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