EXCRETION

Urinary system

with some IGCSE questions

http://biodeluna.wordpress.com/

Homeostasis.

• Homeostasis is the general function that controls and keeps constant the conditions of our body.

Excretionit is the removal from organisms of toxic

materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements.

Substances include carbon dioxide, urea and salts

Urinary system anatomy

• Excretory systems regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of this system in vertebrates include:

the kidneys, liver, lungs, and skin.

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEXCRET.html

Outline structure of a kidney

The kidney

ureter

renal pelvis

renal cortex

renal medulla

pyramids

Kidney function

Removal of urea and excess water and the reabsorption of glucose and some salts, so:

• Remove wastes.• Regulate water levels

The nephron

X section to nephron

Nephron

Nephron function

• role of renal capsule - filtration from blood of water, glucose, urea and salts

• role of tubule - reabsorption of glucose,most of the water and some salts back into the blood, leading to concentration of urea in the urine as well as loss of excess water and salts

How can our body keep the percentage of water in our body

around 60/70%?• 60 – 70 % of the weight of our body is

water (around 40 l of water).

• If it is very hot and we sweat, we lose some of our body water composition.

• If we lose water, we can suffer dangerous dehydration

• We have to” save” water and we must not lose more water through urine.

• The urine will be more concentrated (water is reabsorbed)

• If we drink a lot of water, we have an extra supply of water (that we don’t need).

• Our urine will be more diluted (water will not be reabsorbed in kidneys).

Urea

• Urea is formed in the liver from excess amino acids most of the water and some salts back

How toxic waste from cellular respiration (catabolism) is excreted

• 1- Blood + waste come to kidneys by renal artery.

• 2-Filtration of waste in the nephron.

• 3-Reabsorption of some useful products that could have been filtered, to the capillaries surrounding the nephron.

• 4-Waste is concentrating as urine.

• 5-Urine goes to the -collecting duct - ureter - bladder - and goes out by urethra

Kidney stones (renal calculi)• It is the term commonly used to refer to stones,

or calculi, in the urinary system. Stones form in the kidneys and may be found anywhere in the urinary system. They vary in size. Some stones cause great pain while others cause very little. The aim of treatment is to remove the stones, prevent infection, and prevent recurrence. Both nonsurgical and surgical treatments are used. Kidney stones affect men more often than women.

Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine.

http://thoughtsandstuff.posterous.com/uh-oh-kidney-stonesouch

Renal (kidney) failure• It results when the kidneys are not able to regulate water

and chemicals in the body or remove waste products from your blood. Acute renal failure (ARF) is the sudden onset of kidney failure. This condition can be caused by an accident that injures the kidneys, loss of a lot of blood, or some drugs or poisons. ARF may lead to permanent loss of kidney function. But if the kidneys are not seriously damaged, they may recover. Chronic kidney disease (CKD) is the gradual reduction of kidney function that may lead to permanent kidney failure, or end-stage renal disease (ESRD). You may go several years without knowing you have CKD.

Dialysis• Artificial maintenance

of glucose and protein concentration in blood and diffusion of urea from blood to dialysis fluid.

In case of chronic renal failure…

What about a kidney transplant?

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discuss the advantages and disadvantages of kidney transplants, compared with dialysis

IGC

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– syllabus question

• Advantages: Dialysis takes a HUGE amount of time, and your life revolves around it. You also risk infection.A kidney transplant is permanent

• Disadvantages: Obviously, the risks associated with any surgery, risk of rejection by your body, and you have to take anti-rejection drugs your whole life.

http://answers.yahoo.com/question/index?qid=20090331122335AAJiPAb

Some IGCSE

questions

Sandra Brinkhoff

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• Some concepts taken from IGCSE Biology syllabus 2010

http://blogs.laweekly.com

/style_council/interior-decor/urinary-tract-wallpaper/

• http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEXCRET.html• http://en.wikipedia.org/wiki/Excretory_system• http://kidney.niddk.nih.gov/kudiseases/pubs/Yoururinary/