The circulatory system of insects is open and transports nutrients, waste, and aids in defense. It consists of a hemocoel body cavity and a dorsal vessel heart tube. The hemocoel is divided into three sinuses by diaphragms. Blood flows through ostia into the dorsal vessel which pumps it through the body during systole and diastole. Accessory pulsatile organs help circulate blood to appendages. Phagocytic organs filter the hemolymph. Blood moves posterior to anterior via peristalsis through the hemocoel sinuses and organs before returning to the heart.

1. PRESENTED BY
BHAVNESH THAKUR
ROLL NO- CUHP18ZOO09
Circulatory system of
Insects

2. INTRODUCTION
There are two types of circulatory systemsin theanimal kingdom
In insects the blood flows through the body cavity (i.e., heamocoel)
irrigating various tissues and organs. It is known asopen type ofcirculatory
system.
Circulatory system doesnot carry oxygen along its circulation but it carries
nutrients, salts, hormones, metabolic waste
Also play crucial role in defence as it seal off wounds through clotting
reaction

3. Organs of insect’s circulatory system
1. HAEMOCOEL
2. DORSAL VESSEL
3. ACCESORY PULSATING ORGANS
4. PHAGOCYTIC ORGANS
Main organ

4. Haemocoel of the insects is divided into 3sinuses (or) regions due to
the presence oftwo fibro muscular septa (or) diaphragms composed of
connective tissues
1)Dorsal or Pericardial Sinus: The area lying in between the
tergum and dorsal diaphragm . It containsheart.
2)Ventral or Perineural Sinus: Thearea lying in between thesternum
and ventral diaphragm. It contains nervecord.
3)Visceral Sinus: Thearea in between dorsal and ventral diaphragms .It
harbour the visceral organs like alimentary canal andgonads.

5. T.S. of cockroach showing haemocoel

8. DORSAL VESSEL
It is the mainorganof circulationand is differentiated into 2 parts i.e
anterioraortaand posteriorheart.
The dorsal vessel is a simple tube closed at its posterior end
and bears a number of vulvular openings called as ostia (
prevents back flow of haemolymph)
The number of ostia ranges from 12 to 1

10. Image showing dorsal vessel and ostia

11. Ostium of heart in insects

13. Accessory pulsatile organs
Insects consists of sac like, membranous structures which
are present at the base of the appendages such as wings,
legs and antenna.
They pulsate independently and supply adequate blood to the
appendages.
Function as accesory hearts which pump blood from sinuses
to respective appendage
They often beat at higher rate than dorsal vessel

16. Phagocytic organs
 These are triangular shaped sacs in anterior region of
abdomen
 Dorsal wall is formed of phagocytic cells while ventral is
formed by dorsal diaphragm while ventral wall from dorsal
diaphragm
 Heart open into phagocytic organs by excurrent ostia
 Lumen is filled with multinucleated cells
 Function of phagocytic organ is to filter haemolymph

17. Mechanism of circulation
Cardiac cycle: ( systole & diastole)
Peristaltic wave originate at posteriormost end and Haemolymph
circulation take place from posteriorendtotheanteriorendinforward
direction.
Diastole is myogenic while systole is brought by contraction of
muscles of dorsal vessel
General circulation
Diastole (relaxation ) ostia open (blood go inside heart)
Systole (contraction) ostia closes( prevent outward flow of
blood from heart + forward movement of blood into aorta)

18. Haemolymph discharged from anterior aortic orfice into cephalic
haemocoel now haemolymph flows from head to thorax to abdiminal
haemocoel

20. Circulation in appendages

21. Heart beat
Frequency ranges among insects from 14 beats/min to 150
beats/min
It is higher in preimaginal stage, freshly moulted insect
Pacemaker that initiate the heartbeat is located in posterior most
end of dorsal vessel

22. Relationship between cardiac cycle and haemolymph
volume in dorsal vessel