Transportation in Animals and Plants

The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it. The heart is located in the chest cavity with its lower tip slightly tilted towards the Left. Heart is roughly the size of a fist. To avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide, the heart has four chambers. The two upper chambers are called the atria (singular: atrium) and the two lower chambers are called the ventricles The partition between the chambers helps to avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide.To understand the functioning of the circulatory system, start from the right side of the heart as show in the in Fig and follow the arrows. These arrows show the direction of the blood flow from the heart to the lungs and back to the heart from where it is pumped to the rest of the body.

The walls of the chambers of the heart are made up of muscles. These muscles contract and relax rhythmically. This rhythmic contraction followed by its relaxation constitutes a heartbeat. The rhythmic beating the various chambers of the heart maintain circulation of blood and transport of substances to the different parts of the body.

The cells in the body perform various activities. Waste products such as urea, uric acid and excess water are formed and have to be removed from the body. The removal of waste products is termed excretion. The organs that help in the process of excretion constitute the excretory system, and include the kidneys, the ureters, the urinary bladder and the urethra. The useful and harmful substances in blood enter the kidneys, where the capillaries filter it. The useful substances are reabsorbed, but the harmful substances are removed along with water in the form of urine. The urine from the kidneys comes down through long tubes called the ureters, which open into the urinary bladder where the urine is stored temporarily. When the bladder fills, the urine is disposed.

The main components of bloods are :

1. Plasma: The fluid part of the blood is called plasma.
2. Red Blood Cells (RBC) contains a red pigment called haemoglobin. Haemoglobin bind with oxygen and transports it to all the parts of the body and ultimately to all the cells. It will be difficult to provide oxygen efficiently to all the cells of the body without haemoglobin. The presence of haemoglobin makes blood appear red.
3. White Blood cells (WBC) fight against germs that may enter our body thus provide an effective defence against infection, disease etc.
4. Platelets: They are another type of cells in blood, responsible for the formation of dark red clot in the blood when it comes in contact with air. They help in preventing excess bleeding from the injuries by plugging the skin openings or cuts with a thick dark red clot

• It transports substances like digested food from the small intestine to the other parts.
• It carries oxygen and carbon dioxide to their respective organs and tissues
• It transports wastes for removal from the body.