Glucose regulation pancreas liver

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