excretion Flashcards
definition of excretion
removal of metabolic waste products and toxic substances from the body
what is metabolism?
metabolism = catabolism + anabolism
* anabolism : simple molecules built up into complex molecules with intake of energy
* catabolism: complex molecules broken down into simple molcules with release of energy
why must metabolic waste products be removed from the body?
- harmful if accumulates in body
egestion vs excretion
- egestion: removal of undigested matter not produced by metabolism
- excretion: removal of metabolic waste products
how do unicellular and multicellular organisms carry out excretion
- unicellular: by diffusion
- multicellular: by special excretory organs
parts of urinary system
- hilum
- kidney
- ureter
- bladder
- sphincter muscle
- urethra
what is the hilum
depression where renal artery, renal vein and nerves are connected to kidney
what is the kidney
- bean-shaped organ
- removes nitrogenous waste products (deamination of amino acids), mineral salts (neutralisation reaction) and excess water
- regulates salt and water balance in blood plasma
- mantains pH and composition of blood plasma
what is the ureter
- narrow tube that emerges from hilum
- brings urine from kidney to bladder
what is the bladder
elastic, muscular bag that stores urine
what is the spincter muscle
- found at bottom of bladder
- controls urine flow
what is the urethra!!!!!
duct which urine passes from bladder to outside the body
what do renal arteries vs renal veins do
- renal arteries - bring oxygenated blood containing urea and excess water from heart to kidney
- renal veins - bring deoxygenated blood (no urea or excess water) from kidney to heart
what are the 2 regions of the kidney
- cortex : outer darker red region enclosed by fibrous capsule
- medulla: inner thicker paler red region, contains pyramids
structure of a nephron
- basic functional unit of kidney
- each kidney has 1 million nephrons
- tiny tubules where urine is formed
- open into the collecting duct (tube)
4 main parts of a nephron
- Bowman’s capsule
- proximal convoluted tubule
- Loop of Henle
- distal convoluted tubule
urine is formed through which processes
- ultrafiltration
- selective reabsorbtion
what happens in ultrafiltration
- occurs in glomerulus
- removes small molecules from the glomerular blood capillaries into the bowman’s capsule to form the glomerular filtrate
- FILTERED OFF: water, glucose, amino acids, nitrogenous waste products (urea) , mineral salts (SMALL MOLECULES)
- NOT FILTERED OFF: blood cells, platelets, proteins, fats (LARGE MOLECULES)
2 conditions for ultrafiltration to occur
- high hydrostatic blood pressure in glomerulus due to wide afferent arteriole and narrow efferent arteriole (MAIN force of ultrafiltration)
- membrane that wraps glomerular capillaries are partially permeable with small pores so only water and small molecules can pass through
what happens during selective reabsorbption
- useful substances are reabsorbed from the glomerular filtrate
- occurs through proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct into blood capillaries
- excess water, excess mineral salts and nitrogenous waste products (urea) pass out of the collecting duct as urine
what is reabsorbed at proximal convoluted tubule
1) by active transport & diffusion:
* all glucose
* all amino acids
* most mineral salts
2) by osmosis:
* most water
what is reabsorbed at loop of henle, distal convoluted tubule and collecting duct
- loop of Henle: some water (osmosis)
- distal convoluted tubule: some mineral salts (active transport & diffusion)
- collecting duct: some water (osmosis)
causes of kidney failure
HI DI AL DA CO
1. high blood presure
2. diabetes
3. alchohol abuse
4. damage to kidneys
5. complications due to surgery
ways to treat kidney failure
- kidney transplant
- haemodialysis
- peritoneal dialysis
what happens during haemodialysis
- blood is channelled from a vein to a dialyser of dialysis machine
- tubing is bathed in a specially controlled dialysis fluid, walls are partially permeable
- small molecules (metabolic waste products) diffuse out of the tubing into the dialysis fluid. large molecules remain in the tubing
- filtered blood is return to the person’s vein in their arm
features of dialysis machine
- TUBING OF DIALYSER IS LONG, NARROW AND COILED → increase surface area to volume ratio to speed up exchange of substances
- DIALYSIS FLUID HAS NO METABOLIC WASTE PRODUCTS → steep concentration gradient for metabolic waste products to diffuse out of the tubing into dialysis fluid
- DIALYSIS FLUID HAS THE SAME CONCENTRATION OF ESSENTIAL NUTRIENTS → ensure nutrients do not diffuse out of blood
- DIRECTION OF BLOOD FLOW IN TUBING IS OPPOSITE OF THE FLOW OF DIALYSIS FLUID → mantains concentration gradient between blood and dialysis fluid for removal of metabolic waste products
