Chapter 4 - Excretion
- Created by: stef17
- Created on: 21-04-16 10:31
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- Chapter 4 - Excretion
- The liver
- Formation of urea
- 1. Deamination of excess amino acids - keto acid is respired while ammonia is formed
- 2. Ammonia is toxic and very soluble, so is combined woth carbon dioxide to form urea, CO(NH2)2, during the ornithine cycle
- 3. Urea is still toxic, so is removed from the blood by the kidneys
- Blood supply
- Hepatic artery brings oxygenated blood
- Hepatic vein takes deoxygenated blood back to the heart
- Hepatic portal vein brings blood rich in absorbed nutrients
- Detoxification of alcohol
- Ethanol --> Ethanal --> Ethanoate
- Done by the enzymes ethanol dehydrogenase and aldehyde dehydrogenase
- Effects of excessive alcohol consumption
- Fatty liver
- Cirrhosis
- Ethanol --> Ethanal --> Ethanoate
- Histology
- Made of lobules
- Liver cells are called hepatocytes, there are channels that carry blood between these called sinusoids
- Other channels carry bile (made by some hepatocytes) and are called bile ducts
- Contains Kupffer cells (special, more efficient, macrophages)
- Detoxification of other substances
- Breakdown of hormones
- Breakdown of medicines
- Formation of urea
- The kidney
- Structure
- Has a cortex and a medulla, and is made up of thousands of nephrons
- Nephron structure
- Starts as a renal (Bowman's) capsule, then proximal convoluted tubule, loop of Henle, distal convoluted tubule and finally a collecting duct, which connects to the ureter
- Ultrafiltration
- Filtration on a micro-scale
- Happens in the renal capsule
- Happens under high pressure due to the afferent arteriole being larger than the efferent
- Selective reabsorption
- PCT
- Absorbs all glucose and 65% of water
- Loop of Henle
- Descending limb
- Permeable to water so water leaves due to water potential gradient
- Counter-current system
- Actively pumps out Na+ and Cl- ions
- Counter-current system
- Permeable to water so water leaves due to water potential gradient
- Ascending limb
- Actively pumps out Na+ and Cl- ions
- Descending limb
- DCT and collecting duct
- Ions actively pumped so water can be reabsorbed
- PCT
- Osmoregulation
- ADH released when more water is needed to be reabsorbed,isn't released when body has too much water
- Kidney failure
- Dialysis
- Haemodialysis or peritoneal dialysis
- Can be acute or chronic
- Can be treated with a transplant
- Dialysis
- Structure
- The liver
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