Renal Flashcards
why do we need kidneys?
filter plasma and reabsorb what the body needs. leaves waste products, drugs,
toxins and excess (water), ions
and acid/bicarbonate in the urine.
Kidney - gross structure.
renal cortex (coating), renal medulla (middle) ureter.
kidney - nephron loop.
Renal corpuscle: Glomerulus + Glomerular capsule. Afferent arteriole (afferent: arrival). Peritubular capillaries (peri: around).
basic nephron filtration.
substances (e.g. glucose and water) moves from the blood through the ‘sieve’ and into the nephron tubule. only small molecules can fit due to the small gaps. proteins and cells are too big.
in the glomerulus - like a sieve.
basic nephron reabsorption.
proximal tubule. Reabsorption: movement of useful substances (e.g. glucose and water) out of the nephron tubule back into the blood (stay in the body).
basic nephron secretion.
Secretion: removal of
waste products (e.g. drugs)
from the blood into the
nephron tubule and end up in the urine (leave the body).
what epithelial cells line the renal tubules.
Apical membrane: faces the lumen (into the tube).
Basolateral membrane: faces the interstitial space (outside of the tube).
para-cellular pathway. kideny
‘Between’ cells
* Transport proteins not required
* Only possible in cells with ‘leaky epithelia
Trans-cellular pathway
Through’ cells
* Apical & basolateral membrane transport
* Requires: Permeability (membrane transport proteins etc.). Driving force (gradient or energy)
* Can be: Automatic. Controlled by hormones. Cells with ‘tight epithelia’ allows transcellular reabsorption only
passive transport in kidney.
No energy required, driven by a gradient. Diffusion (solutes) or osmosis (water) down a gradient
Two types:
* Diffusion/osmosis – through the membrane or between cells without assistance.
* Facilitated diffusion – requires a channel or transporter.
active transport in kidney.
Needs a driving force
Two types:
Primary – uses ATP for energy
.Secondary – uses the movement of one substance down its gradient (downhill), to drive the movement of another substance against its gradient (uphill).
Kidney Epithelium – Water movement
osmosis.
Water can move via both the trans and the paracellular pathway – Water has to go via the transcellular pathway using channels = aquaporins (water channels).
how does blood get into the glomerulus
Blood pressure in the glomerular capillaries’ forces fluid, ions & solutes into the nephron.
Glomerular Filtration Rate
Together both kidneys’ filter:
* 125mL blood/min
Which equals
* 180L/day
This is the Glomerular Filtration Rate (GFR)
only 1.5L urine/day max 20L and min 500ml. therefore 99% reabsorped.
GFR gives an indication of how well the kidneys are functioning
Renal Clearance
The amount of blood plasma that is completely cleared (cleaned up) of a substance per minute.
filtration - reabsorption + secretion = clearance.
what is creatine clearance used to estimate and how do we find it?
assess the kidney function.
Creatinine is a chemical waste generated from muscle metabolism and filtered out in the kidneys (and not reabsorbed nor secreted). The amount of blood the kidneys can make creatinine-free is called the creatinine clearance. -125 mL/minute (similar to the GFR).
proximal tubule.
reabsorb 90-99% of water and ions and all of the nutrients that are filtered back into the bloodstream.
90% of water. 90% of Na+. 100% of nutrients (e.g. glucose and amino acids)
has leaky epithelial therefore allowing for paracellular and trans-cellular movement.
proximal tubule cell reabsorption to blood with apical.
high potassium inside and low sodium inside. therefore glucose and amino acids reabsorped using apical membrane. Sodium-coupled secondary active transport. driven by the Sodium electrochemical gradient. electrochemical gradient for sodium created by the Na+/K+ ATPase pumps. Sodium- a positive ion with a high conc outside the cells and low conc inside the cells.
proximal tubule cell reabsorption to blood with basolateral.
facilitated diffusion. - Driven by the:
* Concentration gradients
* created by the secondary
active transport of glucose and
AA’s through the apical
membrane.
how does chloride reabsorb in the proximal tubule?
Where sodium goes:
* Chloride follows via the paracellular pathway, down its electrical gradient.
distal tubule.
Fine-tuning reabsorption
* 1-10% of water
* 1-10% Na+ and Clions
* Acid (H+) and bicarbonate (HCO3-) – pH control are reabsorbed, depending on what the body needs. hormones control. tight epithelial: transcellular movement only.
what causes water and sodium reabsorption
ADH - water. aldosterone (+renin) - sodium. Hormones act by adding or taking away channels for
sodium and water
what does water need to reabsorb into the body?
driving force - osmotic gradient
permeability - as the distal tubule has tight epithelial we cannot use a paracellular pathway.
transcellular pathway - needs water channels (aquaporins) for water to enter and exit the cells.
how does osmolarity of water change in the nephron loop?
Osmolarity increases from renal cortex to medulla. Driving force for water reabsorption in the distal tubule.
