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The digestive system

THE ANIMAL BODY

 

The body is made up of many, many millions of cells which you can not see unless you use a microscope. Special cells come together to make an organ. An organ is a complex structure within the body. It has a special job or jobs to do.

A body system consists of a number of organs which work together to carry out a special job. The animal body is made of 9 systems:


1. Musculo-skeletal system

2. Digestive system

3. Circulatory system

4. Respiratory system

5. Urinary system

6. Nervous system

7. Sensory system

8. Reproductive system

9. Lympho-reticular system


The organs of the body

An organ is a complex structure with a special job or a number of jobs to do. For example:

The eye is the organ of sight.

The kidneys are organs which get rid of water and poisonous materials from the body as urine.

The liver has many jobs and is involved in more than one system.

Various organs are grouped together to form a body system which carries out a special job.

System of the Body Organs in the Body Job or function
Musculo-skeletal muscle (meat) bones Support and move the body
Digestive stomach, liver, intestine, pancreas Digest and absorb feed
Circulatory heart, blood vessels The brood carries substances around the body
Respiratory muzzle, windpipe, lungs Breathing
Urinary kidneys, bladder Get rid of poisons and waste (urine)
Nervous brain, nerves spinal cord Pass messages around the body, control the body
Sensory eyes, ears, nose skin Sense and detect things outside the body
Reproductive testes, penis ovaries, uterus, vagina, vulva, udder To produce and feed young
Lympho-reticular lymph nodes, spleen Protect against infectious diseases, produce blood

The muscular-skeletal system

This system consists of the bones and the muscles (meat).The bones form the skeleton which is the framework within the body. It carries weight and supports the body.

Bones are connected together so they can move. The places where this happens are called joints. The bones are held together at the joints by elastic strands called ligaments. Between the bones is a softer material called cartilage (gristle) which cushions the bones at the joints when the body moves. Bones are very hard and contain minerals. Each bone has a name such as the scapula (shoulder blade) and skull (head). There are about 200 bones in the body.

Muscles are joined at both ends to the bones. The muscles are the meat of the body and when they contract (shorten) or relax (lengthen) they make the bones move. If you bend your arm you can see and feel the muscles in your arm working.

 

The digestive system

The digestive system consists of the teeth, mouth, gullet, stomach, liver, intestine, pancreas, and rectum.

Digestion begins in the mouth where feed is broken down into small pieces by the teeth and mixed with saliva before being swallowed.



In the stomach feed is mixed with the juices to form a soft paste. This then passes into the intestine where bile from the liver and juices from the pancreas are added. The action of these juices is to break down the feed and allow the nourishment it contains to be absorbed by the blood in the walls of the intestine. Waste matter collects in the rectum and passes out of the body through the anus (or cloaca in birds).

 


Date: 2016-04-22; view: 861


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