 In this practical, we will learn about the excretive waste, excretory system, role of excretory system to maintain the homeostasis of animal, different excretory organs that are found in different invertebrates, pathways for the formation of excretive waste in the animal body. First of all, we will see what is the excretory system. Excretory system is basically a passive biological process that is used for waste formation and mostly in that waste are toxins and extra salt, extra water that is present in the excretory waste and it is removed from the body. What is the importance of excretory system in the body of the animal, it is that we consider it as an example. For example, if a green tea is made and what does it do, it stains the leaves and what is the liquid part of it, it is intake. Similarly, in the body of the animal, we also intake the liquid and the solid part of it. But all the compounds, all the nutrients that are present in the body of the animal are not required or are not important for every cell. So, whatever extra nutrients you have, either in the form of heavy metals or different metabolites of drugs or different salts, they should be removed from the body. So, for their removal, there is a system in the animal that we call the excretory system. What is the importance of excretory system is that it maintains the level of salts, water in the animal body. Apart from that, it removes the extra metabolites, toxins, minerals from the animal's body and also maintains the level of pH in the animal's body. Now, we will see how many types of excretory system are present in the excretory system and which excretory organs are present in the excretory system. Invertibrates are basically animals that do not have a backbone. They are mostly in the category of lower animals. If you look at it from an evolutionary point of view, then the first evolution in the animal kingdom is that you have invertebrates. Now, the excretory system of invertebrates is like the rest of the animals. In that, the aquatic invertebrates are mostly excretive ammonia. Which requires a lot of water for removal from the animal's body. And the terrestrial invertebrates have excretive waste, uric acid. For the removal of uric acid, the amount required for water is very less. Now, the aquatic invertebrates also have two categories. One is marine invertebrates and the other is freshwater invertebrates. Now, the marine invertebrates are in the environment where the animal is surviving and where the concentration of salt is very high. So, what happens is that their body fluids and the liquid outside, the composition of the water is more or less similar. So, the urine produced will be an isotonic urine. An isotonic urine means that the composition of the animal's body fluid will be of that urine and the composition of that urine will be similar to the composition of the water. Except that the potassium in the urine will be less and the magnesium will be more. Whereas, if we talk about freshwater invertebrates, they are in an environment where the body fluid and the concentration of salt is more and the outside is less. So, to keep it safe, the animal that produces salt produces an isotonic urine. The salt in that urine has less concentration whereas the urine in the animal's body and the salt in that urine has more concentration. Now, let's look at some invertebrates. For example, we have succinoderms, sponges, and nardarians. There is no such excretory system in them. Mostly, through diffusion, extra water or extra salt is removed from the body. So, the balance of water and salt is maintained on a cellular level. Whereas, if we talk about the other invertebrates, like flatworms, annulates, lescans, arthropods, in that, if we look at the protozones kingdom, we find 5 main types of excretory organs. In that, you have contractile vacuoles, nephrodium, renal glands, coxal glands, and malipigian tubules. Now, we will see one by one which excretory organs are present in the invertebrate animal and how they perform their function. How do we remove the excretory waste from the body? First of all, we will look at contractile vacuole. What is contractile vacuole? Basically, you have a sac-like organelle and it intakes the water inside you and removes it from the body. What is it mostly? It is in the protozones in which we have this uglina. You can see the contractile vacuole inside the uglina. This is the contractile vacuole. This is the circular part and these are the radiating canals through which the water will enter the contractile vacuole. Similarly, we have amoeba. This is the circular shape contractile vacuole. In this, the extra water or the salts come inside it and they are removed from the body from the body of the animal. Now, basically, we will see how the water enters the contractile vacuole and how it is removed. The first thing is that these are radiating canals. What will happen in this? The body of the animal is a cytoplasm through which the water will enter these canals and this contractile vacuole will enter here. When the contractile vacuole is filled with water and there is no capacity to take the water inside these radiating canals will shrink. The contractile vacuole will move from here to the cell membrane and there will be a pore and the extra water through the cell membrane will be removed from the body of the animal. Similarly, the radiating canals will take the water inside and transfer it in the vacuole and the pore will be removed and the water will be removed. This is a continuous cycle. It depends on how much water the animal has and how much water it has to remove and how much salt it has to remove from the body. Next, we have an excretory organ, nephrida. Nephrida is tubular-like excretory structure which is an ancient invertebrate which was present in it. Now, the nephrida is based on the structure and complexity of the structure. We have protonephrida. Protonephrida is mostly flatworms or rotifers or ribbon-like worms. The evolutionary point of view of first animals is evolved. Next, you have metanephrida and metanephrida mostly in which all the animals have metanephrida. Then, we will see what is protonephrida and how it performs its function. This is the simplest form of the excretory system which is developed in the animal. We will see what is present in it and how excretory waste is made and how it is removed from the body. If we look at its structure here, what is here? These are celias. First of all, the structure you are seeing is a plane area. The tubular-like structure you are seeing in the plane area is flame cells. You can see the flame cells. Slits are present and narrow tubules are present in it. There are small thread-like structures called celias. What happens is that these celias move and the extra water comes into these tubules. Water comes into these tubules and the main duct which is called nephridial duct goes into it and it is removed from the body of the animal through nephridial pore. If we look at metanephridia, most of the earthworms are present and in its structure what happens is there is an opening called nephrostome. After that, nephrostome leads a very coiled tubule. Here, its nephridiotubules are present and the nephridiotubules remove the excretive waste from the body through a pore that is called nephridiopore. We will see how the waste is removed. First of all, you can see what you can see in the structure of metanephridia. You can see the very small celias. What do these celias do? These celias when they are beets you have an opening called nephrostome where you have excess water and the salt will come here. After that, the water salt will move in the tubule and the celiated tubule will move here. From here, you can see what is happening here. In the non-celiated tubule in the non-celiated tubule there will be a storage tube where there is a muscular tube which is called a bladder. From the bladder, the air will go out through the nephridiotore through the body of the animal. This is how metanephridia is made and removed from the body. Next, you have the excretive structures in the orthropods which are mostly coxal glands and in the water there are coxal glands in the orthropods. Now, where are the coxal glands basically? As you can see in the structure this is the leg of the animal and on its base there are coxal glands. If we look at the structure of the coxal glands then what is mostly in it? It is a tubular structure and it is divided in different regions and we have given a different name to each region. First of all, the coxal glands are the skeleton, the hydrostatic skeleton or the slumic fluid which is open inside. It is a sac-like structure which is called a secure sac which is given as labyrinth and from labyrinth some of the orthropods like the crabs or lobsters do not have tubules and the fluid that is in the labyrinth goes directly into the bladder. While some of the orthropods are like crayfishes the fluid that is here goes inside the tubule inside the bladder and this bladder here is a small opening and through it the waste that has come in the coxal glands removes it. Next, if we look at the excretive system, moloscans are mostly water living whereas some of them are on land for example land snares This structure that we can see in the picture is a freshwater muscle and its visceral mass its internal anatomy you can see it. In moloscans, nephridia or renal glands are present here. This tubular-like structure is called nephridium and if it is multiple it is called nephridia. What is present here is the structure. So whatever is the Islamic fluid or whatever is the blood will pass through this nephridium and in this nephridium the extra water and salt will go inside it and in this way the blood will become filtered and the extra salt or water or extra nutrients will be filtered and this nephridium-nephridiopore or the mental which is present here will be removed from the waste. The last excretive organ that we are studying in invertebrates are malipigian tubules which are present mainly in insects and also in cockroaches and in honey bees and in ants and in wasps Malipigian tubules are actually blind-end tubes are blind-end tubes which are present in the mid-gut and hind-gut of animals If we look here we can see the structure of cockroaches and here you can see malipigian tubules and these are the digestive parts and these are the malipigian tubules Here you have the hind-gut and in between malipigian tubules are present blind-ends and in the salomic fluid these are the internal organs which are removed to explain basically these malipigian tubules are present in the salomic fluid If we look closely at the structure these are the malipigian tubules and these are the mid-gut and hind-gut and the malipigian tubules are present in the junction If we look at how the excretive waste is made then what happens is that in the malipigian tubules first comes the salts and in salts also there are positive ions for example potassium, sodium, magnesium they all come in these tubules through the diffusion because the salt concentration is more there are positive ions so there will be negative ions like the colorides after that the salt concentration will be more so the water will come through the osmosis from here what we will do the malipigian tubules will move through the hind-gut and when they move towards the hind-gut the extra salt and water will absorb in the animal's body and the waste will be removed from the rectum first of all it will come in the rectum and then it will be removed from the anus so the malipigian tubules have to take the help of the rectum to remove the excretive waste and a single opening is used for the removal of the digestive waste and for the removal of the excretive waste students in today's practical what we have studied excretive organs, invertebrates first of all we have seen contractile vacuoles which are basically in the protozones after that we have studied nephridium and there are two types of nephridium protonephidia and metanephidia protonephidia are in the flatworms metanephidia are in the anidates renal glands and they are basically in the luskens and after that coxal glands are in the atheroports and in the atheroports also in the aquatic atheroports and after that malipigian tubules are mostly in the insects this is all about the excretive structures of invertebrates how they are in their own structures and how they make their excretive I hope that you have understood about excretive structures and mechanism of formation of excretive waste and you can draw it yourself and learn its different excretive structures thank you very much good luck