intestinal physiology Flashcards
intestinal absorption with sodium
na active transported from lumem by atpase
creates a conc gradient
K+ moves out the cell into blood
glucose can enter with sodium via a co transporter protein
factors affecting absorption
Number and structure of enterocytes
Blood and lymph flows
GI motility
Nutrient Intake
factors affecting secretion
irritants
bile
bacterial toxins
what is coeliac disease?
gluten attack
causes damage to lining of gut
define digestion
Breakdown of large, complex organic molecules that can be used by the body.
lactose monomers
glucose and galactose
where does the first stage of protein digestion take place
stomach
Function of enterokinase
to activate trypsin
what does the enyzme colipase target
trigylcerides
what substrate does parietal make
intrinsic factor and gastric acid
what substrate do chief cellsmake
pepsinogen
gastric lipase
gastric phase of gastric regulation secretion
local nervous secretory reflexes
vagal reflexes
gastrin- histamine stimulation
endo and exocrine function of pancreas
endo- secretes insulin and glucagon from islets of Langerhans
exo-secretion of pancreatic juice
where is glucose absorbed
intestines
what happens to glucose in the liver
insulin promotes uptake of glucose in liver
stored in liver as glycogen
some is converted to acetycoa for krebs cycle
excess glucose is converted to triglycerides
what happens to glucose in muscles
stored as glycogen in muscle promoted by insulin
what happens to glucose in RBS
CONVDERTED TO PYRUVATE
as they dont have mitochondria
what happens to triglycerides after absorption
bind to a protein to make lipoprotein as fats not water soluble such as chylomicrons
what happens to glycogen when short fasting
glycogen broken down to glucose by hormone glucagon
GLYOCOGENOLYSIS
where is cortisol produced
adrenal glands
where is adrenaline and noradrenaline produced
adrenal gland
where is throxine produced
thyroid gland
growth hormone are produced where
pituary gland
Why is cortisol important
lipolysis, protein breakdown, gluconeogenesis, glycogen storage
cushings syndrome
excess cortisol levels
central obesity
loss of muscle mass on arms and legs
growth hormone purpose
gluconeogenesis, glycogen synthesis, lipolysis, protein synthesis, decreased glucose use
acromegaly
too much growth hormone
what does leptin do
supresses appetite
what does ghrelin do
stimulates appetite
How is starch broken down
Salivary amylase from parotid glands
By pancreatic amylase ,
Hydrolysis if 1,4 alpha linkages
Makes maltose which is then further broke down with Maltese
Protein digestion and absorption
In stomach pepsin breaks down protein in smaller pieces
In SI peptides are further broken down by endopeptidases
Final digestion - exopeptodases on amino acids
Aa absorbed into bloodstream
Optimum ph for Pepsins
1.6-3.2
Why is pepsin action terminated in the small intestine
Ph of small intestine is too alkaline so denatures
What activates pepsinogen
Low ph
How is glucose absorbed into bloodstream
Glucose and galactose via secondary active transport
Fructose FAC DIFF
How are proteins absorbed into blood stream
Secondary active transport with na
Or basolaterally into capillaries
Fat digestion
Starts in mouth with lingual lipase and make smaller
CCK stimulate bile production to emulsify the fat
Triglycerides into monoglycerides via lipase
Packaged into micelles
Released into enterocytes
How re chylomicrons formed
Triglycerides, phospholipids , and cholesterol combine with proteins inside epithelial lining
How are lipids absorbed and transported into cells
In enterocytes they resterify
Packaged into chylomicrons
Released via exocytosis to lacteals
Thoracic duct then blood
What is the most abundant substance in chyme
Water
Water absorption
8000ml enters SI everyday
1500 ml enters the large i 98% reabsorbed
Most abundant ion in chyme
Na
Where is fe absorbed
Duodenum
Where are vit c and b absorbed
Jejunum
Vit a d e k absorbed where
Ilium
How is bile transported
Enterohepatic circulation
what can vitamins act as /
Gene activators
Free-radical scavengers
Coenzymes or cofactors in metabolic reactions
types of vitamin?
water soluble and fat soluble
where can we get retinoids from?
b- carotene, vegetables such as carrots
functions of vitamin a
vision,
reproduction- spermatogenesis
growth
stabilisation of cellular membranes
signs of vit a deficiency
night blindness, blindness and xeropthalmia
signs of excess vit a
Abdominal pain, nausea and vomiting
Reversible yellowing of the skin
Hair loss, dryness of the lips
Anorexia
function of vit d
Increased intestinal absorption of calcium
Resorption and formation of bone
Reduced renal excretion of calcium
VIT D deficiency
Demineralisation of bone:
Rickets in children
Osteomalacia in adults
where is vit E stored
Non-adipose cells such as liver and plasma – labile and fixed pool
Adipose cells – fixed pool
causes of vit e deficiency
Fat malabsorption (e.g. cystic fibrosis) Premature infants Rare congenital defects in fat metabolism e.g. abetalipoproteinaemia.
what is vit k transferred to
very low LDL and LDL
VIT k FUNCTIONS
amin K is responsible for the activation of some blood clotting factors.
Necessary for liver synthesis of plasma clotting factors II, VII, IX and X.
Where is vit c found
fresh fruit and veg
HOW IS b12 absorbed
Ingested orally Intrinsic factor made by parietal cells B12 binds to intrinsic factor If binds to specific sites on epithelial in terminal ileum B12 absorbed via endocytosis
where is IF-B12 complex absorbed
in the terminal ileum
where is b12 stored
in the liver
functions of folate
Functions as a coenzyme in methylation reactions, DNA synthesis, synthesis of methionine from homocysteine.
how is the extrinsic pathway of clotting activated?
FACTOR 7
