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08 Digestive System

Lab 08
by

Rob Mead

on 27 October 2014

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Transcript of 08 Digestive System

Lab 08
Guts
Digestion begins in the mouth.
You actually begin eating some food, like ice cream cones and lollipops, outside your mouth
Think about what happens in your mouth...
You can eat some food, like jello or
tofu
, without chewing it.
But there's more to chewing...
As you chew, the salivary glands in your mouth
secrete
more saliva.
The lump of food in your mouth has a name?
The
masticated
blob of food in your mouth is called a
bolus
.
Need a map?
Into the Mouth...
The stomach is full of acid...
When the bolus gets to the stomach it is just a gooey mass of chewed food.
Your duodenum is connected to your pancreas...
Your pancreas secretes enzymes that break down sugars, proteins, and fats.
Next, the chyme enters the jejunum and ileum.
The main job of the jejunum and ileum is to absorb nutrients.
Several organs make up the large intestine...
The large intestine consists of the cecum, appendix, colon (four sections), rectum, and anus.
The rectum and anus...
The rectum gets its name from the Latin term for "straight" intestines.
So... what about the kidneys and the liver?
Still confused?
Maybe this video will help clear up some of the confusion.
The guts break down food into individual molecules.
Carbohydrates
Proteins
Vitamins
Minerals
Fats
Our digestive system breaks food down into:
In fact, food preparation really begins when we harvest food and separate the
edible
parts, refine and process it, age and
ferment
it, soak and cook it, and then cut it up with a fork and knife...
When food enters your mouth, you begin to chew it...
...cutting it and crushing it with your teeth...
...and softening it up with your saliva.
Other food, like hard boiled eggs or steak, you chew to avoid choking.
Some food, like cookies or crackers, will eventually dissolve in saliva.
And other food, like corn on the cob, needs to be chewed, or else...
Your body rewards you for your thorough chewing by enhancing the taste of your food. Your
palate
(in your mouth) enjoys food. This
gustatory
pleasure prompts you to keep chewing your food in your mouth a little longer...
Your saliva contains an
enzyme
called salivary amylase.
Salivary amylase is effective in breaking down
starch
(into maltose and dextrin).
The bolus is pushed toward your
esophagus
by your tongue.
The bolus is pushed past your trachea (windpipe) by muscles in your esophagus.
The muscles in your esophagus and throughout your digestive tract
constrict
in waves. This autonomic sequence is called
peristalsis
.
=> Esophagus
=> Stomach
=> Duodenum
=> Small Intestine
=> Large Intestine
=> Rectum
...out the Anus.
The bolus is dumped into the muscular stomach filled with hydrochloric acid and a digestive enzyme called pepsin.
Together, the mechanical and chemical actions of the stomach break down proteins and convert the bolus into
chyme
.
The chyme gets squeezed out the other end of the stomach into the duodenum — the start of the small intestine.
The enzyme "breakdown" of the chyme in the duodenum is a strong chemical
assault
on any food remaining in the bolus.
After the duodenum, the digestive track will focus mainly on absorbing the nutrients in the chyme.
It shows where along the way different types of foods are broken down.
The kidneys are the main organs in the "renal system" and their job is to filter blood and send waste to the bladder.
The liver is the main organ of the "hepatic system" and it's job is to regulate the chemistry of the blood.
The kidneys and the liver have to work closely with the digestive system in order to do their jobs properly.
There is a last-ditch effort to break down any remaining starches.
The nutrients dissolved in the chyme are absorbed through the villi in the jejunum and ileum.
The large intestine extracts water and minerals from the nutrient-depleted chyme.
It also "packages up" solid waste from the body.
The large intestine is about 1.5m long — nearly one fifth of the total length of the intestines.
It is a temporary storage area for waste (feces).
The anus gets its name from the Latin term for "ring."
There are many sphincter muscles in the body, but the most famous sphincters are the two that close off the anus... thus ending the digestive tract.
The small intestine has three parts — the duodenum, the jejunum and the ileum.
The jejunum and ileum absorb about 95% of the nutrients in the chyme.
Salivary amylase continues to digest the
starch in your food as it slides down your
throat into your stomach. When the food "plops" into the puddle of
hydro-chloric acid
(HCl) in your stomach, the salivary amylase is no longer the primary digestive agent.
The jejunum uses a certain set of enzymes to absorb whatever it can. The ileum uses a different set enzymes to absorb Vitamin B12 and bile salts.
But they are more delicate than the rough and tumble organs of the digestive tract that come into contact with the "outside world."
... a doughnut?
... or a pool noodle?
Have you ever thought of how you are similar to ...
You put the food in one end and eventually it comes out the other.
The food just passes through; only a small part of it is absorbed by the inside of the doughnut or the inside of the noodle.
Full transcript