Kidney Anatomy and Nephron Physiology for AIIMS Preparation
Welcome to this module on Kidney Anatomy and Nephron Physiology, a crucial topic for your AIIMS preparation. Understanding the structure and function of the kidneys is fundamental to grasping concepts in excretion, fluid balance, and electrolyte homeostasis.
Gross Anatomy of the Kidney
The human kidneys are a pair of bean-shaped organs located on either side of the spine, just below the ribs and behind the belly. Each kidney is about the size of a fist. They play a vital role in filtering waste products from the blood and producing urine.
The renal cortex and the renal medulla.
The Nephron: Functional Unit of the Kidney
Each kidney contains approximately one million nephrons, which are the microscopic functional units responsible for filtering blood and producing urine. The nephron is a complex structure consisting of a renal corpuscle and a renal tubule.
The nephron begins with the renal corpuscle, which includes the glomerulus (a network of capillaries) enclosed within Bowman's capsule (a cup-shaped structure). Blood enters the glomerulus via the afferent arteriole and leaves via the efferent arteriole. Filtration occurs here, where water and small solutes are forced from the blood into Bowman's capsule, forming the glomerular filtrate. Following the renal corpuscle is the renal tubule, a long, convoluted tube divided into three main parts: the proximal convoluted tubule (PCT), the loop of Henle, and the distal convoluted tubule (DCT). These segments are specialized for reabsorption and secretion, modifying the filtrate into urine. The DCTs of several nephrons empty into a collecting duct, which further processes the urine before it enters the renal pelvis.
Text-based content
Library pages focus on text content
| Nephron Part | Primary Function | Location |
|---|---|---|
| Renal Corpuscle (Glomerulus + Bowman's Capsule) | Filtration of blood | Renal Cortex |
| Proximal Convoluted Tubule (PCT) | Reabsorption of water, ions, glucose, amino acids; secretion of some ions and drugs | Renal Cortex |
| Loop of Henle | Establishes medullary osmotic gradient for water reabsorption | Extends into Renal Medulla |
| Distal Convoluted Tubule (DCT) | Selective reabsorption of ions (Na+, Cl-, Ca2+); secretion of K+ and H+; regulated by hormones | Renal Cortex |
| Collecting Duct | Final adjustment of urine concentration; water reabsorption regulated by ADH | Extends through Renal Medulla to Renal Pelvis |
Physiology of Urine Formation
Urine formation is a complex process involving three main steps: glomerular filtration, tubular reabsorption, and tubular secretion. These processes ensure that waste products are removed from the blood while essential substances are conserved.
Loading diagram...
Glomerular Filtration: This is the initial step where blood plasma is filtered from the glomerular capillaries into Bowman's capsule. The filtration barrier allows water and small solutes to pass but prevents larger molecules like proteins and blood cells from entering the filtrate. The rate of filtration is known as the Glomerular Filtration Rate (GFR).
Tubular Reabsorption: As the filtrate passes through the renal tubule, essential substances like glucose, amino acids, water, and ions are reabsorbed back into the bloodstream. This process occurs in the PCT, loop of Henle, DCT, and collecting ducts, and can be both passive and active.
Tubular Secretion: This process involves the active transport of certain substances from the blood into the tubular fluid. It's crucial for eliminating waste products, excess ions (like K+ and H+), and certain drugs that were not filtered out initially. Secretion primarily occurs in the PCT and DCT.
The interplay of reabsorption and secretion fine-tunes the composition of urine, maintaining the body's internal environment (homeostasis).
Hormonal Regulation of Kidney Function
Several hormones play a critical role in regulating kidney function, particularly in managing water and electrolyte balance. Key hormones include Antidiuretic Hormone (ADH), Aldosterone, and Atrial Natriuretic Peptide (ANP).
Antidiuretic Hormone (ADH).
ADH increases the permeability of the collecting ducts to water, allowing more water to be reabsorbed and producing more concentrated urine. Aldosterone, secreted by the adrenal cortex, promotes sodium reabsorption and potassium secretion in the DCT and collecting ducts, influencing blood volume and pressure. ANP, released by the atria of the heart, opposes the action of aldosterone and ADH, promoting sodium and water excretion to lower blood pressure.
Clinical Significance for AIIMS
Understanding kidney anatomy and nephron physiology is vital for diagnosing and managing various renal diseases, electrolyte imbalances, and hypertension. Questions in AIIMS often test your ability to connect structural details with functional consequences and hormonal influences.
Learning Resources
A comprehensive overview of kidney anatomy and physiology with detailed diagrams and explanations, perfect for visual learners.
An engaging video explaining the structure and function of the nephron, the functional unit of the kidney.
Detailed anatomical description of the kidney, including its gross features, blood supply, and innervation.
An in-depth explanation of kidney physiology, covering filtration, reabsorption, secretion, and hormonal regulation.
Explains the intricate processes of filtration, reabsorption, and secretion that occur within the nephron.
A clear and concise video lecture providing an overview of kidney physiology and its role in homeostasis.
Covers the broader aspects of the renal system, including the kidneys' role in excretion and fluid balance.
Osmosis provides animated videos and articles on medical topics, including detailed kidney anatomy and physiology.
A scientific overview of the hormonal mechanisms that regulate kidney function, essential for understanding fluid and electrolyte balance.
A resource that breaks down kidney physiology into key concepts, including filtration, reabsorption, and secretion.