7th Class Science Transportation in Animals and Plants Lymphatic System

     Lymphatic System

There is one more system that helps in the work of transportation, known as Lymphatic System.

Lymphatic system consists of lymph capillaries, lymph node and lymph. When blood passes through blood capillaries, blood plasma containing glucose and water leaks around the body cells through the walls of capillaries, since walls of capillaries are very thin. Here exchanges of substances occur between the cell and this leaked fluid (tissue fluid). The tissue fluid receives waste materials from the cells and seep back into blood capillaries. Tissue fluid also receives protein molecules, fragment of dead cells, germs etc., which cannot enter into blood capillaries because of their larger size. Therefore, they enter into lymph capillaries through the pores present in their wall. Lymph capillaries by joining together form lymph vessels. Lymph vessels contain lymph nodes, which have lymphocytes. Lymphocytes fight against the pathogens. Lymph contains, germs, fragments of dead cells, proteins etc. which can harm the body. Therefore, function of the lymph node is to clean the lymph and protect the body from diseases. Lymph capillaries reach this fluid into vein and thus liquids once again come in circulation.

Look at the following picture of human circulatory system                 

      Lymph seeps back into lymph capillaries through..........

(a) Pores

(b) Close ends

(c) Open ends

(d) Blood capillaries

(e) None of these

Answer: (a)

         Name the cells of the lymph node, which eats germs, fragment of dead cell etc. and helps in protecting the body from diseases

(a) RBC

(b) WBC

(c) Lymphocyte

(d) Antigens

(e) None of these

Answer: (c)

All the multicellular form of life needs a transport system for transportation of required material and for removing of waste materials.

In plants, xylem is responsible for transportation of water and minerals and phloem is responsible for transportation of food and hormones.

Xylem is made up of dead cells, whereas phloem is made up of living cells.

Evaporation of water through stomata is called transpiration.

Animals require more evolved form of transport system as they have to move from one place to another.

There are four components of blood. These are plasma, RBC, WBC, and platelets.

When pathogens enter our body, WBC of the blood kills them to protect us from the diseases.

Heart is specialized for producing movement in the blood..