excretion Flashcards
def metabolism
the sum of all the chemical reactions within the body of an organism
def excretion
process by which metabolic waste products and toxic substances are removed from the body
impt of excretion
metabolic waste products are harmful if accumulated
what is excreted via skin
urea, excess water, excess salts (sweat)
what is excreted via lungs
carbon dioxide, excess water (expired air)
what is excreted via the liver
bile pigments (feces through intestines)
what is excreted via the kidneys
urea, excess water, excess salts (urine)
func of kidneys
excretion, osmoregulation
func of ureters
connects kidney to bladder
func of bladder
temporary storage of urine
func of urethra
passage through which urine is discharged from the bladder
filtrate in ultrafiltration
water, glucose, amino acids, mineral salts, urea
residue in ultrafiltration
plasma proteins, blood cells, fats, platelets
selective reabsorption: absorbed in the pct
all glucose + amino acids, most water + mineral salts
selective reabsorption: absorbed in the loop of henle
some water
selective reabsorption: absorbed in the dct
some water + mineral salts
selective reabsorption: absorbed in the collecting duct
some water
structure of nephron: highly-coiled
incr sa:v, incr time taken for glomerular filtrate to pass through nephron to incr rate of selective reabsorption
structure of nephron: dense network of capillaries
incr sa contact and maintain steep conc gradient, incr rate of reabsorption
structure of nephron: epithelial cells of coiled tubules contain many mitochondria
release more energy for absorption via AT
what happens if kidney fails
excretory products accumulate in the blood
dialysis procedure:
- blood is drawn from a vein in the patient’s arm
- blood is pumped into the dialysis machine through a tubing
- the tubing is bathed in a dialysis fluid and is semi-permeable
- small molecules (urea) + metabolic products diffuse out of the tubing
- larger molecules (platelets + BCs) remain in the tubing
- the filtered blood is returned to a vein in the patient’s arm
feature of dialysis machine: contains same conc of essential substances as normal blood plasma
ensure no net movement of essential substances from blood into dialysis fluid
ensure substances can flow into patient’s blood if they lack them
feature of dialysis machine: metabolic waste products are absent from fluid
establish a steep conc grad to allow excretory products to diffuse into dialysis fluid for removal
feature of dialysis machine: long, narrow, coiled
incr sa:v, incr rate of exchange of substances btw blood and dialysis fluid
feature of dialysis machine: partially permeable
allow small molecules (urea + mineral salts) to diffuse through tubing but BCs and proteins to be retained in blood
feature of dialysis machine: fluid flows in opposite direction to flow of blood
maintain steep conc grad for removal of waste products
why is a vein used but not an artery?
ensure continuous input of blood because blood travels in spurts in the artery
