lecture 11 - renal physiology 1 Flashcards
gross anatomy of the kidney
- left is slightly higher up due to the presence of the liver
- enclosed in fibres capsule
- outer layer = cortex
- inner later = medulla
- calyx feeds into the ureter
- rich blood supply
- aorta branches into each kidney
- inferior vena cava takes blood away from kidneys
what is the functional unit of the kidney?
nephrons
1 million nephrons per kidney
what are the 2 kinds of nephrons?
cortical
• mainly in cortex
• 80% of all nephrons
juxtamedullary
• fewer
• important in controlling urine concentration
main structures in the nephron
- bowmans capsule
- PCT
- loop of henle
- DCT
- collecting tubes
renal blood supply
input - renal artery
output - renal vein
vascular supply to the nephrons
1) renal arteries branch into afferent arterioles
2) afferent arterioles feed into glomeruli
3) efferent arterioles leave the glomeruli and wrap around the nephron
4) peritubular capillaries or vasa recta
5) renal veins
6) inferior vena cava
functions of the kidney
homeostatic regulation of water and ion content of blood
excretion of metabolic waste products and foreign substances
production of hormones
how do the kidneys control homeostasis?
regulation of osmolarity - maintenance of ion balance
regulation of extracellular fluid volume - BP
regulation of pH
what metabolic waste products does the kidney excrete?
- urea
- creatinine
- urobilinogen
- breakdown products of haemoglobin
what hormones does the kidney produce?
erythropoietin - RBC synthesis
renin - sodium balance
activation of vitamin D - Ca++ balance bond prostaglandins and kinins
what happens in glomerular filtration?
all plasma constituents filtered except proteins > 67 kDa
filtration barrier restricts solute movement on basis of shape and charge
kidneys receive 25% of CO
filtration fraction = 20%
what pressures control the filtration process?
hydrostatic pressure of blood flowing through glomerular capillaries - P(H) - promotes movement of fluid into capsule
colloid osmotic pressure
hydrostatic pressure of fluid in bowmans space
what substances aren’t filtered?
RBCs
serum albumin
what is RBF?
renal blood flow
what happens if you increase afferent resistance?
- decreased RBF
- decreased P(H)
- decreased GFR
what happens if you decrease afferent resistance?
- increased RBF
- increased P(H)
- increased GFR
what happens if you increase efferent resistance?
- decreased RBF
- increased P(H)
- increased GFR
what happens if you decrease efferent resistance?
- increased RBF
- decreased P(H)
- decreased GFR
control of GFR and RBF
remain relatively constant over a wide range of article pressure
this is a protective mechanism
maintained constant by:
• auto-regulation
• neural control
• tubuloglomerular feedback
what does auto-regulation do?
maintains GFR and RBF within narrow limits during fluctuations in mean arterial blood pressure
control mechanisms of auto-regulation
myogenic response • increased BP • stretch of smooth muscle • vasoconstriction • decreased RBF • decreased P(H) • decreased GFR
tubuloglomerular feedback
• fluid flow through tubule influences arteriole resistance and GFR
what are macula densa cells?
specialised epithelial cells
important for tubuloglomerular feedback
detect concentrations of Na+ in the tubule
process of tubuloglomerular feedback
- GFR increases
- flow through tubule increases
- flow past macula densa cells increases - Na+ and Cl- conc sensed
- paracrine factors released from macula densa
- afferent arteriole constricts
- resistance in afferent increases
- hydrostatic pressure in glomerulus decreases
- GFR decreases
what paracrine factors are released from the macula densa?
adenosine
ATP
NO
