kidneys

primary function of kidneys

regulate the composition and volume of blood plasma and other body fluids

kidneys do

osmoregulation, ionic regulation, volume regulation

u/p = 1

urine ion concentration equals plasma ion concention, isosmotic, some marine fish, rare

u/p < 1

urine concentration is less than plasma concentration, urine is hyoposomotic to plasma, kidneys excrete water and retains ions, urine is dilute while plasma is concentrated, common in aquatic animals

u/p> 1

urine concentration is greater than plasma concentration, urine is hyperosmotic to plasma, kidneys retain water and excrete ions, urine is concentrated and plasma is dilute, conserves water, common in terrestrial animals

proximal tubule

secretion and reabsorption change in volume and composition of filtrate, bicarb nacl and water is absorbed

descending loop of henle

reabsorb water

ascending loop of henle

reasborb salt

distal tubule

k and nacl levels regulates

collecting duct

filtrate is more concentrated, minimize water loss

kidneys

consist of tubular elements, produce and elimate aqueous solutions from body fluid, regulate composition and volume of blood plasma

urine travel path

glomerulus, tubules, pelvis, calyx, ureter

nephron anatomy

filtration water and solutes enter filtrate and blood cells and proteins remain in body fluid, reabsorption reclaim glucose vitamins and hormones, secretion adds toxins and excess ions, excretion filtrate leaves body as urine

glomerular filtration rate

rate of primary urine formation by all kidney tubules

definitive urine

loop of Henle and collecting duct

single effect

difference in osmotic pressure and nacl concentration between the ascending limb fluid and adjacent interstitial fluid and the descending limb fluid

tubule secretion and reabsorption

secretion and absorption occur simultaneously to remove waste, control blood pH, and controls blood volume

where is the bulk of reabsorption

proximal tubule

where is regulated reabsorption

distal tubule where it is governed by hormones, na and water reabsorbed

amphibian urine flow

bowmans capsule, neck, proximal convuluted tubule, intermediate segment, distal convoluted tubule, collecting tubule, collecting duct

do amphibians have looping

no

amphibians proximal tubule

na active and cl passive are reabsorbed by prox tubule being permeable to water resulting in tubular fluid remaining isosmotic to blood plasma, site for glucose reabsorption

amphibian distal tubule controls what

controls the amount of water in the body fluids and the concentrations of solutes in the body fluid

amphibian distal tubule reabsorption

reabsorption of nacl continues but distal tubule is less permeable to water and final u/p depends on permeability of distabl tubule

what controls reabsorption within the kidney

hormones thattarget distal tubule, controls permeability

antidiuretic hormone ADH

increase urine concentration to reduce water loss, released by pituitary, alters aquaporin number in collecting tubule to increase water retention,

what does it mean to have more adh

when dehydrates, more concentrated urine to retain water

what does it mean to have less adh

hydrates so less concentrated urine

aldosterone

increase na reabsorption in blood so increases counter current mult, increase k reabsorption in filate whihc results in increase water retention blood volume and osmolarity

renin/angiotensin 2

raise blood pressure

gfr can be controlled by

varying rate of filtration into all nephrons and alter number of nephrons operating at any time

how does osmotic pressure change occur

along length of tubule, the epithelial wall changes in the number and types of ion channels, transporters, aquaporins

fw teleosts distal conv tubules

not permeable to water, close aquaporin, reabsorb salt, enlarged glomerulus so gfr is faster

fw teleosts

many nephrons and high gfr, gills actively absorb nacl and water enters osmotically, active tubular reabsorption of nacl, kidneys excretion of dilute urine

marine teleosts

nephrons lack distal convoluted tubule so no need to produce dilute urine, reduced glomerulus, few nephrons, gills actively secrete nacl, water loss , stomach passively reabsorbs nacl and water, kidney excretion of mgso4 urea little water, active tubular secretion of mgso4

urine formation in birds

have both loopless and looped nephrons, looped nephrons enable urine concentration, no bladder=no storage of fluid

mammal kidneys

loop of Henle between proximal and distal tubules, length is correlated with ability to produce concentrated urine, allows production of hyperosmotic urine