What is the functional unit of kidney? Draw its structure and show its major parts
The functional unit of the kidney is called the nephron. Nephrons are responsible for filtering the blood and producing urine. Each kidney contains millions of nephrons, making them the fundamental building blocks of the kidney’s filtration system. Let’s dive into the structure and major parts of a nephron.
Structure of a Nephron:
A nephron consists of several distinct regions and can be divided into two main parts: the renal corpuscle and the renal tubule.
1. Renal Corpuscle:
The renal corpuscle is the initial filtering component of the nephron. It comprises two structures: the glomerulus and the Bowman’s capsule.
– Glomerulus: The glomerulus is a cluster of tiny, intertwined blood capillaries where blood filtration occurs. It receives blood from the afferent arteriole, which is a small branch of the renal artery.
– Bowman’s Capsule: The Bowman’s capsule is a cup-like structure that surrounds the glomerulus. It collects the filtered fluid (filtrate) from the glomerulus and initiates the process of urine formation.
2. Renal Tubule:
The renal tubule is a long, convoluted tube that continues from the Bowman’s capsule. It consists of several distinct segments, each with specific functions in the reabsorption and secretion processes.
– Proximal Convoluted Tubule (PCT): The PCT is the first segment of the renal tubule. It is responsible for the reabsorption of essential substances such as water, glucose, amino acids, and electrolytes back into the bloodstream.
– Loop of Henle: The Loop of Henle descends into the medulla of the kidney and then returns to the cortex. It plays a crucial role in creating a concentration gradient within the kidney, allowing for the concentration of urine.
– Distal Convoluted Tubule (DCT): The DCT follows the Loop of Henle and is involved in fine-tuning the reabsorption and secretion of certain ions and molecules, maintaining the body’s electrolyte and acid-base balance.
– Collecting Duct: The collecting duct receives urine from multiple nephrons and is responsible for further concentrating the urine as it passes through the medulla of the kidney. The concentrated urine eventually flows into the renal pelvis and exits the kidney through the ureter.
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Major Parts of a Nephron:
The key parts of a nephron are:
1. Glomerulus: The cluster of blood capillaries where blood filtration occurs.
2. Bowman’s Capsule: The cup-like structure that surrounds the glomerulus and collects the filtrate.
3. Proximal Convoluted Tubule (PCT): The initial segment of the renal tubule responsible for reabsorption.
4. Loop of Henle: The U-shaped loop that creates a concentration gradient in the kidney.
5. Distal Convoluted Tubule (DCT): The segment responsible for fine-tuning reabsorption and secretion.
6. Collecting Duct: The structure that receives urine from multiple nephrons and concentrates it.
The nephron’s structural complexity and efficiency in filtering and reabsorbing substances make it a vital component of the kidney’s function in maintaining fluid and electrolyte balance, regulating blood pressure, and eliminating waste products from the body through urine formation.