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Wednesday, 15 July 2009 02:54
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Scoliodon commonly called as shark fish is a poikilothermic (cold blooded) animal. It is cartilaginous fish. Rana (frog) is also poikilothermic and amphibious animal. The circulation of blood in vertebrates is of closed type. The blood vessels which collect blood from various parts of the body are known as veins. The walls of the veins are thin and possess valves. Their lumen is wide. They collect deoxygenated blood from different parts of the body and carry to the heart. The veins are formed by means of capillaries in the respective tissues or organs. The deoxygenated blood first enter into the sinus venosus which is the part of the heart. The portal veins are having capillaries at their both ends. The pulmonary veins possess oxygenated blood.
1. The venous system comprises a system of large thin walled sinuses which collect blood from the different body organs 1. The venous system comprises of thin walled tubular veins.
2. It consists of the following systems i) Anterior cardinal system ii) Posterior cardinal system iii) Hepatic porta! system iv) Ventral veins vi) Cutanecious system 2. It is divided into i) Anterior system of veins ii) Posterior system of veins iii) Portal systems.
3. The anterior cardinal system and the interior jugular sinuses collect blood from the head region through a number of sinuses. 3. The blood from the head region is collected by a pair of precoval veins. Each precaval vein is formed by External jugular, innominate and subclavian veins.
4. The blood from gills is collected by five pairs of dorsal nutrient sinuses and five pairs of ventral nutrient sinuses. 4.The blood from the lungs is collected by a pair of pulmonary veins.
5. The nutrient sinuses carry deoxygenated blood. 5. The pulmonary veins carry oxygenated blood.
6. The nutrient sinuses empty into anterior cardinal and interior jugular sinuses which inturn open into the ductus cuvieri. Thus the blood finally carried to the sinus venosus. 6. The pulmonary veins open into the left auricle.
7. From the posterior part of the body the blood is collected by i) a pair of posterior cardinal sinuses ii) a pair of lateral abdominal veins iii) a pair of brachial veins. 7. The blood from the posterior part of the body is collected by i) renal portal system and ii) Post caval vein.
8. The renal portal system includes the caudal vein and the renal postal veins & Iliac veins. The blood from the pelvic fins is not carried to the kidneys. 8. The renal portal system consists of veins hind limbs i.e. femoral, sciatic and renal portal veins. The caudal vein is absent.
9. It is absent. 9. A part of the blood from the hind-body is transported to the liyer by an anterior abdominal vein.
10. The blood from the kidneys is collected by renal veins which open into posterior cardinals, opening into the cuvierian sinus. 10. The blood from kidneys is collected by four pairs of renal veins which open into the post caval vein.
11. The brachial veins join the lateral abdominals to form sub clavian veins which open into the ductus cuvieri. 11. The brachial veins open into the precaval veins particularly into the subclavian veins.
12. Three pairs cutaneous veins collect blood from the muscles of skin and open into the cardinal sinuses, lateral abdominals and brachial veins. 12. The cutaneous veins are only one pair which join with muscular & brachial and finally open into the subclavian veins.
13. The venus blood does not enter the sinus venosus directly. But it is collected first by the cuvierian sinus present transversely. 13. The blood collected by the two precavals and one post caval veins directly enters into the sinus venosus.
14. The blood from the parts of the alimentary canal is collected by the Hepatic portal vein and empties into the liver and from there it is transported by Hepatic sinuses into the sinus venosus. 14. The Hepatic portal vein collects blood from the different parts of the alimentary canal and empties into the liver. From the blood is transported into the sinus venosus through the hepatic veins and post caval vein.

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Last modified on Friday, 05 January 2018 17:10
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