Nephrons are the functional units of the kidney and play a crucial role in filtering blood and forming urine. Each nephronA nephron is the basic structural and functional unit of the kidney. Its primary role is to filter blood, remove waste products, and regulate water and electrolyte balances in the body. Each nephron consists of a glomerulus for filtration and a tubule system for reabsorption and secretion of various substances. is a tiny, complex structure with several components, each with a specific function. Here’s a detailed look at their structure and functioning:

Structure of Nephrons

A tiny ball of capillaries where blood filtration begins. It’s enclosed in a cup-like structure called Bowman’s capsule.

Bowman’s Capsule:
Surrounds the glomerulus and collects the filtrate produced by the filtration of blood.

Proximal Convoluted Tubule (PCT):
A twisted tube that extends from Bowman’s capsule. It’s lined with microvilli to increase surface area for reabsorption.

Loop of Henle and Collecting Duct

Loop of Henle:
A hairpin-shaped loop that extends into the kidney’s medulla. It has a descending limb that carries fluid down into the medulla and an ascending limb that carries fluid back up toward the cortex.

Distal Convoluted Tubule (DCT):
Similar to the PCT but shorter and with a different cellular structure. It further processes the filtrate.

Collecting Duct:
Multiple DCTs from different nephrons empty into a collecting duct. These ducts pass through the medulla and carry urine to the renal pelvis.

Functioning of Nephrons: Filtration and Reabsorption in the PCT

Blood enters the glomerulus, where high blood pressure forces water, salts, glucose, amino acids, and waste products out of the blood and into Bowman’s capsule, forming the filtrate. Large molecules like proteins and blood cells are too big to pass through and remain in the blood.

Reabsorption in the PCT:
As the filtrate moves through the PCT, most of the water, glucose, salts, and amino acids are reabsorbed back into the blood. This is done through both active and passive transport mechanisms.

Loop of Henle, Reabsorption and Secretion in the DCT

Loop of Henle:
The descending limb is permeable to water but not to salts. As the filtrate moves down, water is reabsorbed into the surrounding blood vessels.
The ascending limb is impermeable to water but allows salts to be reabsorbed. This creates a concentration gradient in the kidney’s medulla, which is important for the kidney’s ability to concentrate urine.

Reabsorption and Secretion in the DCT:
The DCT fine-tunes the composition of the filtrate. Additional ions and water are reabsorbed, and some ions and wastes are secreted into the filtrate.

Collecting Duct and Urine Excretion

Collecting Duct:
The filtrate, now called urine, passes through the collecting duct. The duct’s permeability to water is regulated by the hormone antidiuretic hormone (ADH). In the presence of ADH, water is reabsorbed, concentrating the urine. In its absence, the urine remains dilute.

Urine Excretion:
The concentrated urine is eventually led to the renal pelvis, from where it moves to the bladder for storage before being excreted.

Through these processes, nephrons filter the blood, remove waste products, regulate electrolyte and water balance, and maintain blood pressure. The kidneys contain millions of nephrons, each contributing to the overall function of the kidney in maintaining homeostasis in the body.

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List of Questions of Class 10 Science Chapter 5

Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
What criteria do we use to decide whether something is alive?
What are outside raw materials used for by an organism?
What processes would you consider essential for maintaining life?
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Where do plants get each of the raw materials required for photosynthesis?
What is the role of the acid in our stomach?
What is the function of digestive enzymes?
How is the small intestine designed to absorb digested food?
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
What are the different ways in which glucose is oxidised to provide energy in various organisms?
How is oxygen and carbon dioxide transported in human beings?
How are the lungs designed in human beings to maximise the area for exchange of gases?
What are the components of the transport system in human beings?
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
What are the components of the transport system in highly organised plants?
How are water and minerals transported in plants?
How is food transported in plants?
Describe the structure and functioning of nephrons.
What are the methods used by plants to get rid of excretory products?
How is the amount of urine produced regulated?
How are fats digested in our bodies? Where does this process take place?
What is the role of saliva in the digestion of food?
What are the necessary conditions for autotrophic nutrition and what are its byproducts?
What are the differences between aerobic and anaerobic respiration?
How are the alveoli designed to maximise the exchange of gases?
What would be the consequences of a deficiency of haemoglobin in our bodies?
Describe double circulation of blood in human beings. Why is it necessary?
What are the differences between the transport of materials in xylem and phloem?
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.