L: Excretion Flashcards
(24 cards)
Excretion
The removal of the waste products of metabolism
Kidney
One of two organs in humans which extract impurities from the blood
Metabolic waste
Harmful by-products of metabolic processes
Renal artery
Carries blood to the kidneys
Renal vein
Takes blood away from the kidney
Urea
Produced from the breakdown (deamination) of excess amino acids in the liver
Glomerular filtrate
The fluid forced out of the glomerulus under high pressure. It contains water, glucose, urea, ions and other small molecules, but NOT blood cells and large molecules such as proteins
Selective reabsorption
The process where the substances we need, e.g. glucose, are reabsorbed from the tubules back into the blood stream
Collecting duct
The tubule that receives urine from numerous nephrons. The permeability of its wall to water is controlled by ADH.
Bowman’s capsule
A cup-shaped receptacle in the vertebrate kidney that is the initial, expanded segment of the nephron where filtrate enters from the blood
Ultrafiltration
The process where fluid (called glomerular filtrate) is forced out of the glomerulus under high pressure
Urine
The liquid waste filtered from the blood by the kidney and stored in the bladder pending elimination through the urethra
Glomerulus
A dense network of capillaries where water, ions, glucose and urea are filtered from the blood into the tubules
Pituitary gland
A small gland in the brain that releases several hormones, including ADH
Active transport
The transport of a substance across a biological membrane against a concentration gradient. Energy from respiration is required
Proximal convoluted tubule
Site where the majority of the glomerulus filtrate is reabsorbed. All of the glucose is reabsorbed back into the blood here by active transport
Osmoregulation
The hormonal control of water levels in the blood
Ureter
Transports urine out of the body
Negative feedback
Any mechanism which reverts a change in a system back to its normal value
Urethra
Transports urine out of the body
Nephron
Functional filtering until of the kidney, also knowns as kidney tubules. Each kidney contains about a million of these units
Loop of Henlé
A U-shaped loop that runs down into the medulla of the kidney. It has a complicated role in concentrating the fluid in the tubule to allow more water to be reabsorbed into the blood
Anti-diuretic hormone (ADH)
The hormone which increases the permeability of the collecting ducts, allowing more water to be reabsorbed back into the blood
Hypothalamus
A region of the brain that contains special receptor cells which are sensitive to the solute concentration of the blood. It has several other roles, e.g. it also contains the thermoregulatory centre which detects blood temperature
