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CHAPTER 13: EXCRETION IN HUMAN (Pathway of Urine Production in Kidney (1.…
CHAPTER 13: EXCRETION IN HUMAN
Excretion
:
Removal of toxic materials, waste products of cellular metabolism and substances in excess of requirement from the organism.
Human 3 main excretion products
:
carbon dioxide (from respiration by lungs)
urea (from kidneys)
water (from kidneys & skin surfaces)
Kidneys
Urea Production and Excretion
Urea
: Made from excess proteins and amino acids
Protein being used in Liver:
Protein gets eaten & digested into amino acids
Amino acids absorbed into bloodstream - travel throughout the body (to be transported to cells that needed protein)
Arrived in liver:
nothing happen
liver shall string the amino acids together to form other protein, e.g. fibrinogen (protein to aid blood clotting)
LIVER:
Not all protein will be used to by cells
- excess protein will be stored
stored in the form of carbohydrates or fats
liver needs to break down the excess proteins first - removing nitrogen-containing part (deamination)
broken nitrogen-containing part is being made into urea
What happened to the urea produced in the liver?
Blood flows into the kidneys - plasma squeeze through a filter into kidney
plasma flows through kidney, useful substance (of the plasma:
e.g. glucose, sodium ions & chloride ions
) is being reabsorbed into bloodstream; leaving urea in the tract.
urine: urea + water (produced by the kidney)
if body is dehydrated (lacking of water): urine produced is concentrated (a little of water is allowed to removed out)
if body has water in excess: urine produced is diluted ( a lot of water is removed out)
Urinary System
Ureter
: A tube transport urine that connecting kidney to bladder
Bladder
: Urine temporary storage
Urethra
: A tube transport urine out from the body from bladder
Structure of Kidneys
Medulla
Kidney inside part
Contains thousands of kidney tubules
Cortex
Kidney outer part
Kidney tubules started in cortex: called as
renal capsule
Contains thousands of kidney tubules
Pathway of Urine Production in Kidney
1. Blood delivered into renal capsule.
blood plasma squeeze through walls of capillaries, through walls of capsule, into cavity of renal capsule
2. As the blood passes into the tubule, blood plasma passes through filter.
blocked entrance: cells, big protein molecules
allowed entrance: small molecules, urea, water, glucose, ions (sodium & chloride) :arrow_right: pass/flow along the tubule
3. Anymore useful substances flowing in the tubules, will be reabsorbed into bloodstream
all glucose
most of the water
some sodium ions & chloride ions
4. Anything not useful (waste products) will be gotten rid of
stays in the tubules
most urea stays in tubules - to be excreted out
water being absorbed more and more, urea concentration gets higher steadily
5. Excretion
Urea, water and excess salts will be expelled out of the body - excretion
Kidney Failure
Kidney Transplant
Advantages:
best method
no further treatment is needed (kidney works as previous history)
Disadvantages:
not frequently available (in need of young & healthy donor)
protein of the donor is a good match to recipient - immune response in recipient body)
even if compatible: recipient need to immunosuppressants drug (for lifetime) - suppress immune system to reject kidney
Dialysis
Blood filtering:
dialysis fluid - similar composition to absolute sterile, healthy human plasma (mostly water, glucose & salt)
dialysis tubing - similar to Visking tubing (small pores), allowing diffusion of urea, water, ions & glucose.
How it works - each component will diffusion according to concentration gradient
:
urea in bloodstream (concentrated) :arrow_right: out into dialysis fluid (very diluted to none)
a lot of water in bloodstream (high water potential) :arrow_right: out into dialysis fluid (lower water potential) - pulling back optimum water level in blood plasma
dehydrated (low water potential) :arrow_left: water out from dialysis fluid (higher water potential) - refilling back water balance in blood plasma to optimal