Kidney & Urinary System Anatomy

The general anatomy that makes up the human urinary system consists of the kidneys, ureters, bladder and the urethra.

Together, these structures play a vital role in filtering the blood, removing waste, maintaining electrolyte balance, and regulating fluid levels in the body. The kidneys act as the body's filtration units, removing waste products and excess substances, while the ureters transport urine from the kidneys to the bladder, where it is stored until excretion through the urethra. The system also helps to regulate blood pressure, red blood cell production, and calcium absorption through the hormones it releases. Each part of this system works in coordination to ensure homeostasis is maintained, which is essential for the proper functioning of organs and tissues throughout the body.

To help you visualise and retain complex renal anatomy, explore our selection of high-quality kidney anatomy posters and charts. These clear, full-colour illustrations break down key structures such as the renal cortex, medulla, nephrons and blood supply pathways, making them invaluable tools for students, lecturers and healthcare professionals alike. Whether displayed in classrooms, clinics, or study spaces, these charts enhance your learning experience by turning abstract concepts into digestible visual content.

The kidneys are bean-shaped, reddish-brown organs located in the posterior abdominal cavity on either side of the spine, roughly between the levels of the T12 and L3 vertebrae. The right kidney usually sits slightly lower than the left to accommodate the liver. Each kidney is approximately the size of a closed fist. They are retroperitoneal organs, meaning they sit behind the peritoneum (the lining of the abdominal cavity), providing a stable and well-protected location.

The kidneys are enclosed in three layers:

• Renal capsule- A tough, fibrous layer that directly surrounds each kidney, providing physical protection.
• Perirenal fat- A thick, adipose layer cushioning the kidney against mechanical trauma.
• Renal fascia- A dense connective tissue layer that anchors the kidneys and surrounding structures in place.

Each kidney is made up of filtering units called nephrons. A nephron is the functional unit of the kidney, responsible for filtration, excretion and selective resorption of substances such as ions, amino acids and glucose. The nephrons are located in the renal cortex and the renal medulla.

The renal cortex makes up the space between the fibrous capsule of the kidney (outermost layer of the kidney, also known as the renal capsule) and the renal medulla. It contains the glomerulus and tubules of the nephrons.

The renal medulla is a pyramid-shaped structure found in the innermost region of the kidney, containing the collecting ducts of the nephrons. The renal papilla is where the renal pyramid in the medulla empties urine into the minor calyx. The medulla is surrounded by the renal cortex.

The renal pelvis is the point where the calyces join together and funnel urine into the ureter.

Blood enters the kidney through the renal artery and exits through the renal vein. A duct called the ureter is attached to the kidney through which urine travels down into the bladder. At the inner surface is a hilum (concave shape); this is where arteries, veins and nerves run through.

Our detailed anatomical kidney models offer a hands-on way to examine renal structure, including nephrons, arteries, veins, and the urinary system. Ideal for educational settings, these models help students and healthcare professionals better understand the intricate workings of kidney function and blood filtration. Durable, accurate, and labelled, they provide an excellent addition to revision or demonstration sessions.

The main blood supply comes from the renal arteries which are a branch of the abdominal artery. When the renal artery reaches the hilum, it branches off into the posterior and anterior branch. The posterior branch supplies the kidneys and the anterior branch gives rise to the segmental arteries. Arterioles (small branches of arteries) supply blood to the glomerulus, a network of small vessels; this allows the kidney to filter blood. The arcuate veins transport deoxygenated blood to the renal veins and back to the heart.

Nerve branches from the renal plexus enter the kidney at the hilum alongside the renal artery. The kidneys receive innervation from both the sympathetic and parasympathetic nervous systems.

The kidney has several functions. One of their main jobs is to filter waste products from the blood - these waste products are then excreted from our body as urine. Filtering out waste is important to maintain a healthy and functioning body.

Another important function is to maintain balance of blood pressure by releasing hormones, and to maintain the balance of water and minerals. This balance is known as homeostasis and is important for cells to function and for normal bodily functions to take place.

Some other functions of the organ include the production of vitamin D, the production of red blood cells in our bone marrow, and removing acid from our systems.

Urination is a complex process facilitated by our kidneys and bladder. The ureters attached to each kidney extends down to the bladder, and urine is then released through the urethra.

Micturition, the act of urinating, is regulated by our nervous system and the muscles of our bladder and urethra. Micturition is triggered by stretch receptors when the bladder is full of urine and the detrusor muscle, which surrounds the inner wall of the bladder, contracts. This causes the internal urethral sphincter to relax and for urine to pass through the bladder into the urethra. 

While the kidneys play a central role in filtering blood and producing urine, the rest of the urinary system ensures that urine is safely transported, stored, and eventually removed from the body. The remaining structures include the ureters, bladder, and urethra, each playing a key part in this process.

The ureters are two thin, muscular tubes that connect each kidney to the urinary bladder. They transport urine from the renal pelvis in the kidney to the bladder using rhythmic, wave-like contractions known as peristalsis. The inner lining of the ureters is made of transitional epithelium, which allows them to stretch and accommodate varying volumes of urine.

The bladder is a hollow, muscular organ located in the pelvis, just behind the pubic bone. It temporarily stores urine until it is ready to be expelled from the body. The wall of the bladder contains three layers of smooth muscle known as the detrusor muscle, which contracts during urination. The inner surface of the bladder is lined with transitional epithelium, allowing it to expand and hold between 400–600ml of urine in adults. Two sphincters, internal and external, help control the release of urine.

The urethra is the final passageway in the urinary tract, responsible for transporting urine from the bladder to the outside of the body. Its length and structure differ between sexes: in females, it is approximately 4cm long and opens just above the vaginal opening; in males, it is about 20cm long and passes through the prostate and penis. The external urethral sphincter, made of skeletal muscle, allows voluntary control over urination.

Understanding anatomy can be far more effective with high quality visual tools. Our range of anatomical models, posters and revision guides allow students and professionals to deepen their understanding through visual and tactile learning. Whether you're preparing for an exam, teaching a class, or working in a clinical setting, our resources provide a practical and engaging way to study human anatomy.