Excretion Flashcards
Define catabolic reaction
Reactions that break up complex molecules into simpler molecules
Define anabolic reaction
Reactions which build up simpler molecules into complex molecules
Define excretion
The removal of toxic materials and the waste products of metabolism from organisms
Why is excretion important
Waste products from metabolism can be harmful and prevent the maintenance of a steady state in the body if allowed to accumulate
Define egestion
The elimination of undigested material from the alimentary canal
Function of kidney
Contains numerous kidney tubules which remove urea, excess water and heat from blood to form urine.
Responsible for osmoregulation(process which keeps water potential of the body fluids constant)
Function of ureter
Tube that connects kidney to urinary bladder. Urine flows from kidneys to bladder through the ureter
Function of bladder
Muscular bag which stores urine
Function of urethra
Muscular tube through which urine flows from bladder to exterior
Name five parts of kidney
Nephrons, cortex, medulla, renal pelvis, renal pyramid
Define ultrafiltration
Ultrafiltration is a non-selective filtering process which occurs at the glomerulus.
Describe the process of ultrafiltration(refer to textbook for details)
- splitting of renal artery
- high blood pressure+reason
- blood plasma is forced out
- what remains in blood
Describe process of selective reabsorption(refer to textbook for details)
PCT - glucose, amino acids, vitamins
LoH - water and ions
DCT - water and small conc. of Na and CL ions
CD - remaining water required by body
Define selective reabsorption
The transport of useful substances from the filtrate back to the bloodstream. Useful solutes are reabsorbed back by active transport and facilitated diffusion. Water reabsorbed by osmosis.
Define osmoregulation
The maintenance of a correct balance between water and dissolved solute in blood to maintain constant water potential in the body
How is ADH produced
Produced by the hypothalamus and released by the pituitary gland
Describe effectors involved in osmoregulation when water potential in blood increases
- Pituitary gland releases less ADH into bloodstream, transported to kidneys via
- Walls of DCT and CD less permeable to water
- Less water reabsorbed into blood
- Urine more diluted, higher volume
Describe effectors involved in osmoregulation when water potential in blood decreases
- Pituitary gland releases more ADH into bloodstream, transported to kidney
- Walls of DCT and CD more permeable to water
- More water reabsorbed into blood
- Urine more concentrated, smaller volume
Causes of kidney failure
High blood pressure, diabetes, alcohol abuse, accidents or infections
Describe hemodialysis
Blood drawn by fistula, passed through dialyser, dialysis fluid introduced, small molecules diffusion, blood returned
Features of the dialyser
- Tubing narrow to speed up rate of diffusion between blood and fluid
- Fresh dialysis fluid in contact with tubing where blood about to enter patient, no waste product enters patient
- Direction of blood flow opposite to flow of dialysis fluid. Maintains concentration for removal of waste products
Contents of dialysis fluid
Contains same concentration of essential substances as healthy blood, if there is lack of these substances, substances can diffuse into blood
Why are there no metabolic waste products in dialysis fluid
Sets up suitable concentration gradient for waste products to diffuse out tubing into dialysis fluid. Maintains correct solute concentration and water potential of blood
