LEARNING OBJECTIVES
By the end of this chapter, you should be able to:
- identify excretory products
- trace urine flow
- outline nephron function
- explain deamination
THE BIG IDEA
How lungs, liver and kidneys remove metabolic waste.
This chapter builds each process from its structures, inputs and outputs. Follow the connections rather than memorising isolated facts, then use precise biological terms when explaining cause and effect.
01
SECTION 01
Products and organs
Excretion removes metabolic waste: lungs remove carbon dioxide; kidneys remove urea, excess water and ions.
DETAILED EXPLANATION
- Urine flows kidneys → ureters → bladder → urethra.
- Kidney cortex and medulla contain nephron regions.
- Urea must be removed because it is toxic at high concentration.
1kidneys→
2ureters→
3bladder→
4urethra
02
SECTION 02
Nephron
High glomerular pressure filters water, glucose, urea and ions; cells and large proteins stay in blood.
DETAILED EXPLANATION
- The tubule reabsorbs all glucose, some ions and most water into blood.
- Urine contains urea and excess water and ions.
1glomerulus: filtration→
2tubule: reabsorption→
3collecting region→
4urine
03
SECTION 03
Liver and urea
The liver uses amino acids to make proteins but cannot store excess amino acids.
DETAILED EXPLANATION
- Deamination removes the nitrogen-containing part.
- Urea forms in liver, travels in plasma and is excreted by kidneys.
QUICK CHAPTER SUMMARY
The ideas to carry forward
- Excretion removes metabolic waste.
- Nephrons filter and selectively reabsorb.
- All glucose is normally reabsorbed.
- Deamination forms urea.