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The Body System Series: The Digestive System and its Functions
Alana Monet-Telfer
Digestive System
What is the Digestive System?
The digestive system is a set of organs; which take part in digesting our food and giving us the
necessary nutrients
...

Organs that create this System
 Mouth
 Oesophagus (Gullet)
 Stomach
 Gall Bladder
 Bile Duct
 Liver
 Pancreas
 Duodenum Ileum (Small Intestine
 Colon (Large Intestine)
 Rectum
Types of Digestion
There are 2 main types of digestion; and these two are called Mechanical and Chemical
...
Mechanical: Involves the mouth, teeth, and oesophagus
...
Chemical: Involves the saliva in the mouth, stomach, stomach acid, small intestine, colon,
pancreas and enzymes
...
Ingestion
Ingestion is a process; where food is entered though the mouth, settles in the buccal cavity, and
chewed up into smaller pieces by the teeth
...
This
saliva is secreted by three pairs of glands in the mouth called salivary glands; which have three
separate names, therefore, these three pairs are called parotid, sublingual, and submandibular
salary glands
...
This break down of food increases the surface area for
enzymes to work on, also, the tongue plays a part in breaking down food; since they are able to
taste the food and spread even more digestive juices over the food
...
Swallowing
When the food has been broken down by the saliva; the swallowing process starts
...
This bolus will then go to the
back of the mouth and go down the oesophagus, therefore, when it starts to go down the
oesophagus; a soft palette in the nasal cavity closes itself, the rings of cartilage in the larynx pulls
itself upwards, the opening of the windpipe (trachea) will lie itself under the back of the tongue,
the epiglottis of the windpipe will partly close; due to the contraction of ring cartilages, and finally

the epiglottis helps the food to go down into the oesophagus
...

Peristalsis
Peristalsis is a process where the oesophagus has layers of muscle; which make sets of contraction
for the bolus of food to go down
...
This process takes about six seconds to complete, before the food goes into
the stomach, which therefore, ends the mechanical digestion and starts the chemical digestion
...

Breaks
start
and
carbohydrates into simple
sugars
...

Anti-Inflammatory agent
...
Stomach
Once the bolus of food has gone though the 6 second process of Peristalsis, it finally reaches our
stomach
...
These gastric juices are secreted from glands in the lining of
the stomach; also, a diluted solution of hydrochloric acid is also secreted by the glands of the stomach
lining
...
When an individual smells, sees, or tastes food; impulses from the eyes, nose
and mouth are sent up to the brain, therefore, once the brain receives these impulses, it will send new
impulses back down to the stomach, where it tells the stomach to start secreting gastric juices
...

Stomach Acid: As we eat food, we ingest many different types of bacteria which can cause illnesses
and affect the body, fortunately, most of these bacteria are killed by the stomachs acid
...
However, there’s another question we may ask on
this subject, and that is why hasn’t our stomach been digested by the hydrochloric acid since this acid
is capable of burning and digesting some metals!
The reason our stomachs are not digested by the acid, is because of the body’s marvellous way of
keeping everything safe
...
The mucus provides a physically barrier, so the acid can’t touch the protein wall
itself, while the bicarbonate, which is highly alkaline and is secreted by the stomach cells, neutralizes
the acid
...
The mucus on the
stomach lining also protects the whole stomach from the active pepsinogen
...
The time it takes for the food
to be churned up in there, depends on each individual stomach, therefore, once the food is creamy;
the juice will pass though the pyloric sphincter a little at a time to the small intestine (Duodenum)
...

Stomach Enzymes:

3
...
The pancreas lies below the stomach, and it creates the many different
types of enzymes; to break down the different types of food into smaller molecules
...
com)
Intestine Enzymes:
Enzyme
Protease

Location
Intestine

Lipase

Intestine

Amylase

Intestine/Gut

Function
Breaks down protein to
amino-acids
...


Pancreas Enzymes:

Other Roles of the Pancreas
Other roles of the pancreases are:
 Neutralize Gastric Juices in the stomach: Pancreatic juices are made from Sodium
Hydrocarbonate; therefore, this juice is able to partly neutralize the gastric juices in the
stomach
...


4
...
Therefore, these
hairs are called villi; and the process where the simplest molecules are sucked up for nutrition is
called absorption
...
Once the molecules are sucked up by the villi; the molecules are
then taken into epithelial cells; before being taken though the wall of the capillaries in the villi and into
the bloodstream
...
What this portal vein does is carry the molecules in
the blood to the liver; where it shall be released into the general bloodstream
...
Such roles of the
liver are:
 Regulates sugar in the Blood: If too much sugar is in the blood stream, the livers role is to
take the excess sugar and store it in the body as glycogen
...



Create Bile: Liver cells are in change of making bile in the liver, before sending it to the gall
bladder; to be released into the small intestine though small bile ducts
...




Store Iron: The haemoglobin from dyeing red blood cells is stored in the liver
...




Dextox the Body: Compounds or substances that are poisonous are transformed into
harmless substances by the liver
...
Once this
detoxification is done, it’s sent to the kidneys to be excreted via the renal system
...
This is also the reason why the
liver of an animal is the best organ to get vitamin and nutrients from
...
Small Intestine: Assimilation
Assimilation is where the molecules of different types of food are taken to be used in the body
...
Minerals: Calcium, Magnesium, Chloride, Potassium and Iron are important because they are
needed for our body functions, for example, the functions such as strengthening our bones
and teeth, creating muscle, creating nerves and the constructions of red blood cells
...
Carbohydrates:
Fruits, vegetables, breads, potatoes and cereals contain important
carbohydrates that make up 70% of the mass in a human diet and are what humans need in
order to live, are active and have energy
...
It’s not only humans that need carbohydrates;
plants need carbohydrates too because in the process called photosynthesis, the plant stores
these carbohydrates as starch into their stems
...


3
...
Proteins are similar to carbohydrates, except that the organic compound structure of
protein contains nitrogen, followed by carbon, hydrogen and oxygen
...

4
...
Without fat,
humans would be affected more in cold weather as well as suffer Anorexia Nervosa or
Bulimia
...


5
...
Vitamins are not made in our bodies, so it vital that it is included in an overall
healthy diet
...
Excretion
Large Intestine
Once all the small molecules have gone though absorption and assimilation, the remaining food,
which is mainly roughage, fibre, vegetable fibres, mucus, dead cells, and water, goes into the large

intestine
...
The bile salts and
emulsified fats are reabsorbed by the ileum
...
Excretion: Rectum
Finally, what’s left of the food is a solid called faces, therefore, its passed though the rectum by
peristalsis; before it goes though the process of defecation; in which the faces is pushed out of
the anus
...
com, 2006-2011, Stomach acid is there for a reason
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natural-reflux-cure
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html, Sunday 15th January 2012)
(Natural-Reflux-Core
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natural-reflux-cure
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html, Sunday 15th January 2012)
www
...
com,2000,2011 and 2012, List of Digestive Enzymes,
http://www
...
com/articles/list-of-digestive-enzymes
...
com, 2000-2011, Vitamins and Minerals,
http://www
...
com/cig/biology/vitamins-minerals
...
)
(Mackean, 1996, GCSE Biology second edition, 50 Albemarle Street London W1X 4BD, John
Murray)



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