WHY DO WE NEED A TRANSPORT SYSTEM?
- To distribute the absorbed useful substances like oxygen and food substances (particularly products of digestion - simple sugars, amino acids and fats) throughout the body of the animal (example: glucose is distributed to all respiring cells to generate energy).
- To remove waste products such as carbon dioxide and urea from the body of the animal before these waste products accumulate to harmful levels.
TRANSPORT SYSTEM IN MAMMALS
In mammals, the transport system consists of the:
In mammals, the transport system consists of the:
- Blood system for transporting blood
- Lymphatic system for transporting lymph
(Note: Both blood and lymph are fluids in which substances are distributed all over the body)
The main transport system in mammals is its Blood System (also called the Vascular System). It consists of three important components:
The main transport system in mammals is its Blood System (also called the Vascular System). It consists of three important components:
- The Blood
- The Blood Vessels
- The Heart (a pump which keep the blood flowing through the blood vessels)
The following figure shows the general layout of the transport system (blood system) of a human as seen from the front. 
Notice that the figures above show that the human transport system consists of the SYSTEMIC CIRCULATION and the PULMONARY CIRCULATION. The systemic circulation transports blood all over the body (except the lungs) whilst the pulmonary circulation transports blood only to the lungs.
If you follow the arrows, beginning at the lungs, you can see that the blood flows into the left-hand side of the heart, and then out to the rest of the body. It is brought back to the right hand side of the heart, before going back to the lungs again. This is called a DOUBLE CIRCULATORY SYSTEM because the blood travels through the heart TWICE on one complete journey around the body.
The following figure shows the lymphatic system:
(Note: there is no "pump" in the lymphatic system as in the blood system)
Now, because there is no pump in this system, lymph is prevented from flowing backward by having VALVES along the lymph vessels. The following figure shows the valves in the lymph vessels.
The following figure shows the relationship between the BLOOD SYSTEM and the LYMPHATIC SYSTEM:
Notice that the figures above show that the human transport system consists of the SYSTEMIC CIRCULATION and the PULMONARY CIRCULATION. The systemic circulation transports blood all over the body (except the lungs) whilst the pulmonary circulation transports blood only to the lungs.
If you follow the arrows, beginning at the lungs, you can see that the blood flows into the left-hand side of the heart, and then out to the rest of the body. It is brought back to the right hand side of the heart, before going back to the lungs again. This is called a DOUBLE CIRCULATORY SYSTEM because the blood travels through the heart TWICE on one complete journey around the body.
The following figure shows the lymphatic system:
(Note: there is no "pump" in the lymphatic system as in the blood system)
Now, because there is no pump in this system, lymph is prevented from flowing backward by having VALVES along the lymph vessels. The following figure shows the valves in the lymph vessels.
The following figure shows the relationship between the BLOOD SYSTEM and the LYMPHATIC SYSTEM:
