chapter 3 Flashcards
Digestion
- definition
- type of methods
- gastrointestinal tract consists of
- a multi-step process of breaking down foods into absorbable components
- mechanical and chemical methods in the gastrointestinal tract
- mouth
- esophagus
- stomach
- sm and large intestine
- accessory organs: pancreas, liver and gallbladder
- mouth
where does most digestion happen
in the sm intestine
3 main roles of GI tract
- breakdown food into smaller components
- absorb nutrients
- prevent microorganisms or other harmful compounds in food from entering tissues
how long is the GI tract
-cells lining the GI tract are replaced every
nearly 30 ft long with extensive surface area for nutrient absorption
-3-5 days
Mechanical digestion
-peristalsis
chewing, grinding food to aid in swallowing
-the forward, rhythmic motion that moves food through digestive system (similar to a wave)
Chemical digestion
digestive juices and enzymes breakdown food into absorbable nutrients
peristalsis moves what
chyme
segmentation
(sloshing motion) mixes chyme with chemical secretions
pendular movement
(constructive wave) enhances nutrient absorption in small intestine
actions move chyme at
1 cm per minute
Total contact time in sm intestine
- time
- depends on
3-10 hours
-depending on amount and type of food, stress, meds and disease
where does digestion begin
- what is released
- bolus
- mouth
- saliva
- food mass that moves into pharyx, is swallowed and enters the esophagus
saliva
- what does it contain
- function
- water, electrolytes, mucus and a few enzymes
- softens, lubricates, and dissolves food particles
Epiglottis
closes trachea during swallowing to prevent food from lodging in the windpipe
Esophagus
- function
- what muscle contraction is used
- propels food into the stomach
- peristalsis
lower esophageal sphincter (LES)
- location
- function
- at bottom of esophagus
- relaxes and allows food into stomach; closes to prevent backflow of hydrochloric acid (HCl) from stomach
“reflux” of stomach acid
- what does it cause
- definition
- chronic form
- heartburn
- irritation of esophagus lining
- gastroesophageal reflux disorder (GERD)
Stomach’s mechanical action
churning mixes food with digestive juices for several hours
what does the stomach produce
powerful digestive secretions such as HCl, digestive enzymes and intrinsic factor
HCl
-activates enzyme pepsin, enhances absorption of minerals, breaks down connective tissue of meat and destroys micro organisms
pespin
digests protein; inactive form when secreted
what hormone absorbs vitamin B12
gastrin
what does bolus become
chyme
chyme
semi liquid substance of partially digested food and digestive juices
Gastrin
- definition
- when is it secreted
hormone stimulates digestive activities and increases gastric motility and emptying
-before and after a meal
what exits stomach the fastest
liquids, carbs, low fiber, and low calorie foods
Pyloric sphincter
- location
- allows what
- prevents what
located between the stomach and small intestine
- allows about 1 tsp of chyme to enter the small intestine every 30 sec
- prevents backflow of intestinal contents
Small intestine
- features
- 3 segments
- what is the interior surface tremendously increased by
- long, narrow, coiled
- 1st duodenum (shortest segment)-where most digestion occurs
- 2nd Jejunum
- 3rd Ileum (longest segment)
- 1st duodenum (shortest segment)-where most digestion occurs
- villi, microvilli and circular folds
Large intestine
- length and diameter
- absorbs
- has no
- what is chemical digestion done by
- 5ft long, 2.5 in diameter
- water and electrolytes
- digestive enzymes
- done by bacteria
intestinal matter passes through colon in
12-70 hours depending on age, health, diet and fiber intake
Bacteria in colon produce
- and what do they break down
- what does this produce
vitamin k and biotin
- break down fiber and undigested carbs,
- producing methane, CO2, hydrogen gas and other compounds
where is stool stored
in rectum
- anus is controlled by 2 sphincters
- final defecation is under _____ control
- may be influenced by
- internal
- external
- internal
- voluntary control
- meds, health, age, diet, muscle tone, etc
Ileocecal spincter
prevents backflow of fecal matter into ileum
most nutrients in chyme have been absorbed when in reaches _____
large intestine
large intestine has 2 segments
- cecum
2. colon
colon
-4 parts
- 1.ascending
2. transverse
3. descending
4. sigmoid
Liver
- largest or smallest gland in the body
- produces what
- metabolism of what
- stores 7 nutrient
- detoxifies what
- largest
- bile
- carbs, fat and protein
- Vitamins A, D, B12, E; copper, iron, glycogen (glucose storage form
- alc
bile
- how much is produced per day
- needed for what type of digestion
- 500-1000 ml/d
- needed for fat digestion
gallbladder
- function
- released into GI tract when
- concentrates and stores bile
- fat is digested
Pancreas
- produces what
- bicarbonate
- insulin (lowers) and glucagon (raises) regulate blood glucose
- neutralizes acidic chyme and protects enzymes from inactivation by acid
hormones
-function
- control digestive secretion and regulate enzymes
- gastrin
- ghrelin
- secretin
- cholecystokinin (CCK)
- gastrin
gastrin
stimulates stomach to release HCl and enzyme gastric lipase (aids in fat digestion)
ghrelin
stimulates hunger
secretin
causes pancreas to release bicarbonate to neutralize HCl when food enters stomach
cholecystokinin (CCK)
- function
- controls what
- contributes to
- stimulates pancreas to secrete digestive enzymes, especially when partially digested fats and protein reach small intestine
- pace of digestion
- meal satisfaction
enzymes
- function
- secreted by
- speed up chemical reactions that breakdown food into absorbable nutrient components
- stomach, sm intestine, pancreas and mouth
enzymes from pancreas are responsible for
large portion of digested nutrients
Amylase
digests carbs
Lipase
digests fats
Trypsin, chymotrypsin and carboxypeptidase
digest protein
Bile
- function
- color
- made in
- stored in
- can it be reused
- breaks down large fat globules into smaller fat droplets
- yellowish-green substance
- liver
- gallbladder
- yes through hepatic circulation
After digestion where are nutrients absorbed
through the walls of the intestines into the body’s 2 transport systems
2 transport systems
- circulatory system (blood)
2. lymph system (fluid)
Nutrients are sent where for processing before delivery to the body’s cells
to the liver for detoxification
____% of nutrients from food are digested and absorbed
92 to 97%
Nutrients are absorbed by 3 methods
- passive diffusion
- facilitated diffusion
- Active transport
passive diffusion
- due to concentration gradient
- when concentration in GI tract exceeds that of intestinal cell, nutrient is forced across cell membrane
facilitated diffusion
similar to passive method, but requires specialized protein to carry nutrients
active transport
differs from other 2 methods
-nutrients absorbed from low to high concentration, requiring both carrier and energy
what happens to nutrients after they are absorbed
water-soluable nutrients are transported through the capillary walls in the intestinal villi to the blood stream
circulatory system
distributes nutrients through your blood
lymphatic system
- function
- example
distributes some nutrients through your lymph vessels
-fats, large nutrients
surplus nutrients
-example
-carbs stored as glycogen in liver and muscles, calcium stored in bones
water soluable products are excreted in
urine
how does the nervous system play a role in your use of nutrients
- it stimulates your appetite
- Ghrelin signals your brain to eat
Endocrine system
releases hormones that help regulate the use of absorbed nutrients
-insulin and glucagon help regulate blood
changing the blood glucose
- insulin
- glucagon
- decrease
- increase
Disorders of the mouth and esophagus
- mouth (2)
- esophagus (2)
- Gingivitis
- dysphagia
- Gingivitis
- heartburn
- esophageal cancer
- heartburn
Gingivitis
- chronic form
- definition
- periodontal disease
- inflammation of the gums caused by bacterial plaques. leads to tooth loss
Dysphagia
-caused by
tumors, obstruction or nerve damage
Heartburn
- what form
- chronic form
- results in
- caused by
- acute form
- gastroesophageal reflux disease (GERD)
- results in a burning sensation when HCl flows back into esophagus or throat
- weak lower esophageal sphincter (LES), smoking, drinking alc, reclining after eating, large evening meals
Esophageal cancer
-influenced by
smoking, heavy drinking and obesity worsen condition
Disorders of the stomach
-3
- gastroenteritis
- peptic ulcers
- stomach growling
gastroenteritis
stomach flu
-caused by virus or bacteria
peptic ulcers
sore or erosin caused by drugs, alc or bacteria (heliobacter pylori)
Stomach growling
caused by gas and air pockets that form as chyme is pushed into the sm intestine
gallbladder disease
gallstones
gallstones
- features
- caused by
- what happens if gallbladder is removed
- small, hard, crystalline structures
- thick bile that is high is cholesterol and low in bile acids
- liver will produce bile, but no where to store it. Need to limit fat intake
3 disorders of the intestines
- Flatulence
- constipation and diarrhea
- hemorrhoids
flatulence
release of intestinal gas from rectum
constipation and diarrhea
- constipation often due to
- diarrhea causes
- insufficient fiber or water intake
- loss of fluids and electrolytes; serious if lasting for an extended period of time
hemorrhoids
swelling and inflammation in veins of rectum and anus
Irritable bowel syndrome (IBS)
- definition
- results in
- can be triggered by
functional disorder involving changes in colon rhythm
- patterns of diarrhea, constipation and abdominal pain
- certain foods and stress
Celiac disease
- definition
- causes
- symptoms
- autoimmune, genetic disorder related to gluten consumption
- villi to flatten, decreasing surface area for absorption
- bloating, cramping, gas, weight loss, anemia, fatigue etc.
Crohn’s disease
- definition
- causes
- inflammatory bowel disease of several types
- swelling of small intestines leading to pain, diarrhea and bleeding
colon cancer
- definition
- begin with
- one of the leading forms of cancer, but can be cured if detected early
- polyps lining the colon
