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Circulatory System in Finfish and Shellfisharteriosus. Inspite of containing four parts, the heart of a fish isBlood-circulation (1)arteriosus. Inspite of containing four parts, the heart of a fish is
considered two-chambered.
The heart
Sinus venosus
: The first chamber is called the sinus
venosus, it is the preliminary collecting chamber. In teleosts
it is filled from two major veins called the hepatic veins and
the left and right branches of the Curvierian ducts which in
turn collect blood from the paired (left and right) lateral veins
the inferior jugulars, the anterior cardinals and the posterior
cardinals. However in the elasmobranchs only one hepatic
vein leads into it.
Atrium
. From the sinus venosus the blood flows into the
atrium. the atrium is the largest of the chambers and weakly
muscular. It pushes the blood, with weak contractions in the
ventricle.
Ventricle
. The ventricle is the only well muscled chamber,
nearly as large as the atrium it is the work horse of the heart,
its contractions drive the blood around the body.
Bulbus arteriosus
The last chamber of the fish heart is called the bulbus
arteriosus in the teleosts, but the cornus arteriosus in the
elasmobranchs. The difference between these chambers
is that the cornus arteriosus of sharks and rays contains
many valves while the bulbus arteriosus of bony fish
contains none. Both are alike in being primarily elastic
and work to reduce the pulsed nature of the blood leaving
the ventricle giving it a more even, constant flow.
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