The Excretory system Flashcards
What is excretion?
The removal of wastes from the body, including CO2, urea, toxins, excess water, and salts.
Why is excretion important?
To maintain an environment of homeostasis.
What do the lungs excrete?
Carbon dioxide and water vapor.
What do the sweat glands in the skin excrete?
Salt and urea.
What does the liver excrete?
Toxins.
What do the kidneys excrete?
Urea, water, salts, and toxins (not blood or glucose).
What is the main organ of excretion?
The kidneys.
Where does glomerular filtration occur?
In the renal corpuscle (glomerulus).
What happens during glomerular filtration?
Blood plasma is filtered, separating small molecules and water from larger molecules and blood cells.
Why is glomerular filtration important?
It’s the first step in urine formation and it filters waste and excess fluids from the blood plasma.
What enhances glomerular filtration?
Short renal artery, wide afferent arteriole, coiled glomerulus with high surface area.
What does filtrate consist of?
Water, amino acids, urea, toxins, salts. 180L made per day.
Where does selective reabsorption occur?
In the proximal convoluted tubule (PCT).
What happens during selective reabsorption?
Useful substances like glucose, amino acids, ions, and water are reabsorbed into the blood.
Why is selective reabsorption important?
It prevents the loss of essential nutrients and maintains internal balance.
Where does tubular secretion occur?
In the distal convoluted tubule (DCT) and collecting duct.
What happens during tubular secretion?
Waste substances like H+, K+, creatinine, drugs, and toxins are added to the filtrate.
Why is tubular secretion important?
To remove harmful substances that weren’t filtered and to regulate blood pH and electrolytes.
What does urine consist of?
Water, urea, excess salts/ions, creatinine, hormones, toxins, drug residues.
How much urine do we excrete per day?
About 1.5 L.
What are the components of urine by percentage?
Water 96%, Urea 2%, Ions 1.5%, Other 0.5%.
What should not be in urine?
Glucose or large amounts of amino acids.
What characterises concentrated urine?
High in urea, low in water, small volume.
What characterises dilute urine?
Low in urea, high in water, large volume.
