Q27
5 marksLong AnswerSection C

(a) Write the correct sequence of steps followed during journey of oxygen rich blood from lungs to various organs of human body.

(b) What happens when the system of blood vessels develop a leak?

Life Processes
Transportation in Human Beings
Official Answer

(a) Sequence of steps followed during the journey of oxygen-rich blood from lungs to various organs of the human body:


  1. Oxygenation in Lungs: Blood absorbs oxygen in the lungs and becomes oxygen-rich.
  2. Entry into Heart: This oxygen-rich blood is carried from the lungs to the left atrium of the heart via the pulmonary veins.
  3. Expansion of Left Atrium: The left atrium relaxes while collecting this oxygenated blood.
  4. Transfer to Left Ventricle: The left atrium then contracts, while the muscular left ventricle expands, transferring the blood into the left ventricle.
  5. Pumping to Body: When the left ventricle contracts, the oxygen-rich blood is forced out of the heart into the aorta (the main artery).
  6. Distribution to Organs: The aorta branches into smaller arteries, distributing the oxygen-rich blood to various organs and tissues of the body.


Lungs (Oxygenation)Pulmonary Vein (Oxygen-rich blood)Left Atrium (Relaxes to collect, contracts to pump)Left Ventricle (Thick muscular wall)Aorta (Main Artery)Body Organs/Tissues (Oxygen delivered)


(b) What happens when the system of blood vessels develop a leak:

  • Loss of Pressure: Leakage leads to a loss of blood from the closed circulatory system, which naturally reduces the pressure within the system.
  • Reduced Pumping Efficiency: This drop in pressure reduces the efficiency of the pumping system (the heart).
  • Role of Platelets: To prevent this, the blood contains specialized cells called platelets. Platelets circulate around the body and plug these leaks by helping to clot the blood at the point of injury, thereby maintaining system pressure and preventing excessive blood loss.
Pulmonary veinLeft atriumLeft ventricleAortaOxygen-rich bloodLoss of pressurePumping efficiencyPlateletsClotting

Marking Scheme

  • 1Trace blood from lungs to left atrium via pulmonary vein with correct chamber states (relaxation/contraction) (1.5 marks)
  • 2Trace blood from left atrium to left ventricle, and then out through the aorta to body organs (1.5 marks)
  • 3Explain the consequence of a leak (loss of pressure and reduced pumping efficiency of the heart) (1 mark)
  • 4Explain how platelets plug the leak by forming a blood clot at the site of injury (1 mark)

Hint

Trace the path of blood starting from the lungs, through the pulmonary vein, into the left chambers of the heart, and out through the aorta. For part (b), think about blood pressure and the clotting cells of the blood.

Quick Oral Answer

Oxygenated blood goes from the lungs to the left atrium via the pulmonary vein, then to the left ventricle, and is pumped to the body through the aorta. If a leak occurs, blood pressure drops, reducing pumping efficiency; platelets prevent this by clotting the blood at the leak site.

Analysis & Explanation

The human heart is a multi-chambered muscular organ designed to prevent the mixing of oxygen-rich blood with carbon dioxide-rich blood. Oxygenated blood from the lungs must enter the left side of the heart (atrium then ventricle) before being forcefully pumped to the rest of the body. Because this is a high-pressure closed system, any physical leak (injury) can cause a drop in pressure, compromising circulation. Platelets act as an immediate cellular defense mechanism to clot blood and seal leaks.

Common Mistakes

  1. 1Confusing the left and right sides of the heart (remember, the left side always handles oxygenated blood, while the right side handles deoxygenated blood).
  2. 2Writing that the pulmonary artery carries oxygenated blood (it is the pulmonary vein that carries oxygenated blood from the lungs to the heart).

Interesting Facts

The left ventricle has much thicker muscular walls than the right ventricle because it has to pump blood to the entire body, whereas the right ventricle only pumps blood to the nearby lungs.

Spotted a mistake or something unclear?

Tell us — we fix reported answers fast.

Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 5 marks in the CBSE Class 10 Science 2020 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Life Processes" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Transportation in Human Beings" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This is a Long Answer question from Section C in the CBSE Class 10 Science 2020 paper.