DIGESTIVE SYSTEM
The process of altering the chemical and physical composition of food so that it can
be absorbed and used by body cells is known as digestion and is the function of the
digestive system. The digestive system’s main organs form an irregular shaped tube
open at both ends, called the GI tract. Food undergoes various types of processing
in the GI tract:
1.
Stages of the Digestive Process
Define the following terms


Ingestion …Taking food in by the mouth……………..
Digestion …The breakdown of complex nutrients so they can be absorbed
into the blood

Absorption …The movement of digested food from the digestive
system into the blood…...

Metabolism …Chemical reactions in the body required for life….

Egestion ……The removal of waste production of digestion from the
anus..
2.
Kinds of Digestive systems
There are two methods of classifying animal digestive systems.
a)
b)
Based on the animals diet
Define the following terms:

Herbivore ……Eat plant material only……………

Carnivore ……Eat animal material only……………..

Omnivore ……Eat both plants and animals…………
Based on the anatomy of the digestive tract
Define these terms:

Ruminant (eg cow) …Has a four chambered ruminant stomach……………

Non ruminant herbivore (eg horse) …Has an enlarged caecum & colon for
digestion of cellose

3.
Monogastric (eg dog) …Any animal with a single stomach.…...
Other Terminology
Define the following: (Some are new to you and you will need to look them up)

Prehension ……Grasping with the lips……………..

Mastication ……Chewing……………………..

Deglutition ……Swallowing……………………………
1

Eructation ……Removal of gas from the stomach
“Belching”…………………………….

Regurgitation …Movement of food up the oesophagus from the stomach
to the mouth…
2
Rat Dissection
Structures of the Monogastric Digestive Tract
Using the demonstrated dissection identify the structures
indicated by the lines and label the following diagram.
Trachea
Thymus
Lung
Heart
Diaphragm
Liver
Pancreas
Colon
Stomach
Caecum
Ileum
Spleen
Duodenum
Jejunum
Mesentery
Urinary Bladder
Anus
Urinary opening
3
Pig’s Digestive system: Also monogastric.
Examine the pig’s digestive system provided and label the parts indicated by the
lines and numbers on the diagram below.
Oesophagus
Liver
Gall bladder
Bile duct
Stomach
Duodenum
Pancreas
Small intestine
Spleen
Caecum
Large intestine
Large intestine
4
Ruminant Dissection
Work in groups to examine the fresh digestive tract of the ruminant provided.
1.
Find the oesophagus, the hollow muscular tube that carries food from the
mouth to the stomach or rumen. Find the Cardiac sphincter. What purpose
does this sphincter serve?
___Cardiac sphincter controls the movement of food between the oesophagus
and the stomach____
2.
On the specimen note the rumen, reticulum, omasum and abomasum. Note
in each of these compartments the mucosa has a different appearance.
Describe the mucosa in the
a.Reticulum
Papillae form a honeycomb pattern
b.Omasum
Papillae covered folds project into the limen “Like pages of a book”
c. Rumen
Papillae cover the surface “like a carpet pile”
3.
Find the pancreas, liver and spleen (if available). Does this animal have a
gallbladder? Where would you look to find it?
______________________________________________________________
_____Yes the sheep has a gall bladder and we found it attached under the
liver___________________________________________________
4.
Locate the pancreas again. What role in digestion does it play?
___Produces enzymes to break down the long macromolecule chains to
shorter lengths ___________
5.
Move on to the small intestine and identify the
 duodenum
 jejunum
 ileum
6.
Trace the ileum to its junction with the ascending colon. The junction is called
the ileo-caecal valve or junction. Note the pouch caudal to this valve. In
humans this is the appendix. Identify the caecum and the ascending,
transverse and descending parts of the large intestine.
7.
The descending colon ends with the anus. Find the anus and bisect it. What
type of structure do you see and what purpose does it have?
____ It is the anal sphincter muscle. I prevents faeces leaving until the rectum
is ready to release it. ______________________
8.
Notice along the length of the intestinal tract there are numerous bean shaped
areas of lymphatic tissue. What are they? These are lymph nodes
5
The Liver:
1.
Label the diagram below as indicated by the lines:.
Lobes of the liver
Gall bladder
Bile duct
Duodenum
Pancreas
Pancreatic duct
2.
(i)
Name FOUR functions of the liver
___________________________________________________________
(ii)
___________________________________________________________
(iii)
___________________________________________________________
(iv)
___________________________________________________________
4.
What are hepatocytes?
____Liver cells
Digestion
1.
What is the function of hydrochloric acid (HCl) in the stomach?
Why does the acid not affect the stomach lining?
_HCl denatures proteins (unfolds the chains so they are easier to digest)
Mucous is secreted oner the surface of the stach when food enters the
stomach. Also HCl is only secreted when there is food in the stomach.
6
2.
Name THREE modifications of the intestinal wall that increases the surface
area for absorption.
3.
(i)
The long length of the small intestine ______________
(ii)
Villi and microvilli in the small intestines ____________________
(iii)
Folds in the walls of the intestines __________________
Name the enzyme produced by the pancreas which digests the following:
(i)
Starch _ Amylase ________
(ii)
Protein __Pepsin, Trypsin, Peptidases __________
(iii)
Fat
__Lipase ___________
DIGESTIVE SYSTEM
The process of altering the chemical and physical composition of food so that it can
be absorbed and used by body cells is known as digestion and is the function of the
digestive system. The digestive system’s main organs form an irregular shaped tube
open at both ends, called the GI tract. Food undergoes various types of processing
in the GI tract:
1.
Stages of the Digestive Process
Define the following terms


Ingestion …Taking food in by the mouth……………..
Digestion …The breakdown of complex nutrients so they can be absorbed
into the blood

Absorption …The movement of digested food from the digestive
system into the blood…...

Metabolism …Chemical reactions in the body required for life….

Egestion ……The removal of waste production of digestion from the
anus..
2.
Kinds of Digestive systems
There are two methods of classifying animal digestive systems.
a)
Based on the animals diet
Define the following terms:

Herbivore ……Eat plant material only……………

Carnivore ……Eat animal material only……………..

Omnivore ……Eat both plants and animals…………
7
b)
Based on the anatomy of the digestive tract
Define these terms:

Ruminant (eg cow) …Has a four chambered ruminant stomach……………

Non ruminant herbivore (eg horse) …Has an enlarged caecum & colon for
digestion of cellose

3.
Monogastric (eg dog) …Any animal with a single stomach.…...
Other Terminology
Define the following: (Some are new to you and you will need to look them up)

Prehension ……Grasping with the lips……………..

Mastication ……Chewing……………………..

Deglutition ……Swallowing……………………………

Eructation ……Removal of gas from the stomach
“Belching”…………………………….

Regurgitation …Movement of food up the oesophagus from the stomach
to the mouth…
8
Rat Dissection
Structures of the Monogastric Digestive Tract
Using the demonstrated dissection identify the structures
indicated by the lines and label the following diagram.
Trachea
Thymus
Lung
Heart
Diaphragm
Pancreas
Liver
Ileum
Stomach
Caecum
Spleen
Jejunum
Mesentery
Urinary Bladder
Anus
Urinary opening
9
Pig’s Digestive system: Also monogastric.
Examine the pig’s digestive system provided and label the parts indicated by the
lines and numbers on the diagram below.
Oesophagus
Liver
Gall bladder
Bile duct
Stomach
Duodenum
Pancreas
Small intestine
Spleen
Caecum
Large intestine
Large intestine
10
Ruminant Dissection
Work in groups to examine the fresh digestive tract of the ruminant provided.
1.
Find the oesophagus, the hollow muscular tube that carries food from the
mouth to the stomach or rumen. Find the Cardiac sphincter. What purpose
does this sphincter serve?
___Cardiac sphincter controls the movement of food between the oesophagus
and the stomach____
2.
On the specimen note the rumen, reticulum, omasum and abomasum. Note
in each of these compartments the mucosa has a different appearance.
Describe the mucosa in the
a.Reticulum
Papillae form a honeycomb pattern
b.Omasum
Papillae covered folds project into the limen “Like pages of a book”
c. Rumen
Papillae cover the surface “like a carpet pile”
3.
Find the pancreas, liver and spleen (if available). Does this animal have a
gallbladder? Where would you look to find it?
______________________________________________________________
_____Yes the sheep has a gall bladder and we found it attached under the
liver___________________________________________________
4.
Locate the pancreas again. What role in digestion does it play?
___Produces enzymes to break down the long macromolecule chains to
shorter lengths ___________
5.
Move on to the small intestine and identify the
 duodenum
 jejunum
 ileum
6.
Trace the ileum to its junction with the ascending colon. The junction is called
the ileo-caecal valve or junction. Note the pouch caudal to this valve. In
humans this is the appendix. Identify the caecum and the ascending,
transverse and descending parts of the large intestine.
7.
The descending colon ends with the anus. Find the anus and bisect it. What
type of structure do you see and what purpose does it have?
____ It is the anal sphincter muscle. I prevents faeces leaving until the rectum
is ready to release it. ______________________
8.
Notice along the length of the intestinal tract there are numerous bean shaped
areas of lymphatic tissue. What are they? These are lymph nodes
11
The Liver:
1.
Label the diagram below as indicated by the lines:.
Lobes of the liver
Gall bladder
Bile duct
Duodenum
Pancreas
Pancreatic duct
2.
(i)
Name FOUR functions of the liver
___________________________________________________________
(ii)
___________________________________________________________
(iii)
___________________________________________________________
(iv)
___________________________________________________________
4.
What are hepatocytes?
____Liver cells
Digestion
1.
What is the function of hydrochloric acid (HCl) in the stomach?
Why does the acid not affect the stomach lining?
_HCl denatures proteins (unfolds the chains so they are easier to digest)
Mucous is secreted oner the surface of the stach when food enters the
stomach. Also HCl is only secreted when there is food in the stomach.
12
2.
Name THREE modifications of the intestinal wall that increases the surface
area for absorption.
3.
(i)
The long length of the small intestine ______________
(ii)
Villi and microvilli in the small intestines ____________________
(iii)
Folds in the walls of the intestines __________________
Name the enzyme produced by the pancreas which digests the following:
(i)
Starch _ Amylase ________
(ii)
Protein __Pepsin, Trypsin, Peptidases __________
(iv)
Fat
__Lipase ___________
13