Renal system Flashcards
(23 cards)
4 roles of kidney
- excrete waste products
- Excrete foreign compounds e.g. drugs
- long term acid base balance
- long term control of blood pressure
- Process 180L of plasma per day
how much cardiac output and functional unit?
25%, 1/4
- nephrons- 200,000 to 1.8 million
3 parts of kidney, what artery? and mode of blood flow
- cortex
- medulla
- pelvis
- renal artery
- Renal artery to cortex (artery divides into small parts- blood vessels), filtration then that filtered blood goes to medulla to pelvis and exits through the ureter (duct). What doesnt get filtered, goes back into the renal vein, back into the system.
Order of blood vessels in the kidney- artery and veins
Renal artery
segmental artery
interlobar
arcuate
interlobular
afferent arteriole
- blood to glomerulus Glomerulus-
- ball of capillaries- small blood vessels where filtration takes place (more info later).
- Filtration unit of kidney
efferent arteriole
- blood away from glomerulus
peritubular capillaries
- wrapped around the tubules, and important in exchanging fluid inside the tubules into capillaries and vice versa
interlobular vein
arcuate vein
interlobar vein
renal vein
tubular system
Bowman’s capsule
- surrounds the glomerulus; collects filtrate
Proximal (convoluted and straight) tubule
- drains Bowmans capsule
- Majority of reabsorption
Loop of Henle
- thin descending limb,
- thin ascending limb
- thick ascending limb
- urinary contraction
- important for producing urine of varying concentrations
Distal tubule/Collecting duct
- Controlled reabsorption (esp Na+ and H20) and secretion (K+ and H+)
Renal pelvis
- Collects urine and funnels to ureter/bladder
Blood flow to the kidney
- renal blood flow in a healthy adult is 1.2l/min
20-25% cardiac output
Kidney only 1-2% of total body weight - ensures a high plasma filtration rate- entire plasma volume- 3L and glomerular filtration 125ml/min or 180l/day
- Entire plasma volume filtered -60 times a day
- allows precise and rapid control of volume and composition of body fluids.
Glomerular filtration rate
What is FF
GFR- volume of plasma filtered per min
- GFR is an important indicator of kidney function
- Filtration fraction (FF)- fraction of the renal plasma flow that is filtered in the glomerulus during a single pass through the kidney= GFR/Renal Plasma flow.
Forces that drive glomerular filtration
1) capillary pressure pressure
2) Hydrostatic pressure in filtrate- pressure due to plasma
forces that oppose glomerular filtration
1) Pressure in glomerular capsule Glomerular capsule= Bowman’s capsule
2) Osmotic force due to proteins in plasma- plasma osmotic pressure
Affect of:
Glomerular capillary pressure
Afferent arteriolar resistance
Efferent Arteriolar resistance
Increase
Glomerular capillary pressure
Decrease
Afferent arteriolar resistance
- less blood, less GFR
- Increase- more blood enter= GFR
Efferent Arteriolar resistance
- Decrease in size- increase GFR
- Increase GFR= Decrease GFR
how to measure GFR
Es. of GFR= Urine concentration of Cr/ Plasma concentration of Cr times urine flow rate.
Filtered but not reabsorbed in body which allows to see the rate
3 components of the glomerular filtration barrier
- endothelial cells
- Basement membrane (-ve charge)
- The podocyte with their slit diaphragm
Glomerular capillaries more efficient filters than other capillaries- very large fenestrations, high hydrostatic pressure driving filtration , needed for filterability of solutes, size and charge, most proteins precented due to negative charge they carry
WHAT IS GFR and what are two mechanisms that that keep it in place? GFR?
Amount of plasma that gets filtered per minute into the glomerulus
Auto-regulation of GFR
- keeping GFR constant
- controlled regulation of GFR usually involves changes in glomerular capillary pressure
- An increase in glomerular capillary pressure will increase GFR (assuming no other alterations)) if there was no autoregulation
- Independent of renal perfusion pressure
two auto-regulation parts
Myogenic mechanism
- is property of arteriolar smooth muscle; it involves contraction of the muscle in response to stretch
-thus, an increase in MAP will reduce the diameter of the afferent arteriole and limit the increase in glomerular capillary pressure
Tubuloglomerular feedback
- Macula densa cells: the macula densa is a collection of specialized epithelial cells in the distal convoluted tubule that detect sodium concentration of the fluid in the tubule
- e.g. Increase in GFR increases NaCl reaching macula densa cells so macula densa sends a signal to afferent arteriole to constrict - reduce GFR- reduce NaCl reaching macula densa
what is the part just before the loop of hanle called?
Tubular lumen
The membrane facing the tubular lumen is called luminal membrane and the one facing the capillaries is basolateral membrane
the wall is made up of epithelial cells
define glomerular filtration, tubular reabsorption and tubular secretion
glomerular filteration
- the movement of fluid and solutes from the glomerular capillaries into bowman’s space
tubular reabsorption
- movement of materials from the filtrate in the tubules into the peritubular capillaries
- taking fluid back into the body
Tubular secretion
- the movement of solutes from the peritubular capillaries into the tubules
- removing fluid from the body
Excretion= filtration- reabsorption + secretion
reabsorption quantitatively large and selective
quantitatively large
- plasma volume- 3L
- GFR 125ml/min or 180/day
- without tubular reabsorption, whole plasma volume and essential solutes excreted within 30 mins
Selective
- some substances almost completely reabsorbed
- many ions highly reabsorbed
- waste products poorly reabsorbed
what is water and sodium in loop of henle
first
Descending limb
- impermeable to sodium,
- permeable to water
second
ascending limb
- permeable to sodium
- impermeable to water
where is sodium reabsorbed
- Proximal tubules- 64%
- loop of henle ascending- 28%
- distal tubule and collecting duct- 7%- aldosterone increases sodium reabsorption only in that part
Angitensin converting enzyme
Angiotensin converting enzymes (ACE) convert angiotensin 1 to angiotensin 2 which then stimulates secretions aldosterone- promotes sodium reabsorption
where is water reabsorbed
water follows salt
- proximal tubules- 67%
- loop of henle descending- 25%
- distal tubule and collecting duct- 9%- fine control ADH (anti-diuretic hormone) (vasopressin)- pressence, increases water reabsorption
what is bodys response to dehydration
increase esf osmolarity , osmoreceptors- thirst, ADH increases, water reabsorption increase, excretion decrease, minimise loss
