The insect circulatory system is referred to as an open system because the hemolymph ("blood") is not contained in a vessel (artery & vein) system, but circulates freely within the hemocoel (body cavity).

The dorsal vessel is located just beneath the dorsal sclerites (tergum).

divided into two regions, a posterior heart and anterior aorta.

•The heart has a series of ostia (valved openings) that open to allow hemolymph to flow into the vessel.

The location of the heart and dorsal aorta of a bee.

Examples of the flow of the blood through the body of an insect.

dorsal vessel consists of an anterior aorta (located in the thorax) and a posterior series of hearts (located in the abodomen).

Contractions move posterior to anterior and carry blood from the abdomen toward the head.

Functions of the heart:1) Transport of nutrients around the body2) Movement of limbs, mouthparts, antennae.3) Molting -- by increasing pressure in certain parts

of the body.4) Thermoregulation

The haemolymph (blood)1. Is a clear fluid, colourless.2. Because of certain pigments (slightly

yellow and green)3. 5% - 40% of the total body weight.4. pH 6-7

Functions of blood1) Lubricant.2) Hydraulic medium (newly emerged

butterflies expand their wings by forcing blood through them)

3) Transport 4) Protection (blood cells) Phagocytosis = ingestion of foreign

particles such as bacteria, debris Encapsulation = clumping around invading

organisms, e.g. internal parasites Detoxification - e.g. rendering insecticides

non-toxic Blood clotting.

Blood contains:1. Water - about 90%2. Inorganic ions - dissolved salts of Na, K, Ca,

Mg.3. organic molecules - amino acids, sugars for

muscle use4. Blood cells Types of blood cells1. Proleukosit- small cell, large nukleus.2. Fagosit- large cell, wound healing.3. Enositoid.- large cell

CIRCULATORY SYSTEMS

Types of hemocytes.