glucose regulation pancreas liver
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Glucose RegulationWhat is diabetes?
Cells need sugar—ATP and the Krebs Cycle
What comes in through the gut—basic nutrition
Role of liver in processing nutrients, storing glucose
Absorptive Pathways and role of insulin from pancreas
Post-absorptive Pathways
Understanding Diabetes
Diabetes mellitus—”starvation amidst plenty”
Type IJuvenile onset
Pancreas beta cells die, no insulin produced
Type IIAdult onset
Complicated set of factors, some insulin production
Goal—understand why we need insulin
Cells and GlucoseAll cells of body need constant glucose supply, especially nervous tissueMost other nutrients can be converted into glucose or derivatives for making ATPATP is celluar “gasoline”
Glycolysis and Kreb’s CycleMain way that cells make ATP
Glucose is principle reactant
Why not eat just sugar?
Essential Amino AcidsOnly additional nutrients that body can’t produce
Needed for making proteins
Also some vitamins and minerals must come from diet
What happens to the rest of what we eat?
Interconversion of NutrientsAlmost everything we eat can be converted and used by Kreb’s cycle
We need some other nutrients—essential amino acids, vitamins, minerals
Our body also uses fats and proteins directly from diet
Why not eat just sugar?
What keeps sugar constantly available in blood?
Immediately after a meal, nutrients are flowing into blood across wall of stomach, small intestines
Between meals, when food has mostly been digested, nutrients are not available
Nonetheless, blood sugar levels are kept virtually constant
How is this possible?Role of liver in temporary storage of glucose as glycogen
Differences in “absorptive” and “post-absorptive” metabolic pathways
Liver
STRUCTURELarge ventral organ of abdominal cavity with multiple lobes (learn them!!)Sets against inferior surface of diaphragm on left sideForms as outpocketing of gut--common bile duct is left as connectionBile duct is two-way street (bile from hepatic duct is stored in gall bladder and later expelled to common bile duct to duodenum)
FUNCTIONDigestion--bile is digestive enzymes plus RBC breakdown productRemoves nutrients and toxins from blood (hepatic portal system brings gut blood directly to liver)Glucose metabolism (with pancreas--see below)
General blood supply to gut--ventral branches off of aorta
Celiac a.--to stomach, liver, pancreas, spleen, duodenumSuperior (cranial mesenteric a.--to small intestines and most of colonInferior (caudal) mesenteric a.--to descending colon, rectum
Liver: Blood SupplyHepatic Vein
from inferior vena cava
Hepatic Artery from abdominal aorta
Hepatic Portal VeinCarries nutrient-rich blood from stomach + intestines to liverPortal system = 2 capillary beds!
pg 660
Hepatic Portal System--anatomy
Hepatic Portal System--concept
Directs blood that has already been through gut capillaries into liver capillaries (or sinusoids)
Allows nutrients and toxins to be removed from blood
Fig. 19.22, M&M
How does liver work?Blood from portal vein and hepatic artery enter into central vein of liver lobules
Leaky capillaries called sinusoids then bring blood into contact with hepatocytes or liver cells
Liver functionVersatile hepatocytes do the following:
Process nutrients including storage of glucoseStore fat-soluble vitamins for later use by bodyDetoxification of blood
Other macrophage-like Kupffer cells also remove debris such as worn-out RBC’s
Following a meal, with nutrients flowing into blood from gut
Role of insulin in take-up of glucose (from pancreas beta cells) by cells during absorptive state
Between meals, with no nutrients flowing into blood from gut
Role of glucagon (from pancreas alpha cells) in release of glucose by cells during post-absorptive state
Pancreas
STRUCTURESmaller, diffuse glandHead in C of duodenumTail extends towards spleen
FUNCTIONDigestion--produces most digestive enzymesGlucose metabolism--Islets of Langerhans
Beta cells make insulinAlpha cells make glucagon
“How Stuff Works” Diabetes:http://www.howstuffworks.com/diabetes1.htm
Liver receives blood from intestines (don’t forget hepatic portal systemAfter meal, in response to insulin from pancreas, glucose stored as complex carbohydrate--glycogen--in liverBetween meals, in response to glucagon from pancreas, glucose is releasedPancreas releases insulin when sugar levels in blood go upInadequate or zero insulin production results in hyperglycemia or high blood sugarOverproduction or over-dosing of insulin results in hypoglycemia or low blood sugar--insulin shockDiabetes is insufficient production of insulin
Type I--juvenile onset with elimination of Islets of langerhans and zero insulin productionType II--adult onset with gradual loss of insulin production
Glucose metabolism