Would you give these answers full marks? They're both out of 7 marks.

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Question 1

Describe the structure of arteries and explain how their structure is related to their function. (7)

Arteries carry oxygenated blood away from the heart (apart from the pulmonary artery that carries de-oxygenated blood to the lungs). They have several features that help them to perform this function:

  • The lumen is relatively small, which helps to maintain the high pressure.

  • The walls are thick and contain collagen, that gives the arteries the strength to withstand the high pressure and prevents them from bursting.

  • Elastic fibres allow the arteries to stretch and recoil as the heart pumps. This allows the arteries to maintain a high pressure when the heart relaxes.

  • The endothelium is folded, so that the artery can stretch without breaking, as the blood is pumped.

Question 2

Describe how the heartbeat is initiated and how the contractions of the four chambers are coordinated. (7)

  • The heartbeat is initiated by the sinoatrial node. It sends an electrical impulse to the atria. The wave excitation spreads across the atrial muscle walls, causing them to contact. Therefore the atrial systole occurs, and the blood is pumped from the atria to the ventricles, through the atria-ventricular valves.

  • The atrioventricular node located in the septum of the heart, delays the signal sent by the SAN, so that the ventricles and atria don't contract at the same time. This allows the blood to flow into the ventricles before they start to contract.

  • When the atria relax, the impulse from the AVN travels down the septum to the base of the ventricles in the Purkyne tissue.

  • The Purkyne tissue causes the ventricles to contract from the base upwards to force the blood out of the heart, through the semi-lunar valves into the arteries. The blood pressure in the ventricles increases so the atria-ventricular valves close, to prevent the blood from flowing back into the atria. 

Posted Mon 15th October, 2012 @ 16:54 by Natalia

1 Answer

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These would definitely get full marks!!! The examiner would have to be very harsh not to. :) 

Answered Wed 17th October, 2012 @ 18:00 by Former Member