Download Digestion Notes - Net Start Class

The Journey
of a Cracker
Mouth
The first step of digestion is ingestion – to take in food.
The second step of digestion also begins here, which is
digestion. Digestion of the cracker begins here. Teeth
physically (mechanically) crush and chop the food while
the tongue mashes the food around. Saliva which is
excreted by salivary glands, contains water, mucus, and
enzymes which chemically break large carbohydrate
(starch) molecules into smaller sugar molecules called
(glucose) Only starches (carbohydrates) are digested
here.
Esophagus
Wavelike muscle action called peristalsis moves the bolus
(chewed food) from the mouth to the stomach. (no digestion
takes place, though physical changes in shape and texture
occur).
Epiglottis
The epiglottis is a small flap of tissue that closes over the
opening of the trachea, or wind pipe (breathing tube) when
you swallow, keeping food out of your lungs.
Stomach
Food enters the stomach through a valve. The
stomach is a “j” shaped muscular organ that
churns and mixes food mechanically like a
blender. Gastric juices (Hydrochloric acid,
enzymes such as pepsin and mucus) break it
down chemically. The cracker is now a thin
liquid and leaves the stomach after about 4
hours by way of another valve.
Small Intestine
The thin liquid enters the first curve of the
small intestine called the duodenum. Most
chemical digestion and absorption of nutrients
into the blood stream takes place here (first 10
inches). After digestion, the third step of
digestion, absorption of the nutrients through
the intestinal wall (the villi) takes place. The
cracker is now glucose molecules which leave
the villi and enter the blood stream, which
carries them to cells for energy production.
Liver
Manufactures bile – an enzyme that
mechanically breaks down lipids (fat) into
smaller pieces of fat called fatty acids. Food
does not enter the liver. Bile is secreted into
the small intestine through a tiny tube.
Gall Bladder
Small sac under the liver that stores the bile
until needed. The bile is released into the
duodenum of the small intestine. Food
does not enter the gall bladder.
Pancreas
Gland which produces enzymes such as insulin which break
down proteins, starches, and fats chemically. These
enzymes are secreted into the duodenum also. Food does
not enter the pancreas. If the pancreas fails to produce the
right amount of insulin, diabetes or hypoglycemia can result.
The pancreas also produces trypsin which breaks down
proteins into amino acids and lipase, which breaks down fats
into fatty acids and monoglycerides.
Large Intestine
Water, salt and minerals are absorbed from
the undigested material forming solid waste
called feces. Bacteria break down some
fiber. Vitamins B and K are also produced
here by bacteria and absorbed into the blood.
Cellulose from the cracker provides fiber for
peristalsis to work. The large intestine is
often called the colon.
Rectum
The last vertical section of the large
intestine through which solid waste
(feces) travels.
Anus
Muscular opening where solid waste is
released (excreted) from the body.
Excretion is the final step of digestion.
The Path of Food
Main Organs/Structures of
Digestion the Food Passes
Through (all lined with epithelial
tissue).
Organs/Structures of Digestion
that Food Does NOT Enter
(Accessory Organs)
Physical or Chemical Change?
Action
Teeth chop, crush and grind food
Saliva has chemicals called enzymes (Amylase) that break down starches into sugar
Involuntary contractions of smooth muscles, called Peristalsis, moves chewed food
down the esophagus to the stomach (and through the rest of the digestive system),
changing shape and texture
Gastric juices including the enzyme pepsin breakdown proteins into amino acids
Stomach blends food into a liquid
Enzymes and chemicals from the pancreas and gall bladder are secreted into the small
intestine to break down fats, proteins and sugars into smaller units
Bile from the gall bladder cuts lipids into smaller pieces of lipids
Villi in the small intestine absorb nutrients into the blood stream
Water from food is absorbed back into the blood stream in the large intestine
Bacteria in the large intestine convert some wastes into vitamins B and K.
In the rectum, waste is compressed into solid form and then eliminated through the anus.
Physical or Chemical
Major functions of the digestive
system
1. To ingest (take in) food
2. To digest (break down) large molecules of food
such as starches into smaller molecules such as
sugars, fats into fatty acids and proteins into
amino acids that the body can use
3. To absorb nutrients from digested food into the
bloodstream to be delivered to cells
4. To excrete (eliminate) undigested wastes from
the body
Warm-Up (9/15/16)
Make this T-Chart then list the organs that should go on each side.
Warm-Up (9/15/16)
Make the following T-Chart and list the
organs that should go on each side!
Main Organs/Structures of
Digestion the Food Passes
Through (all lined with epithelial
tissue).
Organs/Structures of Digestion
that Food Does NOT Enter
(Accessory Organs)
Warm-up (9/15/16)
1. Digestion begins in the________.
2. Which 3 digestive organs DO NOT have food pass
through them?
3. In what part of the small intestines does most chemical
digestion and nutrient absorption take place (check your
notes)?
4. What tiny structures allows for the absorption of nutrients
in the small intestines( check notes starts with a V)?
5. What is the difference between chemical and physical
change?
6. _____ is the process that causes big molecules to be
broken down into smaller molecules?
7. ______ is a protein that breaks large molecules into
smaller molecules.
Warm-Up (9/16/16)
1. What is another word for ingestion?
2. What is the process of breaking down large molecules into smaller
molecules called?
3. What is another word for excretion?
4. What organ stores bile?
5. What organ creates the most digestive enzymes?
6. T or F? Food moves through the salivary glands.