Lecture 52- Intestinal Transport And Liver Physiology

Question 1

Why is the enterosystemic fluid cycle important?

Answer 1

To reabsorb secretion is delivered to proximal part of the SI

Question 2

What is a substantial fraction of ECF volume?

Answer 2

Secretory fluids from accessory organs, stomach and intestine itself

Question 3

What is the enterosystemic fluid cycle?

Answer 3

Net movement of fluid into and out of intestinal lumen every 24 hours

Daily exchange of several times total volume of body water

Question 4

What are the major reabsorptive sites?

Answer 4

Distal SI and LI

Question 5

Do carnivores or herbivores have larger volumes of secretion in the enterosystemic fluid cycle?

Answer 5

Herbivores

Question 6

What are the intestinal crypts lined with?

Answer 6

Epithelial cells

Question 7

What do the intestinal crypts secrete?

Answer 7

Fluid and electrolytes

Question 8

What type of channels do apical membranes have?

Answer 8

Cl- membranes

Question 9

____ follows ____ passively into lumen, _____ follows _____

Answer 9

Na follows Cl

Water follows NaCl

Question 10

What are the two transporters that the basolateral membrane contains?

Answer 10

Na+/K+ ATPase

Na+/K+/2Cl- co-transporter

Question 11

Cl channels open in response to?

What specifically causes Cl channels?

Answer 11

Cl- channels normally closed, but will open in response to hormones and neurotransmitters binding basolateral membrane

Choleratoxins causes Cl channels to open

Question 12

What are the mechanisms for fluid and electrolyte absorption

Answer 12

Transcellular and paracellular

Question 13

What determines the route for fluid and electrolyte absorption?

Answer 13

Permeability of tight junctions between enterocytes

Question 14

what happens if the junction is tight?

Answer 14

Transcellular route

Tight in stomach and colon

Question 15

What happens if the junction is leaky?

Answer 15

Then paracellular route

Leaky in duodenum and Jejunum

Question 16

Fluid absorbed is always ________.

Answer 16

Isosmotic

Question 17

Where is a major site for Na absorption?

Answer 17

Jejunum

Question 18

How does Na absorption occur in the Jejunum?

Answer 18

Occurs via Na dependent co-transporters in enterocyte apical membrane

Question 19

Other than the Jejunum where else is Na absorbed?

Answer 19

Ileum

Question 20

What exchange occurs in the enterocyte apical membrane in the ileum?

Answer 20

Cl-/HCO3-

Question 21

What is the overall net absorption of in the ileum?

Answer 21

NaCl

Question 22

What transporter does the ileum have in the enterocyte basolateral membrane?

Answer 22

Cl-

Question 23

What channels does the colon have?

Answer 23

Na+ and K+ channels in apical membrane

Question 24

Colon

What does synthesis of Na increase?

Answer 24

Increase Na absorption

Increase K secretion

Question 25

Colon What is the synthesis of Na channels induced by

Answer 25

Aldosterone

Question 26

Why are fecal concentrations of K+ high in herbivores?

Answer 26

K high in grass, colon helps excrete excess K

Question 27

During diarrhea there is an increased loss of K. Why is this?

Answer 27

Increased flow rate of intestinal fluid

Question 28

What does a large loss of large volumes of ECF-type fluids result in

Answer 28

Causes decreased ECF volume Decreased intravascular volume Decreased arterial pressure

Question 29

What are issues associated with severe diarrhea

Answer 29

Circulatory collapse Hypercholermic metabolic acidosis with normal anion gap

Question 30

What is another term for high K+ losses?

Answer 30

Hypokalemia

Question 31

What are examples of normal anion gap?

Answer 31

Diarrhea Renal Tubular Acidosis Carbonic Anhydrase inhibition

Question 32

What does a loss of bicarb from GIT result in?

Answer 32

Signal to kidneys to reabsorb NaCl because Na usually lost Kidney starts to excrete more H, need more ammonia for buffering

Question 33

What is osmotic diarrhea?

Answer 33

Non-absorbable solutes Causes retention of water

Question 34

What does diarrhea caused decreased surface area for absorption

Answer 34

Infection Inflammation of SI

Question 35

What is a secretory diarrhea?

Answer 35

Excessive secretions of fluid by crypt cells

Question 36

What does secretory diarrhea permanently activate?

Answer 36

Adenylyl cyclase CAMP levels high

Question 37

What are the functions of the liver

Answer 37

Process absorbed substances Synthesis and excretion of bile acids Bilirubin production and excretion Metabolism of nutrients Detoxification and excretion of waste products

Question 38

Where does the liver receive portal blood from ?

Answer 38

Stomach SI LI Pancreas Spleen

Question 39

What does causes jaundice?

Answer 39

Results from increased destruction of RBC Obstruction of bile duct Liver disease

Question 40

What does the mononuclear phagocyte system remove?

Answer 40

Remove senescent RBC

Question 41

Mononuclear phagocyte system Degrades ________ -> _______ -> _________

Answer 41

Degrades hemoglobin —> biliverdin —> bilirubin

Question 42

Mononuclear phagocyte system Bilirubin binds ______ in blood -> ______ -> conjugated to _______ ______ -> resulting compound of ______/______ in liver

Answer 42

Bilirubin binds albumin in blood -> liver -> conjugated to glucuronic acid -> resulting compound of detoxification/degrade in liver

Question 43

Mononuclear phagocyte system Conjugated _____ excreted in ____ AND secreted in ______ -> terminal _____ and _____ -> deconjugated to _______ AND ______ + _________

Answer 43

Bilirubin Urine AND bile Ileum and colon Urobilinogen Urobilin + stercobilin

Question 44

What is considered the “first pass metabolism”? And why?

Answer 44

Liver Liver receives ALL substances absorbed from the GIT

Question 45

What are bacteria phagocytized by?

Answer 45

Hepatic Kupfer cells

Question 46

Examples of phase I reactions

Answer 46

Oxidation/reduction/hydrolysis/cyclization reactions

Question 47

Examples phase II reactions

Answer 47

Conjugation reactions (solubility compound;transfereases)

Question 48

What does lipid metabolism synthesize ?

Answer 48

Lipoproteins, cholesterol, phospholipids, bile acids

Question 49

What does protein metabolism synthesize?

Answer 49

Non-essential amino acids Plasma proteins

Question 50

What does protein metabolism modify?

Answer 50

Modify amino acids **so that clucogenic AA can enter gluconeogenesis

Question 51

What are the three types of carbohydrate metabolism?

Answer 51

Gluconeogenesis Glycogenesis Glycogenolysis

Question 52

What is glycogenolysis?

Answer 52

Break down glycogen to release glucose

Question 53

What is glycogenolysis stimulated by?

Answer 53

Glucagon and epinephrine

Question 54

What is glycogenesis?

Answer 54

Highly branched chains of stored glucose=stimulated by glucagon and epinephrine

Question 55

What does gluconeogenesis use to synthesize glucose?

Answer 55

Use glycerol and glucogenic AA to synthesize glucose AFTER glucose stores are depleted

Question 56

What does protein metabolism convert ammonia to?

Answer 56

Ammonia to urea