What is the name of the functional unit within the kidneys that functions to remove waste from blood?

The kidneys are the primary organs of the urinary system. The kidneys are the organs that filter the blood, remove the wastes, and excrete the wastes in the urine. They are the organs that perform the functions of the urinary system. The other components are accessory structures to eliminate the urine from the body.

The paired kidneys are located between the twelfth thoracic and third lumbar vertebrae, one on each side of the vertebral column. The right kidney usually is slightly lower than the left because the liver displaces it downward. The kidneys, protected by the lower ribs, lie in shallow depressions against the posterior abdominal wall and behind the parietal peritoneum. This means they are retroperitoneal. Each kidney is held in place by connective tissue, called renal fascia, and is surrounded by a thick layer of adipose tissue, called perirenal fat, which helps to protect it. A tough, fibrous, connective tissue renal capsule closely envelopes each kidney and provides support for the soft tissue that is inside.

In the adult, each kidney is approximately 3 cm thick, 6 cm wide, and 12 cm long. It is roughly bean-shaped with an indentation, called the hilum, on the medial side. The hilum leads to a large cavity, called the renal sinus, within the kidney. The ureter and renal vein leave the kidney, and the renal artery enters the kidney at the hilum.

The outer, reddish region, next to the capsule, is the renal cortex. This surrounds a darker reddish-brown region called the renal medulla. The renal medulla consists of a series of renal pyramids, which appear striated because they contain straight tubular structures and blood vessels. The wide bases of the pyramids are adjacent to the cortex and the pointed ends, called renal papillae, are directed toward the center of the kidney. Portions of the renal cortex extend into the spaces between adjacent pyramids to form renal columns. The cortex and medulla make up the parenchyma, or functional tissue, of the kidney.

The central region of the kidney contains the renal pelvis, which is located in the renal sinus, and is continuous with the ureter. The renal pelvis is a large cavity that collects the urine as it is produced. The periphery of the renal pelvis is interrupted by cuplike projections called calyces. A minor calyx surrounds the renal papillae of each pyramid and collects urine from that pyramid. Several minor calyces converge to form a major calyx. From the major calyces, the urine flows into the renal pelvis; and from there, it flows into the ureter.

Each kidney contains over a million functional units, called nephrons, in the parenchyma (cortex and medulla). A nephron has two parts: a renal corpuscle and a renal tubule.The renal corpuscle consists of a cluster of capillaries, called the glomerulus, surrounded by a double-layered epithelial cup, called the glomerular capsule. An afferent arteriole leads into the renal corpuscle and an efferent arteriole leaves the renal corpuscle. Urine passes from the nephrons into collecting ducts then into the minor calyces.

The juxtaglomerular apparatus, which monitors blood pressure and secretes renin, is formed from modified cells in the afferent arteriole and the ascending limb of the nephron loop.

Anatomy and Function of the Urinary System

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How does the urinary system work?

The body takes nutrients from food and changes them to energy. After the body has taken the food components that it needs, waste products are left behind in the bowel and in the blood.

The kidney and urinary systems help the body to get rid of liquid waste called urea. They also help to keep chemicals (such as potassium and sodium) and water in balance. Urea is produced when foods containing protein (such as meat, poultry, and certain vegetables) are broken down in the body. Urea is carried in the blood to the kidneys. This is where it is removed, along with water and other wastes in the form of urine.

The kidneys have other important functions. They control blood pressure and produce the hormone erythropoietin. This hormone controls red blood cell production in the bone marrow. The kidneys also control the acid-base balance and conserve fluids.

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Kidney and urinary system parts and their functions

• Two kidneys.  This pair of purplish-brown organs is located below the ribs toward the middle of the back. Their function is to:

  • Remove waste products and medicines from the body

  • Balance the body's fluids

  • Balance a variety of electrolytes

  • Release hormones to control blood pressure

  • Release a hormone to control red blood cell production

  • Help with bone health by controlling calcium and phosphorus

The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries (glomerulus) and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.

• Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls keep tightening and relaxing. This forces urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.

• Bladder. This triangle-shaped, hollow organ is located in the lower belly. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder's walls relax and expand to store urine. They contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to 2 cups of urine for 2 to 5 hours.

• Two sphincter muscles. These circular muscles help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder.

• Nerves in the bladder. The nerves alert a person when it is time to urinate, or empty the bladder.

• Urethra. This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten. This squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals happen in the correct order, normal urination happens.

Facts about urine

• Normal, healthy urine is a pale straw or clear yellow color.

• Darker yellow or honey-colored urine often means you need more water.

• A darker, brownish color may mean a liver problem or severe dehydration.

• Pinkish or red urine may mean blood in the urine.

What is the name of the functional unit within the kidneys that functions to remove waste from blood indicated with arrow in image below?

What is the name of the functional unit of the kidney?

What part of the kidney removes waste?

What is the medical term for the functional unit of the kidney that removes waste products and excess water from the blood?