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December 11, 2024Excretory System: Our bodies have efficient and complex systems that help us survive and keep us healthy. While we eat food daily with nutrients, it is the excretory system that is responsible for carefully sifting hazardous materials from the waste generated by the food and eliminating it regularly so that these harmful toxins do not stay in our bodies. Along with the respiratory, circulatory and digestive systems, the Excretory System is one of the most significant biological systems in our bodies.
Students must understand the human body and the functions that it performs. In this article, we will discuss in detail about different excretory organs present in humans and their functions and how urine is formed inside our body. Continue reading to know more.
The Excretory System is defined as a biological system that helps in the elimination of the nitrogenous waste products of metabolism and also helps in maintaining homeostasis in our body.
Animal Group | Excretory Organs |
Protozoans, Poriferans, Coelenterates | The plasma membrane, pellicle, and general body surface |
Ctenophora | Anal pores |
Platyhelminthes (flatworms) | Protonephridia with Flame cells |
Nemathelminthes or Aschelminthes (Roundworms) | Protonephridia and canals and Renette cells |
Annelida | Metanephridia and chloragogen cells |
Arthropoda | Malpighian tubules, coxal gland, green glands, or antennary glands |
Mollusca | Renal gland or organ of Bojanus and Keber’s organ |
Echinodermata | Tube feet (podia) and dermal branchiae (thin walls of gills) |
Chordata | Protonephridia, neural gland, pharyngeal nephridia, and Hatschek’s nephridium in cephalochordates, a pair of kidneys in vertebrates |
The human excretory system consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
The human excretory system includes the following organs:
3. Malpighian body is formed of Bowman’s capsule and Glomerulus which filters out large solutes from the blood and delivers small solutes to the renal tubule for modification.
Name | Description | Function |
Glomerulus | The tuft of thin-walled capillaries is formed by the branching of the afferent arteriole (a fine branch of the renal artery). | Involved in the ultrafiltration of blood. |
Bowman’s capsule | The double-walled, cup-like structure surrounds the glomerulus. | Receives the glomerular filtrate and passes it to the PCT. |
4. Renal tubule is a long, thin tubule attached to Bowman’s capsule with four distinct regions as follows:
Name of the parts | Description | Functions |
Proximal Convoluted Tubule (PCT) | 1. Located behind the neck of the Malpighian corpuscle making few coils. 2. Restricted to the cortical regions of the kidney. | 1. Majority of the reabsorption takes place here only. 2. Absorption of nearly all essential nutrients, \(70-80\%\) of electrolytes and water, \(\mathrm{HCO}_{3}^{-}\)ions. 3. Selective secretion of \(\mathrm{H}^{+}\)and \(\mathrm{K}^{+}\)ions and ammonia. 4. Also maintains the pH and ionic balance of the body fluids |
Henle’s Loop | 1. Quite narrower and U-shaped tube. 2. Having a descending limb that ends into the medulla and an ascending limb that extends back from the medulla into the cortex. | 1. Reabsorption of water, \(\mathrm{Na}^{+}, \mathrm{K}^{+}\),\(\mathrm{Mg}^{2+}\)and \(\mathrm{Cl}^{-}\). 2. The ascending limb is permeable to the urea. 3. Maintains the high osmolarity of medullary interstitial fluid. |
Distal Convoluted Tubule (DCT) | Thicker and highly coiled structure situated in the cortex. | 1. Active reabsorption of\(\mathrm{Na}^{+}\)ions and water. 2. With associated secretion of\(\mathrm{K}^{+}\), \(\mathrm{H}^{+},\) ammonia, some \(\mathrm{Cl}^{-}\)and \(\mathrm{HCO}_{3}^{-}\) ions are also reabsorbed. 3. Maintains the pH and \(\mathrm{Na}^{+}-\)\(\mathrm{K}^{+}\)balance in the blood. |
Collecting tubule (or Straight tubule) | 1. Last part of the nephron that combines and opens into a large collecting duct. 2. Extends from the cortex of the kidney to the inner parts of the medulla. 3. Many collecting tubules open into a large collecting duct. | 1. Water is reabsorbed as it is highly permeable to water. 2. \(\mathrm{Na}^{+}\) ions are also reabsorbed along with small amounts of water to maintain the osmolarity. 3. Maintains the pH and ionic balance of the blood by selective secretion of \(\mathrm{H}^{+}\)and \(\mathrm{K}^{+}\)ions. |
Kidney serves the following functions:
The ureter is a long, muscular tube that continues with the pelvis and emerges at the hilum, and opens into the urinary bladder.
It is a thin-walled, pear-shaped, white transparent sac present in the pelvic cavity and temporarily stores urine.
The formation of urine by the kidney takes place in the following three steps:
Following are the functions of the excretory system:
Following are the disorders of the excretory system:
Excretion is one of the most important physiological processes accomplished by the excretory system. This system helps in expelling the toxic nitrogenous wastes from the body and osmoregulation. It also helps in the filtration of blood by ultrafiltration. Humans excrete urea which is formed in the liver. Besides kidney, skin, liver, lungs, intestine and salivary glands also help in the excretion of certain substances.
Let’s look at some of the commonly asked questions about Human Excretory System:
Q.1: Draw a diagram of the excretory system?
Ans:
Q.2: How does the excretory system work?
Ans: The excretory system works by the following three steps:
Q.3: What is an excretory system?
Ans: Excretory system is one of the biological systems in our body that helps in the elimination of unwanted and toxic nitrogenous wastes as well as helps in maintaining the salt-water balance in the body.
Q.4: Name the instrument which is used in dialysis.
Ans: The name of the instrument which is used in dialysis is called Haemodialyser.
Q.5: What are the four parts of the renal tubule?
Ans: The four parts of the renal tubule are:
Q.6: Name the functional unit of the human kidney?
Ans: Nephrons are the structural and functional unit of our kidneys.
Q.7: What are the accessory excretory organs in our body?
Ans: Besides kidneys, skin, and lungs helps in the excretion of some amount of salt and carbon dioxide from our body. They are the accessory excretory organs.
Q.8: Name the major product that we excrete.
Ans: Human beings are ureotelic animals, as urea is the major excretory product.
Learn About Excretion in Animals Here
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