Question

How many chambers are present in the heart of a fish? How many times does the blood flow through its heart during each cycle?

Answer 1

Heart is the organ pump that generates the driving pressure for the circulation of blood. The heart of fishes is understood as a branchial heart, because its main function is to pump blood to ventral aorta into gills (branchial) so to somatic vasculature. Thus branchial and systemic vascular beds are arranged asynchronously with the heart.

Complete answer:
The hearts of fishes are two chambered, they need only 1 atrium and one ventricle. The fish heart resembles the embryonic condition of all other vertebrate animals. Afferent branchial arteries develop from aortic arches 3, 4, 5, and 6 to provide blood to the gills. The conus arteriosus could be a muscular extension of the ventricle which leads into the ventral aorta. At the posterior end of the center is the sinus venosus, a skinny walled space where blood from the veins gathers before entering the atrium. Blood strolling back from the fish's body enters the sinus venosus, a thin-walled sac where the most important veins coalesce. Expansion of the weakly muscular atrium pulls blood from the sinus venosus. Blood then flows from the atrium to the ventricle, strong contractions of the ventricle's thick muscular wall send the blood into bulbus arteriosus. From there, the blood flows into the ventral aorta and on through the gills. There are three valves within the heart to stop back flow during the expansion of the pumping chambers.

Fish have a really air mass vascular system. There's little pressure within the venous system and return to the guts is aided altogether by species by skeletal contraction and in some species by accessory hearts. By the time the blood reaches the sinus venosus, pressure is actually zero. Contractions of the atrium draw the blood from the sinus venosus and help fill the ventricle. Ventricular contractions generate the pressure to maneuver the blood through the body.

The bulbus arteriosus is neither contractile nor valved, but elastic. It expands with each ventricular contraction because it fills with blood and maintains aortic pressure during ventricular diastole. In terms of pressure, the gills are somewhat restrictive, with blood cells meeting resistance within the lamellae. When the ventricle contracts, it sends a charge of blood into the bulbous, when the ventricle expands, the valve between the bulbous and therefore the ventricle keeps the blood from going back to the ventricle. Let alone the resistance of the gills, this causes the elastic bulbous to expand, then because the blood continues to flow through the gills the bulbous begins to "deflate", then comes another charge of blood from the ventricle. The bulbous functions to average out the pressure extremes and keep a steadier flow of blood inquiring the gills.

If teleosts didn't have a bulbous, then the blood would strongly pulse over the gills. It appears to be adaptive for the fish to maneuver the blood across the gills at a more constant rate. However, there's some pulsing even with the bulbous, and fish actually synchronize their heartbeat with their opercular movements so as to match peak blood flow with the water pulses related to the buccal pump. This can be especially evident when fish are subjected to hypoxia.

In fish, the center only has one atrium and one ventricle. Oxygen-depleted blood that returns from the body enters the atrium, then the ventricle, and is then pumped out to gills where it is oxygenated, so it. Hence, blood flows just once within the fish. First the deoxygenated blood enters the atrium and so enters the ventricle. The blood is pumped towards the gills where the blood gets oxygenated and pumped to any or all body parts.

Note: In elasmobranchs, agnathans, and holosteans, the fourth chamber, termed conus arteriosus, isn't elastic, but fairly rigid, and its wall contains a series of valves to forestall backflow of blood. Since the conus may be a more primitive condition, we are able to think about teleosts having the conus reduced to 1 valve (between bulbus arteriosus and ventricle) with the bulbus arteriosus evolved from the ventral aorta. In lungfish and amphibians, there's a septum dividing the atrium into two chambers, but not the ventricle.