Week 11 - Overview of Kidney Function Flashcards
Is there a link between high bp and salt intake
Only a minority of people with high salt diets will have high bp because of this
4 examples of water and electrolyte homeostasis problems
Haemorrhage
Unusual eating/drinking behaviour
Severe dehydration, rapid fluid loss from the gut or after burns.
Unintended consequences of drug actions
What is the bodies typical water intake and output
2.5L/day
Intake - water, food and metabolic
Output - urine, sweat, faeces, insensible loss
What is insensible loss
Water that comes out the body through means other than the ureter e.g respiratory water loss, water out the skin not as sweat
In hot conditions/humid or during heavy exercise what can sweat loss increase to
between 2-10L per day
UK recommendation for salt intake
6g/day
What percentage of blood goes to the kidney
25% of the entire CO
What is blood pressure in the glomerular capillaries
50-60mmHg e.g high
Renal artery structure
Short and relatively large radius
Describe the sequence of blood vessels
Afferent arteriole -> Glomerular capillaries -> efferent arteriole -> tubular capillaries -> venule
What drains the fluid from the collecting duct
Ureter
Cortex
Region between medulla and capsule
What is the functional unit of kidney
Nephron
How many nephrons in each kidney
1000000
What are the 2 types of nephron
Superficial and juxta-medullary
Which type of of nephron is water reabsorption more effective in
Longer juxta-medullary nephrons
What are the 4 sections of nephron in order
Proximal convoluted tubule loop
Loop of Henle
Distal convoluted tubule
Collecting duct
What is the filtration rate of the glomerular capillaries
90-140ml/min
3 functional stages of renal glomerular filtration system
Ultrafiltration - filtration through glomerular capillaries and driven by high blood pressure
Reabsorption - active pumping from filtrate into efferent arteriole.
Secretion - active pumping from efferent arteriole to tubules.
Which substances are retained during reabsorption
Water, glucose, amino acids, electrolytes
Examples of substances which are secreted
Hydrogen
Ammonia
Uric acid
Some drugs
What structure do water and small molecules pass through during ultrafiltration
Slits in the podocytes
Which molecules can fit through the slits of the podocytes
Small proteins, urea, ions, glucose, amino acids,
Which molecules are fully reabsorbed into the efferent arterioles from the the proximal convoluted tubules
Glucose
Amino acids
Which molecules are partially
Na+
Water
By what fraction does the volume of the filtrate reduce
1/3
Compare the thickness of loop of henle in the medulla
Ascending is thicker than descending
What happens to the osmotic pressure of the loop of henle
Ion pumping develops high osmotic pressure at the tip of the loop
How does electrolyte and water re-absorption differ between DCT and PCT
Less intense electrolyte and water re-absorption
What drug/hormone sets collecting duct permeability
Anti-diuretic hormone
(ADH/AVP)
What happens when ADH is present
Aquaporins are inserted into the luminal membrane to allow water movement
What happens to plasma osmolarity when someone is dehydrated
It increases
What happens to plasma osmolarity when someone drinks too much
Plasma osmolarity decreases
What is the role of renin
When blood pressure is too low, glomerular hypofiltration occurs. Renin is secreted by the juxtaglomerular apparatus. Renin splits angiotensinogen to produce angiotensin I which is converted into angiotensin II - a powerful vasodilator.
What is the role of aldosterone
Is secreted by glomerulosa cells of the adrenal cortex when electrolyte concentration falls.
Aldosterone increases reabsorption of Na,Cl ions from loop, distal tubules and duct cells. It also increases K+ secretion.
Electrolyte reabsorption also causes increased water reabsorption.
