Human Excretory System Class 10 - Description
Dear readers, today we are going to provide the Human Excretory System Class 10 PDF for all of you. Excretion is the removal of nitrogenous waste products and excess salts produced as a result of metabolic processes. The organs related to excretion are called excretion organs. The excretory organs are collectively called the excretory system.
The life of every living being depends on some fundamental processes. Excretion is one of them. Organisms remove waste from their bodies, plants remove gaseous waste through stomata, and animals remove carbon-dioxide waste through respiration. They remove undigested solid waste through defecation.
The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion. If you studying in class 10 from the CBSE board then through our post, you can easily get human excretory system notes pdf class 10 which can be very useful for your exam preparation.
Human Excretory System Class 10 PDF
Excretory System Organs
The human excretory system organs include:
- A pair of kidneys
- A pair of ureters
- A urinary bladder
- A urethra
Kidneys are bean-shaped structures located on either side of the backbone and are protected by the ribs and muscles of the back. Each human adult kidney has a length of 10-12 cm, a width of 5-7 cm and weighs around 120-170g. The kidneys have an inner concave structure.
The blood vessels, ureter and nerves enter the kidneys through the hilum, which is a notch at the inner concave surface of the kidney. The renal pelvis, a large funnel-shaped space present inner to the hilum, has many projections known as calyces.
Structure of Kidney
The structure of the kidney is explained below:
The outer layer is called the capsule. Inside the kidney, there are two zones- the outer zone is the cortex and the inner zone is the medulla. The cortex extends in between the medullary pyramids as renal columns called columns of Bertin.
Nephrons are the functional units of the kidney to filter the nitrogenous waste, excess of water and electrolytes from the blood. Each nephron has two parts- Malpighian corpuscles and renal tubules. The malpighian body consists of the glomerulus and Bowman’s Glomerulus. The Bowman’s capsule is a double-layered, cup-like structure. The glomerulus consists of a bunch of capillaries formed by afferent arterioles.
Blood from the glomerulus is carried away by efferent arterioles. The renal tubule is a long and convoluted structure that extends from the Bowman’s capsule and can be divided into three parts based on function.
- The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus; it stays in the renal cortex.
- The second part is called the loop of Henle, or the nephritic loop because it forms a loop (with descending and ascending limbs) that goes through the renal medulla.
- The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex.
A pair of thin muscular tubes called the ureter comes out of each kidney extending from the renal pelvis. It carries urine from the kidney to the urinary bladder.
It is a muscular sac-like structure, which stores urine. The urinary bladder is emptied by the process of micturition, i.e. the act of urination.
This tube arises from the urinary bladder and helps to expel urine out of the body. In males, it acts as the common route for sperms and urine. Its opening is guarded by sphincter muscles.
Excretion in Human Beings
- A pair of kidneys, a pair of ureters, a urinary bladder and a urethra constitute the human excretory system.
- Kidneys are present on either side of the backbone in the abdomen. Each human adult kidney has a length of 10-12 cm, a width of 5-7 cm and weighs around 120-170g.
- Kidneys produce urine The urine from the kidney passes through the ureters into the urinary bladder and remains stored there until it is released through the urethra.
- Each kidney has millions of microscopic filtration units to filter the nitrogenous waste, excess water and electrolytes from the blood, each one is called Nephron.
Mechanism of Excretion in Humans
The process of excretion in humans takes place in the following steps:
The urine is formed in the nephrons and involves the following steps:
It is the primary step in urine formation. In this process, the excess fluid and waste products from the kidney are filtered out of the blood into the urine collection tubules of the kidney and eliminated from the body.
The amount of filtrate produced by the kidneys every minute is known as Glomerular Filtration Rate (GFR).
It is the absorption of ions and molecules such as sodium ions, glucose, amino acids, water etc. Water involves passive absorption, while glucose and sodium ions are absorbed by an active process.
Potassium ions, hydrogen ions, and ammonia are secreted out to maintain the equilibrium between the body fluids.
The functions of the various tubules involved in the process are:
Glomerulus- filters the blood
Proximal Convoluted Tubules (PCT)- reabsorb water, ions and nutrients. They remove toxins and help in maintaining the ionic balance and pH of the body fluids by secretion of potassium, hydrogen and ammonia to filtrate and reabsorbing bicarbonate ions from the filtrate.
Descending Loop of Henle- is permeable to water and the filtrate gets concentrated as it is impermeable to electrolytes.
Ascending Loop of Henle- it is impermeable to water and permeable to electrolytes. The filtrate gets diluted due to the movement of electrolytes from the filtrate to the medullary fluid.
Distal Convoluted Tubule (DCT)- allows the reabsorption of water and sodium ions. It also helps in maintaining pH and ionic balance by secretion and reabsorption of ions like PCT.
Collecting Duct- a large amount of water is reabsorbed from the filtrate by the collecting duct.
Steps in Urine Formation
The kidney performs three functions as steps involved in urine formation – ultra-filtration, selective reabsorption and tubular secretion.
- Ultra-filtration is the process in which nephrons filter almost all components of the blood plasma ( e.g. minerals, nitrogenous wastes and water etc.) but retain blood cells, proteins and large molecules. This filtrate is called ‘Renal filtrate’. Around 180 litres of renal filtrate is produced in the kidneys in a day. It takes place in
Malpighian corpuscle (Glomerulus).
- Selective reabsorption involves re absorption of some useful substances of the initial renal filtrate, such as glucose, amino acids, salts, and a major amount of water.
- Tubular secretion involves the secretion of substances not required by the body into the filtrate by the cells of the distal convoluted tubule before it leaves the kidney.
The functions of the various tubules involved in urine formation are:
- Glomerulus filters the blood
- Proximal Convoluted Tubules reabsorb ions, water, and nutrients, remove toxins, and maintain the pH of the filtrate. Descending Loop of Henle allows water to pass from the filtrate into the interstitial fluid through aquaporins.
- Ascending Loop of Henle reabsorbs sodium and chloride ions from the filtrate into the interstitial fluid.
- Distal convoluted Tubule reabsorbs and secretes selective ions and maintains the pH of the blood.
- Collecting Duct, solutes, and water is reabsorbed from the filtrate by the collecting duct.
Under certain circumstances such as poor blood flow to the kidneys, infections, injuries, etc. the kidneys fail to perform their functions. In such situations, artificial kidneys are used for blood filtration and this process is called dialysis.
Dialysis is the process which involves the separation of nitrogenous wastes from the blood artificially. Dialysis is performed using a device which removes nitrogenous wastes from the blood in case of kidney failure.
- An artificial kidney contains a number of tubes with a semi-permeable lining suspended in a tank filled with dialysing fluid.
- The osmotic concentration of this dialysing fluid is maintained similar to the concentration of the patient’s blood.
- The patient’s blood (with nitrogenous wastes) is passed through these tubes.
- During this passage, the nitrogenous waste products from the blood diffuse out into the dialysing fluid.
- The purified blood is pumped back into the patient body.
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