Download The Digestive System

The Digestive System
Also Known As…
You gotta know how this show is
going to end...it’s awesome!!!
Eaters Digest
• The job of the digestive system is to break down
the food we eat into nutrients – the small
molecules that our cells need to survive.
• Food is digested – cut up into smaller pieces –
through both chemical and mechanical process.
• Mechanical digestion refers to the muscular
action that we use to break down the food.
• Chemical digestion involves the use of
chemicals, such as enzymes, to chemical
breakdown the food.
What Goes In…
• Your digestive system is actually a muscular
tube that has an opening at two different ends.
One end is at the mouth or oral cavity.
• Do you know where the other end of this
digestive tube is?
• If you guessed the anus, you’re right!
• This muscle in this tube can being longitudinal or
circular.
• Longitudinal muscle travels down the length of
the organ while circular muscle wraps itself
around the organ.
• This tube forms the digestive tract or
alimentary canal.
The Four Step Program
•
The process of digestion has four steps:
1. Ingestion – The actual acquiring of food
and the placement of it in your mouth.
2. Digestion – The breakdown of the food into
nutrients.
3. Absorption – The absorbing of the nutrients
into the bloodstream so they can be taken to
the cells.
4. Elimination – The unused parts of food
have to removed from the body.
Digestion – Step-By-Step!
•
So you want to eat eh?...Lets see what really happens
to your food.
Oral Cavity
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Food enters the oral cavity or mouth and undergoes
mechanical digestion thanks to the teeth and tongue.
The teeth cut, tear and crush food into pieces that form
a ball-like mass called the bolus.
Your tongue works to re-position the food being
chewed back onto the teeth so they can continue to
physically grind it down.
Chemicals such as saliva and mucous lubricate the
food so that it does not get stuck in your throat.
The Teeth – Structure & Function
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1.
2.
3.
4.
The teeth are used for
mechanical digestion.
There are four types of
teeth in your mouth.
Incisors – Sharp cutters
at the front.
Canines – Pointed tearing
teeth at side of front.
Premolars – Grinding
teeth a little further back.
Molars – Large grinders
found the furthest back.
Pharynx & Epiglottis
Pharynx
• When food has been chewed well and is ready to be
swallowed, it is pushed back into the pharynx.
• The pharynx is a tube found at the back of the throat
that acts like a traffic intersection.
• The pharynx joins the nasal cavity, oral cavity,
esophagus and trachea.
• A small flap of tissue called the epiglottis is found at the
base of the pharynx near the tops of the trachea and
esophagus and its job is to direct food into the
esophagus and prevent choking.
• The epiglottis folds over the top of the trachea (wind
pipe) when food or beverage is being consumed so they
do not attempt to go down to the lungs.
Why You Don’t Choke!!!
Esophagus – Gateway to the Gut!
• So, the food has been successfully directed
down the food pipe instead of the wind pipe –
giddy up!
• The food pipe that extends from the pharynx
down to the top of the stomach is called the
esophagus.
• The esophagus is a tube of smooth muscle that
is about one foot in length. Smooth muscle acts
on its own and once you swallow – it pushes the
food through the system automatically. This
pushing of food through the digestive tract by
rhythmic contraction of smooth muscle is know
as peristalsis. (Part of Mechanical Digestion)
The Stomach – Acid Hot Tub
• The stomach is a “J”-shaped organ that can stretch to hold the
food you eat.
• The stomach contains hydrochloric acid (HCl) and digestive
enzymes that break food down via chemical digestion. The acid
in the stomach is very strong.
• The stomach protects itself from its own acid using a thick
mucous lining that is continually secreted from the cells that line
the inner wall of the stomach.
• The acid and stomach contents are kept in the stomach by a
pair of sphincters – muscular drawstrings. The top of the
stomach has the lower esophageal sphincter (aka cardiac
sphincter) and the bottom of the stomach has the pyloric
sphincter. These sphincters keep the acid from damaging the
esophagus at the top and the small intestine at the bottom.
• The muscular wall of the stomach also causes it to churn and
move food about so it gets thoroughly soaked in the
acid/enzyme mixture. This is mechanical digestion - peristalsis.
Look At Your Gut!!!
The Small Intestine
• The small intestine is a thin, muscular tube
about 2.5cm in diameter but measures
anywhere from 6-7m in length. It’s found in the
abdominal cavity below the stomach.
• The small intestine has three sections – the
duodenum, the jejunum and the ileum.
• Digestion is completed in the duodenum as
additional enzymes are added to the food.
• After this, the process of absorption begins as
the nutrients are absorbed through the wall of
the small intestine.
The Villi
• The villi are small fingerlike projections that line
the inner wall of the small
intestine. They greatly
increase the surface area
of the small intestine to
maximize nutrient
absorption.
• The villi have blood
vessels in them that take
in the nutrients and
deliver them to the rest of
the cells of the body.
Small Intestine & Villi
Large Intestine, Rectum & Anus
• The large intestine is also known as the colon and it
has the extra special job of reabsorbing water and
mixing it with the unabsorbed material from food to make
feces.
• The first section of the large intestine is the caecum – it
connects to the ileum via the ileocecal valve.
• The large intestine has different sections – the caecum,
ascending colon, transverse colon, descending colon
and sigmoid colon.
• Feces are produced in the colon and stored in the
rectum until it can be released.
• The anus is another sphincter that controls the
movement of feces out of the body. The anal sphincter
keeps you from pooping in your pants 24/7!
Large Intestine, Rectum & Anus
That’s All I Got…How Do You
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