IB SEHS Topic 2

The ventilatory system takes in air to the lungs where ______________ are exchanged. (1 mark)

• hydrogen and oxygen

• oxygen and carbon monoxide

• carbon dioxide and oxygen

• (CO)2 and O

Answer explanation

(CO)2 is ethylenedione, a compound of 2 CO molecules and thought to be theoretically impossible.

Which structure is responsible for moistening air entering the ventilatory system? (1 mark)

• The mouth

• The mouse

• The larynx

• The nose

Residual volume is _______________. (1 mark)

• how much air remains in the lungs after a maximal exhalation.

• the volume of air moved into or out of the lungs during quiet breathing.

• the volume of air breathed out after the deepest inhalation.

• volume of air in the alveoli.

Stroke volume is: (1 mark)

• the force exerted on the arteries during ventricular contraction

• the amount of blood pumped from the ventricle in a minute

• the number of times the heart beats in a minute

• the amount of blood pumped from the ventricle with each heartbeat

Diastolic blood pressure measures... (1 mark)

• ...the force exerted by blood on arterial walls when the atria relax.

• ...the force exerted by blood on arterial walls when the atria contract.

• ...the force exerted by blood on arterial walls when the ventricles relax.

• ...the force exerted by blood on arterial walls when the ventricles contract.

Explain the mechanics of inhalation in the human lungs (3 marks).

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Answer explanation

The mechanics of breathing follow Boyle’s Law (pressure and volume have an inverse relationship).

The diaphragm contracts and chest wall expands therefore lung volume increases. The result is a decrease in lung pressure in comparison to the atmosphere so air rushes in the airway.

(No need to mention exhalation. It is not asked for in the question.)

Describe the functions of erythrocytes, platelets and leucocytes (3 marks).

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Answer explanation

Erythrocytes (red blood cells) carry oxygen from the lungs to the body tissues and carbon dioxide (waste product) from the tissues and back to the lungs.

Leukocytes (white blood cells) fight infections and ingest old RBCs and dead body cells.

Platelets (thrombocytes) cause blood clotting. They are small and group together to form clumps on a blood vessel to stop bleeding.

Identify parts 1, 2, 9, 4, 12 and 10 (3 marks).

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Answer explanation

1 - aorta

2 - right atrium

9 - left ventricle

4 - tricuspid valve

12 - mitral valve

10 - vena cava

Tags

NGSS.HS-LS1-2

NGSS.HS-LS1-3

Distinguish between pulmonary circulation and systemic circulation (3 marks).

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Answer explanation

"Auricle" is another word for atrium.

Explain the process of oxygen exchange at the alveoli (3 marks).

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Answer explanation

Gaseous exchange occurs in the alveoli by diffusion, which occurs between the surface of the alveoli and pulmonary capillaries. Oxygen, once in the lungs, is passed from the alveoli into the bloodstream (capillaries) for distribution to the rest of the body. This occurs because there is a higher concentration of O₂ in the alveoli than in the blood. There, O₂ diffuses across to the capillaries where there is a lower concentration. At the same time, CO₂ goes from the high concentration in the capillaries to a low concentration in the alveoli and is breathed out during exhalation.

Tags

NGSS.HS-LS2-3

NGSS.HS-LS2-5