the kidneys

what does urinary excretion allow us to remove from the body 3

excess water, electrolytes and metabolic waste

briefly, how does the kidney form urine

• filters blood

• reabsorb wanted ions/water

• excrete waste/urine

which part of the kidney does blood filtration happen in

• what is the specific name for this process

• what is the capillary structure called in bowman’s capsule

• renal cortex

• ultrafiltration

• glomerulus

what cells is bowman’s capsule made of

• what enters and exits

epithelial cells

• afferent - efferent arterioles

• what type of capillaries does the kidney have

• what does GRF stand for and mean

• Kf and σ

• fenestrated capillaries (discontinuous endothelium)

• glomerular filtration rate (rate of fluid filtration from the renal capillaries into bowman’s space)

• filtration coefficient (permeability of capillary to water)

• reflection coefficient (how IMpermeable the capillary is to proteins)

• what is this the equation for: Kf • [(PGC – PBS) - σ(πGC – πBS)]

• what part of the equation is responsible for high filtration rate

• what is the secondary barrier in filtration - how

  • what are the different parts of these cells

• GRF

• Kf - increased filtration coefficient

• podocytes - they wrap round glomerular capillaries to prevent cells and proteins entering

• podocyte cell body - primary processes - secondary processes - foot processes

• what are the two types of nephrons (extra info)

• under a microscope, what is the difference between PCT and DCT

• Cortical (superficial) and Juxtamedullary

• PCT - brush border of villi (most Na+ absorption), spaced nuclei / DCT - no brush border, dense nuclei

reabsorption:

• what are the two routes this can happen by (TC/PC)

• what 3 things is it driven by

• what 2 types of transport can power transcellular transport against a conc gradient

• Transcellular - requires both the luminal and basolateral membrane to be permeable to water or the solute of interest

• Paracellular - depends on the tightness of the junction between the cells (tight/leaky)

• concentration/ osmosis/ electrical gradients between tubular and interstitial fluids

• primary/secondary active transport

reabsorption in PCT:

• what is the process called IFR

• how does it slow flow and what does this allow

• fluid entering loop of henle will be ….

• example of 3 things absorbed

• isosmotic fluid reabsorption

• it reduces volume of fluid - slow - allows more time for exchange in the rest of nephron

• isosmotic

• HCO3-, aa, glucose

isosmotic reabsorption

• how do glucose and amino acids enter blood, what does this drive the uptake of

• how is Cl- absorbed

• reabsorption of NaCl creates what gradient

  • what is absorbed as a result and how

• transcellular reabsorption, drives Na+ uptake

• Cl- enters paracellularly

• osmotic gradient

• water enters paracellularly - leaky junctions

• how is a Net Filtration maintained in glomerulus

• how is BP reduced in efferent arteriole

• how is colloid osmotic pressure increased

• what two pressures favour a net reabsorption of fluid into capillaries

• high BP and low colloid (albumin/protein) pressure

• filtration of plasma from blood

• proteins are retained in smaller plasma volume

• low BP, high CP

ENDOCRINE SIGNALS: what effect do these have on reabsorption

• anti-diuretic hormone ADH

• NORADRENALINE

• Aldosterone

• ^^ water plasma

• ^^ Na+ plasma

• ^^ Na+ plasma so — K+ leaves

• what is osmolarity measured by

mOsmoles/L

state and explain the 3 types of tonic solutions

• what can we do to bring it back to normal level

• what are the 5 parts of a nephron

• what do they each absorb (in the absence of signal)

• PCT, thin descending limb, thick ascending limb, DCT, collecting duct

• PCT - all aa, sugar, HCO3-, ions, water (isosmotic fluid reabsorption)

• TDL - water

• TAL - actively reabsorbs NaCl

• DCT + collecting duct - NaCl

osmoreceptors:

• when plasma is hypertonic, what channels open (S-IIC)

• what happens to the cell polarity and what firing is increased

• where are signals sent to in the brain

• what 2 things are increased as a result of hypertonic plasma

• stretch-inhibited ion channels when the cell shrinks

• cell depolarises, ^^AP firing

• hypothalamus receives signals

  • increased thirst

  • increased ADH secretion from posterior pituitary (excrete less urine)

water permeability:

• where is water impermeable, what type of junction

• where is water permeable, what type of junction

• when does transcellular water absorption happen

• tight junction - found everywhere after PCT

• leaky junctions - found in PCT, paracellular water movement (water is also permeable in the thin descending limb and collecting duct (variable))

• with aquaporins (need both luminal and basolateral channels)

• what is countercurrent multiplication

• what is high osmolarity and what is its trend going down to the medulla

• what does high osmolarity mean for collecting ducts

• high NaCl conc from the ascending limb in the medulla so water can leave the descending limb

• how concentrated solution is with solute, increased down to medulla

• water is drawn out from collecting ducts as conc urine leaves by osmosis

countercurrent multiplication

• characteristic of PCT fluid

• what does the TDL have to make it permeable to water

• what does the TAL do with NaCl, effect on interstitial fluid

• what happens to NaCl conc of tubular fluid

• what happens to NaCl in ascending limb

• characteristic of tubular fluid leaving loop of henle

• isosmotic to plasma

• expresses aquaporin 1

• actively pumps out NaCl to mame interstitial fluid hyperosmotic to plasma (osmotic gradient created for TDL)

• increased salt conc in tube - preconcentrated tubular fluid

• so it gets actively transported out - water and salt gets semi balanced

• hyposmotic to blood plasma, more NaCl reabsorbed compared to water back to blood

• without ADH, what happens to collecting duct and urine concentration

• how does ADH work

• effect on urine and blood osmolarity

• collecting duct is impermeable to water, dilute urine

• binds to receptor on CD, causes exocytosis of vesicles containing aquaporin 2 on tubule lumen

• create conc urine, water reabsorbed into blood - lower blood osmolarity

diabetes insipidus DI:

• what is it

• 2 things it can lead to if untreated

• what is polyuria and polydipsia

• 2 causes

• Caused by lack of antidiuretic hormone (ADH/vasopressin) or kidney resistance to it, affecting water retention - not related to blood sugar (produce very dilute urine and very thirsty)

• potentially leading to hypotension (low BP), hypernatraemia (high blood Na+) if untreated

• PU - excessive urination, PD - excessive thirst

• A failure of ADH secretion or A failure of the collecting duct to respond to ADH