Excretion in Humans Flashcards
What is meant by excretion?
Excretion is the process by which metabolic waste products and toxic substances are removed from the body of an organism.
What is meant by metabolism?
Metabolism refers to all chemical processes (anabolic and catabolic) that take place in living cells in order to keep the organism alive.
Why is there a need for excretion?
Excretion is essential as the accumulation of metabolic waste products can be toxic.
How is carbon dioxide excreted?
Through the lungs as gas in expired air.
What are examples of nitrogenous waste products?
Urea, uric acid, creatinine
How are excess mineral salts and nitrogenous waste products formed?
Through the kidneys as urine, or the skin as sweat
How is excess water excreted?
Through the kidneys as urine, the skin as sweat, or the lungs as water vapour in expired air
How are bile pigments excreted?
Through the liver as a constituent of faeces, via the intestines
What features of the glomerulus allow ultrafiltration to occur?
High hydrostatic blood pressure ->The afferent arteriole (brings blood to glomerulus) is wider than the efferent arteriole (carries blood away). This results in a high blood pressure in the glomerulus, forcing water and small molecules out of the glomerulus into the Bowman’s capsule.
Partially permeable membrane -> Wraps around glomerulus and works like a fine filter. It only allows small molecules to pass through.
Where is water reabsorbed in the nephron?
Mostly absorbed in the proximal convoluted tubule. Some water is reabsorbed in the loop of Henlé, the distal convoluted tubule and the collecting duct.
Where is glucose and amino acids reabsorbed in the nephron?
ALL are absorbed in the proximal convoluted tubule through diffusion and active transport.
What happens to the concentration of urine when a person has a protein-rich diet?
More urea would be present because excess amino acids will be deaminated in the liver.
What happens to the concentration of urine when a person gets diabetes?
Glucose would be present. This is because the nephrons are unable to reabsorb high amounts of glucose fast enough.
What is osmoregulation?
Osmoregulation is the control of water and solute concentrations in the blood to maintain a constant water potential in the body.
What happens to the kidneys when a person sweats too much?
Sweat
- > Less water in body
- > Water potential in blood plasma decreases
- > Pituitary gland releases more ADH into bloodstream
- > Cells in walls of collecting ducts become more permeable to water
- > More water is reabsorbed from collecting duct into blood capillaries
- > Urine produced is more concentrated but of lower volume
- > Water potential of blood returns to normal
