucrose - GLUT5 transporter
at the basolateral membrane how are glucose, fructose and galactose absorbed
all absorbed via GLUT2 transporter
what are proteins broken down to before they can be absorbed
oligopeptides and amino acids
where does the most important part of protein digestion occur and what happens
duodenum - pancreatic proteases convert oligopeptides into amino acids
how are amino acids absorbed in the enterocyte
via secondary active transport mediated by Na+ dependent transport
define malabsorption
failure of the small intestine to absorb nutrients correctly
what are the main causes of malabsorption
coeliac disease chronic pancreatitis Crohn's disease primary biliary cholangitis infection
what are the main symptoms of malabsorption
steatorrhoea
diarrhoea
fatigue
weight loss
what is a sign of vitamin C and K deficiency
easy bruising
what is kolonychia and what is it a sign of
spooning of the nails
sign of iron deficiency
what is leukonychia and what is it a sign of
white patches on the nails
sign of calcium and zinc deficiency
what is glossitis and what is it a sign of
swollen tongue
sign of vitamin B12 or iron deficiency
what is angular cheilitis a sign of
sign of vitamin B12 or iron deficiency
what is Coeliac disease
autoimmune response causing reaction to a component to gluten (wheat, flour)
what is the overall effect of coeliac disease on absorption
damages enterocytes and reduces absorptive capacity
what immune cells produce the response in Coeliac disease and what structures change
T cells produce response
causes villous atrophy, flat duodenal mucosa and reduced SA for absorption
what are the symptoms of Coeliac disease
smelling stools that wont flush away (steatorrhoea) diarrhoea abdo pain and bloating apthous ulcers weight loss and fatigue
what investigations are carried out to diagnose Coeliac disease
biopsy but avoided in children
serology - IgA anti-TTG (anti-transglutaminase)
or TTG if someone has IgA deficiency
what is the main treatment for Coeliac disease
gluten free diet - available from pharmacist
what is the most common type of emergency operation to occur
appendicitis
what causes appendicitis
aetiology unknown but could be due to faecal obstruction or irritation - can lead to oedema, necrosis and perforation
appendicitis most commonly presents in which age group
children but also in the elderly
what are the main symptoms of appendicitis
periumbilical pain that moves to RIF
mild fever and tachycardia
anorexia
possible nausea and vomiting
on examination what is found if someone has an appendicitis
abdominal guarding
pain on percussion
Rosvings sign
what is Rosvings sign
pain in RIF when palpating the LIF
what investigations are required for appendicitis
ultrasound - gold standard
CRP and WCC
urinanalysis
what is the treatment for appendicitis
analgesia
antipyretics
urgent lap appendicectomy
what treatment is required after surgery for appendicitis
antibiotics and IV fluids
what is Meckels diverticulum and are the complications of it
congenital condition which when becomes irritated can mimic the symptoms of appendicitis - complications include bleeding, obstruction and diverticulitis
what are the two classifications for mesenteric ischaemia
acute and chronic
what causes acute mesenteric ischaemia
embolus formed elsewhere travels to the SMA and becomes lodged causing infarction
what causes chronic mesenteric ischaemia
angina of the gut - SMA becomes atherosclerosed
what are the symptoms of mesenteric ischaemia
severe abdominal pain (possibly colicky) with no obvious signs on examination
possible signs of hypovolaemic shock
what investigation is carried out for suspected mesenteric ischaemia
abdominal contrast CT - will show gasless abdomen
what is the treatment and complications of mesenteric ischaemia
surgical resection and re-anastomose
what are the three ways the small bowel can become obstructed and examples of each
in the lumen - food, gallstone, bezoar
in the wall - tumour, radiation, Crohn’s
outside wall - adhesions, herniation
what happens to bowel proximal to the obstruction during bowel obstruction
becomes distended due to formation of gas that cannot pass through
what are the signs and symptoms of bowel obstruction
extreme vomiting (possibly faeculent) absolute constipation distension burping no bowel sounds
what is the treatment for small bowel obstruction
nil by mouth IV fluids NG tube for draining not feeding antibiotics and anticoagulants surgery if becomes strangulated
what is intestinal failure
umbrella term to describe conditions where there is an inability to maintain adequate nutrition or fluid status
lipids make up what % of total energy intake
50%
lipids are soluble true/false
false - either poorly soluble or completely insoluble
what two areas are lipids digested
stomach and small intestine
what enzyme breaks down lipids in the stomach
gastric lipase
what enzyme breaks down lipids in the small intestine and when is it released
pancreatic lipase and released in response to CCK
what is the function of bile salts
released from gallbladder into duodenum to help emulsify large fat droplets into small ones
what is the function of colipase
allows access of lipase to hydrophobic core of small droplets
what is B12 required to bind to for correct absorption and where is it released from
intrinsic factor - released from parietal cells
what are the fat soluble vitamins
A, D, E, K
what are the water soluble vitamins
B (except B12) C and H
