Zusammenfassung der Ressource
Excretion
- Liver
- Regulates blood glucose
- Blood glucose increase control by insulin from pancreas
- Stores to glycogen (glycogenesis), fatty acids and
triglycerides in liver, muscle and adipose tissue
- Uses glucose in glycolysis to
release energy
- Blood glucose decrease control by
glucagon from pancreas
- Releases glucose
from glycerol
stored in liver
- Releases glucose from
amino acids in muscle
by gluconeogenesis.
- Regulation of amino acids (excess toxic)
- Excess transferred to liver by hepatic portal vein from intestine
- Deamination
- Converts to ammonia
(toxic) which combines
with carbon dioxide to
form UREA in the
ORNITHINE cycle
- Transamination
- The twelve amino acids which can be made by the body are produced by
converting one type of amino acid into another – transamination.
- Production of plasma proteins
- Regulation of body temp
- Other functions
- Pancreas
- Islets of Langerhans produce insulin
- Alpha cells
- Detects low blood sugar
- Glucagon causes release of glucose from glycerol
stored in liver and converts amino acids from
proteins in muscle into glucose by gluconeogenesis
(non-carbs). Glucagon releases energy from fatty
acids in muscle to provide energy for process.
- Beta cells
- Detects high blood sugar
- Insulin causes take up of glucose in liver, muscle
and adipose tissue (converts to glycogen).
- Kidney
- Removal of nitrogenous and other waste from the body
- Urea from liver (ornithine cycle)
- Bowmans cup contains glomerulus. The high pressure forces small molecules such as water,
glucose, amino acids, sodium chloride and urea through the filter i.e. from the blood in the
glomerular capsule across the basement membrane of the Bowman's capsule and into the nephron.
Ultrafiltration: The fluid formed in this way is called glomerular filtrate. Large molecules such as
plasma proteins and blood cells do not pass through the filter because they are too big.
- The filtrate contains toxic substances such as urea which it is necessary toremove from the body but
it also contains substances such as glucose which are required by the body. The function of the
proximal convoluted tubule is to reabsorb these useful substances.
- Similar mechanisms result in the re-absorption of many of the amino acids and up to 90% of the
sodium ions from the tubule fluid. The removal of all these soluble substances results in an osmotic
gradient between the fluid in the tubule and the cells which line it. Water is therefore drawn out of
the tubule fluid by osmosis, and passes into blood. This process is responsible for 85-90% of water
re-absorption in the Nephron. It is only the remaining 10-15% which is regulated in the loop of Henle
and collecting duct.
- The ability to produce concentrated urine is important in allowing terrestrialmammals to conserve
water. The loop of Henle and the collecting ductform a system known as a countercurrent multiplier
whose function isto remove water from the fluid in the tubule and produce a concentratedurine.
- Uric acid from deamination of purines (adenine and guanine)
- Ammonia from deamination of amino acids. Ammonia is
secreted into the urine by cells in the kidney tubule.
- Maintaining constant internal environment by helping to regulate
pH, water and sodium ionconcentrations in the blood and tissues