10 Completing digestion/absorption Flashcards
How does the jejunum differ from the ileum in terms of structure?
Jejunum= in upper left quandrant
Ileum= in lower right quadrant
(B12 absorption= in ileum)
What is the marginal artery? (aka artery of Drummond)
Anastomotic channel= combination of multiple arteries including:
- Ileocolic (SMA)
- Right colic (SMA)
- Middle colic (SMA)
- Left colic (IMA)
- Sigmoid arteries (IMA)
Fill in the missing labels:
Fill in the missing labels:
Inferior mesenteric vein drains into splenic vein
How is the bolus moved within the small intestine and why is it moved in this way?
Bolus shuttled back and forth- so contents has more time in contact with the wall of the lumen
Describe structure of the mucosa of the small intestine.
Folded into villi, surface covered in microvilli (brush border)
What are the arrows pointing to in the following diagram? (aka valvulae conniventes)
Plica circularis
(permanent crescentic folds of mucous membrane found in the small intestine especially in the lower part of the duodenum and the jejunum)
What specialised epithelial cells can be found in the intestinal epithelia amnd what are their functions? (5)
Paneth cells- produce antimicrobial peptides - innate mucosal defence cells
What are the crypts found within the wall of the small intestine called?
Crypts of lieberkuhn
What ion is required to transport glucose?
Na+
What bonds does amylase break?
What enzyme is required to break down the alpha 1,6 bonds in the alpha dextrins?
Isomaltase
Name 2 enzymes which are integrated in the brush border ?
What are the functions of each of the following in the gut?
- Na+/K+ ATPase (on basolateral membrane)
- SGLT-1
- GLUT2
- GLUT5
How is trypsinogen converted to trypsin? Why is this important?
Trypsinogen converted to trypsin by enteropeptidase (enterokinase)
Trypsin activates other proteases
What is the difference between exopeptidases and endopeptidases? Give examples of each
Via what transporter can enterocytes absorb short peptides? What happens to these short peptides once they enter the enterocyte?
peptide transporter 1 (PepT1)
Broken down by cytosolic peptidases
With what ion are amino acids co-transporter with into the enterocyte?
How is water absorbed in the small intestine?
Absorption driven by movement of sodium into enterocytes
Water follows sodium
Osmotic gradient
(Diarrhoea may occur as water uptake by small intestine= limited)
How does water uptake differ between the small intestine and the large intestine?
Basolateral membrane: Both have Sodium-Potassium ATPase
Apical membrane: see image
How does oral rehydration work? (what does it contain)
Glucose and salt- stimulates maximum water uptake
How do we get water out into the gut lumen(water secretion) (ie in duodenum)?
Driven by chloride
Give some causes of vitamin B12 deficiency (cobalamin) (4) and 2 major consequences of this deficiency.
Causes:
- Lack of intrinsic factor (secreted by parietal cells)
- Hypochlorhydria (inadequate stomach acid)
- Eg gastric atrophy, PPIs
- Inadequate food intake (strict vegetarians)
- Inflammatory disorders of ileum eg Crohn’s
Conseuqences:
- Megaloblastic anaemia (bone marrow produces unusually large, structurally abnormal, immature red blood cells)
- Neurological symptoms (damage to myelin sheath)
Why does lactose intolerance cause diarrhoea?
Lactose can’t be absorbed
Remains in gut lumen
High osmotic effect- water drawn into lumen
What are some symptoms of irritable bowel syndrome?
What are some risk factors/ associations for IBS? (3)
Outline the pathophysiology of coeliac disease:
Give some of the symptoms of coeliac disease:
Microcytic anaemia
What investigations can be done into coeliac disease?
How is coeliac disease treated?
Strict gluten free diet (especially children as it will affect their growth)
(may take weeks/months to see histological improvement by clincial improvement= days/weeks)
