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Introduction
Every organism’s existence is predicated on a set of fundamental processes. Excretion is just one of the many bodily functions that take place. Excreta are produced in a variety of ways depending on the organism. Excretion in humans and other complex organisms is handled by a specialised mechanism termed the human excretory system.
It doesn’t matter how we get our nutrients; our bodies break them down and use them. After a series of metabolic reactions, the body begins to filter out the good from the bad in a person’s system. It is well-known that toxic buildup can be dangerous, and as a result, the body uses the excretion process to remove all metabolic waste.
When it comes to excretion methods, the environment and feeding habits of an organism determine which organ(s) uses which method (kidneys, lungs, skin, or eyes).
When it comes to the excrement of birds and insects, for example, ammonia and uric acid are the most common waste products. Urea is the primary excretory product of humans.
Excretory System Organs
Kidneys
On each side of the backbone are two bean-shaped organs known as kidneys, which protect each other from harm. An adult human kidney measures 10-12 cm in length, 5-7 cm wide, and weighs 120-170g.
The kidneys have a concave configuration inside of the organs. The hilum, a notch on the kidney’s inner concave surface, is where blood arteries, ureters, and nerves enter the kidneys. An inner portion of the renal pelvis, a huge funnel-shaped area, is known as a calyx.
Structure of Kidney
The following is a description of the kidney’s structure in more detail:
Capsule- The capsule refers to the outermost layer. The cortex and the medulla are two distinct regions of the kidney. Between the medullary pyramids, the cortex extends as renal columns known as columns of Bertin.
Nephrons- The kidney’s functional units are nephrons. The glomerulus and the renal tubule are the two components of each nephron.
Afferent arterioles from capillaries in the glomerulus. Different arterioles remove blood from the glomerulus.
Bowman’s capsule is a cup-like structure that surrounds the glomerulus in the renal tubule. The glomerulus and the Bowman’s capsule make up the malpighian body. The proximal convoluted tubule is the heavily coiled structure in the tubule adjacent to Bowman’s capsule.
Henle’s loop- In the following section of the tubule, we get Henle’s loop, which has both an ascending and descending portion to it. In the distal tubule, the ascending loop is continued as a convoluted strand. Many nephrons have distal convoluted tubules that enter into the collecting duct at their distal end.
The medullary region of the kidney has a loop of Henle, while the cortical region contains the malpighian corpuscle, the proximal convoluted tubule, and the distal convoluted tubule.
Cortical nephrons and juxtamedullary nephrons are the two main varieties. The Henle loop in the cortex is extremely short and only reaches a small portion of the medulla. The loop of Henle in juxtamedullary is quite lengthy and extends far into the medulla.
Ureter- The ureters, which are narrow, muscular tubes that extend from the renal pelvis, exit each kidney. From the kidney, urine flows into the urinary bladder through this tube.
Urinary Bladder- Urine is stored in a muscular structure that resembles a sac. Micturition, or the act of urinating, is the mechanism by which the urine bladder is emptied.
Urethra- In order to get rid of waste, the urinary bladder has a tube that connects to it. In males, it serves as both a sperm and urine conduit. Sphincter muscles keep it closed.
Excretion in Humans
The process of excretion is the removal of all metabolic wastes from the organism. In humans, excretion is carried out by various body parts and internal organs.
Lower species use diffusion as the most common method of excretion. The human body is a unique machine that concurrently performs a variety of life activities (respiration, circulation, digestion, etc.). Carbon dioxide, water, and nitrogenous waste products including urea, ammonia, and uric acid are just a few of the many types of waste products generated by our bodies as a result.
Medications and hormonal products also generate toxins and other harmful molecules. These wastes cannot be eliminated from our bodies by diffusion alone. In order to get rid of waste, we’ll require more involved and detailed procedures.
The compounds found in the blood can be both beneficial and dangerous. As a result, we have kidneys that reabsorb helpful molecules and excrete poisonous ones.The blood is filtered in the kidney’s nephron, a structural filtration unit. A million nephrons are found in each kidney.The kidneys’ capillaries remove waste from the blood and reabsorb vital chemicals such as glucose, amino acids, minerals, and water.
Humans excrete urine as a waste product of excess water and nitrogenous waste. The ureters then carry the urine to the bladder, where it can be expelled. There is a direct link between the Central Nervous System and the bladder’s function. We expel our urine through the urethra, which is a tube that connects the bladder to the urethra.
The Human Excretion Mechanism
The following are the steps involved in human excretion:
Formation of Urine
Glomerular Filtration – In the process of producing urine, it is the first and most important stage. There are a number of ways that excess fluid and waste can be removed from the blood, and this process is one of the most common.Glomerular Filtration Rate refers to the amount of filtrate generated by the kidneys each minute (GFR).
Tubular Reabsorption – Sodium ions, glucose, amino acids, and water ions are just a few examples of the ions and molecules that can be absorbed this way. In contrast to water, glucose and sodium ions are taken up by an active absorption process.
Secretion- Body fluids are kept in balance by the secretion of electrolytes such as potassium, hydrogen and ammonia.
In this process, numerous tubules serve the following purposes:
Glomerulus: Blood is filtered through the Glomerulus.
Peptides, ions, and nutrients are reabsorbed via the Proximal Convoluted Tubules (PCT). Using potassium, hydrogen, and ammonia to filter the filtrate, and reabsorbing bicarbonate ions from the filtrate, they assist in maintaining the body’s ionic equilibrium and pH.
The Descending Loop of Henle- is water-permeable, but electrolytes are impermeable, therefore the filtrate becomes concentrated.
Ascending Loop of Henle- While electrolytes are not able to pass through it, the Ascending Henle Loop is. The electrolytes in the filtrate go to the medullary fluid, diluting the filtrate.
The Distal Convoluted Tubule (DCT)- enables water and sodium ions to be reabsorbed. As with PCT, it aids in pH regulation and ionic equilibrium maintenance.
Collecting Duct- a large amount of water is reabsorbed from the filtrate by the collecting duct.
Micturition: The nephrons produce urine, which expands the bladder and causes it to fill up. The bladder walls include receptors that convey signals to the Central Nervous System, allowing the sphincter muscles to relax and enable the urine to flow out of the bladder. It’s called micturition.
Conclusion
To maintain the right balance of water, salts, and nutrients in the body, excretory systems filter metabolic wastes. The kidneys, liver, lungs, and skin are all part of this system in vertebrates. The endocrine system and the excretory system work together to keep the body in a state of equilibrium. Hormones are chemical messengers that tell the kidneys how much water or salt to filter from the blood.
