excretion Flashcards
excretion def
Excretion def: the process by which the metabolic waste products and toxic substances are removed from the body of a organism
two impt processes in Urine formation:
- ultra filtration
- selective reabsorption
ultra filtration
- Occurs due to high hydrostatic pressure at the glomerulus
- Partially permeable basement membrane around the glomerular capillaries
- Afferent arteriole entering Bowman’s capsule is wider with a larger diameter than efferent arteriole
-> Creates a high pressure in glomerulus
-> Substances in blood plasma forced out of glomerulus into Bowman’s capsule - Partially permeable basement membrane of glomerular blood capillary has small pores that only allow small molecules (water, aa, nitrogenous waste products, glucose, dissolved mineral salts) to move into the Bowman’s capsule to form glomerular filtrate
- Large molecules are not filtered out and are retained in blood (plasma proteins, blood cells, platelets, fats)
selective reabsorption
- Allows useful substances to be selectively reabsorbed
1. At the proximal convoluted tubule,
All glucose molecules, aa molecules, most of dissolved mineral salts are selectively reabsorbed through the cells of the walls of tubule into surrounding blood capillaries via diffusion and active transport
Most of water molecules are selectively reabsorbed via osmosis
2. At the loop of Henle
Some water molecules are selectively reabsorbed from into the blood capillaries
3. At the distal convoluted tubule,
Some dissolved mineral salts and water molecules are selectively reabsorbed into blood capilary
4. At the collecting duct,
Some water molecules are selectively reabsorbed into the blood capillaries
Excess mineral salt ions, excess water molecules, metabolic waste products (urea, creatinine) pass thru ureter to bladder to be stored as urine
kidney dialysis adaptation
1.Consists of a long coiled partially permeable tubing in dialysis fluid
Blood is drawn out from vein and pumped through dialysis tubing
Increases surface area to volume ratio to increase rate of diffusion of substances between blood and dialysis fluid
2. Pores in dialysis tubing allow small molecules to pass through into the surrounding dialysis fluid
Dissolved mineral salts, glucose molecules, and urea molecules
Blood cells and protein are larger than pores of membrane, cannot pass through
3. Dialysis fluid consists of a solution of salts and sugar of the same concentration as blood of hleathy patients
To prevent a loss of glucose molecules and essential dissolved minerla salts from blood
To ensure diffusion of these substances from dialysis fluid into blood if blood lacks these essential substances
4. Does not contain metabolic waste products
Set up a concentration gradient of metabolic waste molecules
Diffuse out of tubing into dialysis fluid
Waste products are removed from blood
5. Direction of blood flow is opposite to the flow of dialysis fluid
Maintains the steep concentration gradient of metabolic waste molecules btwn blood and dialysis fluid for faster rate of diffusion of these substances into dialysis fluid
requirements of dialysis fluid
Correct pH and orrect temp and glucose concnetratiom -> affects cellular activities
correct BP -> affects rate of blood flow in body
when does kidney dialysis stop?
Exchange between blood & dialysis fluid continue until equilibrum
Nephron func
responsible for urine formation
Glomerulus func
Glomerulus -> a ball of capillaries
Bowman’s capsule
surrounds glomerulus
Proximal convoluted tubule, distal convoluted tubule contains many…?
contains many mitochondria for AT bc of selective reabsorption
kidney vs kidney dialysis (4)
kidney VS kidney dialysis
Diffusion, osmosis, AT //////// Diffusion, osmosis
Ultrafiltration and selective reabsorption ////// No ultrafiltration and selective reabsorption
Involves ADH ////// NO hormones involved
Pressure by LV of heart + pressure from narrower lumen of effernet arteriole than afferent arteriole /////// Pressure by dialysis machine
adaptations of nephron
- cells in bowmans capsule hv mitochondria for AT to absorb and also microvioli that increase sa to vol ratio
- afferent and efferent desc, hydrostatic pressure + force out molecules
- branched network glomerular blood cap high sa to vol ratio, higher rate of ultrafiltration
- endothelium of blood cap of glomerulus and cells in walls of bowman cap is ppm , will rebasorb the nutirents body needs and leave behind unwanted molecukes
- surface of glomerular blood cap are in close contact to bowmans capsule, shorter dist, filtrate can enter capsule directly
