THE CIRCULATORY SYSTEM IN INSECTS
The circulatory system in insects mainly consists of dorsal vessel, the diaphragm and sinuses,
accessory pulsatory organs and blood. Insects have an open circulatory system. The blood
(hemolymph) occupy all the body cavity (haemocoel), the internal organs and tissues are exposed
freely to it.
DORSAL VESSEL
Circulatory system is usually open with only a single closed vessel referred to as DORSAL VESSEL.
The dorsal vessel is open anteriorly and closed posteriorly except in larval mayfly. It consists of
(a) anterior segment- AORTA and posterior segment called the HEART.
(A) AORTA: a uniform contractile tube with no ostium. It is slender anterior prolongation of the
heart, it carries the blood from the heart. It ends abruptly anteriorly. From this point the
blood supply simply percolates backwards through the tissue
(B) The HEART: The heart is located dorsally below the terga in the pericardial sinus.
It is often restricted to the abdomen or it may extend as far as the prothorax. It is provided
with series of valves.
The heart may be directly bound to the dorsal wall or suspended from it by elastic filaments.
A pair of alary muscles are attached laterally to the walls of each chamber.
The wall of the vessel is perforated by openings (ostia). In cockroach there are 13 contractile
heart chambers one connected to another (1, 2, 3= thoracic segment; 4- 13= abdominal
segment). The contraction is myogenic rhythm and hormonal control.
Alary muscles: These are muscles that are closely associated with the heart.
In Orthoptera ten abdominal and two thoracic pairs are present.
They form integral part of the dorsal diaphragm which spreads between them as
connective tissue membrane
,
The circulatory system in insects mainly consists of dorsal vessel, the diaphragm and sinuses,
accessory pulsatory organs and blood. Insects have an open circulatory system. The blood
(hemolymph) occupy all the body cavity (haemocoel), the internal organs and tissues are exposed
freely to it.
DORSAL VESSEL
Circulatory system is usually open with only a single closed vessel referred to as DORSAL VESSEL.
The dorsal vessel is open anteriorly and closed posteriorly except in larval mayfly. It consists of
(a) anterior segment- AORTA and posterior segment called the HEART.
(A) AORTA: a uniform contractile tube with no ostium. It is slender anterior prolongation of the
heart, it carries the blood from the heart. It ends abruptly anteriorly. From this point the
blood supply simply percolates backwards through the tissue
(B) The HEART: The heart is located dorsally below the terga in the pericardial sinus.
It is often restricted to the abdomen or it may extend as far as the prothorax. It is provided
with series of valves.
The heart may be directly bound to the dorsal wall or suspended from it by elastic filaments.
A pair of alary muscles are attached laterally to the walls of each chamber.
The wall of the vessel is perforated by openings (ostia). In cockroach there are 13 contractile
heart chambers one connected to another (1, 2, 3= thoracic segment; 4- 13= abdominal
segment). The contraction is myogenic rhythm and hormonal control.
Alary muscles: These are muscles that are closely associated with the heart.
In Orthoptera ten abdominal and two thoracic pairs are present.
They form integral part of the dorsal diaphragm which spreads between them as
connective tissue membrane
,
