excretion Flashcards
excretion
all animals must do– it controls osmoregulation and controls the solute concentration in body fluids- excretion is to remove nitrogenous wastes (breakdown of aa and proteins) UREA- NH3 is converted into urea and it is less toxic, terrestrial animals do this, fish just excrete urea directly and reptiles, birds, and insects convert NH3 into uric acid which forms crystals and minimizes water loss
osmoconformers are isosmotic with surroundings and osmoregulators control internal osmolarity independent to environment
excretory processes
transport epithelia- one or more layers of specialized epithelial cells that can move particular solutes and they are arranged in tubular networks to increase sa
-all animals produce urine
1.filtration- excretory tubules collect filtrate from blood
2reabsorption-transport epithelium reclaims valuable substances from filtrate returns that to blood
3.secretion- toxins and ions removed from the blood and body fluids
4. excretion- urine leaves
invertebrates
flatworms excretory system - proteonephrida and it is a network of dead end tubules connected to openings. flame clubs at the end of branches have tubule cell and a cap cell. a tuft of cilia projecting into tubule beat and draw in H20 and solutes the filtrate is released into the tubular network and empties out of pores, urine has a low solute concentration helping with osmoregulation. other flatworms are isoosmotic- their function of protonephridia is used for NH3 removal natural selection has allowed the proteoniphridia to evolve to do different tasks in different environments
insects/ arthropods
malpighian tubules (transport epithelium) - secrete certain solutes and wastes into lumen of tubule and filtrate moves to digestive track- the solutes pumped back into hemolymph then H2O reabsorption , the urine is excreted with faces.
kidney description
aorta brings blood to the renal artery which supplies blood to the afferent arteriole to the glomerulus which is in the bowmans capsule these two structures together are known as the renal corpuscle. this is where pressure filtration occurs. the filtrate then moves into the proximal convoluted tubule where selective reabsorption occurs the filtrate moves down the descending loop which is permeable to H2O and as the filtrate approaches the loop of henle the medulla becomes increasingly concentrated. the loop of henle however must become impermeable to water because the filtrate becomes so concentrated and has enough op to pull the water back into the nephron. the countercurrent mechanism in the ascending loop combats this by actively pumping sodium ions out of the nephron and into the medulla. the filtrate then goes through the distil convoluted tubule where tubular excretion occurs it then goes to the collecting duct and eventually into the renal pelvis and from there into the ureter which takes the urine to the bladder and then from there it leaves through the urethra. the efferent arteriole takes blood away from the glomerulus and the renal vein takes blood to the posterior vena cava and eventually to the heart.
three processes in the kidney
- pressure filtration - 80% of small molecules out of blood - nutrient and waste no formed elements (plasma proteins) – vasoconstriction occurs at the efferent arteriole to ensure that the glomerulus has high pressure.
- selective reabsorption- molecules passively and active are reabsorbed into the blood– 100% of glucose reabsorbed, and amino acids. sodium ions are actively pumped back into blood and cl ions and water follow by diffusion – cuboidal epithelial cells with microvilli facilitate 3.tubular secretion-bloods last chance to remove toxins and control the pH which should be between 7.35 and 7.45
nephron types
cortical nephron- go short distance into medulla
juxtamedullary nephrons- extend deeper in medulla closer to the higher solute concentration so more water can be pulled from the nephron and reabsorbed into the blood- animals in dry climates have this
what occurs at each structure
pct selective reabsorption occurs
descending loop- H2O is reabsorbed from aqua porins and no solutes leave the more hypertonic the loop gets as it moves to the medulla
ascending loop- returns to cortex and is impermeable to water- thickens as it approaches the DCT solutes and NaCl diffuses out and makes the outside hypertonic and towards the top the NaCl needs to be pumped out.
DCT- controls the acid content of the blood if the blood is acidic the DCT accepts H+ ions which bind with bicarbonate HCO3. if blood is alkaline H+stay in creatinine uric acid and penicillin are pumped into filtrate
collecting duct- filtrate now called urine and it is impermeable to H2O unless ADH is present which opens aquaporins
urea reabsorption
44% of urea is reabsorbed to maintain op of blood
CAPD
continous ambulatory peritoneal dialysis - dialysate fluid is dumped into peritoneal cavity and left for hours. the waste diffuses through walls of mesenteric and peritoneal capillaries into this fluid. waste fluid drained and replaced dialysate isotonic to blood plasma
pH control
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