Marking scheme lymphatic question

(b)(i)    Able to state the meaning of lymph

Sample answer:

 - a (pale) fluid within the lymphatic system

             - composed primarily of interstitial fluid and  lymphocytes.

  

 (b)(ii)   Able to describe how lymph is formed from blood until it is incorporated back into the

            blood circulatory system.

Sample Answer :

P1: When the blood flows from arteries into capillaries, there is higher hydrostatic 

      pressure at the arterial end of the capillaries

P2: (This high pressure) forces some plasma to pass through the capillary walls into the

      intercellular spaces (between the cells)  by ultrafiltration process.

P3: Once the fluid leaves the capillary walls, it is called interstitial or tissue fluid // The

       interstitial fluid fills the spaces between the cells and constantly bathes the cells

P4: 90% of the interstitial fluid diffuses back into blood capillary

P5: 10% of the interstitial fluid that has not been reabsorbed into the bloodstream goes

       into the lymph capillaries.(Once inside the lymph capillaries) the fluid is known as

       lymph.

P6: The lymph capillaries unite to form larger lymphatic vessels.

P7: From the lymphatic vessels, lymph eventually passes into one of two main channels,

       the thoracic duct or the right lymphatic duct.

P8: The right lymphatic duct( receives lymph from the right arm, shoulder area, and the

       right side of the head and neck) and empties Its lymph into the right subclavian vein.

P9: The thoracic duct (receives lymph from the left of the head, neck and chest, the

       upper limb and the entire body below the ribs) and empties its lymph into the left

       subclavian vein.

P10:Hence, lymph  drains back into the blood circulatory system from / by subclavian

        vein.

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Madam Boon @ Embun Bt. Eli