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

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.