HeartThe rear part of the dorsal vessel, in the abdomen. Its chambers pump hemolymph forward.
AortaThe slender front part of the dorsal vessel. It opens near the brain.
Dorsal vesselThe whole tube along the back. The heart is its rear part and the aorta its front part.
OstiaSlits in the side walls of each chamber. Hemolymph enters the heart through them.
Alary musclesFan-shaped muscles from the heart to the body wall. Together they make up the dorsal diaphragm.
The body cavity 5
Hemocoel (body cavity)The body cavity. Hemolymph fills it, around all the organs.
HemolymphThe blood of an insect. It flows through the body cavity and bathes the organs.
Pericardial sinusThe space around the heart, above the dorsal diaphragm.
Dorsal diaphragmA thin sheet under the heart, formed by the alary muscles.
Ventral diaphragmA thin sheet over the nerve cord. It lies along the floor of the abdomen.
How this list was compiled: Every name checked on 2026-10-02 in two sources. North Carolina State University, General Entomology (ENT 425), Circulatory System, https://genent.cals.ncsu.edu/bug-bytes/circulatory-system/. J. H. Comstock, An Introduction to Entomology (1920, public domain), the circulatory system and the suspensoria of the viscera, https://archive.org/details/introductiontoen00coms. Wikipedia, Insect physiology and Insect morphology, the circulatory system, https://en.wikipedia.org/wiki/Insect_physiology. L. Bataillé and others, Frontiers in Cell and Developmental Biology 2024 (open access), on the alary muscles, https://europepmc.org/article/PMC/PMC10822924. T. Göpel and C. S. Wirkner, PLoS ONE 2018 (open access), on the heart of a cockroach, https://europepmc.org/article/PMC/PMC6147405. Licence: own work
The drawing: Drawn for this site on 2026-10-02 from plain geometry; nothing traced. Licence: own work
How it works
This insect heart diagram shows an insect cut along its length. The heart is the rear part of one tube along the back, the dorsal vessel. A frame shows three of its chambers from above.
Read the full guide
Follow the hemolymph
Hemolymph enters the heart through the ostia. The chambers squeeze one after another, from the rear forward, and push it into the aorta. The aorta opens near the brain. From there the hemolymph flows back through the hemocoel, around the organs, to the abdomen.
Around the heart
The alary muscles fan out from the heart to the body wall and form the dorsal diaphragm. The space above it is the pericardial sinus. The ventral diaphragm lies over the nerve cord. Press Quiz me to find each part yourself.
An insect has no veins or arteries. Outside the dorsal vessel, its blood moves freely through the body cavity.
Questions and answers
Do insects have a heart?
Yes. An insect's heart is the rear part of the dorsal vessel, a tube along its back. It lies in the abdomen, is divided into chambers and pumps hemolymph forward to the head.
What is the dorsal vessel of an insect?
It is the one main blood vessel of an insect, a tube just under the back. The part in the abdomen is the heart, and the slender part through the thorax to the head is the aorta.
What are the ostia of an insect heart?
Ostia are slit-like openings in the side walls of the heart, usually a pair in each chamber. Hemolymph enters through them, and a valve closes each one when the chamber squeezes.
Does insect blood carry oxygen?
Almost never. Hemolymph has no red blood cells. Oxygen reaches an insect's body through air tubes called tracheae, so the blood carries food, wastes and other substances.
Is a cockroach heart diagram the same?
A cockroach is an insect, so a cockroach heart diagram shows these same parts: a chambered heart along the back, an aorta in front and ostia in the heart's side walls. The number of chambers differs between insects.