Transport In Humans

Question 1 Define the term transport?

Question 2 What is the function of platelets in body?

Question 3 What is blood? Name the components of blood?

Question 4 Why transport of materials necessary in plants and animals?

Question 5 Why is blood needed by all the parts of our body?

Question 6 What is heart? Describe the function of heart?

Question 7 Define arteries, veins and capillaries?

Question 8 How does food and oxygen reach all the parts of our body?

Question 9 What is a heartbeat? Name the instrument used by doctors to listen to our heartbeat?

Question 10 Explain why the heart beat faster during and after an exercise?

Question 11 What is stethoscope? name its various parts?

Question 12 What is pulse? what is the pulse rate of an adult person while resting?

Question 13 How do food, oxygen , carbon dioxide and other materials transported in animals such as hydra and sponges?

Question 14 Name the various parts of human circulatory system?

Question 15 Which side of heart pumps

(a) blood into the lungs

(b) blood into the body organs

Question 16 Define the term oxygenated and deoxygenated blood?

Transport

Transport is a life process in which a material absorbed (or made) in one part of the body of an organism is carried to other parts in its body.

 

All the living organisms (animals and plants) need a continuous supply of different materials such as food, water and oxygen for their survival. These materials must reach the various parts of an organism where they are needed.

All the living organisms also produce some waste materials like carbon dioxide as a result of chemical processes occurring in their body cells. These waste materials are harmful and have to be removed from the body.

All the living organisms (animals and plants) need a transport system to supply them with food, water and oxygen, and to carry away the harmful waste materials produced in their bodies.

In most of the animals, the blood that circulates in their body transports (or carries) food, water and oxygen to cells in all the parts of their body. The blood also transports the waste materials made in the body cells to different parts of the body for excretion (or removal).

Circulatory System

In the circulatory system, blood carries digested food, water and oxygen to all the parts of the body. It also takes away the waste products like carbon dioxide made in the body cells.

The various organs of the circulatory system in humans are : Heart , blood and Blood vessels. In the circulatory system, the heart acts as a pump to push out blood. The blood vessels (arteries, veins and capillaries) act as tubes or pipes through which blood flows in the whole body.

(1) Blood

Blood is a red coloured liquid which flows in blood vessels and circulates in our body. Blood is red because it contains a red pigment called haemoglobin. Blood has many different cells which perform different functions. Blood consists of four components : plasma, red blood cells, white blood cells and platelets.

Plasma is a liquid and red blood cells, white blood cells and platelets keep floating in it.

The blood is able to transport various substances in the body due to the presence of different components in it.

 

The four components of blood and their functions

(1) Plasma

The liquid part of blood is called plasma. Plasma is a pale yellow, sticky liquid. It is 90 per cent water and 3.5 per cent common salt. Plasma contains dissolved substances such as digested food and waste products (like carbon dioxide and urea). Plasma carries water and dissolved substances such as digested food and waste products from one part to another part in the body. Red blood cells, white blood cells and platelets are immersed in this liquid called plasma.

(2) Red blood cells (RBC)

Red blood cells are red in colour due to the presence of a red pigment called haemoglobin inside them. Red blood cells carry oxygen from the lungs to all the cells of the body. It is actually the haemoglobin present in red blood cells which carries oxygen in the body. Haemoglobin binds with oxygen and transports it to all the parts of the body and ultimately to all the cells. If there is a deficiency of haemoglobin in the blood of a person, it becomes difficult to provide oxygen efficiently to all the cells of his body. It is the presence of haemoglobin which makes the blood appear red.

(3) White blood cells (WBC)

The white blood cells fight infection and protect us from diseases. This is because white blood cells help to fight against germs which may enter our bodies and cause diseases. Some white blood cells can eat up the germs (like bacteria) which cause diseases. Other white blood cells make chemicals known as antibodies to fight against infection.

(4) Platelets

Platelets are the tiny fragments of special cells formed in the bone marrow. Platelets help in the clotting of blood in a cut or wound. When a cut or wound starts bleeding, then platelets clot the blood (make the blood semi-solid) due to which further bleeding stops.

If a child falls down while playing a game and his knee (or any other body part) gets injured, then blood starts flowing from the cut made by the injury. After some time, however, a dark red clot is formed which plugs the cut and bleeding stops. The blood clot (which stops bleeding) is formed due to the presence of the cells called platelets in the blood.

 

Functions Of Blood

(1) Blood carries digested food from the small intestine to all the parts of the body.

(2) Blood carries water to all the parts of the body.

(3) Blood carries oxygen from the lungs to different parts of the body

(4) Blood carries the waste product carbon dioxide from the body cells to the lungs for breathing out

(5) Blood carries a waste product called urea from the liver to the kidneys for excretion in urine.

(6) Blood protects the body from diseases.

Blood circulates in our body in two forms : oxygenated blood and deoxygenated blood.

The blood carrying oxygen in it is called oxygenated blood. Thus, oxygenated blood is rich in oxygen. We get oxygenated blood in the lungs where the fresh oxygen of air passes into the blood.

The blood having no oxygen in it is called deoxygenated blood. The deoxygenated blood is formed in all the organs of the body (except the lungs). This is because when the oxygenated blood passes through the organs of the body, the body cells use up its oxygen and make it deoxygenated. The deoxygenated blood carries carbon dioxide in it.Thus, deoxygenated blood is rich in carbon dioxide. Oxygenated blood is bright red whereas deoxygenated blood is darker.

(2) Heart

The heart is an organ which pumps blood to all the parts of our body through a network of tubes called blood vessels. The heart works like a pump non-stop throughout our life.

(1) Our heart is located in the chest cavity slightly towards the left side.

(2) The heart lies between the two lungs and above the diaphragm.

(3) The size of our heart is roughly equal to our fist.

(4)The heart is made of special muscle called cardiac muscle. The heart is hollow inside.

(5) The heart has four compartments called chambers. The upper two chambers of heart are called atria (singular of atria is atrium), and the lower two chambers of heart are called ventricles.

(6)On the left side of the heart are left atrium and left ventricle. On the right side of the heart are right atrium and right ventricle.

(7) The top side of left atrium is connected to pulmonary vein which brings oxygenated blood into it from the lungs. The lower side of left atrium is connected to left ventricle. Oxygenated blood from left atrium goes into left ventricle.

(8)The other side of left ventricle is connected to main artery (called aorta). The left ventricle pumps oxygenated blood into main artery for taking it to all the body organs (except lungs)

(9) The top side of right atrium is connected to main vein (called vena cava) which brings deoxygenated blood into it from all the body organs (except lungs).The lower side of right atrium is connected to right ventricle.

(10) Deoxygenated blood from right atrium goes into right ventricle. The other side of right ventricle is connected to pulmonary artery. The right ventricle pumps deoxygenated blood into pulmonary artery for taking it to lungs.

(11) The left side of heart is completely separated from its right side by means of a partition wall called septum which is  made of thick muscle.The partition wall (or septum) in the heart prevents the mixing of oxygenated blood on its left side with the deoxygenated blood on its right side.

(12) A sheath of tissue called ‘pericardium’ protects the heart. All the atria and ventricles of the heart contract and relax (expand) at appropriate times and make the heart behave like a pump.

(13) The heart is a double pump. The left side of heart and right side of heart act as two separate pumps. The left side of heart acts as one pump which pumps oxygenated blood into the whole body (except the lungs). The right side of heart acts as another pump which pumps deoxygenated blood only to the lungs.

(14) The left side of heart has oxygen rich blood (oxygenated blood) whereas the right side of heart has carbon dioxide rich blood (deoxygenated blood). It is necessary to keep the oxygen rich blood separate so that it may supply good amount of oxygen to the body cells for respiration and release of energy.

 

Blood Vessels

Blood vessels are a kind of tubes (or pipes) which carry blood throughout our body.There are three types of blood vessels in the body: arteries, veins and capillaries.

(i) Arteries

Arteries are the blood vessels which carry blood from the heart to all the parts of the body. The arteries lie quite deep under our skin and hence they are not seen easily. Blood leaves the heart at high pressure through arteries. The arteries have thick and elastic walls. This is because blood flows through them at high pressure. The thick and elastic walls of arteries can withstand the high pressure of blood flowing through them. The main artery (called aorta) is connected to the left ventricle of the heart.

The main artery carries oxygenated blood from the left ventricle to all the parts of the body (except the lungs ) Artery called pulmonary artery is connected to the right ventricle of the heart. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.

One artery called pulmonary artery carries deoxygenated blood (rich in carbon dioxide) from the heart to the lungs.

(ii) Veins

Veins are the blood vessels which carry blood from all the parts of the body back to the heart. The veins are less deep than arteries and hence can be seen easily. The greenish-blue lines which we see just below the skin on our hands and legs are the veins. The deoxygenated blood returns to the heart at low pressure through the veins. Since the blood flows at low pressure through the veins, so the veins have thin walls. Veins have valves in them which allow the blood in them to flow in one direction only towards the heart. The valves prevent the back flow of blood in veins.

The main vein is connected to the right atrium of the heart. The main vein carries deoxygenated blood from all the parts of the body (except lungs) back to the heart. Another vein called pulmonary vein is connected to the left atrium of the heart.

(iii) Capillaries

Capillaries are the extremely thin blood vessels which connect arteries to veins. Every cell of the body is near a capillary.

The capillaries have extremely thin walls which allow substances to pass from blood into the body cells, and also from body cells into the blood.

The oxygenated blood from arteries enters into the capillaries in all the parts of the body. The various dissolved substances present in the blood (like food and oxygen) pass into body cells through the thin walls of the capillaries. At the same time, the waste products (like carbon dioxide) formed in the body cells enter into blood through the thin walls of capillaries.

Thus, the exchange of substances (like food, oxygen, carbon dioxide, etc.) between the blood and the body cells takes place through capillaries. The other ends of capillaries are joined to veins. The deoxygenated blood (containing waste products like carbon dioxide) coming from the capillaries enters into veins and carried back to the heart.

 

Working of the Circulatory System

The blood is circulated in the human body by the rhythmic (regularly occurring) contractions and relaxation of heart muscles which make up the atria and ventricles.

The two atria contract together and relax together. Similarly, the two ventricles (left ventricle and right ventricle) contract together and relax together. The contraction of two atria is immediately followed by the contraction of two ventricles and leads to the continuous flow of blood in human body.

(1) When blood passes through the capillaries of the lungs, then oxygen from air enters into blood and we get oxygenated blood

(2) Pulmonary vein brings oxygenated blood from the lungs into the left atrium. When the left atrium  contracts, the oxygenated blood is pushed into left ventricle

(3) When the left ventricle contracts, it pumps oxygenated blood into the main artery.This main artery then branches into many smaller arteries which go into different body organs.

(4) The arteries carry oxygenated blood to all the organs (or parts) of the body like head, chest, arms, stomach, intestines, liver, kidneys, trunk and legs.

(5) All the body organs have capillaries in them which are joined to arteries. When oxygenated blood from arteries passes through the capillaries of the body organs, then it gives food and oxygen to the body cells. At the same time, carbon dioxide produced as a waste product in the body cells during respiration, enters into blood through capillaries.

(6) The deoxygenated blood (rich in carbon dioxide) coming from the body organs enters from the capillaries first into smaller veins and then into main vein. The main vein carries deoxygenated blood to the right atrium.

(7) When the right atrium contracts, the deoxygenated blood is pushed into right ventricle.

(8) When the right ventricle contracts, it pumps deoxygenated blood (rich in carbon dioxide) into the lungs.

(9) In the lungs, deoxygenated blood gives out the waste product carbon dioxide and absorbs fresh oxygen from the air being breathed in. So, the blood becomes oxygenated again.

(10) The oxygenated blood is again sent by the lungs to the left side of the heart for circulation in the body once again. This process is repeated continuously, all day and all night, even when we are asleep.

In this way, the blood keeps on circulating in the body without stopping due to which all the parts of the body keep on getting digested food, oxygen and other materials all the time. At the same time, blood circulation keeps on removing waste products like carbon dioxide formed in the body cells.

The circulation of blood was discovered by an English physician named William Harvey.

Heartbeats

The heart pumps blood into arteries by contracting. When the heart contracts, it becomes smaller in size and pushes the blood into main artery with a great force. Then the heart relaxes (comes back to its original size) and gets filled up with blood from pulmonary vein. The heart keeps on contracting and relaxing again and again to pump blood into the body continuously.

One complete contraction and relaxation of the heart is called a heartbeat. 

The average heartbeat of an adult person while resting is 72 to 80 per minute. This is called the heart rate. We can feel our heartbeats if we place our hand on the left side our chest just above the heart region. The number of heartbeats increase too much during and after a physical exercise or when a person is excited.

The faster beating of heart pumps blood more rapidly to the body organs which supplies more oxygen to the body cells for rapid respiration to produce more energy. The increase in number of heartbeats caused by exercise, excitement, fear or nervousness, however, lasts for a short time after which it becomes normal.

A doctor listens to our heartbeats with the help of an instrument called stethoscope. The stethoscope amplifies (makes louder) the sound of heartbeats so that the doctor can hear the heartbeats clearly.

Parts of stethoscope

A stethoscope consists of three parts :

(1) A chest piece (which carries a sensitive diaphragm at its bottom). The diaphragm amplifies the sounds of heartbeats.

(2) Two ear pieces (which are made of two metal tubes). These are put by the doctor into his ears.

(3) A rubber tube which joins the chest piece to the ear pieces. The rubber tube transmits the sound from the chest piece into the ear pieces.

A stethoscope is used to hear clearly the heartbeats by placing the chest piece over the heart region of chest. The diaphragm amplifies the sounds of heartbeats coming from within the body and the rubber tube and ear pieces transmit these sounds to the ears of the doctor. Doctors can get clues about the condition of our heart by listening to the heartbeats through the stethoscope.

Pulse

The expansion of an artery each time the blood is forced into it, is called pulse.

Each heartbeat generates one pulse in the arteries, so the pulse rate of a person is equal to the number of heartbeats per minute.

Since the heart beats about 72 to 80 times per minute, therefore, the pulse rate of an adult person while resting is 72 to 80 per minute. Thus, the pulse rate is the same as the heart rate. The pulse rate of a person is higher after a physical exercise or when a person is excited.

Most of our arteries lie deep inside our body and hence cannot be used to feel the pulse. But at some places in our body like the wrist, temple and neck, the arteries are close to the surface of skin and pass over bones. So, we can feel the pulse at wrist, temple and neck by pressing the artery lightly with our finger tips

Sponges and Hydra

(1) Sponges live mostly in sea water whereas hydra lives in freshwater.

(2) Sponges and Hydra do not have blood, blood vessels or heart.Sponges and Hydra do not possess any circulatory system.

(3) In sponge and hydra, the  water also carries away carbon dioxide and other waste materials as it moves out of their bodies.

(4) Amoeba and Paramecium are also tiny animals which live in water and do not have blood in them.