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Cockroach Circulatory System Short Notes

In this article we will discuss about the cockroach circulatory system

Cockroach Circulatory System

Cockroach circulatory system is an open type
The cockroach circulatory system is poorly developed and consists of haemolymph, haemocoel and heart

Haemolymph

Circulating fluid does not flow through vessels, rather comes in direct contact with tissues.
Haemolymph of cockroach is composed of colourless plasma and numerous types of haemocytes
The blood of cockroach is colourless due to the lack of respiratory pigment
They do not transport oxygen through the blood
Plasma serves transportation of dissolved substances
Haemocytes help in phagocytosis and blood clotting

Haemocoel

Body cavity is filled with blood, thus it is called haemocoel
Two diaphragm are present in body cavity
They are dorsal diaphragm and ventral diaphragm. These have pores called fenestrae
The diaphragm divides the haemocoel into three regions
1. Dorsal sinus – pericardial sinus has hearts
2. Middle sinus – perivisceral sinus has alimentary canal and fat body
3. Ventral sinus – perineural sinus has nerve cord

Heart

Elongated, contractile lying along the mid dorsal line of thorax and abdomen
Cockroach has a 13 chambered tubular heart
Heart is differentiated into funnel shaped chambers with ostia on either side. These pores act as valve.
12 pairs of triangular fan-like muscles found in the heart of the cockroach is called alary muscles
Alary muscles involved in the role of contraction and relaxation of the heart
Blood enters from pericardial sinus to heart through ostia when heart chamber relaxes
Each heart chamber pumps blood into anterior chamber when it contracts, and thus blood reaches into head sinus

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How Circulatory System Works?

Heart pump blood into head sinus through a long tubule called anterior aorta
Blood moves from head sinus to perineural sinus
Fenestrae help blood flow from perineural sinus to perivisceral sinus
Finally blood flows from perivisceral sinus into pericardial sinus
In addition contraction of dorsal diaphragm also helps in rapid circulation of haemolymph
The rate of heart beat in periplaneta is 49 beats/minutes
Blood circulation in cockroach is completed in 5-6 minutes.

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