In the circulatory system of the Scoliodon heart is the main compartment, the heart in Scoliodon is surrounded by pericardium and the heart in Scoliodon is the branchial heart or venous heart.
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Heart and Pericardium in Scoliodon:
The respiratory organ in Scoliodon is the five pairs of gills, the gills are highly vascularized and the heart pumps the blood through the gill for gaseous exchange between the blood and the water. Such type of heart present in Scoliodon is known as branchial heart or venous heart.
Position of the Heart in Scoliodon:
In Scoliodon the heart is present on the ventral side of the body in the head region beneath the pharynx. The heart is supported by the coracoid cartilage of the pectoral girdle, the present at the mid-ventral position.
The heart in Scoliodon is protected by a double membrane covering known as pericardium which protects the heart from different types of mechanical injuries. The body cavity has two chambers, the smaller anterior body cavity is known as the pericardial body cavity in which the heart is present, the inner lining of the pericardial body cavity is made of the covering of pericardium.
Structure of Heart in Scoliodon:
In Scoliodon the heart is tubular S-shaped, the heart in Scoliodon has four chambers – sinus venosus, auricle, ventricle, conus arteriosus. Sinus venosus and conus arteriosus are only associated with the heart but the one auricle and one ventricle are the only chambers of the heart, so the heart in Scoliodon is two-chambered.
Sinus Venosus:
It is a thin-walled elastic triangular-shaped heart chamber present on the posterior end of the heart, sinus venosus receives deoxygenated venous blood from the whole body. On either later side of sinus venosus one large vein, ductus Cuvieri present, the paired ductus Cuvieri collects the venous blood from the whole body and sends it into the sinus venosus.
One pair of veins, hepatic sinuses also open in the sinus venosus in the posterior end of the sinus venosus, they also send the venous blood into the sinus venosus. The sinus venosus opens into the auricle a sinu-atrial or sinu-arterial aperture, the sinu-arterial aperture is guarded by a pair of valves that prevents the flow back of blood from the auricle to sinus venosus.
The highly contractile tissue present in this region generates the pumping activity of the heart and helps in the contraction of other parts of the heart.
Auricle:
It is a thick-walled triangular muscular sac present over the ventricle, on the anterior side of the sinus venosus, present dorsally in the pericardium. The two lateral sides of the auricle are extended laterally over the ventricle-like wings. The auricle is connected to the ventricle by an auriculo-ventricular aperture which is guarded by two-valve, the valve prevents the backflow of blood from the ventricle to the auricle.
Ventricle:
It is a thick-walled muscular pear-shaped sac-like structure present ventrally in the pericardium below the auricle. The inner wall of the ventricle has numerous muscle strands, chordae tendineae which are connected to the opposite sidewall of the ventricle, which prevents the heart to expand beyond a certain limit.
Conus Arteriosus:
The ventricle in the anterior part of the Pericardium opens into a tubular part, conus arteriosus. In the lumen of the conus arteriosus, two rows of the semilunar valve are present which prevents the backward flow of blood from the ventricle to the conus arteriosus.
The flow of Blood Through the Heart in Scoliodon:
In Scoliodon the heart only receives deoxygenated blood so the heart in Scoliodon is known as venous or branchial heart. The sinus venosus receives the deoxygenated blood from different parts of the body through the paired ductus Cuvieri and hepatic sinuses, the blood from sinus venosus goes inside the auricle.
From the auricle, the blood enters into the strong muscular chamber ventricle, from the ventricle the blood flows into the conus arteriosus. The rhythmic contraction of different parts of the heart pumps the blood through the branchial system of Scoliodon.
Detailed Study On
Respiratory System of Scoliodon
Digestive Glands and Feeding Mechanism in Scoliodon
Coelom and Viscera in Scoliodon
Placoid Scales In Scoliodon (Exoskeleton)
Skin of Scoliodon (Integument)
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