GI Flashcards
What is the main blood supply to the foregut, midgut and hindgut?
foregut: coeliac trunk
midgut: superior mesenteric artery
hindgut: inferior mesenteric artery
What is the main nerve supply to the foregut, midgut and hindgut? Where do each of them leave the spinal cord?
foregut: greater splanchnic nerve: T5-T9
midgut: lesser splanchnic nerve: T10-T11
hindgut: least splanchnic nerve: T12
Where on the spinal cord does the sympathetic chain run?
T1 - L2
Describe the structure of the stomach.
Oesophagus Cardiac sphincter Cardia Fundus Body Antrum Pylorus Pyloric sphincter Duodenum
Smaller c-shaped curve= lesser curvature
Larger c-shaped curve= greater curvature
What is the name for the muscular ridges in the stomach?
reggae
What is the name for the two openings of the stomach?
top= cardiac orifice bottom= pyloric orifice
What two sphincters are in the stomach?
cardiac sphincter
pyloric sphincter
Describe the arterial supply to the stomach.
Blood supply arises from coeliac artery
Branches of coeliac artery are:
Hepatic artery- supplies liver
Splenic artery- supplies spleen
Left gastric artery- supplies left side of lesser curvature
Splenic artery branches to:
Short gastric: supplies fundus
Left gastroepiploic: supplies left side of greater curvature
Hepatic artery branches to:
Right gastric: supplies right side of lesser curvature
Pancreatoduodenal: supplies duodenum
Pancreatoduodenal artery branches to:
Right gastroepiploic: supplies right side of greater curvature
Describe the arterial supply to the midgut.
Supplied by superior mesenteric artery
Superior mesenteric branches to:
Ileocolic/ ileocecal artery: supplies cecum and ileum
Right colic: supplies ascending colon
Middle colic: supplies 2/3 of transverse colon
The marginal artery of Drummond is formed from ileocecal, right colic and middle colic arteries. Coming off this is the arcades and vasa recta which lie in the mesentery and supply the jejunum
Describe the arterial supply of the hindgut.
Supplies by inferior mesenteric artery
Inferior mesenteric branches to:
Left colic: supplies remaining 1/3 of transverse colon and descending colon
Sigmoid: supplies sigmoid colon
Superior rectal: supplies rectum and upper part of anal canal
What are the 4 parts of the duodenum?
starts at pylorus superior duodenum descending duodenum inferior duodenum ascending duodenum ends at duodenaljejunal junction
Where does the common bile duct empty into?
the descending duodenum
Where does the main pancreatic duct empty into?
the descending duodenum
Via what entrance does the common bile duct and main pancreatic duct drain into?
The major duodenal papillae
Describe the mucosa of the duodenum.
superior duodenum has smooth mucosa, the rest has plicae circularis
What is the function of plicae circularis?
increase surface area of duodenum
List the differences between the jejunum and the ileum.
length: ileum longer
diameter: jejunum wider
wall: jejunum thick double wall, ileum thin wall
colour: jejunum deep red, ileum pale pink
peyer’s patches: jejunum has very few, ileum has many
blood supply: jejunum has longer arteries and few vasa recta, ileum has short arteries and many vasa recta
mesentery: more fatty at ileum
crypts of lieberkuhn: jejunum has shallow crypts, ileum has normal depth crypts
villi: jejunum has long and narrow villa, ileum has short and wide villi
What is the function of Peyer’s patches?
immune surveillance of small intestine
Describe the anatomy of the large intestine
ileum leads into cecum via ileocecal valve appendix attached to cecum ascending colon right colic (hepatic) flexure transverse colon left colic (splenic) flexure descending colon sigmoid flexure sigmoid colon rectum anus
What are taenia coli?
3 longitudinal ribbons of smooth muscle on the outside of ascending, transverse, descending. sigmoid colon
What are haustra?
the pouches of the colon
What is the venous drainage of the colon?
ascending, transverse colon: superior mesenteric vein
descending, sigmoid colon: inferior mesenteric vein
What is the marginal artery of Drummond?
anastomosis of the superior and inferior mesenteric artery and gives of arcades and vasa recta, important in ensuring blood supply to colon
List the differences between the small and large intestine.
size: small intestine longer and thinner, large intestine shorter and wider
muscle: small intestine has longitudinal muscle layer that is continuous, large intestine is not continuous but has 3 muscles= tenae coli
wall: small intestine has smooth wall, large intestine has haustrations
plique circularis: internal membrane of small intestine has PC, colon doesn’t
villi: small intestine mucous membrane has villi, colon doesn’t
peyer’s patches: small intestine has them, colon doesn’t
haustrations: small intestine has none, colon does
What are the three muscles of the abdominal wall and what is the function of each?
- External Oblique- contralateral rotation of torsa
- Internal Oblique- bilateral contraction compresses abdomen, unilateral contraction ipsilaterally rotates torso
- Transverse Abdominus- compression of abdomen
In what direction do the fibres of the external oblique run?
inferomedially (as if into your pockets)
In what direction do the fibres of the internal oblique run?
superomedially
What joins the muscles of the abdominal wall?
aponeurosis called the RECTUS SHEATH
What is another name for the arcuate line and where does it lie?
semicircular line of Douglas
about 1/3 of distance between umbilicus and pubic symphysis
Name the 9 sections of the abdomen from right to left, up to down.
right hypochondrium
epigastric
left hypochondrium
right lumbar
umbilical
left lumbar
right iliac
hypogastric
left iliac
What vertical and horizontal lines separate the 9 sections of the abdomen?
vertical:
2 midclavicular lines
horizontal:
upper: subcostal plane
lower: intercristal plane
Where is McBurney’s point and what is it’s significance?
2/3 of the way from umbilicus to anterior iliac spine
this is where the appendix lies
Where is the transpyloric plane? What does it cross?
L1
gallbladder, pancreas, pylorus, duodenal-jejunal flexure, kidney
What are the boundaries of the foregut, midgut and hindgut?
foregut: mouth to common bile duct
midgut: common bile duct to 2/3 along transverse colon
hindgut: 2/3 along transverse colon to anal canal
What does the remnant of the urachus give?
median umbilical ligaments
What does the remnant of the foetal umbilical arteries give?
medial umbilical ligaments
Describe the epithelium of the lips.
outer= highly keratinised squamous epithelium inner= less keratinised squamous epithelium
Describe the epithelium of the tongue.
stratified squamous (dorsal- keratinised, ventral- nonkeratinised)
Describe the epithelium of the oral cavity.
stratified squamous non-keratinising
Describe the epithelium of the oesophagus.
stratified squamous non-keratinising
Describe the epithelium of the stomach.
simple glandular columnar
Describe the epithelium of the small intestine.
simple columnar with crypts and villi
Describe the epithelium of the colon and rectum.
simple columnar with no villi
Describe the epithelium of the anal canal.
stratified squamous, becomes keratinised at distal end
What are the 3 types of tongue papillae and where do each type lie?
filiform: anterior 2/3
fungiform: mushroom-shaped at sides and tip
circumvallate: dome-shaped, arranged in a V- shape, separates anterior 2/3 and posterior 1/3
What type of tongue papillae don’t contain tastebuds?
filiform
What are Fordyce’s spots?
non-pathological papule that contain serous glands and can be found on the surface of the inner lip and genitalia
What are the two muscle layers of the oesophagus?
outer: longitudinal
inner: circular
What can GORD/ Barrett’s oesophagus do to the lower oesophagus?
can transform it into more of a gastric mucosa
What 2 components are found in the stomach epithelium?
gastric pits
contains secretory cells
What are the 3 muscle layers of the stomach?
outermost: longitudinal fibres
middle: circular fibres
innermost: oblique fibres
List the cells of the stomach, what they secrete and where they are found.
Mucous: secretes mucous, found in mucosa
Parietal: secretes HCl and intrinsic factor, found in body and fundus
Chief cells: secretes pepsinogen, found in body and fundus
Enteroendocrine/ G cells: secretes gastrin, found in pyloric antrum
ECL cells: secrete histamine, found in mucosa
D cells: secrete somatostatin, found in antrum
What are the layers of the stomach?
mucosa
submucosa
muscular propria
serousal surface
Where are Brunner’s glands and what do they do?
in the duodenum only
secrete alkaline mucus to neutralise chyme
What is the distribution of goblet cells in the small intestine?
few in duodenum
many in jejunum
increase in number towards distal end of ileum
Where are the lymph nodes in the jejunum?
lamina propria
Where in the ileum are the Peyer’s patches?
lymphoid tissue in submucosa
What are the 3 longitudinal bands of muscles in the colon?
taeniae coli
What are the functions of saliva?
lubricant for mastication
maintaining oral pH
begins starch digestion
antibacterial
How does saliva maintain oral pH? What is an appropriate range range for oral
bicarbonate/ carbonate buffer system
pH 6.2 - 7.4
What enzyme is found in saliva?
alpha amylase
What are the two types of saliva secretion and what is their function?
mucous: mucins for lubrication
serous: alpha amylase for starch digestion
What are the 4 types of salivary gland, what innervates them and what type of secretion do they release?
Parotid: serous
Glossopharyngeal parasympathetic
Sublingual: mucous
Facial parasympathetic
Submandibular: mixed
Facial parasympathetic
Minor: all mucus except Von Ebner’s serous glands
Facial parasympathetic
What are the differences between serous and mucus acini?
Serous: dark staining nucleus nucleus in basal third small central duct secretes water and alpha amylase
Mucus: pale staining "foamy" nucleus nucleus at base large central duct secretes mucous (water and glycoproteins)
What are the components of a salivary duct?
Acini
Intercalated duct
Striated duct
Interlobular/ excretory duct
What is the function of gastric mucous?
lubrication
protection of mucosa
What is the function of gastric acid?
digestion
activates pepsinogen
kills pathogens
What is the function of intrinsic factor?
absorption of vitamin B12 in terminal ileum
What is the function of pepsinogen?
converted to pepsin which is a protease enzyme for digestion
What is the function of gastric histamine?
stimulates HCl secretion
What is the function of gastrin?
stimulates HCl secretion
stimulates histamine secretion
What is the function somatostatin?
inhibits HCl secretion
What are the stages of gastric acid secretion?
cephalic stage: ON
gastric stage: ON
gastric stage OFF
intestinal phase OFF
What stimulates pepsinogen secretion?
acetylcholine- parasympathetic
At what pH is pepsinogen converted to pepsin?
pH 2
What percentage of protein digestion is done by pepsin?
20%
What is the volume of an empty and max volume stomach?
empty stomach: 50mL
max volume: 1.5L
How does the volume of the stomach increase when eating?
via receptive relaxation
How is receptive relaxation mediated?
acetylcholine: parasympathetic (vagus nerve)
nitric oxide + serotonin (enteric)
Describe the process of peristalsis in stomach.
occurs in response to arriving food
ripple movement begins in body
more powerful contraction wave in antrum
pyloric sphincter closes (so not much chyme can enter duodenum)
antral contents forced back to body for mixing
What are the pacemaker cells of the stomach?
interstitial cells of cajal
How often does the stomach contract?
3 times per minute
What increases the strength of gastric contractions?
gastrin
gastric distension
What decreases the strength of gastric contraction?
duodenal distension increased duodenal fat increase in duodenal osmolarity decrease in duodenal pH increased sympathetic NS stimulation decreased parasympathetic NS stimulation
What are the protective mechanisms of gastric mucosa?
alkaline mucus on luminal surface
tight junctions between epithelial cells
rapid cell replacement of damaged cells by stem cells in base of pits
feedback loops for regulation of gastric acid secretion
What is the consequence of insufficient gastric mucosa defence?
peptic ulcers
What are the causes are peptic ulcers?
helicobacter pylori infection
NSAIDs
chemical irritants (alcohol, bile salts)
gastronome
What is BMR?
basal metabolic rate = the amount of energy needed to stay alive at rest
What is an approximate value for BMR in general?
24kcal/kg/day
What factors increase BMR?
overweight fever being male pregnancy caffeine hyperthyroidism exercise low temperature
What factors decrease BMR?
increase in age being female malnutrition starvation hypothyroidism
What is BMI?
body mass index
What is the formula for BMI?
weight / (height)^2
kg/m^2
What are the categories for BMI values?
<18.5 underweight 18.5-25 normal 25-30 overweight 30-40 obese >40 morbidly obese
What vitamins are fat soluble?
A D E K
Where are fat soluble vitamins absorbed?
ileum
What vitamins are water soluble?
B, C
Where are water soluble vitamins absorbed?
jejunum
How is vitamin B12 absorbed?
B12 ingested orally
intrinsic factor produced by parietal cells in stomach
B12 binds to intrinsic factor
intrinsic factor binds to specific sites of terminal ileum epithelial cells
B12 absorbed via endocytosis
What are the functions of vitamin A?
cellular growth and differentiation
vision
lymphocyte production
skin and mucous membranes
What are the sources of vitamin A?
liver diary fruit and veg oily fish margarine
What are the consequences of vitamin A deficiency?
night blindness
growth retardation
increased infection susceptibility
impaired hearing, taste and smell
What is the function of vitamin C?
collagen synthesis
antioxidants
absorption of non-haem iron
What are the sources of vitamin C?
citrus fruit
green veg
potatoes
What are the consequences of vitamin C deficiency?
scurvy
bleeding gums
aching bones
What is the function of vitamin B12?
erythrocyte formation
DNA synthesis
brain development
What are the sources of vitamin B12?
meat and fish
eggs
milk
What is the consequence of vitamin B12 deficiency?
pernicious anaemia
What is pernicious anaemia?
decrease in red blood cells due to lack of vitamin B12
What is the function of vitamin D?
calcium absorption in gut
What are the sources of vitamin D?
plants
mushrooms
UV light
What are the consequences of vitamin D deficiency?
frequency bone fractures
muscle weakness
bone pain
What is the function of vitamin E?
antioxidant
protects cell walls
What are the sources of vitamin E?
nuts and seeds
vegetable oil
What are the consequences of vitamin E deficiency?
muscle weakness
degeneration of retina
What is the function of vitamin K?
formation of clotting factors 2, 7, 9, 10 in liver
What are the sources of vitamin K?
green leafy veg
meat, eggs, cereal
What are the consequences of vitamin K deficiency?
no clotting factors
gum bleeding
easy bruising
Where does starch digestion begin? By what enzyme? By what pH?
alpha amylase in mouth at pH 6.7
What percentage of starch digestion occurs in small intestine?
95%
What enzymes in the small intestine digest starch?
pancreatic alpha amylase
Describe digestion and absorption of starch.
Digestion begins in mouth by alpha amylase
95% of digestion occurs in small intestine by pancreatic alpha amylase
broken down into disaccharides
enzymes of luminal surface membranes of small intestine epithelial cells break down disaccharides into monosaccharides
monosaccharides are absorbed into the bloodstream
Describe protein digestion and absorption.
digestion begins in stomach by pepsin which breaks protein chains down into smaller fragments
in small intestine peptides are further fragmented by pancreatic enzymes (endopeptidase)
final digestion of acids by exopeptidase:
by carboxypeptidase from pancreas in intestinal lumen
by amino peptidase on luminal membrane of SI epithelial cells
by intracellular peptidases
absorbed into bloodstream
What is the most abundant substance in chyme?
water
How much water enters small intestine every day? How much of this enters the colon?
8000ml
1500ml enters colon
What percentage of water absorption occurs in small intestine?
80%
Where is most water absorbed?
jejunum
What percentage of fluid is reabsorbed and what percentage in lost in stools?
98% reabsorbed
2% lost in stools
How many ml of water is lost in stools every day?
200ml
How is sodium absorbed?
active transport
co-transport with glucose and amino acids
Why is sodium reabsorption important?
enhances osmotic gradient for water absorption
How is potassium absorbed?
passive diffision
How is chloride absorbed?
active transport in exchange for bicarbonate
Why is chloride absorption important?
makes intestinal contents more alkaline
