Transcript Gut Tube and Digestion

Glucose Regulation
What 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 I
Juvenile onset
Pancreas beta cells die, no insulin produced
Type II
Adult onset
Complicated set of factors, some insulin
production
Goal—understand why we need insulin
Cells and Glucose
All cells of body
need constant
glucose supply,
especially nervous
tissue
Most other nutrients
can be converted
into glucose or
derivatives for
making ATP
ATP is celluar
“gasoline”
Glycolysis and Kreb’s Cycle
Main way that cells make ATP
Glucose is principle reactant
Why not eat just sugar?
Essential Amino Acids
Only 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 Nutrients
Almost everything we eat can be
converted and used by Kreb’s cycle
Why not eat just sugar?
We need some other nutrients—
essential amino acids, vitamins,
minerals
Our body also uses fats and proteins
directly from diet
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
STRUCTURE
Large ventral organ of abdominal cavity
with multiple lobes (learn them!!)
Sets against inferior surface of diaphragm
on left side
Forms as outpocketing of gut--common
bile duct is left as connection
Bile duct is two-way street (bile from
hepatic duct is stored in gall bladder and
later expelled to common bile duct to
duodenum)
FUNCTION
Digestion--bile is digestive enzymes plus
RBC breakdown product
Removes 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,
duodenum
Superior (cranial
mesenteric a.--to
small intestines and
most of colon
Inferior (caudal)
mesenteric a.--to
descending colon,
rectum
Liver: Blood Supply
Hepatic Vein
from inferior vena cava
Hepatic Artery
from abdominal aorta
Hepatic Portal Vein
Carries nutrient-rich
blood from stomach +
intestines to liver
Portal system = 2
capillary beds!
pg 660
Hepatic Portal System--anatomy
Hepatic Portal System--concept
Fig. 19.22,
M&M
Directs blood that has already been through gut
capillaries into liver capillaries (or sinusoids)
Allows nutrients and toxins to be removed from
blood
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 function
Versatile
hepatocytes do
the following:
Process nutrients
including storage
of glucose
Store fat-soluble
vitamins for later
use by body
Detoxification 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
postabsorptive
state
Pancreas
STRUCTURE
Smaller, diffuse gland
Head in C of duodenum
Tail extends towards spleen
FUNCTION
Digestion--produces most
digestive enzymes
Glucose metabolism--Islets
of Langerhans
Beta cells make insulin
Alpha cells make glucagon
“How Stuff Works”
Diabetes:
http://www.howstu
ffworks.com/diabet
es1.htm
Glucose metabolism
Liver receives blood from intestines (don’t forget hepatic portal system
After meal, in response to insulin from pancreas, glucose stored as complex
carbohydrate--glycogen--in liver
Between meals, in response to glucagon from pancreas, glucose is released
Pancreas releases insulin when sugar levels in blood go up
Inadequate or zero insulin production results in hyperglycemia or high blood
sugar
Overproduction or over-dosing of insulin results in hypoglycemia or low blood
sugar--insulin shock
Diabetes is insufficient production of insulin
Type I--juvenile onset with elimination of Islets of langerhans and zero
insulin production
Type II--adult onset with gradual loss of insulin production