Kidney

Excretion is a crucial part of an organism’s life processes. The ingested food is assimilated and the byproducts are eliminated from the system to keep the physiological systems free from toxicity. In humans, kidneys are the prime organs that filter the blood and extract byproducts of metabolism to keep it clean. Here, we will study the different aspects and features of the kidney diagram and understand its functioning.

What are Kidneys?

A pair of bean-shaped organs present at the lower portion of the abdomen of human beings that are responsible for the formation of urine is the pair of kidneys. If you observe the kidney diagram labeled, you will find that these organs are a part of an intricate excretory system that opens in the anus. A kidney of an adult is 10 to 12 cm long and 5 to 7 cm wide. It weighs 120 to 170 grams.

Both the organs lie right behind the floating ribs and are protected by the rib cage. Kidneys are reddish-brown in colour due to the presence of a complex network of blood vessels and nephrons (the structural unit of these organs).

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Structure of Kidneys with Diagram

These organs have an inner concave space where many smaller structural units are stacked. The blood vessels connect and enter these organs through a small notch present at the inner concave portion called the hilum. In fact, the ureter also emerges from this notch and enters the urinary bladder.

The Different Parts of a Kidney are as Follows.

• Capsule: As per the structure of kidney diagram, the outermost layer of this organ is called a capsule. Inside the kidney, two prominent zones are found. The outer zone is called the cortex and the inner one is called the medulla. The former part that is the cortex extends and forms the columns of Bertin amidst the medullary pyramids.

• Nephrons: The structural and functional units of the kidneys are called nephrons. Each unit has two significant parts named renal tubule and glomerulus. The Bowman’s capsule is a cauldron-shaped head-like structure where an intricate network of blood capillaries enter and leave. These capillaries emerge from the afferent arteriole to form a complex network of thin capillaries and then reunite to form the efferent arteriole to leave. This network is called glomerulus and the entire head-like system is called renal or Malpighian corpuscle.

• Renal Tubule: The renal tubule, at the lower part of a nephron, originates from the Bowman’s capsule to form a long tube-like structure. The highly-coiled part of the renal tubule right after the Bowman’s capsule is called the proximal convoluted tubule.

• Henle’s Loop: The next part of the functional unit of the kidney according to the kidney diagram is Henle’s loop. It ascends from the proximal convoluted tubule and emerges as the distal convoluted tubule. The renal tubule portion of the nephron is also surrounded by blood capillaries for the re-absorption of different compounds from the urine into the bloodstream. The distal convoluted tubules of all the nephrons emerge and form the ureter where the urine is deposited.

• Ureter: It extends from the renal pelvis of each kidney. Its prime function is to carry and deposit urine in the urinary bladder. If you look at the kidney diagram labeled closely, you will understand how this thin urine pipe emerges from each kidney.

To summarize the structure of kidney diagram, the renal cortex comprises the outer part of this organ where the Malpighian corpuscles and the convoluted tubules of the nephrons exist. It is surrounded by fatty tissue at the outer portion for shock absorption and protection.

The renal medulla is the part where the Henle’s loop of all the nephrons lies. It also contains the renal pyramids of the kidneys. These pyramids are the structures that contain the tubules and nephrons. These tubules are used for the transportation of a fluid that collects and forms urine.

Every nephron ends in a collecting duct through which the fluid exits after filtration. These collecting ducts are also present in the renal medullar portion of the kidneys. Eventually, these ducts enter the renal pelvis where they form the ureter to create a seamless connection between the kidney and the urinary bladder.

The ureter then exits the kidney through the hilum and runs down to reach the urinary bladder. Through this hilum, the renal artery enters and the renal vein leaves the kidneys. The renal artery carries blood into the kidneys for purification. Once done, the blood is carried back to the heart by the renal vein. This is an elaborate description of the internal structure of kidney diagram.

Functions of Kidneys

If you look at the kidney diagram in human body, you will understand the position of this organ and its functions can be easily correlated. 

• Removal of waste products arising from the metabolism of food and medicines.

• Balancing the level of body fluids.

• Maintaining a proper balance between the electrolytes in blood and cellular plasma.

• Hormonal release for maintaining blood pressure.

• The formation of red blood cells is also controlled by the hormone released by the kidneys.

• Controls the excretion of phosphorus and calcium and keeps the bones strong.

This is all about kidneys and their diagrammatic explanation. Understanding the kidney structure will help students to relate to the functions of each part of the kidney better.