Intesinal Secretion & Absorption Flashcards
What is the primary function of the small intestine?
Absorption of:
Nutrients, water & electrolytes
What makes up the small intestine?
Duodenum, jejunum, and ileum
Where had fast absorption rate?
Duodenum and upper jejunum
What ions are partially absorbed and why?
Calcium and iron
Bigger molecules because of larger hydration shell
What is important about the ingestion of food?
Regulates the rate of caloric absorption
What are the ways to increase surface area?
Folds, villi, microvilli
Describe the absorption of water and electrolytes in the small intestine
99% of water and electrolytes absorbed
Defecation of water, Na+, Cl- and K+
What happens when water and electrolytes are not absorbed?
Rapid dehydration & circulatory collapse
What regulates water transport?
Electrolyte transport
To take water out, salt needs to be removed = to create osmotic pressure
What is the composition of intestinal juice?
Higher bicarbonate and lower Cl- than plasma
HCO3-/Cl- exchanger
Why are enzymes present in the small intestine?
What is the function of intestinal juice?
Fluidity of chyme
Neutralize the chyme, because juice is slightly alkaline
What triggers intestinal juice secretion?
Mechanical irritation of the mucosa
Distension of the gut
ACh & gastrin triggering increase in calcium
Secretin, CCK & GIP = triggering increase in cAMP
What is the pH like in the GIT?
pH varies through the GI tract = 1.5-8
Name some factors that affect pH?
Drugs and disease
What does pH have an effect on?
pH afects the % of un-ionized molecules
un-ionized = non-polar
More lipid soluble
Describe the properties of colon/large intestine
90-150cm long
No villi
Microflora present
VIscous material = end point of material
What is the function of the large intestine?
Similar to small intestine = absorption
What does the large intestine secrete?
Mucuc and intestinal juice
What is the composition of K+ and HCO3-?
High K+ and HCO3- = pH of 8-8.4
Not a major K+ excretion site
Buffer against H+ produced by bacterial fermentation
What stimulates large intestinal secretion?
Parasympathetic nerve impulses
Mechanical or chemical irritation of the mucosa
What inhibits large intestine secretion?
Sympathetic nerve impulse decrease secretion
When stressed = alica and mcuus is thick
What happens when we fail to absorb electrolytes normally and what is the cause?
Congenital Cl- diarrhoea
Lacking Cl-/HCO3- exchanger
Retention of HCO3- cause metabolic alkalosis
What does failure to absorb nutrients cause?
Carbohydrate malabsorption syndromes
Name types of oral rehydration therapy
Glucose-saline solution = monosaccharide causes absorption of Na+ to lose less water
Amino acid saline solution
What causes secretory diarrhoea?
Enhanced secretion of water and electrolytes = wash out toxic substances
