The kidney
Your two kidneys filter all of your blood many times a day. They remove urea and keep the water and salts in your blood at the right level. A human kidney holds about a million tiny tubes, called nephrons, which run through both the dark outer layer and the paler inner layer you can see here.
By the end of this page you can
- Describe the kidney’s two jobs: excretion and osmoregulation
- Name the parts of a nephron and say what each does
- Follow blood through the kidney until it becomes urine
- Define ultrafiltration, selective reabsorption and ADH
- Answer exam questions on the kidney and dialysis
Goals tick themselves off as you try the activities below.
Photo: Jurfeld, CC BY 4.0, via Wikimedia Commons. Resized, JPEG q72.
A lamb’s kidney, the kind used in school dissections. Outside to inside: cortex, medulla, then the pelvis that collects urine.
How often it shows up in past papers
Paper 1 counts come from our past-paper bank of CSEC Biology Paper 1s. Paper 2 is not included yet.
Two jobs, every minute
The kidneys clean the blood and control how much water it holds. When they fail, a machine has to do the first job for them. Tap each card.
The nephron and the way out
A nephron is one kidney tubule; each kidney has about a million. Tap each part, then the ureter.
What does each part do?
Tap a part on the list to see its job.
Urine is what is left: water, urea and some salts. No glucose and no protein in a healthy person.
From blood to urine
Put the stops in order, from blood arriving at the kidney to urine leaving it. Drag or tap each card into its slot.
Which vessel brings the blood in?
Seven terms to know cold
Say what each term means before you flip the card. Kidney questions often ask for two of these in one answer.
Six quick questions, then a real one
Pick an answer to see why it’s right or wrong.
Where does ultrafiltration take place?
In a healthy person, which substance is filtered but ALL taken back into the blood?
On a hot day a footballer sweats a lot. What happens?
Dialysis fluid contains no urea so that
Which is the correct route for urine?
Which is NOT normally found in the urine of a healthy person?
exam style · 3 marks
Explain how ADH helps to keep the water content of the blood constant when a person sweats a lot on a hot day.
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Practice questions are written by My V.I.P. Academy. They are not official CXC papers.