Digestion and Excretion

From Food to Waste: the Story of Digestion and Excretion

Copy this story, replacing the ellipses with information from your outlined science notes.  You can also find information in BC Science 8 (McGraw-Hill Ryerson, 2006).  You may use phrases, as well as words, to ensure the story makes sense.

Did you know that the digestive process starts the instant you put food in your mouth?  First of all, your teeth start to mechanically… Your salivia gets involved and…. Then your pharynx, the place where…, and your epiglottis, the…, help by…. Your esophagus, the…, and the process of peristalsis also help you by….

When those boli, those little bits of food, reach your stomach, chemical digestion really gets to work. Gastric juice, containing…,  breaks down the food. … breaks down the protein. Soon, all your food turns into a liquid called… That liquid is fortunately prevented from leaking out by a … at either end of your stomach.  And your body is protected from the acid in you stomach by….

After awhile, your sphincter opens and lets a bit of … , that liquid food, into your ….  The first part is called the … and is only one metre long.  It connects to tubes, or ducts, that connect to your…, which …., your …, which…, and your … , which….

After that first metre, the chyme enters the last … metres of the small intestine.  The surface of this part is covered with … which increases the … so you can absorb more nutrients.  The chyme moves along for .. to .. hours by the process of ….

Then it reaches the large intestine, which is only …. metres long but … centimetres in diameter.  It takes 12 to 24 hours for food to pass through this area and, in the process, … and some … are reabsorbed by your body. Vitamin … is also made here,  an important nutrient that helps your ….
Finally, all that is left of the food you ate is the part that is indigestible. This material is called …. , and it is stored in your …  It exits your body through your …, and the whole process from ingestion to elimination can take up to … hours.

Your excretory system eliminates the nonsolid wastes.  Your … filter your blood and remove what is not needed.  Two tubes, called your …, carry the urine along, your … stores your urine, and your … carries the urine out of your body.

Digestive System
A. Ingesting – taking in
1. mouth

B. Digesting – breaking down
1. teeth (mechanical)
a. bolus
2. salivia (chemical)
3. pharynx and epiglottis (mechanical)
4. esophagus and peristalsis (mechanical)
5. stomach (chemical)
a. gastric juice and hydrochloric acid
b. mucus (a protective inner lining)
c. pepsin breaks down protein
d. bolus becomes liquid chyme
e. sphincter at each end controls flow
6. small intestine (6 m x 2.5 cm)
a. duodenum (1 m long)
b. ducts connecting to…
i. liver (creates bile to digest fat)
ii. pancreas (produces enzymes)
iii. gall bladder (stores bile)
C. Absorbing
1. small intestine (last 5 m)
a. villi (increase surface area)
b. food moves by peristalsis
c. takes 5 – 6 hrs.
2. large intestine (1.5 m x 5 cm)
a. reabsorbs water
b. reabsorbs some minerals
c. makes vitamins such as K
which helps blood clot
d. takes 12 – 24 hrs.
D. Eliminating
1. feces (undigested materials)
2. rectum (storage area)
3. anus (exit from body)
4. ingestion to elimination 20-30 hrs.
Excretory System
Removes liquid and gas wastes.
A. Kidneys (filter blood and remove wastes)
B. Ureters (carry urine)
C. Bladder (holds urine)
D. Urethra (flushes urine from body)

This page may be copied for use with students if the following credit is provided:
©2012 Sophie Rosen.

Did you know that the digestive process starts the instant you put food in your mouth? First of all, your teeth start to mechanically break down the food into bolus. Your salivia gets involved and starts to chemically break down the food with enzymes. Then your pharynx, the place where your airway passage and the rest of your digestive system meet and your epiglottis, the small flap of flesh, covers the airway tube. Your esophagus, the long tube that connects the pharynx and the stomach, carries the bolus down to the stomach and the process of peristalsis comes into play by squeezing and pushing the food down with muscles and contractions.
When those boli, those little bits of food, reach your stomach, chemical digestion really gets to work. Gastric juice, containing hydrochloric acid, mucus, and enzymes, breaks down the food by covering the boli and moving it around in your stomach with contraction of your stomach muscles. An enzyme called pepsin starts to break down the protein. Soon, all your food turns into a liquid called chyme. That liquid is fortunately prevented from leaking out by a sphincter at either end of your stomach. And your body is protected from the acid in your stomach by covering the stomach lining with mucus.
After awhile, your sphincter opens and lets a bit of chyme, that liquid food, into your small intestine. The first part is called the duodenum and is only one metre long. It connects to tubes, or ducts, that connect to your other organs such as the pancreas, where digestive enzymes are produced that pass into your small intestine. Your liver produces a substance called bile which is stored in the gall bladder and breaks the globs of fat into smaller droplets.
After that first metre, the chyme enters the last five metres of the small intestine. The surface of this part is covered with villi which increase the surface area available to absorb more nutrients. The chyme moves along for five to six hours by the process of peristalsis.
Then it reaches the large intestine, which is only  1.5 metres long but five centimetres in diameter. It takes 12 to 24 hours for food to pass through this area and in the process, undigested material and some water are reabsorbed by your body. Vitamin K is also made here, an important nutrient that helps your blood clot.
Finally, all that is left of the food you ate is the part that is indigestible. This material is called feces, and it is stored in your rectum. It exits your body through your anus, and the whole process from ingestion to elimination can take up to 20-30 hours.
Your excretory system eliminates the nonsolid wastes. Your excretory system filters your blood to remove what is not needed. Two tubes, called your ureters, carry the urine along, your bladder stores your urine, and your urethra carries the urine out of your body. [Patricia]

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