Venous system – In Scoliodon, the venous blood from the entire body is returned to the heart by the veins.. Veins have thinner walls in comparision to arteries and possess valves to prevent backward flow of blood. Many veins form wide irregular spaces devoid of walls called sinuses which is the characteristicof venous system of elasmobranchs. The venous system of Scoliodon includes – (i)Anterior cardinal system – The anterior cardinal system collects blood from the parts of the body lying anterior to the heart (Fig.9.15).It consists of – (a) Inferior jugular sinus – It is the smaller median ventral sinus which collects blood from the floor of bucco-pharyngeal region, gill pouches and pericardial region before opening into the ductus cuvierius. b) Internal jugular vein or sinus – It is the larger dorso-lateral sinus which collects blood from the dorsal region of head and gill pouches through different sinuses.
(i)Posterior cardinal or renal portal …show more content…
Posteriorly, it receives blood from pelvic fin, anteriorly, it collects blood from pectoral fins and forms a subclavian vein which enters the ductus cuvierius laterally.
(iv) Cutaneous system – *The cutaneous system consists of a dorsal, a ventral and two lateral cutaneous veins. *The inferior lateral cutaneous vein joins with the lateral cutaneous vein near the anterior end of the pectoral fin. *Each lateral cutaneous vein lastly opens into the brachialvein. *These collect blood from their respective parts of skin and finally pour it into the sinus venosus through ductus