L11 Renal System Flashcards
What is the role of juxtamedullary nephrons?
Involved in making concentrated urine
Outline the vascular supply to the nephrons
Afferent arterioles feed into the glomeri
-> efferent arterioles leave the glomeruli and wrap around the nephron
-> peritubular capillaries or vasa recta
-> renal veins
-> inferior vena cava
Name 3 functions of the kidney
1) homeostatic regulation of water and ion content of blood
2) excretion of metabolic waste products and foreign substances
3) production of hormones
What does the kidney regulate?
Regulation of osmolarity - maintenance of ion balance
Regulation of extracellular fluid volume - blood pressure
Regulation of pH
Which hormones does the kidney produce?
Erythropoietin - red blood cell synthesis
Renin - sodium balance
Activation of vitamin D - calcium ion balance
Prostaglandins and kinins - renal blood flow
What is glomeralur filtration?
Blood is filtered at the glomerulus
What is tubular reabsorption?
Fluid and solutes are reabsorbed from the filtrate and returned to the blood
What is tubular secretion?
Substances are secreted from the blood and into the filtrate
What is filtered during glomerular filtration and why?
All plasma constrituents except proteins
- filtration barrier restricts solute movement on basis of size and charge
What structures make up the filtration barrier?
Capillary
Endothelial cell
Basement membrane
Podocyte
Podocyte foot process
Fenestration pore
Filtration slit
What can pass through filtration slits?
Formed elements and most proteins in the blood are too large to fit through
- however, water and small solutes can pass through and enter the filtrate
Which pressures control filtration?
1) Hydrostatic pressure of blood flowing through the glomerular capillaries - promotes movement of fluid into capsule
2) Colloid osmotic pressure caused by proteins in blood - favours fluid retention in/movement back into capillaries
3) Hydrostatic pressure of fluid into Bowman’s space - opposes movement of fluid into capsule
How does increased resistance influence renal blood flow?
- increased resistance of afferent arteriole reduces blood flow to glomerulus
- increased resistance to efferent arteriole increases blood flow/pressure in the glomerulus
How does decreased resistance influence renal blood flow?
- decreased resistance of afferent arteriole increases blood flow to glomerulus
- decreased resistance of efferent arteriole increases blood flow out of/decreases pressure in glomerulus
Outline the myogenic response in autoregulation
1) myogenic response
- increased blood pressure leads to the stretch of smooth muscle cells, vasoconstriction, decreased RBF, decreased Ph, decreased GFR
- important in afferent arteriole
Outline the tubuloglomerular feedback response in autoregulation
Fluid flow through tubule influences arteriole resistance and GFR
1) GFR increases
2) Flow through tubule increases
3) Flow past macula densa increases
4) Paracrine factors released from macula densa
5) Afferent arteriole constricts
6) Resistance in afferent arteriole increases
7) Hydrostatic pressure in glomerulus decreases
8) GFR decreases
What is the role of autoregulation?
Maintains RBF and GFR within narrow limits during fluctuations in mean arterial blood pressure
What is the role of autoregulation?
Maintains RBF and GFR within narrow limits during fluctuations in mean arterial blood pressure via local control mechanisms
What’s the role of macula densa cells?
They sense distal tubule flow and release paracrines that affect afferent arteriole diameter
How are GFR (glomerular filtration rate) and RBF ( renal blood flow) maintained?
By autoregulation, neural control and tubuloglomerular feedback
What is the filtrate?
Solution entering the proximal convoluted tubule
- contains H2O, Na ions, K ions, Ca ions, Cl ions, HCO ions, glucose
- no blood cells, no serum proteins
What structures does the nephron cortex include?
Proximal tubule
Distal tubule
Collecting tubules
Bowman’s capsule
Descending limb of loop begins
Ascending limb of loop ends
What structures does the nephron medulla include?
Collecting duct to the bladder
Loop of Henle
Descending limb
Ascending limb
Why doPCT have interdigitations on their basolateral membrane?
They shorten the distance between the mitochondria and basolateral carrier proteins used for active transport
