26 terms

IGCSE Biology - The Kidney

Key terms from Edexcel IGCSE Biology on the topic of The Kidney
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Homeostasis
Maintaining a constant internal environment
Osmoregulation
Keeping the water and salt content of the internal body environment constant
Excretion
Removal of metabolic waste from the body
Three organs of excretion
The kidneys, lungs and skin
Urine
Fluid stored in the bladder and discharged through the urethra. Composed of mainly water, salts and nitrogenous waste products.
Nitrogenous waste
e.g. ammonia and urea
Urea
Waste product of metabolism made by liver from excess protein - must be removed as it is harmful to the body
Kidney
A homeostatic and excretory organ that controls the water and salt concentration in the body and helps to eliminate nitrogenous waste.
Renal artery
Supplies oxygenated blood to the kidneys
Renal vein
Transports deoxygenated blood from the kidneys
Ureter
Tube connecting each kidney to the bladder.
Bladder
Muscular bag that stores urine
Urethra
Tube that takes urine from the bladder out of the body
Cortex
Outer layer of the kidney
Medulla
Middle layer of the kidney that is roughly divided into pyramids
Kidney tubule / Nephron
Filtration unit found in the kidney. Each kidney has millions.
Pelvis
Funnel-shaped cavity of the kidney into which urine is emptied before it passes into the ureter
Bowman's capsule
Hollow cup of cells that surround the glomerulus. This is where filtrate enters the nephron
Glomerulus
A ball of blood capillaries under high pressure, which act as the site of ultrafiltration
Glomerular filtrate
Fluid forced from the blood out of the capillaries of the glomerulus into the Bowman's capsule. Composed of water, salts, glucose and urea.
Ultrafiltration
The process where small molecules are forced from the blood out of the capillaries of the glomerulus, under high pressure, into the Bowman's capsule.
Loop of Henlé
U-shaped loop that runs down into the medulla of the kidney, from which water and salts are resorbed into the blood
Collecting duct
The ends of several nephrons join to make this structure. Urine passes down this tube on its way to the ureter.
Anti-diuretic Hormone (ADH)
A hormone produced by the pituitary gland when the body is dehydrated. It causes the kidneys to reabsorb more water into the blood making the urine more concentrated.
Hypothalamus
A region of the brain that coordinates the activity of the pituitary gland and monitors blood concentration.
Selective reabsorption
Process where certain moleules are removed from the nephron and put back into the blood. Occurs in the first coiled tubule of the nephron.
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