VMBO Year 2 · HAVO/VWO Years 2–3 · Circulation · Section 3.4
Excretion
Kidneys and the urinary tract
The kidneys lie on either side of the spine, towards the back of the abdomen below the diaphragm. Renal arteries bring oxygenated blood that also contains waste substances from body tissues.
The kidneys filter blood and selectively return useful substances to the circulation. They remove wastes and regulate the amounts of water and salts excreted. The resulting liquid is urine.
Kidney structure
- Renal cortex and renal medulla: Regions containing the structures that filter blood, reabsorb useful substances and form urine.
- Renal pelvis: Collects the urine before it leaves the kidney.
Urine travels along the ureters to the urinary bladder, where it is temporarily stored. This means you do not need to pass urine continuously.
During urination, urine leaves the bladder through the urethra. Renal veins return blood from the kidneys towards the heart.
Glossary
- Renal veins
- Vessels returning blood from the kidneys towards the heart.
- Renal pelvis
- The collecting region where urine gathers before entering the ureter.
- Renal medulla
- The inner kidney region involved in urine formation and concentration.
- Renal cortex
- The outer kidney region containing filtering structures and tubules.
- Renal arteries
- Vessels supplying the kidneys with blood containing oxygen and substances to be processed.
- Kidneys
- Organs removing wastes and regulating water and salts in the blood.
- Urine
- Fluid containing water, dissolved waste products and varying amounts of salts and other excreted substances.
- Urinary bladder
- The organ temporarily storing urine.
- Urethra
- The tube carrying urine from the bladder to the outside.
- Ureters
- The tubes carrying urine from the kidneys to the bladder.