Lecture 52- Intestinal Transport And Liver Physiology Flashcards
Why is the enterosystemic fluid cycle important?
To reabsorb secretion is delivered to proximal part of the SI
What is a substantial fraction of ECF volume?
Secretory fluids from accessory organs, stomach and intestine itself
What is the enterosystemic fluid cycle?
Net movement of fluid into and out of intestinal lumen every 24 hours
Daily exchange of several times total volume of body water
What are the major reabsorptive sites?
Distal SI and LI
Do carnivores or herbivores have larger volumes of secretion in the enterosystemic fluid cycle?
Herbivores
What are the intestinal crypts lined with?
Epithelial cells
What do the intestinal crypts secrete?
Fluid and electrolytes
What type of channels do apical membranes have?
Cl- membranes
____ follows ____ passively into lumen, _____ follows _____
Na follows Cl
Water follows NaCl
What are the two transporters that the basolateral membrane contains?
Na+/K+ ATPase
Na+/K+/2Cl- co-transporter
Cl channels open in response to?
What specifically causes Cl channels?
Cl- channels normally closed, but will open in response to hormones and neurotransmitters binding basolateral membrane
Choleratoxins causes Cl channels to open
What are the mechanisms for fluid and electrolyte absorption
Transcellular and paracellular
What determines the route for fluid and electrolyte absorption?
Permeability of tight junctions between enterocytes
what happens if the junction is tight?
Transcellular route
Tight in stomach and colon
What happens if the junction is leaky?
Then paracellular route
Leaky in duodenum and Jejunum
Fluid absorbed is always ________.
Isosmotic
Where is a major site for Na absorption?
Jejunum
How does Na absorption occur in the Jejunum?
Occurs via Na dependent co-transporters in enterocyte apical membrane
Other than the Jejunum where else is Na absorbed?
Ileum
What exchange occurs in the enterocyte apical membrane in the ileum?
Cl-/HCO3-
What is the overall net absorption of in the ileum?
NaCl
What transporter does the ileum have in the enterocyte basolateral membrane?
Cl-
What channels does the colon have?
Na+ and K+ channels in apical membrane
Colon
What does synthesis of Na increase?
Increase Na absorption
Increase K secretion
Colon
What is the synthesis of Na channels induced by
Aldosterone
Why are fecal concentrations of K+ high in herbivores?
K high in grass, colon helps excrete excess K
During diarrhea there is an increased loss of K. Why is this?
Increased flow rate of intestinal fluid
What does a large loss of large volumes of ECF-type fluids result in
Causes decreased ECF volume
Decreased intravascular volume
Decreased arterial pressure
What are issues associated with severe diarrhea
Circulatory collapse
Hypercholermic metabolic acidosis with normal anion gap
What is another term for high K+ losses?
Hypokalemia
What are examples of normal anion gap?
Diarrhea
Renal Tubular Acidosis
Carbonic Anhydrase inhibition
What does a loss of bicarb from GIT result in?
Signal to kidneys to reabsorb NaCl because Na usually lost
Kidney starts to excrete more H, need more ammonia for buffering
What is osmotic diarrhea?
Non-absorbable solutes
Causes retention of water
What does diarrhea caused decreased surface area for absorption
Infection
Inflammation of SI
What is a secretory diarrhea?
Excessive secretions of fluid by crypt cells
What does secretory diarrhea permanently activate?
Adenylyl cyclase
CAMP levels high
What are the functions of the liver
Process absorbed substances
Synthesis and excretion of bile acids
Bilirubin production and excretion
Metabolism of nutrients
Detoxification and excretion of waste products
Where does the liver receive portal blood from ?
Stomach
SI
LI
Pancreas
Spleen
What does causes jaundice?
Results from increased destruction of RBC
Obstruction of bile duct
Liver disease
What does the mononuclear phagocyte system remove?
Remove senescent RBC
Mononuclear phagocyte system
Degrades ________ -> _______ -> _________
Degrades hemoglobin —> biliverdin —> bilirubin
Mononuclear phagocyte system
Bilirubin binds ______ in blood -> ______ -> conjugated to _______ ______ -> resulting compound of ______/______ in liver
Bilirubin binds albumin in blood -> liver -> conjugated to glucuronic acid -> resulting compound of detoxification/degrade in liver
Mononuclear phagocyte system
Conjugated _____ excreted in ____ AND secreted in ______ -> terminal _____ and _____ -> deconjugated to _______ AND ______ + _________
Bilirubin
Urine AND bile
Ileum and colon
Urobilinogen
Urobilin + stercobilin
What is considered the “first pass metabolism”? And why?
Liver
Liver receives ALL substances absorbed from the GIT
What are bacteria phagocytized by?
Hepatic Kupfer cells
Examples of phase I reactions
Oxidation/reduction/hydrolysis/cyclization reactions
Examples phase II reactions
Conjugation reactions (solubility compound;transfereases)
What does lipid metabolism synthesize ?
Lipoproteins, cholesterol, phospholipids, bile acids
What does protein metabolism synthesize?
Non-essential amino acids
Plasma proteins
What does protein metabolism modify?
Modify amino acids
**so that clucogenic AA can enter gluconeogenesis
What are the three types of carbohydrate metabolism?
Gluconeogenesis
Glycogenesis
Glycogenolysis
What is glycogenolysis?
Break down glycogen to release glucose
What is glycogenolysis stimulated by?
Glucagon and epinephrine
What is glycogenesis?
Highly branched chains of stored glucose=stimulated by glucagon and epinephrine
What does gluconeogenesis use to synthesize glucose?
Use glycerol and glucogenic AA to synthesize glucose AFTER glucose stores are depleted
What does protein metabolism convert ammonia to?
Ammonia to urea
