Excretion Flashcards
Define excretion
removal of metabolic waste
What is metabolic waste?
products of reactions that have no use in the human body
Why is excretion important?
some products of reactions can be toxic
Give examples of toxic products of reactions
urea
carbon dioxide
How is co2 produced?
respiration
How is urea produced?
deamination
Where is co2 produced?
respiring cells
Where is urea produced?
liver cells
Where is co2 removed?
lungs via blood plasma
Where is urea removed?
kidneys and skin
Describe the structure of the kidney
cortex
medulla
pelvis
1000s of nephrons
What is deamination?
break down of amino acids that produces carbohydrates
What are the carbohydrates produced in deamination?
glucose - respiration
ammonia - toxic - urea
Describe the process of deamination
- amino acids filtered into liver by hepatic artery
- amino acids broken down
- carbohydrates produced (glucose, ammonia)
- ammonia converted into urea (less toxic)
- amino acids and urea back into blood stream by hepatic vein
Why is ammonia converted into urea?
less toxic
Why are the amino acids broken down into carbohydrates in deamination?
body cannot store excess amino acids
What is the kidney?
organ that filters blood
What processes happen in the nephron?
ultrafiltration
selective reabsorption
water reabsorption
What does the nephron contain?
glomerulus
bowman’s capsule
pct
loop of henle
dct
collecting duct
What is ultrafiltration?
process that filters blood into the glomerulus at high pressures to form glomerular filtrate
What is the glomerular filtrate made of?
water, urea, amino acids and glucose
How is a high pressure created in the glomerulus?
afferent arteriole has larger diameter at entrance of glomerulus compared to efferent arteriole at exit
What is the Bowman’s capsule?
collection of capillaries
What is the glomerulus?
where glomerular filtrate is created
What does the high pressure in the glomerulus mean for the glomerular filtrate?
only small molecules can move from the capillaries in the glomerulus into the Bowman’s capsule
large molecules cannot cross the basement membrane
Which large molecules cannot enter the glomerular filtrate?
red blood cells
white blood cells
proteins
What is selective reabsorption?
selective uptake of useful substances like glucose, water and amino acids
Where does selective reabsorption happen?
proximal convoluted tubule
How is the pct adapted for selective reabsoption?
mitochondria
microvilli
Why does the pct have lots of mitochondria?
respiration
makes ATP
for active transport
glucose and amino acids move against conc gradient - want to absorb all
Why does the pct have lots of microvilli?
increases surface area
increases rate of diffusion and active transport
Which processes transport glucose, amino acids and salts out of the pct?
active transport
diffusion
Why does water move out of the pct during selective reabsorption?
glucose and amino acids are removed so water potential is increasing in pct
water moves by osmosis down conc gradient
water follows glucose and amino acids
What happens in the loop of Henle?
concentration of urine
What happens in the collecting duct?
water reabsorption
Describe how the loop of henle concentrates urine
salts and ions selectively reabsorbed
water potential increases
water moves by osmosis down conc gradient
water follows
What is the role of ADH?
makes collecting duct more permeable by making small holes in it
How does ADH respond to the body being dehydrated?
more holes
reabsorb as much water as possible
= osmoregulation
What is in urine?
urea
water
some salts
What is in blood plasma?
glucose
urea
water
some salts
red blood cells
white blood cells
protein
What is osmoregulation?
collecting duct responding to ADH
absorbing as much water as possible because of dehydration
ureter
tubes that carry urine from the kidneys to the bladder
urethra
tube that carries urine from the bladder out of the body
Give two advantages of having a kidney transplant rather than treatment by dialysis
dialysis - regular hospital treatements
transplant - continuous, no build-up
Give two possible disadvantages of having a kidney transplant.
rejected by other tissues - foreign object
infection
