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This is known as single cycle circulation. The heart of fish is therefore only a single pump (consisting of two chambers). Fish have a closed-loop circulatory system. The heart pumps the blood in a single loop throughout the body. In most fish, the heart consists of four parts, including two chambers and an entrance and exit. [20]
Fish have the simplest circulatory system, consisting of only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as single cycle circulation.
In lungfish and tetrapods, the renal portal vein is joined by a vein traveling upwards from the abdominal vein, [4] which can bring venous blood from the hind limbs and ventral body wall into the renal portal system, or alternatively, enable blood from the tail and groin to pass into the hepatic portal system, already served by blood from the gut, via the hepatic portal vein, and from the hind ...
Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. Within the gill filaments, capillary blood flows in the opposite direction to the water, causing counter-current exchange. The gills push the oxygen-poor water out through openings in the sides of the pharynx.
A venous heart is the type of heart in which only blood with CO₂ circulates. Venous hearts receive blood from veins and pumps it for oxygenation. This type of heart is generally found in fishes. Its also known as the original heart and every other heart evolved from it, it has a accessory chamber where both oxygenated and deoxygenated blood ...
The blood is pumped by three separate hearts: two branchial hearts pump blood to the cuttlefish's pair of gills (one heart for each), and the third pumps blood around the rest of the body. Cuttlefish blood must flow more rapidly than that of most other animals because haemocyanin carries substantially less oxygen than haemoglobin.
Cephalopods are the only molluscs with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts ) that move blood through the capillaries of the gills . A single systemic heart then pumps the oxygenated blood through the rest of the body.
In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange. The muscles on the sides of the pharynx push the oxygen-depleted water out the gill openings. In bony fish, the pumping of oxygen-poor water is aided by a bone that surrounds the gills called the operculum. [6]