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FDNS 2100 8/30/11 11:01 AM
Enzymes, Hormones, and Bile Aid Digestion
Complete digestion of chyme requires:
o ENZYMES: break down food into absorbable nutrient
components
Secreted by stomach, small intestine, pancreas
Amylases (break down c
Carbs), lipases (lipids), proteases (proteins)
o HORMONES: gastrin, insulin, glucagon, secretin,
cholecystokinin
Control digestive secretions and regulate enzymes
The stomach normally maintains a ph 1.5-1.7. How does it stay that way?
Gastrin
o Secreted from stomach
o in response to food in stomach
o acts to cause HCL secretion
As the chyme enters the intestine, the pancreas adds bicarbonate. How does
the pancreas know how much to add?
Secretin:
o Secreted from small intestine in response to chyme
o acts on pancreas to cause sodium bicarbonate release-
neutralize acidity
When fat is present in the intestine, the gallbladder squirt Bile (not an
enzyme, but moves fat; if bile is not there, fat will not digest/break down and
it will stay in lumps). How does the gallbladder get the message that fat is
present?
Cholecystokinin (CCK)
o Secreted from small intestine in response to fat
o Acts on gallbladder to cause release of bile into the small
intestine
The Liver, Gallbladder, and Pancreas Are Accessory Organs
LIVER: largest gland in body
o produces bile needed for fat digestion *(does not store bile)
o detoxifies alcohol
GALLBLADDER: concentrates and stores bile
o released into GI tract when fat is ingested
PANCREAS:
o produces hormones: insulin and glucagon regulate blood
glucose
o sodium bicarbonate neutralizes acidic chyme, protects
enzymes from inactivation by acid
o Digestive enzymes:
amylase: digests carbohydrates
lipase: digests fats
pepsin: digests proteins
Digestion Allows Us to Absorb Nutrients from Foods
After digestion, nutrients are absorbed through the walls of the
intestines into the body:
o Circulatory system (blood)
o Lymph system
Sent to the liver for processing before delivery to the body’s cells
GI tract is highly efficient: 92 to 97 percent of nutrients from food
are digested and absorbed.
Types of Absorption
Passive or Simple diffusion
o Intestinal wall is permeable to the nutrient
Facilitated
o A carrier shuttles substances into the absorptive cells
o Going from higher to lower concentration and NO energy
expended.
Active
o uses a carrier and energy (ATP) Energy in CELLS
Absorption and Transportation of Nutrients
LYMPHATIC VESSELS (products of fat digestion and a few vitamins),
later delivering them to the bloodstream.
The BLOOD VESSELS carry the products of carb and protein
digestion, most vitamins and the minerals from the digestive tract
to the liver.
Storage Systems
Humans are designed to eat at intervals of about 4 to 6 hours
Cells need nutrients 24 hours a day
Body’s major storage sites for nutrients are:
o Liver
o Muscles
o Fat cells
When I Eat More Than My Body Needs, What Happens to the Extra Nutrients?
Nutrients from the digestive system arrive at the liver
Liver processes nutrients
Excess nutrients are converted to:
o Glycogen (a carb)
o fat
What Are Some Common Digestive Disorders?
Disordors of the MOUTH and ESOPHAGUS:
o Gingivitis and periodontal disease (can lose teeth)
o Swallowing problems: dysphagia (common in elderly)
o Esophageal problems
Heartburn (acid reflux) may be caused by weak LES
(weakening of the sphincter connected to it)
What should you do to avoid heartburn or GERD?
o lose weight
Disorders of the stomach:
Peptic ulcers
o Caused by bacteria (stress, pain killers, caffeine, etc. can
stimulate the bacteria to grow)
o Need to get antibiotic to kill bacteria
Gallbladder disease:
Gallstones
o Associated with accumulation of minerals
o Treatment: laser to break it down so it will come out when
urinate… If this doesn’t work, surgery.
Disorders of the intestines:
Flatulence (constipation) (treatment is fiber)
Constipation and diarrhea
Hemorrhoids (many years of constipation)
Common/more serious digestive disorders? Irritable Bowel Syndrome (IBS)
o Cover 3 serious:
Ulcerative colitis
Proctitis
Chron’s disease
o Affects 20% of Americans
o S/S (aka symptoms): cramps, gas, bloating, irregular bowel
function
o Possibly caused by altered intestinal peristalsis and decreased
pain threshold.
o Rx: individualized, elimination diet, moderate caffeine, low fat,
small meals, stress reduction
Celiac disease (autoimmune disorder)
o I.e. Gluten-sensitive condition
o Antibodies attack microvilli
o Managed by gluten-free diet (no wheat)
POINTS TO REMEMBER: People with celiac disease
cannot tolerate gluten, a protein in wheat, rye, barley,
and possibly oats.
Untreated interferes with nutrient absorption
Celiac disease is hereditary
Crohn’s disease
Colon cancer Diverticula and Diverticulitis:
o Diverticulum is the outpouching of the intestinal mucosa
o Diverticulosis is the presence of multiple diverticula
o Diverticulitis is inflammation of diverticula
CELIAC DISEASE
8/30/11 11:01 AM
8/30/11 11:01 AM