how do we get from this… …to this. digestive system parts mouth – chewing, lubrication,...
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Digestive System Parts Mouth – chewing, lubrication, digestion Pharynx and Esophagus - swallowing Stomach - some digestion Small intestine – most digestion and absorption (of
water and nutrients) Large intestine – some absorption Colon and Rectum - packaging Liver and Gall Bladder - produces bile - aids in fat
digestion Pancreas - produces many digestive enzymes
Food Processing Most food consists of what
macromolecules? Carbohydrates, lipids, and proteins
Why is food chemically broken down? The macromolecules are too large to pass
through cell membranes They must be broken down into monomers, so
that the organism can make their own polymers
Human Digestion: Mouth At sight or smell of food, salivary glands
secrete saliva On part helps protect & lubricate lining of mouth Antibacterial agents – help prevent us from
getting sick Amylase (enzyme) to begin digesting starch
Why do you chew your food? Easier to swallow Expose more surface area to enzymes
Tongue pushes mass of food (bolus) to back of oral cavity & into pharynx
- This organ is a stretchy sack shaped like the letter J. Has lots of fold inside.
- It has three important jobs: temporarily stores the food you've eaten breaks down the food into a liquid mixture (called
CHYME) Begins protein digestion by gastric
juices
The Stomach
Small intestine
Long, narrow, intricately folded and twisted compartment of the digestive tube. All chemical digestion is completed and nutrients are
absorbed through the villi of the lining
Almost 90% of our daily fluid intake is absorbed in the small intestine.
Villi - increase the surface area of the small intestines, thus providing better absorption of materials
Human Digestion: small intestine Protein digestion
Pancreas and small intestine secretes enzymes that break polymer into monomers (amino acids)
Fat digestion Liver and gall bladder secrete enzymes to help
break down fat. Nucleic acid digestion
Pancreas and small intestine secrete enzymes which breakdown DNA & RNA polymers into
Nitrogenous bases, sugars, phosphates
Human Digestion: small intestine Lipid digestion
Lipids reach stomach almost completely undigested
Why? Fats are hydrophobic
Bile salts from gallbladder coat tiny fat droplets that keep them separated from each other
Why is the separation of fats into small droplets beneficial for digestion?
More surface area is exposed, which allows the enzyme to breakdown the fats quickly
Human Digestion: small intestine Capillaries that drain away from the small
intestine converge into larger blood vessels and eventually into a main vessel that leads directly to liver Converts many of nutrients into new
substances the body needs Liver removes excess glucose and stores it as?
Glycogen in liver cells
Blood is then transported to heart, which pumps blood and nutrients to all parts of the body
Human Digestion: large intestine Colon absorbs water –approximately 90% of the 7
liters of fluid that enters the canal a day are reclaimed (most in small intestine)
Remains of undigested food become more solid as water is absorbed Feces
Consists mainly of plant fibers and bacteria Diarrhea occurs when the colon is irritated and is less
effective at reclaiming water Constipation occurs when muscle contractions move the
feces too slowly Colon reabsorbs too much water and feces becomes too
compacted Diet low in plant fiber or lack of exercise
Nutrition There are 3 needs which demand a
healthy diet Fuel to power our bodies Organic raw materials needed to make our own
molecules Essential nutrients that we cannot make
ourselves and must obtain in a prefabricated form
So, what happens when something harmful gets past all the acids and enzymes??You would think with a pH of 0 and nasty
enzymes floating around, your stomach would kill anything you swallow. This is not the case. Some bacteria and protists can survive your stomach’s defenses and cause you misery or worse!!Ex: Salmonella, E.coli, Giardia, campylobacter, amoebic dysentery, botulism, and listeria are a few.
Inflammatory Bowel Disease (IBD) Is an inflammation of the small intestine,
large intestine, and/or the colon. Can have a variety of causes including
Crohn’s and Celiac Diseases Produces constipation, diarrhea, nausea,
vomiting, skin rashes, weight loss or gain, impaired nutrient absorption and a variety of other symptoms.
DiabetesDisease in which the pancreas
does not produce enough insulinBlood sugar is too highCan take insulin injections