INTRODUCTION ABOUT TRANSPORT SYSTEMS AND MECHANISMS.

INTRODUCTION ABOUT TRANSPORT SYSTEMS AND MECHANISMS.

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NEED OF TRANSPORT SYSTEMS.

In large and more complex Organisms, transport system is necessary because

(1) The ratio A/V diminishes and so the rate at which nutrients and other substances diffuse decreases.

(2) Substances have to move greater distances.

MATERIALS FOR TRANSPORTATION.

(1) IN PLANTS.

These include water, mineral salt, manufactured food and carbon (IV) oxide.

(2) IN ANIMALS.

Materials for transport in animals include digested food, vitamins, mineral salts, oxygen, carbon (IV) oxide, urea, salts, hormones, water and antibodies.

MEDIA FOR TRANSPORTATION.

(1) Blood and lymph in the vertebrates.

(2) cytoplasm in unicellular Organisms.

(3) cell sap or latex in most plants.

(4) Body fluid in invertebrates.

(5) closed and open circulation.

THE COMPOSITION, STRUCTURE AND FUNCTION OF HUMAN BLOOD.

COMPOSITION.

The blood consists of the fluid portion, called the plasma and cellular elements which includes the red blood cells or erythrocytes, white blood cells or leucocytes and the blood platelets or thrombocytes.

STRUCTURE AND FUNCTIONS.

RED BLOOD CELLS.

They are flat, circular and biconcave discs. They are produced in the erythrocytes bone marrow and have no nucleus. They contain a red pigment ( rich in iron ) called haemoglobin which readily combines with oxygen to form oxyhaemoglobin.

FUNCTION.= The respiratory pigment, called the haemoglobin transports oxygen in form of oxy- haemoglobin.

RED BLOOD CELLS OR LENCOCYTES.

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They are irregular in shape and have nuclei. They are large but fewer in number than the red blood cells. They are produced in the marrow, lymph nodes and spleen.

FUNCTIONS= They defined the blood against infection hence phagocytic in function.

BLOOD PLATELETS OR THROMBOCYTES.

They are square or star- Like or irregular in shape. Thrombocytes are produced in the red bone marrow.

FUNCTION= They helps in the clotting of blood to prevent excessive bleeding and entry of bacteria in the body through the wound.

PROCESS OF BLOOD CLOTTING.

(1) when the blood vessels are damaged, platelets break up releasing thrombokinase in the presence of vitamin k and calcium salts.

(2) Thrombokinase converts prothrombin into thrombin.

(3) Thrombin acts on fibrinogen to form insoluble fibrin which is the clot.

BLOOD PLASMA.

The blood plasma is the liquid portion of lookthe blood. It constitutes 55% of the total Volume of blood. It consists 92% water, dissolved nutrients, blood proteins, certain hormones and antibodies.

FUNCTIONS.

(1) plasma transport some oxygen and carbon (IV) oxide.

(2) It Contains antibodies which destroy invading bacteria by products.

REFERENCE.

http://m.ivyroses.com/Biology/Transport/Transport-Systems.php