Circulatory System Of Cockroach :
The cockroach shows open or lacunar type of blood vascular system. Blood, i.e, haemolymph freely flows in sinuses or lacunae.
Haemocoel :
Body cavity of cockroach is called haemocoel (haema=blood, coel=cavity) as it is filled with blood called haemolymph. Haemoceol is divided into three comparetments by the performed horizontal muscular septa called dorsal and ventral diaphragms. So, all the three compartments are in communication with one another. Three compartments are:- a) Dorsal sinus is pericardial sinus showing presence of tubular heart,
b) The middle sinus is perivisceral sinus containing visceral sinus containing visceral organs and
c) Ventral sinus is perineural sinus showing presence of central nerve cord.
Heart :
Heart is elongated muscular tube situtated in the pericardial sinus. It is closed behind and open in front. It is 13 chambered and extends along the mid dorsal line of body. There are three thoracic chambers and ten abdominal chambers. Each chamber has a pair of openings in posterolateral position called ostia. It allows to flow the blood from posterior to anterior direction peristaltically.
Heart extends in head sinus as anterior aorta. Haemolymph has no role in transport of respiratory gases as it is devoid of respiratory pigment. Haemolymph is composed of plasma and haemocytes. Plasma consists of absorbed blood and nitrogenous wastes. About 30000 haemocytes are present per cubic millimeter of blood.
Alary muscles :
There are 12 pairs of alary muscles which are attached to dorsal diaphragm. Pointed outer ends of alary muscles are connected tp terga.
Blood Circulation :
Pulsations of heart are caused due to the muscular wall probably assisted by alary muscles During diastole, the haemolymph from pericardial sinus enters into the heart through ostia, while during systole, ostia get closed and haemolymph is propelled forward. The heart chambers and anterior aorta contract peristaltically from behind forwards driving the blood into the head sinus. From the head sinus, the blood returns back to the perineural sinuses
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| Circulatory system of cockroach |
The mechanism of circulation is shown by following chart-
