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Doctors Medicines MCQs Q&A

Which of the following statements are correct?  a. So as to prevent oxygenated blood from mixing with deoxygenated blood birds and mammals have four chambered hearts. b. Amphibians and some reptiles tolerate some mixing of oxygenated and deoxygenated blood and therefore have three chambered hearts. c. Fishes have only two chambered hearts as here blood is pumped to gills to get oxygenated which then passes to the rest of the body.  

Which of the following statements are correct?  a. So as to prevent oxygenated blood from mixing with deoxygenated blood birds and mammals have four chambered hearts. b. Amphibians and some reptiles tolerate some mixing of oxygenated and deoxygenated blood and therefore have three chambered hearts. c. Fishes have only two chambered hearts as here blood is pumped to gills to get oxygenated which then passes to the rest of the body.   Correct Answer a, b and c

The Correct Answer is A, B & C.

  • Birds & mammals have a 4-chambered heart which comprises 2 arteries & 2 ventricles.
    • It helps in complete separation of oxygenated blood from de-oxygenated blood.
    • The right ventricle pumps blood to the lungs, while the left ventricle pumps blood to the rest of the body.
      • Hence, Statement 1 is correct.
    • The left ventricle has to generate greater pressure to pump blood throughout the body so, the walls of the left ventricle are much thicker & more muscular than the right ones.
  • Amphibians have a three-chambered heart which comprises two arteries and one ventricle.
    • The gas exchange also occurs through the skin during pulmonary circulation.
    • Amphibians have two circulatory routes: one for oxygenation of the blood through the lungs and skin, and the other to take oxygen to the rest of the body.
      • Hence, Statement 2 is correct.
  • Fish have the simplest circulatory systems of the vertebrates.
    • Blood flows unidirectionally from the two-chambered heart through the gills and then the rest of the body.
    • The heart does not require additional chambers beyond the first two. 
      • Hence, Statement 3 is correct.

Important Points

  • Human Heart:
    • The heart is a muscular organ of the size of a fist, located behind and slightly left of the breastbone (Sternum).
    • The heart pumps blood through the network of arteries and veins, called the cardiovascular system.
  • Four chambers:
    • Right atrium: Receives blood from the veins and pumps it to the right ventricle.
    • Right ventricle: Receives blood from the right atrium and pumps it to the lungs, where it gets oxygenated.
    • Left atrium: Receives oxygenated blood from the lungs and pumps it to the left ventricle.
    • Left ventricle: Pumps oxygen-rich blood to the rest of the body. 
  • The left ventricle’s contractions create our blood pressure.
  • The coronary arteries run along the surface of the heart and provide oxygen-rich blood to the heart muscle. 
  • The Left ventricle is the strongest chamber of the heart.

Additional Information

  • In amphibians, reptiles, birds, and mammals, blood flow is directed in two circuits:
    • First, through the lungs and back to the heart called the pulmonary circulation.
    • Second, throughout the rest of the body and its organs including the brain called the systematic circulation.
  • Hummingbirds have the largest hearts (relative to body mass) of all birds.
  • Some of the major arteries in Bird's circulatory system:
    • Carotids: Delivers blood to the head (& brain).
    • Brachial: Takes blood to the wings. 
    • Pectorals: Delivers blood to the flight muscles (pectoralis). 

Related Questions

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