chapter 3: digestion and absorption

what are the parts of the gastrointestinal tract?

alimentary canal and accessory organs

what is included in the alimentary canal?

1. oral cavity

2. pharynx

3. esophagus

4. stomach

5. small intestine

6. large intestine

what are the parts of the small intestine?

duodenum, jejunum, ileum

what are the parts of the large intestine?

cecum, colon, rectum

what are accessary organs of the gastrointestinal tract?

salivary glands, liver, gallbladder, and pancreas

what is chemical action?

digestive enzymes

what is mechanical action?

chewing, churning

what is peristalsis?

wavelike muscle contractions that move food in the correct direction

what do sphincters and valves do?

act as doors between segments

what does the liver do in the digestive system?

filters harmful substances, stores fat soluble vitamins and minerals

what does the stomach do in the digestive system?

mixes food with hydrochloric acid and enzymes to aid in digestion and kill microorganisms

what is chyme?

the semi-liquid mixture in the stomach

how much absorption occurs in the stomach?

limited amounts

what does the large intestine do in the digestive system?

absorbs water and some ions; forms and stores feces

what does the rectum do in the digestive system?

stores and expels feces

what does the anus do in the digestive system?

exit for fecal expulsion

what does the oral cavity do in the digestive system?

chemical and mechanical digestion

what is mastication?

the breaking down of food into small enough particles to be swallowed

what does chewing stimulate?

the alveolar bone that supports the teeth

what breaks down lipids?

lipase

what does amylase do to starch?

allows large starch molecules to become fermentable carbs

what kind of sensation is taste?

gustatory sensation

what kind of sensation is smell?

olfactory sensation

what is the only sense full developed at birth?

taste

what is anosmia?

loss of smell

where are taste buds?

throughout oral cavity, not just tongue

how often do taste buds turn over?

frequently

what does saliva act as in the mouth?

a solvent

what is dry mouth called?

xerostomia

what is the loss of taste called?

hypoguesia

what is smell?

a protective mechanism

what percent of flavor comes from smell?

75%

what form do flavor molecules have to be in to be detected?

vapor form

what does anosmia inhibit?

sense of taste

what declines significantly with age?

taste and smell

what is a possible side effect of upper dentures?

blunting taste sensations by covering taste buds

what do goblet cells produce?

mucus

what do parietal cells release?

gastric acid (mostly hydrochloric acid)

what do chief cells produce?

pepsinogen and lipase

what is pepsinogen?

precursor to pepsin

what is pepsin?

enzyme that breaks down protein

what is lipase?

enzyme that breaks down fats

what activates pepsinogen to pepsin?

stomach acid

what is the average time of food in the stomach?

3-4 hours

where does most of food digestion occur?

small intestine

how long is the small intestine?

~15 feet

how long is food in the small intestine?

3-10 hours

what does the small intestine contain?

digestive enzymes (many from pancreas)

what do carbohydrases do?

breaks down carbs

what is released from the gallbladder?

bile

what is bile used for?

lipid/fat digestion (emulsifier)

what are the 2 types of absorption?

passive or active

what is passive absorption?

along concentration gradient

what is active absorption?

requires energy

what is osmosis?

passage of liquid through semipermeable membrane

where are nutrients transported?

lymphatic system or hepatic portal stream

how do nutrients get transported through the lymphatic system?

blood

what nutrients get transported through the lymphatic system?

fats and fat soluble vitamins (A, D, E, K)

how do nutrients get transported through the hepatic portal stream?

through the liver from general circulation

what nutrients get transported through the hepatic portal stream?

digested carbohydrates, protein, most vitamins and minerals

how much digestive activity happens in the large intestine?

very little

what is excretion?

elimination of undigested by-products of food and other substances

what are examples of waste excretion?

urination, defecation, perspiration, respiration

what is celiac disease?

autoimmune response to gluten in wheat, barley and rye

what are symptoms of celiac disease?

damaged small intestinal lining, oral manifestations (ulcers, enamel defect in developing teeth)

what is bioavailability?

amount of a nutrient available to the body after absorption

what does bioavailability depend on?

chemical form, food structure, cooking method, consumption of other foods