A detailed
ladled description of the digestive system. 3
Outline the
structure and function of the digestive system.. 4
Main Structure. 5
?     Mouth. 5
?     Teeth. 5
?     Pharynx. 5
?     Oesophagus. 5
?     Stomach. 5
?     Duodenum.. 5
?     Bile
duct 5
?     Ileum.. 5
?     Villus. 5
?     Appendix. 5
?     Caecum.. 5
?     Colon. 5
?     Rectum.. 5
?     Anus. 5
?     Hepatic
Portal System.. 5
Accessory Organs 5
?     Salivary
Glands. 5
?     Liver 5
?     Gall
Bladder 5
?     Pancreas. 5
Identify the
four layers of the alimentary canal 6
Submucosa. 6
Muscularis layer 6
Serosa. 6
Explain the
five stages of the digestion. 6
1.    Ingestion. 6
2.    Digestion. 6
3.    Absorption. 6
4.    Assimilation. 6
5.    Egestion. 6
two disorders of the Digestive System.. 6
1.    Coeliac
Disease. 6
Symptoms. 7
Available Treatments. 9
2.    Disorder
Two Irritable Bowel Syndrome + Description. 9
Symptoms. 9
Treatments available. 9
References. 10


A detailed ladled
description of the digestive system.

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        Fig 1.0 – Diagram of the Digestive


Outline the
structure and function of the digestive system

Human Digestive System is the system used by the human body for the digestion
of nutrients. It consists mainly of the Digestive tract, also known as the
Gastrointestinal Tract (G.I. Tract), and is supplemented by a number of
accessory organs. This series of structures and organs are the methods through
which solids and liquids pass through the body and are converted into form
absorbable into the bloodstream. The system also contains structures which
facilitate the isolation and elimination of waste products from the body.

G.I. Tract begins at the lips and ends at the anus, consisting of the mouth and
teeth for mastication, and the tongue to mix food with saliva produced by the
salivary glands; the oesophagus; the stomach the small intestine, consisting of
the duodenum, the jejunum and the ileum; and the large intestine, consisting of
the cecum, the assenting colon, the transverse colon, the descending colon and
the sigmoid colon, which leads to the final section of the digestive system,
the rectum. 

juices aiding digestion are produced in the salivary glands, the gastric glands
in the stomach lining, the pancreas, and the liver and the gall bladder. These
organs all contribute to the mechanical and chemical disintegration of ingested
food and to the eventual elimination of non-digestible wastes2.


Main Structure3


The Mouth is the first
part of the digestive system. At this stage mechanical digestion occurs and
solid food is broken down into smaller pieces through the process of
mastication. The teeth are responsible for this mechanical digestion. Little
digestion takes place during this stage, it is mainly to prepare food for
further digestion at later stages in the system. Bolus is formed in the mouth
when food is mixed with saliva


The Teeth are hard,
white structures found in the mouth and used in mastication. The shape and function
of the teeth are specific to the diet of the animal. Because Humans are
Omnivores, we contain a wide variety of teeth with specialisation somewhere
between Herbivores and Carnivores to consume both meat and plants. Because few
animals can digest cellulose, the cells are broken apart through mastication so
that the cells condense are exposed to digestive enzymes4.
There are 4 types of teeth: Incisors, Canines, Premolars and Molars.



The Pharynx (also known
as the throat) is a “cone-shaped passageway
leading from the oral and nasal cavities in the head to
the oesophagus and larynx”5. The lower chambers
of the Pharynx contain a small flat that separate the oesophagus from the
trachea.  Peristalsis begins in the



The oesophagus is a long muscular tube
about 25 cm long who’s function is to pass food from the pharynx to
the stomach. The upper third of the oesophagus is composed of striated
(voluntary) muscle. The movement of objects down through the oesophagus is
accomplished by peristalsis; which, as noted above, originate in the pharynx. Bolus
enters the stomach at the base of the oesophagus6.




The Stomach is a muscular
J-shaped organ in the abdominal cavity. It has a capacity of approximately 1.5 Litres
and can store food for up to 4 hours. Food is churned in the stomach and
gastric juices added to form Chyme (partially digested food). The highest part
of the stomach is called the Fundus and acts as a reservoir to accept food
after it enters the stomach. The largest anatomical structure of the stomach is
called the body. This section maintains “the acid secreting glands which
contributes to digesting semi-solid food in to smaller particles.”7
The lowest part of the stomach is called the Antrum. This is where liquified, Chyme
is passed into the small intestine.


Bile duct

bile duct is a long connecting tube line organ that connects the Liver to the
Intestine though the Duodenum. “The bile from the liver is transported to the
intestine by the bile duct. 8”



The first part of the small
intestine is known as the Duodenum. The Duodenum is the shortest part of the intestine,
receives Chyme from the stomach and begins the absorption of nutrients. The Chyme is
mixed with chemical secretions form the Liver, Gall Bladder and Pancreas to
prepare it for further digestion. This is where the pH of the Chyme is altered
to real a level more acceptable for digestion in the intestine.



This is the middle segment of the small
intestine between the duodenum and the ileum. “Most of the nutrients present in
food are absorbed by the jejunum before being passed on to the ileum for
further absorption.”9
The nutrients in the Chyme are absorbed through making contact with the villi



This is the final
segment of the small intestine. The Ileum is about 3.5 meters in length. This is where
the absorption of the vitamin B12
occurs and is also responsible for
the reabsorption of conjugated bile


The Villus (Plural: Villi) are tiny projection like structures surrounding the walls of the interior of
the small intestine. “The villi
number about 10 to 40 per square millimetre (6,000 to 25,000 per square inch)
of tissue. They are most prevalent at the beginning of the small intestine and
diminish in number toward the end of the tract. They range in length from about
0.5 to 1 mm (about 0.02 to 0.04 inch).”11 The
primary function of the Villi are to increase the available surface area in the
small intestine so as to increase the rate of nutrients abortion.



The Appendix is a organ located at intersection between
the large intestine and the cecum widely believed to be vestigial. However, there
are many in the field of immunology who believe the appendix serves a function in
the immune system12.
“Also, the worm-shaped organ outgrowth acts like a
bacteria factory, cultivating the good germs… If a person’s gut flora dies,
they can usually repopulate it easily with germs they pick up from other people…
But before dense populations in modern times and during epidemics of cholera
that affected a whole region, it wasn’t as easy to grow back that bacteria and
the appendix came in handy,” said Duke surgery
professor Bill Parker.






Hepatic Portal System


Accessory Organs

The Accessory Organs have been determined using notes
acquired during lectures13.

Salivary Glands

digestion begins in the mouth by mixing with Saliva released from the salivary
glands. The three major parts of the salivary glands are: the parotid, the
submandibular, and the sublingual glands. The secreting cells of the parotid
glands are of the serous type; those of the submandibular glands,
of both serous and mucous types. Saliva contains a starch-digesting enzyme
called amylase which begins the process of enzymatic hydrolysis.14



Gall Bladder



The Tongue is an extremely mobile
and muscular organ located on the floor of the mouth. Its function is the guide
and maintain the food between the teeth during mastication. The tongue’s glands
produce some of the saliva necessary to swallow.



Identify the four
layers of the alimentary canal

shown in Chapter 23. The Digestive System15, the
four tissue layers of the Alimentary canal are as follows           





Muscularis layer




Explain the five
stages of the digestion






Describe two
disorders of the Digestive System

Coeliac Disease

According to the website of the Irish Charity, Coeliac
Society of Ireland16,
Coeliac Disease can be described as follows: Coeliac Disease is an auto-immune disease that
causes some individuals to react to the protein (gluten) found in wheat, barley
and rye. If a person with coeliac disease eats gluten, the small villi located
along the wall of the small intestine becomes damaged, reducing their ability
to absorb the nutrients from food.

Coeliac is classified as an auto-immune disease because the
bodily mistakenly identifies Gluten as a threat to the body and causes an
inflammatory response in the small intestine damaging the micro-villi.


listed on the HSE’s public information website, the symptoms of Coeliac Disease
“can vary widely from person to person. A method
that is often used to classify possible symptoms of coeliac disease defines
three types of the condition, based on the associated symptoms.”

1)      Silent
Coeliac Disease

Symptoms or very mild Symptoms.

Long-term complications can still occur,
including: Osteoporosis, or failure to grow at a normal rate.


2)      Minor
Coeliac Disease


mild abdominal (stomach) pain


occasional changes in bowel habit, such as episodes
of mild diarrhoea or constipation

anaemia (tiredness, breathlessness and an irregular
heartbeat, caused by a lack of iron in the blood)

loss of appetite

weight loss

tingling and numbness in your hands and feet

vomiting (usually only affects children)

some loss of hair (alopecia, usually only
affects adults)


3)      Major
Coeliac Disease

diarrhoea, which can often suddenly occur during
the night, resulting in incontinence

weight loss

stomach cramps

muscle spasms

swelling of your hands, feet, arms and legs, caused
by a build-up of fluid (oedema)


Available Treatments

Because Coeliac Disease is an adverse reaction to the Gluten Protein,
abstaining from Glutton is the only way to relieve the systems of Coeliac
Disease. Adhering to a Gluten Free diets is the main treatment option as there
is currently no cure.

treatments may include18

Treatment of the small intestine with
corticosteroids temporarily if the inflammation is severe.
Taking dietary supplements if nutritional
deficiencies are found. However, once the small intestine heals there
should be no need for dietary supplements if your diet is well-balanced
and nourishing. You should ask to see a dietitian to help you get started
on a gluten-free diet which includes all the nutrients you need.



Disorder Two Irritable
Bowel Syndrome + Description


            Treatments available



1. (2018). Chapter
33: The Human Digestive System. image Available at:
Accessed 15 Jan. 2018.

2.       Encyclopedia Britannica. (2018). Human digestive
system. online Available at: Accessed 18 Jan. 2018.

(2018). Chapter 33: The Human Digestive System. online Available
Accessed 15 Jan. 2018.

Encyclopedia Britannica.
(2018). Human digestive system – The teeth. online Available at: Accessed
18 Jan. 2018.

Encyclopedia Britannica.
(2018). Pharynx | anatomy. online Available at: Accessed 23 Jan. 2018.

Encyclopedia Britannica.
(2018). Human digestive system – Esophagus. online Available at: Accessed
23 Jan. 2018.

Bhandari, R.
(2018). Dr. Bhandari – Gastro Patient Education – The Stomach.
online Available at:
Accessed 23 Jan. 2018.

(2018). What is the gallbladder and the bile duct. online
Available at:
Accessed 23 Jan. 2018.

9.       Innerbody. (2018). Jejunum.
online Available at:
Accessed 24 Jan. 2018.

Britannica. (2018). Ileum | anatomy. online Available at: Accessed 23 Jan. 2018.

Britannica. (2018). Villus | anatomy. online Available at:
Accessed 24 Jan. 2018.

(2007). Scientists may have found appendix’s purpose. online Available at: Accessed 24 Jan. 2018.

White, S. (2018). Anatomy
and Physiology (5N0749).

Encyclopedia Britannica.
(2018). Human digestive system – Salivary glands. online
Available at:
Accessed 23 Jan. 2018.

15. (2018). 23.1 Overview of the Digestive
System | Anatomy and Physiology. online Available at:

23.1 Overview of the Digestive System

Accessed 17 Jan. 2018.

16.    Coeliac Society of Ireland. (2018). What is Coeliac
Disease? – Coeliac Society of Ireland. online Available at: Accessed
15 Jan. 2018.

Ireland’s Health Service.
(2018). Symptoms of coeliac disease – Ireland’s Health Service.
online Available at:
Accessed 15 Jan. 2018.

Coeliac Society of
Ireland. (2018). Treatment After Diagnosis – Coeliac Society of Ireland.
online Available at:
Accessed 15 Jan. 2018.

1 (Chapter 33: The Human Digestive System)

2 (Encyclopedia
Britannica, 2018)

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4 (Encyclopedia
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5 (Encyclopedia
Britannica, 2018)

6 (Encyclopedia
Britannica, 2018)

7 (Bhandari, R.

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9 (teachmeanatomy,

10 (Encyclopedia
Britannica, 2018)

11 (Encyclopedia
Britannica, 2018)

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13 (White,

14 (Encyclopedia
Britannica, 2018). 

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16 (Coeliac
Society of Ireland, 2018)

17 (Ireland’s
Health Service, 2018)

18 (Coeliac
Society of Ireland, 2018)