EXCRETION Flashcards
What are the 3 main roles of kidneys
- REMOVAL OF UREA from the blood.
- ADJUSTMENT OF ION (salt) LEVELS in the blood.
- ADJUSTMENT OF WATER CONTENT in the blood.
Where is urea produced?
In the liver from excess amino acids
Describe the process of ultrafiltration
- Blood from RENAL ARTERY flows through GLOMERULUS
- HIGH PRESSURE is built up squeezing WATER. UREA, IONS and GLUCOSE out of blood and into BOWMAN’S CAPSULE
- Membranes between blood vessels in glomerulus and Bowman’s capsule act like FILTERS, so Big molecules stay in the blood.
Describe the process of réabsorption
- All the glucose is réabsorbed from PROXIMAL CONVOLUTED TUBULE so it’s used in respiration.
- Reabsorption of glucose involved process of active transport
- Sufficient ions are reabsorbed, excess ions aren’t
- SUFFICIENT WATER is reabsorbed from collecting duct into bloodstream by osmosis
What does urine consist of
Urea
Excess mineral ions
Excess water
What happens if the water content of the blood is too high?
The pituitary gland releases less ADH which leads to less water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become less permeable to water)
As a result, the kidneys produce a large volume of dilute urine
What happens if the water content of the blood is too low?
The pituitary gland releases more ADH which leads to more water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become more permeable to water)
As a result, the kidneys produce a small volume of concentrated urine
Dangers of waste products: CO2
Carbon dioxide dissolves in water easily to form an acidic solution which can lower the pH of cells. This can reduce the activity of enzymes in the body which are essential for controlling the rate of metabolic reactions
Dangers of waste products: water
Osmotic effect - body fluids can become more concentrated due to higher amounts of waste products
Concentrated body fluids can cause water to move out of cells, changing their water potential and preventing them from carrying out essential reactions
Dangers of waste products (pt. 3)
Using up necessary storage - space within an organism is limited and is required for the storage of more useful molecules
2 functions of urinary system
To filter waste products from the blood and expel it from the body as urine
To control the water levels of the body (osmoregulation)
What is each kidney connected to
The renal artery which comes from the aorta and delivers oxygenated blood to the kidney
The renal vein which delivers the deoxygenated blood from the kidney to the vena cava
Where is glucose reabsorbed
PCT
Why can’t réabsorption of glucose take place anywhere in the nephron?
the gates that facilitate the active transport of glucose are only found in the proximal convoluted tubule
What happens in glucose réabsorption of diabetics
People with diabetes cannot control their blood glucose levels and they are often very high, meaning that not all of the glucose filtered out can be reabsorbed into the blood in the proximal convoluted tubule
As there is nowhere else for the glucose to be reabsorbed, it continues in the filtrate and ends up in the urine
