The Accessory Organs
of Digestion
What is an “Accessory” Organ?
The digestive system has several accessory
organs that aid in the process of digestion. An
accessory organ is one that helps with the
breakdown of food without the food ever
traveling through them – they are not part of
the digestive tract or tube.
The accessory organs of digestion include:
1.
2.
3.
4.
Salivary Glands
Liver
Gall Bladder
Pancreas
The Salivary Glands
The salivary glands are
small organs found both
above and below the oral
cavity. The secrete a watery
substance, called saliva,
that contains both amylase
and mucus.
Amylase is an enzyme that
digests starch – a
polysaccharide made of
many glucose molecules
linked together.
The mucus is a thicker fluid
that lubricates the food so it
can pass through the
digestive tube more easily.
The Liver & Gall Bladder
The liver is the second largest organ on the body and
it’s located just below the ribs and to the right. The main
role of the liver is to produce bile – a fluid that aids in the
breakdown of fats.
The liver also detoxifies the blood while leaving the
nutrients in active circulation.
Alcohol is a toxic substance that the liver breaks apart
into less harmful molecules. If too much alcohol is
consumed on an ongoing basis, the hepatocytes (liver
cells) can die.
The gall bladder is a small sac, found just under the
liver, that stores bile.
The liver and gall bladder connect to the digestive tract
using the common bile duct – a tube that extends down
into the duodenum - the first part of the small intestine.
The Liver & Gall Bladder
The Pancreas
The pancreas is a bubbly, leaf-shaped organ that lies
just below the stomach. It secretes a great deal of
digestive enzymes – more than any other organ.
The pancreas has the pancreatic duct which is a small
tube that leads to the first section of the small intestine –
the duodenum. This tube delivers enzymes directly to
the chyme as it travels in the small intestine.
The pancreas is responsible for such enzymes as
lipases, carbohydrases and proteases.
The pancreas is also an acid-fighting super hero. It
releases a basic solution (bicarbonate) into the
duodenum as chyme enters it from the stomach.
Chyme is the mixture of food and acid that exits the
stomach. The small intestine and other organs can’t
handle the acidic content in chyme so its acidic
properties are neutralized by the bicarbonate solution.
Chemical Digestion
Amylase
Pepsin
Trypsin
Lipase
Carbohydrase
Hydrochloric Acid
(HCl)
Bile
Bicarbonate
Starch in mouth and after.
Proteins in Stomach.
Proteins in Duodenum (SI).
Fats in Duodenum (SI).
Carbs in Duodenum (SI).
All biomolecules in stomach.
Emulisfy Fats in Duodenum.
Neutralize stomach acid found
in chyme – acts in duodenum.
Homeostasis & Blood Sugar
Homeostasis is the process of maintaining a
stable internal environment despite changes in
the external environment.
Your body operates under a set of normal
levels and ranges. These levels and ranges
apply to everything from body temperature, to
heart rate, blood pH and blood sugar. (These
are only a few!)
If the one of these normal levels strays to far
above or below the normal range – a health
problem (or death!) may ensue.
This is why the body uses a system called
negative feedback to assist in homeostasis.
Negative Feedback
Negative feedback is a method of maintaining
homeostasis whereby the system on acts when
there is a perceived threat to normal body function.
(“If it ain’t broke – don’t fix it & save energy.”)
A negative feedback system has three parts:
– Monitor – checks normal levels in body – looks for
things to be out of the ordinary. (Usually nerve of brain.)
– Coordinating Centre – evaluates threat and brings
about corrective response. (Usually brain.)
– Regulator – Acts to correct the problem as per direction
from coordinating centre. (Organs & Muscles.)
Your home’s temperature is regulated this way!
Regulating Blood Sugar
The body’s normal level for glucose in the blood
(blood sugar) is 4-6mmol/L.
If the blood sugar gets too high…
– Pancreas produces and secretes insulin into the blood
stream. This causes cells to adopt glucose from the blood
and helps to lower blood sugar levels.
– The liver is told to remove glucose from the blood and
make glycogen from it. Again, more sugar withdrawn
from the blood and levels go down.
If the blood sugar gets too low…
– The pancreas produces and secretes glucagon which
goes to the liver and begins the breakdown of glycogen
into glucose which is released into the blood.
That’s All I Got…