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Excretion Summary
Key Terms Excretion
Excretion:removal of metabolic waste from the Carbon dioxide from respiration and urea from
body excretion are produced in very large amounts and
Metabolic Waste:consists of waste need to be gotten rid of. Urea is produced in the
substances that might be toxic or are produced…

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The Liver
Hepatocytes carry out many important metabolic
processes and the liver has an important role in
homeostasis so it needs a good blood supply.

Blood flow to the liver -
Source 1 - oxygenated blood from the heart: from
aorta via hepatic artery
Source 2 - deoxygenated blood from…

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The Kidney
Kidneys are supplied with blood from a renal artery, and the blood is drained from the renal vein. The kidneys
remove waste products from the blood to produce urine. It is comprised of: the cortex, the medulla, and the
pelvis which leads into the ureter.
The Nephron -…

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Formation of Urine
Ultrafiltration - blood flows from the afferent arteriole into the glomerulus, the afferent arteriole is
wider than the efferent arteriole to ensure the blood is under high pressure to push fluid from the
blood into the Bowman's capsule.
There are three layers the barrier between the blood…

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How this is achieved -
Low water potential in medulla is
due to:
- loss of water by osmosis to the
surrounding tissue fluid
- diffusion of sodium and chloride
ions into the tubule from
surrounding tissue fluid
Higher water potential in cortex is
due to:
- at base of…

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Adjusting the concentration of ADH in the
blood -
· water potential of blood monitored by
osmoreceptors in hypothalamus
· respond to the effects of osmosis, low
water potential - osmoreceptor cells
lose water so they shrink and stimulate
neurosecretory cells
· neurosecretory cells (specialise
neurones) produce and release ADH,…

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Kidney Failure
Common causes of kidney failure:
- diabetes mellitus (both type I and type II sugar diabetes)
- hypertension
- infection
Without the kidneys the body cannot remove excess water and certain waste products, it is also
unable to regulate levels of water and salts in the body, and…

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Kidney Transplants
Advantages Disadvantages

Freedom from time-consuming dialysis Need immunosuppressants for the life of the kidney

Diest is less limited Need major surgery under a general anaesthetic

Feeling better physically Risks of surgery include infection, bleeding, and
damage to surrounding organs

A better quality of life, e.g. able to travel…

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