Lecture 52- Intestine Transport And Liver Physiology Flashcards
What is the importance of the enterosystemic fluid cycle?
Reabsorb secretions delivered to proximal part of SI
What is a substantial fraction of the 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
Do herbivores, carnivores, or omnivores have the largest secretions during the enterosystemic fluid cycle?
Largest volumes of secretions in herbivores
Where are the major reabsorpitive sites?
Distal SI and LI
What is the definition of reabsoprtion in relation to the enterosystemic fluid cycle?
Ions and fluid recovery need to recover to maintain ECF volume AND the BP
What type of cells line intestinal crypts? What do they secrete?
Epithelial cells line intestinal crypts
Secrete fluid and electrolytes
_____ follows _____ passively into lumen, then ___ follows _____
Na follows Cl passively into lumen, water follows NaCl
What channels does the Apical membrane have?
Cl Channels
What does the basolateral membrane contain?
Na+/K+ ATPase
Na+/K+/2Cl- co-transporter
What do Cl- channels open in response to?
Hormones and neurotransmitters binding basolateral membrane
Choleratoxins also cause Cl channels to open
What are two mechanisms for fluid and electrolyte absorption?
Transcellular and paracellular routes
What happens if tight junction is “tight”? Where are the junctions “tight”?
If tight, then goes transcellular route
Tight in stomach and colon
What happens if tight junction is “leaky”? Where are the junctions “leaky”?
If leaky, then go paracellular route
leaky in duodenum and Jejunum
What determines which route for fluid and electrolyte absorption?
Permeability of tight junctions between enterocytes
In intestinal absorption the 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
What is exchanger is present in the enterocyte apical membrane in the ileum? What is the transporter that the ileum uses in the basolateral membrane?
Cl-/HCO3- exchange in enterocyte apical membrane
Cl- transporter in enterocyte basolateral membrane
What is the overall net absorption that occurs in the Ileum?
NaCl
In the Ileum _____ and ____ are absorbed.
Na+ and NaCl
In the colon what are the channels located in the apical membrane?
Na+ and K+
Synthesis of Na channels induced by aldosterone in the colon causes what?
Increased Na absorption AND increased K secretion
Why is there an increased loss of K+ during diarrhea?
Due to increased flow rate of intestinal fluid
Are fecal concentrations of K+ in herbivores higher or lower?
potassium high in grass, colon helps excrete excess K+
What is the term for high K+ losses?
Hypokalemia
What happens when there is a loss of bicarbonate from the GIT?
Kidneys are signaled to reabsorb NaCl because Na is usually lost when bicarbonate is lost. The kidney excretes more H, because it needs more ammonia for buffering.
What can lead to hyper holte ich metabolic acidosis with normal anion gap?
High HCO3- losses relative to Cl losses
What are clinical examples of things that result in normal anion gaps?
Diarrhea, Renal tubular acidosis, carbonic anyhdrase inhibition
What are four things that result in a normal anion gap?
- Hyperchlomeric acidosis
- GI or renal loss of bicarbonate
- Impaired renal acid secretion
- Reabsorption of chloride
What causes osmotic diarrhea?
Non-absorbable solutes -> causes Renton of water
What causes secretory diarrhea? What does secretory diarrhea permanently activate? What levels are very high?
-excessive secretions of fluid by crypt cells
-permanently activates Adenylyl cylase
-cAMP levels
Where does liver receive portal blood from?
Stomach, SI, LI, pancreas, spleen
What are the (5) 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
What organ is considered the “first pass metabolism”?
The LIVER because it receives all substances absorbed from the GIT
What are bacteria phagozytized by?
Hepatic Kupfer cells
What is considered a phase I reaction?
Oxidation/reduction/hydrolysis/cyclization reaction (mixed function oxidases)
What is considered phase II reactions?
Conjugation reactions (solubility compound; transferases)
What occurs during lipid metabolism in the liver?
Fatty acid oxidation
What does lipid metabolism synthesize?
Lipoproteins, cholesterol, phospholipids, bile acids
What does protein metabolism synthesize?
Non-essential amino acids and plasma proteins (albumin)
What does protein metabolism in the liver modify? What does it convert?
Modify: amino acids -> so glucogenic AA can enter gluconeogenesis
Convert: ammonia (toxic) -> urea (non-toxic)
What are the three metabolisms of the liver?
- Carbohydrate metabolism
- Protein metabolism
- Lipid metabolism
In what species does glucogenesis continue to make glucose from propionate?
Ruminants
How does glycogenolysis function in the carbohydrate metabolism of the liver?
Breaks down glycogen to release glucose — stimulated by glucagon and epinephrine
How does glycogenesis function in the carbohydrate metabolism of the liver?
Highly branched chains of stored glucose (occurs after a meal)
How does gluconeogenesis function in the carbohydrate metabolism of the liver?
uses glycerol and glucogenic AA to synthesize glucose after glucose stores are depleted
(Glucose storage = glycogen)
What is jaundice a result of? (4)
Increase destruction of red blood cells, obstruction of bile ducts, liver disease, conjugated bilirubin that can’t be excreted in bile
Conjugated bilirubin excreted in urine AND secreted in bile -> terminal _____ and colon _____ -> deconjugated to ________ AND _____ + _______
Ileum and colon
Deconjugated to urobilinogen AND urobilin + stercobilin
What does the mononuclear phagocyte system remove?
Senescent RBC
When bilirubin binds albumin in blood and conjugated to glucoronic acid…what does this result in?
Resulting compound of detoxification/degrade in liver
The mononuclear phagocyte system purpose is to degrade ______, which results in ______, and the end product is _______.
Hemoglobin
Biliverdin
Bilirubin
