Database results:
examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Urinary System Structure
Your body is constantly working to maintain balance. One of the most important ways it does this is by removing waste products and excess substances through excretion. The urinary system plays a crucial role in this process, helping to filter your blood and produce urine that carries waste out of your body.
Key Definitions:
Imagine if you never took the rubbish out of your house. It would pile up, start to smell and eventually make your home uninhabitable. Your body works the same way! Waste products like urea (from protein breakdown) and excess water, salts and other substances must be removed to keep your internal environment balanced and healthy.
Beyond just waste removal, your urinary system helps regulate blood volume and pressure, controls levels of electrolytes and metabolites in body fluids, maintains proper pH and produces hormones that help make red blood cells, promote bone health and regulate blood pressure.
The urinary system consists of several organs working together to filter blood and create urine. Let's explore each component:
The kidneys sit at the back of the abdominal cavity, one on each side of the spine, just below the rib cage. The ureters run down from the kidneys to the bladder, which sits in the pelvis. The urethra extends from the bladder to the outside of the body.
Each kidney is about the size of your fist and has a distinctive bean shape. If we were to cut a kidney in half, we would see three main regions:
The outer region of the kidney, reddish-brown in colour. Contains the glomeruli and convoluted tubules of the nephrons.
The inner region, containing pyramid-shaped structures. These pyramids contain the loops of Henle and collecting ducts.
A funnel-shaped collecting area that connects to the ureter. Urine collects here before moving to the bladder.
Blood enters the kidney through the renal artery and leaves through the renal vein. The kidney is protected by a layer of fat and a tough fibrous capsule.
Each kidney contains about one million tiny filtering units called nephrons. These microscopic structures are where the actual work of the kidney happens.
A nephron consists of:
Nephrons filter your blood in three main steps:
The formation of urine is a complex process that involves filtering blood, reabsorbing what the body needs and eliminating what it doesn't.
Blood pressure forces water and small dissolved substances out of the glomerular capillaries into Bowman's capsule. This creates the glomerular filtrate, which contains water, glucose, amino acids, salts and waste products like urea.
As the filtrate moves through the tubules, about 99% of the water and all of the glucose and amino acids are reabsorbed back into the bloodstream. Some salts are also reabsorbed, while others are left in the filtrate.
Certain substances like hydrogen ions, potassium ions and drugs are actively secreted from the blood into the tubules to be eliminated in the urine.
The final product, urine, consists mainly of water (95%), urea, uric acid and various salts. The composition can vary depending on your body's needs, which is how the kidneys help maintain homeostasis.
Once urine is formed in the nephrons, it follows a specific path out of the body:
Chronic kidney disease affects millions worldwide. When kidneys fail, waste products build up in the blood, causing symptoms like fatigue, swelling and high blood pressure. Patients may need dialysis, where a machine filters their blood, or a kidney transplant. Many cases are preventable by managing conditions like diabetes and high blood pressure, staying hydrated and avoiding overuse of painkillers that can damage kidneys.
Bacterial infections that can affect any part of the urinary system. Symptoms include a burning sensation when urinating, frequent urination and cloudy or strong-smelling urine. More common in females due to their shorter urethra.
Hard deposits of minerals and salts that form inside the kidneys. They can cause severe pain as they pass through the urinary tract. Staying hydrated helps prevent them from forming.
Taking care of your urinary system is essential for overall health. Here are some tips:
The colour of your urine can tell you a lot about your hydration status. Pale yellow means you're well-hydrated, while dark yellow or amber suggests you need to drink more water. Completely clear urine might mean you're drinking too much water!
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.