Arthropoda
Arthropods are a phyla that many people see today as simply spiders. There are many forms of arthropods that people do not recognize such as insects and crustaceans. You see them from spiders to centipedes. Arthropods are seen at least once in someone's daily life. This is the largest of the animal phyla with over one million species and an impressive estimate of more than one quintilian individuals alive to this day. In only insects, there is an estimated ratio of two hundred-million insect for a single person. This does not include millipedes, centipedes, crustaceans and spiders.
General Arthropods
Arthropods possess what we call an open circulatory system. There system consist a dorsal heart and arteries. The heart and arteries can be very limited, as to the body of an insect, or very extended, as to the body of a crab. The blood is pumped by the heart. It then moves through the body cavities to reach the internal organs. There are no veins to bring the blood back to the heart. It is for this reason that blood for the insects is called "hemolymph". Regular body movements allow for the blood to travel to the dorsal, also known as pericardial, sinus. Tiny valves open from the heart in other for the hemolymph of the insect to enter the hear once more. The cycle is then repeated for the duration of the insects life. The circulatory system also plays a role in defense for its organism.
Insects
The circulatory for the insect is again an open circulatory system. This system seals off wounds, destroys internal parasites, and produces toxins to ward off predators. In some insects, the circulatory system aids in ways as a thermoregulation in which it helps cool or heat the body. A dorsal vessel, heart, is important for the cell circulatory system. This a vessel in which it flows through the thorax and abdomen. This is a usually a fragile membranous structure that collects hemolymph to carry it towards the head. The heart is divided into segments that are separated by valves. This is to ensure a one way flow of the hemolymph. Alary muscles are attached to the walls of each chamber. The blood flow is controlled by peristaltic contractions. Basically, hemolymph flows through the heart to the head. Then the hemolymph flows to the internal organs. The blood flow then flows the opposite direction of the heart and reaches the end in which it flows back to the heart. he heart rate varies between each insect.
Spiders
The blood for spiders is colorless and is also called hemolymph. They are not entirely considered insects so they get there own section in this site. The circulation of blood transport nutrients throughout the body. Not only does it do that, but it helps in order body functions. Spiders The blood is used to raise pressure for when moulting, or shedding there skin, and stretching there legs. The spider is like the insect in that there are no veins to allow blood flow. the spider has hemolymph pumped through the heart which it then goes into sinuses surrounding the internal organ. The blood contains hemocyanin which is a respiratory protein that taints the hemolymph to its clear faint blue color. The dorsal vessel, heart is located in the abdomen and it is not divided into segments, it is like a tube. Through contractions, the aorta is able to move the blood to the and past the anterior of the heart. The heart allows hemolymph to enter one end of the heart and leave at the other end of it.