![]() ![]() Bulbus aorta or synangium: short distal thin-walled.Conus arteriosus or pylangium: long basal thick-walled.The spirally twisted cavity of truncus arteriosus is divided unequally by another set of 3 semilunar valves into:.These valves prevent the backflow of blood from truncus into ventricle.3 semilunar valves guard the opening of ventricle into truncus arteriosus.Chordae tendineae are thread like structure that connects the flaps of auriculo-ventricular valves to the wall of ventricle.These highly reduce the cavity of ventricle.Columnae carnae or trabeculae (irregular strands or ridges).The ventricle has thick muscular and spongy wall.This aperture is guarded by two pairs of flap-like auriculo-ventricular valves.Both auricles open into ventricles by a common large auriculo-ventricular aperture.Likewise, the common pulmonary vein opens into left auricle, near septum, by a small opening without valves.It is guarded by a pair of flap-like valves. Sinus venosus lies close to the inter-auricular septum.The sinu-auricular aperture is a large transverse oval aperture.Sinus venosus opens into dorsal wall of the right auricle through the sinu-auricular aperture.The left auricle is smaller than the right.They are thin walled and are completely separated from each other by a thin vertical inter-auricular septum.There are two auricles, left and right.In order to keep the unidirectional flow of blood, the various chambers are separated by valves.When the frog is sectioned, its internal structure is visible.It immediately bifurcates anteriorly into two branches, each again breaks into three arches i.e.Truncus arteriosus: It is a tubular chamber that arises anteriorly from the right ventral side of ventricle.Sinus venosus: It is dark colored, thin-walled and triangular chamber. ![]() Two additional chambers are present in the heart of the frog i.e.However, a narrow transverse auriculo-ventricular groove or coronary sulcus clearly marks off the two auricles from ventricle.A very faint longitudinal inter-auricular groove demarcates the two auricles externally.One ventricle: It is pink colored, conical and lies posteriorly.Two atria or auricles (right and left): It is dark colored and lies anteriorly.There are 3 chambers in a heart of frog.Visceral pericardium closely invests the heart.The inner wall of pericardium is termed as visceral pericardium.The outer wall of pericardium is termed as parietal pericardium.It is thin, transparent, two-layered sac.It has the broad base which is directed anteriorly and the narrow apex posteriorly.It is somewhat conical or triangular in shape.It is protected by the pectoral girdle.Heart lies mid-ventrally inside the anterior trunk region.It drives blood through the closed circulatory system.The heart is muscular central pumping station.It also brings away the liquid and gaseous wastes of metabolism to the organs of elimination. Its main function is to transport all essential liquid and gaseous materials to the living tissues.The blood vascular or circulatory system of frog is closed. ![]()
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