phase 1 week 10 Flashcards
Describe the blood supply to the kidney
renal artery divides into segmental arteries, which then divide to become lobar arteries. Between the medullary pyramids they branch to become interlobular arteries. These extend towards the cortex then arch round the bases of the medullary pyramids to form the arcuate arteries. From the arcuate arteries, interlobular arteries penetrate the cortex. Branches of the interlobular arteries called afferent arterioles carry blood directly into nephrons
What is the normal intake of fluids in an adult?
about 1200ml water
1000ml food
metabolic 300ml
total about 2.5 litres
What is the normal fluid output for adults?
urine about 1500ml sweat about 100ml faeces about 200ml insensible loss about 700ml total about 2.5 litres
describe the sequence of blood vessels in the kidney
afferent arteriole glomerular capillary efferent arteriole tubular capillary venule
How many nephrons are there?
10 to the power of 6
what are the 2 types of nephron ?
junta-meduallry
superficial
Describe a nephron
each nephron is a tube
the nephron wall is a continuous layer of epithelium
the cell shapes in the wall are very different
this reflects activity; surface area, ion pumping etc
What is meant by ultrafiltration?
driven by blood pressure
high renal blood flow
high filtration rate
what is meant by reabsorption?
active pumping from filtrate into tubules
water, glucose, amino acids, electrolytes etc
What is meant by secretion?
active pumping into tubules
for substances to be eliminated faster than filtration alone allows
what are pumping rates controlled by?
hormones
Describe glomerulus ultrafiltration
high glomerular capillary pressure
filtration of small molecules through slits between podocytes (ions, water, glucose, amino acids etc)
limit is space between posocyte processes
filtration rate 90-140ml/min
Describe what happens at the proximal convoluted tubule
active reabsorption
brush border
active reabsorption of glucose, Na+, K+ ions
Co transporters, aqueous channels, membrane pumps
Substantial water reabsorption
What has occurred by the end of the PCT?
complete reabsorption of glucose, amino acids
Substantial reabsorption of Na+, water
volume filtrate reduced by 2/3
Describe what happens at the loop of Henle
counter-current concentration
thinner wall during descent into medulla
thicker wall during ascent -active pumping out of tubule
solute diffuses into descending tubule;
countercurrent mechanism “recycles” solutes
ion pumping develops high osmotic pressures at the tip of the loop
no net reabsorption here
Describe what happens at the distal convoluted tubule
more solute reabsorption and secretion
similar structure and function to proximal tubule
no need for glucose transported
less intense electrolyte and water reabsorption
DCT ion pumping can be controlled by hormones like aldosterone to “fine tune” Na+ and K+ exchange
describe what happens at the collecting duct
concentration of urine
if CDs are permeable to water it may be drawn out by the high osmotic pressure present at the tip of the loop of Henle
Duct permeability set by ADH
if ADH is present aquaporins are inserted into the luminal membrane to allow water movement
Describe the kidneys control of the blood pressure
hypofiltration and sympathetic stimulation initiates secretion of renin by the juxtaglomerular apparatus
renin converts angiotensinogen to angiotensin II which is a powerful vasoconstrictor
Describe the kidneys control of salt balance
When electrolyte concentrations fall aldosterone is produced by the glomerulosa cells of the adrenal cortex
This increases the reabsorption of Na+, CL- and therefore water
It increases the secretion of K+ ions
Describe the pathophysiology of benign prostate hyperplasia
BPH is a benign increase in the size of the prostate
hyperplasia of prostate stromal and epithelial cells in the transition zone of the prostate
may impinge on the urethra and increase resistance in the flow of urine from the bladder
increased likelihood of urinary tract infections
What is the pathophysiology of BPH?
benign prostatic hyperplasia
BPH is a benign increase in size of prostate stromal and epithelial cells in the transition zone of the prostate
May impinge on the urethra and increase resistance in flow of urine from the bladder
Describe PSA screening and why it is not used in the UK
prostate specific antigen screening
PSA tests are unreliable and can suggest prostate cancer where there is none
20% of men with prostate cancer don’t have elevated PSA
PSA testing alone can’t determine whether symptoms are due to BPH or prostate cancer because both conditions can elevate PSA levels
