Transcript The Human Digestive System - Frontenac Secondary School

The Digestive
System
SNC2D
The Digestive Tract
The digestive system consists of the digestive
tract, a series of hollow organs which may be
thought of as a long twisting tube connecting
the mouth to the anus, and other organs that
produce or store chemicals that help break
down or absorb food.
Those Other Organs
The other organs include the
liver and the pancreas, and
the chemicals they produce
reach the intestine through
small tubes called ducts.
Those Other Organs
The other organs include the
liver and the pancreas, and
the chemicals they produce
reach the intestine through
small tubes called ducts.
The chemical produced by
the liver is called bile, and it
may be stored in the
gallbladder between meals.
The Mouth
Digestion begins in the mouth where an
enzyme (a chemical that speeds up other
chemical reactions) in the saliva produced
by the salivary glands start to break down
those carbohydrates known as starches.
Peristalsis
Once the food is swallowed, it
is moved through the
digestive tract by peristalsis,
involuntary muscle
contractions triggered by the
nervous system.
To The Stomach
Food travels down the esophagus to the
stomach. Between the esophagus and the
stomach there is a muscle called the lower
esophageal sphincter, which opens to let food
pass through.
To The Stomach
Food travels down the esophagus to the
stomach. Between the esophagus and the
stomach there is a muscle called the lower
esophageal sphincter, which opens to let food
pass through. If it opens when it shouldn’t, you
get acid reflux
(heartburn).
In the Stomach
Glands in the stomach lining produce
stomach acid and an enzyme to break
down proteins. A thick layer of mucus
helps protect the lining of the stomach
from its own acids.
Bacterial infections can thin
the mucus so that the
stomach eats away at its
own lining: this is an ulcer.
In the Stomach
Glands in the stomach lining produce
stomach acid and an enzyme to break
down proteins. A thick layer of mucus
helps protect the lining of the stomach
from its own acids.
In the Stomach
Glands in the stomach lining produce
stomach acid and an enzyme to break
down proteins. A thick layer of mucus
helps protect the lining of the stomach
from its own acids.
Muscle action of the stomach mixes the
food with the digestive juices, and this
mixture is then emptied into the small
intestine through the pyloric sphincter.
The Intestines
The first part of the small
intestine, where the
chemicals produced by the
other organs enter the
digestive process, is called
the duodenum. Here, the
bile produced by the liver
dissolves fat.
The Intestines
The small intestine is folded into fingerlike
projections called villi. This folding increases
the surface area of the small intestine through
which food molecules are absorbed into the
bloodstream.
The Intestines
The large intestine, or colon, does not break
down food but absorbs water and some
nutrients before what remains of the food is
removed from the body as waste.
The Intestines
The large intestine, or colon, does not break
down food but absorbs water and some
nutrients before what remains of the food is
removed from the body as waste.
Note that the waste will
also include some cells
shed by the digestive
system itself.
The Body’s Defences
The digestive system’s first defence
against contaminants is vomiting, which
can forcibly remove contents from the
middle of the small intestine and up.
Really, you don’t want any images here.
Very Limited Defences
There is really nothing else to prevent
contaminants from being absorbed into
the bloodstream although the liver can
help filter the blood.