Excretion - kidneys Flashcards
What are the 3 main roles of the kidney
- remove urea from blood
- adjust levels of salt
- adjust levels and concentration of water
Describe the general structure of a
kidney
- Contains a cortex and medulla
- Renal artery carries blood to the kidney
- Renal vein carries blood away from the kidney
- Each kidney contains many nephrons
- Ureter carries fluid from the kidneys to the bladder
Give 3 waste products produced in the
body
Urea
- Carbon dioxide
- Excess salt and water
Name 3 excretory organs
- The lungs
- The kidneys
- The skin
State the 4 roles of the kidneys
- Filtration
- Selective reabsorption
- Excretion
- Osmoregulation
What does the ureter do?
It carries urine from the kidneys to the
bladder for excretion.
State the 5 main parts of a kidney
nephron
- Glomerulus
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
What is the difference between the
ureter and the urethra?
- The ureter leads from the kidneys to
the bladder - The urethra leads from the bladder out
of the body
How does ultrafiltration work in the Bowman’s
capsule?
- Blood vessel leading to the glomerulus is wider than the
one leading away which increases the pressure of the
blood as it travels along - Small items in the blood are squeezed out under this high
pressure (big proteins and cells stay in the blood)
State 4 components of glomerular filtrate
- Urea
- Salts
- Water
- Glucose
What is the purpose of selective
reabsorption?
To prevent the excretion of useful
substances
What does ADH stand for?
Antidiuretic hormone
When is ADH released?
- When the body lacks water
- Controls permeability of collecting duct
Describe the process of ADH being released
- It is released in the pituitary gland by the pancreas when a receptor in the brain detects that the blood is too concentrated
- It travels in the blood to the kidney tubules
- An increased amount of ADH reaching the tubules increases their permeability to water so more water moves into the bloodstream
- This means that urine and blood is less concentrated
Describe the negative feedback loop when over hydration is detected
- Less ADH is released
- Dilute urine is produced
- Salts are retained to maintain correct ratio of salts to water
Give 3 components of urine
- Water
- Urea
- Ions
What is osmoregulation?
The scientific term used to describe the process that controls water and salt content of the body
All of what substance is reabsorbed from the proximal convoluted tubule and why?
Glucose - so it can be used in respiration but needs to be reabsorbed into the blood by active transport
How many ions are reabsorbed?
A sufficient amount not all though as that would mean they would be in excess
Where is water reabsorbed?
In the collecting duct (back into the bloodstream) by osmosis
What happens after urine passes down the collecting duct?
The remaining substances (water, ions and urea) form urine and travels down the ureter to the bladder, when it is stored before being released out of the body before of the urethra
How does osmoregulation work?
It constantly adjusts the volume and concentration of water in your body by the kidneys or sweating
What happens in terms of osmoregulation when you have drunk too much water (hypo hydration)?
Less ADH will be released in your bloodstream because the collecting duct does not have to be permeable because there is no need for more water in your bloodstream, so it is released and there is more urine, and it is more dilute
What happens in terms of osmoregulation when you have drunk too little water (dehydration)?
More ADH will be released into your bloodstream to make the collecting duct more permeable, so water can be reabsorbed back into your blood/body. Therefore, there is less urine, and it is more concentrated
Why does reabsorption take place in the loop of Henle?
It is in the medulla where the rate of osmosis is higher therefore it is more efficient
What is reabsorbed in the proximal convoluted tubule? and WHY?
- Glucose
- Amino acids
- Most mineral Ions
- Vitamins and hormones
- because they are needed in the blood and elsewhere in the body (they have their own functions)
What is reabsorbed in the Loop of Henle?
- Water
- Salts
What is reabsorbed in the distal convoluted tubule?
- Water
What travels through the collecting duct?
- Water
- Urea
- Ions
What is in the blood, after it has been filtered?
- RBC, WBC
- platelets
- proteins
- more water
- more salt
- glucose
- amino acids
What is the role of the bladder
- To store urine before it is expelled from the body via the urethra
Where is water reabsorbed back into the blood after ADH had been released?
- from the collecting duct into the blood capillaries by osmosis
How is urine produced?
- Blood (containing water, salts, protein, glucose and amino acids) travels through the renal artery and then arterioles (within the kidney) until it reaches a bundle of capillaries called the glomerulus situated at the beginning of the nephron. Due to the high pressure of the blood when entering the glomerulus, smaller molecules (everything except for protein as it is too large) are forced out through the small gaps in the cell membrane of the glomerulus and dribble down into the bowman’s capsule as the filtrate. This process is called ultrafiltration. However, some important components needed in blood are currently in the filtrate, so selective reabsorption takes place by osmosis and active transport. The filtrate travels along the tubule and reaches the proximal convoluted tubule where all the glucose, most amino acids and salts get reabsorbed back into the blood nearby. It continues travelling and reaches the loop of Henle where water is reabsorbed because the rate of osmosis is higher in the medulla. It then reaches the distal convoluted tubule when small adjustments to the filtrate are made before the filtrate passes down the collecting duct and into the renal pelvis where it will be removed from the body as urine.
Explain why reducing the level of sugar in food should decrease the number of people developing type 2 diabetes
- diet containing less sugar
- so less increase in blood sugar levels
- so less insulin produced
- by pancreas
- so decreased chance of insulin resistance developing
What is a symptom of high blood pressure
- proteins in urine
- (haven’t been filtered due to high blood pressure)
