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Chapter 6

The Circulatory System

Class 6 - Concise Biology Selina


Multiple Choice Questions

Question 1

Function of WBCs is to

  1. Transport oxygen
  2. Help in clotting of blood
  3. Provide immunity
  4. Provide storage of food

Answer

Provide immunity

Reason — WBCs provide immunity by destroying the disease causing germs and producing antibodies.

Question 2

Blood Capillary is a

  1. Broad tube
  2. Artery with thick wall
  3. Vein with large lumen
  4. Narrow tube made up of endothelium only

Answer

Narrow tube made up of endothelium only

Reason — Blood capillary is narrow blood vessel whose walls have a single layer of cells called endothelium.

Question 3

Nucleus is absent in

  1. RBCs
  2. WBCs
  3. All blood cells
  4. Liver cells

Answer

RBCs

Reason — RBCs have no nucleus because they need space for haemoglobin to store more amount of oxygen.

Question 4

The only artery which carries deoxygenated blood is

  1. Hepatic artery
  2. Pulmonary artery
  3. Aorta
  4. Renal artery

Answer

Pulmonary artery

Reason — Pulmonary artery leaves the right ventricle of the heart carrying the deoxygenated blood to the lungs for oxygenation.

Question 5

Sphygmomanometer measures

  1. Pulse rate
  2. Heart beat
  3. Blood pressure
  4. Brain activity

Answer
Blood pressure

Reason — Sphygmomanometer is an instrument which is used to find out blood pressure of the body.

Question 6

Pulmonary vein carries

  1. Oxygenated blood
  2. Deoxygenated blood
  3. Glucose rich blood
  4. Carbon dioxide laden blood

Answer

Oxygenated blood

Reason — Oxygenated blood from the lungs returns to the left auricle via pulmonary veins.

Question 7

The blood tastes saltish due to the presence of dissolved

  1. Sodium chloride
  2. Potassium chloride
  3. Ammonium nitrate
  4. Sodium nitrate

Answer

Sodium chloride

Reason — The blood tastes saltish due to dissolved minerals like sodium chloride.

Short Answer Questions

Question 1(a)

Differentiate between Platelets and WBC

Answer

Difference between Platelets and WBCs:

PlateletsWBCs
Platelets help in clotting of blood.WBCs provide immunity by destroying the disease causing germs and producing antibodies.
Platelets are the smallest of the blood cells.WBCs are larger than RBCs and Platelets.
Platelets does not have a nucleus.WBCs have a distinct oval or lobed nucleus.

Question 1(b)

Differentiate between Pulmonary artery and Pulmonary vein

Answer

Difference between Pulmonary artery and Pulmonary vein:

Pulmonary arteryPulmonary vein
The Pulmonary artery arises from the right ventricle of the heart.The Pulmonary vein drains blood in the left atrium of the heart.
It carries deoxygenated blood from the right auricle of the heart to each lung.It carries oxygenated blood from each lung to the left atrium of the heart.

Question 1(c)

Differentiate between Vena cava and Aorta

Answer

Difference between Vena cava and Aorta:

Vena cavaAorta
Vena cava is a large vein.Aorta is the largest artery.
It carries deoxygenated blood from the upper and lower parts of the body to the right auricle of the heart.It leaves the left auricle of the heart carrying oxygenated blood to all parts of the body through its branches.

Question 1(d)

Differentiate between RBCs and WBCs

Answer

Difference between RBCs and WBCs:

RBCsWBCs
RBCs do not have nucleus at maturity.WBCs have a large distinct oval or lobed nucleus .
WBCs are larger than RBCs.RBCs are small in size.
RBCs have red colour due to the presence of haemoglobin protein.WBCs are colourless and they lack haemoglobin.
RBCs carry oxygen from lungs to all the body tissues and cells and remove carbon dioxide produced in the cells and carry it back to the lungs.WBCs provide immunity by destroying the disease causing germs and producing antibodies.

Question 2

Give any three differences between an Artery and a Vein.

Answer

Three differences between an Artery and a Vein are:

ArteryVein
Arteries carry blood away from the heart to various body parts.Veins carry blood from different body parts to the heart.
Arteries have thick elastic and more muscular walls.Veins have thin and less muscular walls.
Arteries carry oxygenated blood (except the pulmonary artery).Veins carry deoxygenated blood (except the pulmonary vein).

Question 3

Blood consists of two parts - a liquid part and a cellular part. Name these parts and briefly describe them.

Answer

Blood is a red coloured fluid which consists of two parts:

  1. Liquid part — The liquid part of the blood is called Plasma. Plasma is yellow in colour. 90% of Plasma is water and the remaining 10% consists of dissolved proteins, nutrients, waste product and hormones.
  2. Cellular part — The cellular part of the blood is called Corpuscles. The corpuscles are of three types:
    1. Red Blood Cells (RBCs) — RBCs are also called as Erythrocytes. They carry oxygen from lungs to all the body tissues and cells and remove carbon dioxide produced in the cells and carry it back to the lungs. RBCs are circular or biconcave disc shaped. A mature RBC does not contain nucleus. Haemoglobin present in RBCs helps in transport of oxygen and gives them the red colour.
    2. White Blood Cells (WBCs) — WBCs are also called Leukocytes. They are colourless and lack haemoglobin. They are larger than RBCs and have a distinct oval or lobed nucleus. WBCs provide immunity by destroying the disease causing germs and producing antibodies
    3. Platelets — The platelets are also called Thrombocytes. They are round in shaped and the smallest in size. They help in the clotting of blood which prevents excessive blood loss and direct entry of disease causing germs into the blood through cuts and wounds.

Question 4

What is the role of haemoglobin in the blood?

Answer

Haemoglobin is an iron and protein compound present in the Red Blood Cells (RBCs). It acts as the Oxygen carrier as it binds with Oxygen transporting it to all the body tissues and cells. It also helps to remove carbon dioxide produced in the cells and carry it back to the lungs.

Question 5

Fill in the blanks with suitable words:

(a) The colour of a red blood cell is due to ...............

(b) The two lower chambers of the heart are called ...............

(c) The blood plasma contains dissolved substances such as ............... and ...............

(d) The ............... artery takes the blood from the ventricles to the lungs

(e) The instrument used to find out the blood pressure is known as ...............

(f) The blood loaded with carbon dioxide from the body comes into the ............... of the heart.

(g) The oxygen-rich blood from the lungs comes into ............... of the heart.

(h) The oxygen-rich blood is pumped into different parts of the body through ...............

(i) The carbon dioxide loaded blood from the right ventricle is pumped into the lungs through ............... artery.

Answer

(a) Haemoglobin

(b) Ventricles

(c) Nutrients, Proteins, waste products and Hormones

(d) Pulmonary

(e) Sphygmomanometer

(f) Right Auricle

(g) Left Ventricles

(h) Aorta

(i) Pulmonary artery

Question 6

In which organ of our body does blood become oxygenated?

Answer

Blood becomes oxygenated in the lungs.

Question 7

Which side of the heart (left or right) contains oxygenated blood?

Answer

The left side of the heart contains oxygenated blood.

Question 8

Name the disease in which the number of platelets reduces to 25,000 - 30,000 per cu mm of blood. State its major symptoms.

Answer

Dengue fever is one such disease in which the number of platelets reduces to 25,000 - 30,0000 per cu mm of blood. The major symptoms of dengue are high fever, rashes or red spots on body, vomiting, pain in abdomen or back of the eyes and muscles.

Long Answer Questions

Question 1

Name the three kinds of blood vessels found in human beings. With the help of suitable diagrams, differentiate between them.

Answer

The three kinds of blood vessels found in human beings are Arteries, Veins and Capillaries.

Below diagram shows the differences between Artery, Vein and Capillaries:

Name the three kinds of blood vessels found in human beings. With the help of suitable diagrams, differentiate between them. The Circulatory System, Concise Biology Solutions ICSE Class 6.
ArteriesVeinsCapillaries
An artery is a vessel which carries the blood away from the heart to other parts of the body.A vein is a vessel which carries the blood from an organ towards the heart.Capillaries are the terminal branches of an artery, which rejoin to form a vein.
An artery has thick, elastic and more muscular walls.A vein has thin and less muscular walls with valves.Walls of the capillary are made up of single layer of cells (endothelium) with no muscles.
The blood in it flows with jerk and under great force.The valves prevent the back flow of the blood flowing towards the heart.The wall of capillary is very thin, to enable an exchange of nutrients waste products and gases between the blood and the body fluids.

Question 2

State briefly, the difference between white blood cells and the red blood cells.

Answer

Difference between White blood cells and Red blood cells:

White Blood CellsRed Blood Cells
WBCs are amoeboid having irregular shape.RBCs are circular or biconcave disc shaped.
WBCs have distinct oval or lobed nucleus.RBCs do not have nucleus at maturity.
WBCs are larger than RBCs.RBCs are small in size.
RBCs have red colour due to the presence of haemoglobin protein.WBCs are colourless and they lack haemoglobin.
RBCs carry oxygen from lungs to all the body tissues and cells and remove carbon dioxide produced in the cells and carry it back to the lungs.WBCs provide immunity by destroying the disease causing germs and producing antibodies.

Question 3

You can see some blood vessels on the outside of the hands specially in older people.Are those veins or arteries? How can you confirm your answer?

Answer

These blood vessels seen on the outside of the hands are Veins. Usually, arteries are deeply placed in the body whereas Veins are placed more superficially.

Question 4

Given alongside is a diagram of human heart showing its internal structure. Label the parts marked 1 to 5, and answer the following questions.

Given alongside is a diagram of human heart showing its internal structure. Label the parts marked 1 to 5. The Circulatory System, Concise Biology Solutions ICSE Class 6.

(a) Which type of blood is carried by the blood vessel marked 2?

(b) Name the main artery which takes the blood from heart to different parts of the body?

(c) Which chamber of the heart receives oxygenated blood from the lungs?

Answer

The marked parts are:

  1. Left pulmonary artery
  2. Superior vena cava
  3. Left pulmonary vein
  4. Right auricle
  5. Left ventricle

a) Deoxygenated blood is carried by the blood vessel marked 2 (Superior vena cava).

b) Aorta

c) Left auricle

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