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BIOLOGY-XI, BODY FLU, 384, The, the, Intern, • Th, back to the major veins., – The fluid present in the lymphatic system is called lymph. Lymph performe u, following functions:, -, atr, (i) Lymph contains specialised lymphocytes, which are responsible for the immus, responses of the body., (ü) It is also an important carrier for nutrients, hormones etc., (üi) The lymph present in the lacteals in the intestinal villi is involved in the absorntion, of fatty acids and glycerol., Circulatory Pathways, The circulatory patterns are of following two types:, (i) Open circulatory system, cavities called sinuses e.g., in arthropods and molluscs., (ü) Closed circulatory system, closed network of blood vessels e.g., in annelids and chordates., - The closed circulatory system is more advantageous as the flow of the blood can, be more precisely regulated., - the blood is pumped by heart into open spaces or body, -, -the blood pumped by the heart is circulated through a, -, Types of Hearts, All vertebrates possess a muscular heart, which may be 2, 3 or 4 chambered., (i) 2-chambered heart with an atrium and a ventricle is present in fishes., - It pumps out deoxygenated blood, which is oxygenated by the gills and supplied to, the body parts and returned to the heart after deoxygenation (single circulation)., (üi) 3-chambered heart with two atria and a single ventricle is present in amphibians and, reptiles (except crocodiles)., - Here, the left atrium receives oxygenated blood from the gills/lungs/skin and the, right atrium gets the deoxygenated blood from other body parts., - The two types of blood get mixed up in the single ventricle, which pumps out, mixed blood (incomplete double circulation)., -, -, (iii) 4-chambered heart with two atria and two ventricle is present in crocodiles, birds., and mammals., - Here, oxygenated and deoxygenated blood received by the left and right atria, respectively, and passes on to the ventricles of the same sides., - The ventricles pump it out without any mixing up i.e. there are present w, separate pathways of circulation (double circulation)., -, Human Circulatory System, Human circulatory system, also called blood vascular system consists of:, (i) a muscular chambered heart,, (ü) a network of closed branching blood vessels, and, (ii) blood, (the circulating fluid)., Heart, lungs, slightly tilted to the left., • It has the size of a clenched fist.