The Urinary System (Leaving Cert Biology): Revision Notes
📚 Revision Notes
The Urinary System
Structure of the Urinary System
- The main organs of the urinary system are the kidneys.
- The kidneys filter the blood and produce urine which is sent to the bladder for storage until they leave the body.
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The adrenal glands sit above the kidneys. They produce hormones such as adrenaline.
Key Components of the Urinary System
- The urinary system consists of:
- Kidneys (2)
- Ureters (2)
- Bladder
- Urethra
- Kidneys:
- The kidneys are bean-shaped, fist-sized organs found in the small of the back, below the diaphragm.
- Function: Filter the blood to remove urea, salt, and water, which are then sent to the bladder.
- Ureters: Tubes that carry urine from each kidney to the bladder.
- Bladder: Stores urine until it is ready to leave the body.
- Urethra: A single tube that carries urine from the bladder out of the body.
Urea Formation
- Urea is formed in the liver through the breakdown of excess amino acids in a process called deamination.
- Urea, excess salt and water travel through the blood to the kidneys for excretion.
- These are sent to the bladder for storage and released through the urethra and out of the body.
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Excess protein can't be stored in the body because it contains nitrogen, which is toxic. The liver breaks down excess amino acids (including the nitrogen) in a process called deamination. This produces urea. Urea then travels through the blood to the kidneys.
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Exam Tip: Remember, each person has 2 ureters (one from each kidney) but only 1 urethra. This is a common mistake made in the exam.
Ureters carry urine from the kidneys to the bladder, while the urethra is the tube that carries urine out of the body.
| Renal artery | Supply blood to the kidneys. |
|---|---|
| Renal vein | Carries blood from the kidney to the heart. |
| Ureters | Connect the kidneys to the bladder, transporting urine. |
| Bladder | A muscular, elastic organ that stores urine until urination. |
| Urethra | A tube that carries urine from the bladder out of the body during urination. |
| Sphincter muscle | Found at the top of the urethra. It stays contracted until urination. When it relaxes, urination occurs. |