[Biology Class Notes] on Malpighian Tubules Pdf for EXAM

Malpighian tubules are the structures that are present in insects and they are helpful in the process of excretion and osmoregulation. We will learn about them by taking the example of cockroaches. There are a number of Malpighian tubules in cockroach. The main function of malpighian tubules is to help in the process of excretion. In this system of malpighian tubules, branched tubules are present and these tubules are extending from the alimentary canal of the cockroach. This system helps in the absorption of water, solutes, and waste from the surrounding tissue that is the hemolymph. In the form of calcium oxalate and nitrogenous molecules, these wastes are released into the surrounding. Malpighian tubules in humans are absent. Instead of malpighian tubules, we have the kidneys that help us in filtering out the waste products from our body. Now we will learn more about cockroaches and the malpighian tubules present in them. 

Cockroaches

These are nocturnal animals, which means that these animals come out at night. They are placed in the  Phylum Arthropoda and they are insects. They have jointed legs and are termed cursorial animals as they run on legs. These organisms are omnivorous in nature. They are found almost everywhere. They are found in places of warmth and damp environments and also where plenty of organic food material is present. They are a cause of several diseases and major agents of food poisoning. 

Excretory System in Cockroaches

For the process of excretion, malpighian tubules are present in cockroaches. There are a number of malpighian tubules in cockroach that help in the process of excretion and osmoregulation. The amount of water, nitrogenous materials, and inorganic salts are regulated by the help of these structures. Malpighian tubules are also helpful in regulating the hemolymph. To the junction of the midgut and hindgut, these structures are connected. A number of malpighian tubules in cockroaches are blind tubules that are present freely in the hemolymph. They are very fine in nature. They are yellowish in color and unbranched in nature. Glandular epithelium helps in lining each of the malpighian tubules. At some places, brush bordered ciliated cells are also present. The function of malpighian tubules is to absorb the nitrogenous waste products and then help them to convert into uric acids. These uric acids are then excreted out from the hindgut. This states that cockroaches are uricotelic in nature. 

This gives us a clear understanding of what are malpighian tubules. Apart from malpighian tubules, there are other excretory glands that are present in cockroaches. 

They are Listed below:

• Fat Body: As the name suggests, fat cells are present in it. These cells are present below the body wall. These cells help in filling most of the spaces that are present in the body where internal organs are not present. The function of these cells is to store uric acid and also helps in accumulating and producing uric acid. 

• Nephrocytes: These cells are large and colorless in nature. They are present as binucleate cells and are attached to the dorsal diaphragm in the body cavity. Also, these structures are found attached to the sides of the heart. 

• Uricose Glands: Uricose glands are present in some of the species of cockroaches. Uric acid is synthesized by these glands. 

Respiratory System in Cockroaches

It is more efficient in cockroaches than that present in earthworms. This is because there are definite respiratory organs that are present in cockroaches. Blood is not used for respiration, because the oxygen from the atmosphere comes directly in contact with all the organs of the body. Spiracles, trachea, and tracheoles comprise the respiratory network of the cockroaches. The spiracles are slit-like openings that are present in 10 pairs. Bristles and hair help to guide them from the dirt. Sphincters help in regulating the opening of the spiracles. These spiracles then reach the tracheal chamber and then from there arises the main tracheal trunk. The trachea is elastic and branched air tubes that are present in the hemocoel. They have a tissue fluid at the distal end and this helps in playing a very important role in the exchange of gases. They are further divided into tracheoles. They penetrate to all parts of the body.