Fill in the blanks.
(i) The blood from the heart is transported to all parts of the body by the.
(ii) Haemoglobin is present in cells.
(iii) Arteries and veins are joined by a network of .
(iv) The rhythmic expansion and contraction of the heart is called.
(v) The main excretory product in human beings is.
(vi) Sweat contains water and.
(vii) Kidneys eliminate the waste materials in the liquid form called.
(viii) Water reaches great heights in the trees because of suction pull caused by .

(i) Arteries                                                                                                                                                                                                                                           Arteries have a thick, elastic layer to allow stretching and absorb pressure; it maintains the pressure in the circulatory system. The blood from the heart is transported to all parts of the body by the arteries and the arterioles. The arteries are the blood vessels that carry oxygenated blood from the heart to the tissues of the body through the capillaries.  

(ii) Red blood                                                                                                                                                                                                                                    Red blood cells are red in colour due to the presence of red pigment which is known as haemoglobin. Red blood cells carries oxygen from the lungs to all the cells of the body.                                                                                                                                                                                                                 

(iii) Capillaries                                                                                                                                                                                                                                  Capillaries are the extremely narrow blood vessels (less than 1mm long) which connect arteries to veins and are present in all regions of the body. Capillaries are also known as ‘blood capillaries. Usually blood passes from the heart in the sequence through arteries, arterioles, capillaries, venules and veins and then get back to the heart. 

(iv) Heartbeat                                                                                                                                                                                                                                  The spontaneous rhythmic contraction and relaxation of the heart to pump out and receive the blood to and from the body and completes one cycle of it, is called a heartbeat. The heart beats about 72 times in a minute that can be counted easily by counting the pulses. 

(v) Urea                                                                                                                                                                                                                                          Urea is a major waste product that is produced in our body. It is excreted through the urine is the major function of the kidney. 

(vi) Salts                                                                                                                                                                                                                                             Sweat contains water and salts, and a little of urea and which is removed from the body by sweat glands through the skin. 

(vii) Urine                                                                                                                                                                                                                                           The urea and other unwanted salts dissolve in water in the body to form a yellowish liquid waste of which excretion is important; called urine. For the production of urine, nephrons and collecting ducts performs three processes: glomerular filteration, tubular reabsorption and tubular secretion.

(viii) Transpiration                                                                                                                                                                                                                Transpiration is the loss of water from the aerial parts of the plants like leaves in the water vapours form; and this occurs through the stomata, cuticle or lenticels of the plants which is known as stomatal, cuticle and lenticels transpiration respectively.