Renal Phisological Flashcards
Osmolarity
-concentration of “osmotically” active particles in a solution (solvent) that contribute to the solution’s osmotic pressure(osmoles of solute/particles per litre of solvent (Osm/L))
Osmolality:
concentration particles expressed as osmoles of solute/particles per kg of solvent (Osm/kg)
functions of the kidney
-regulating the composition of most ECF/plasma ions such as Na+, CL- etc..
-help maintain blood PH
-excreting the end products of metabolism e.g.urea
-producing renin =modulation of arterial blood pressure by RAA system
-converting vitamin D into its active form
nephron
the functional unit of the kidney
tubular components of the nephron
-bowmans capsule
-proximal tubule
-loop of henle has peritubular capillaries wrapped around
-distal tubule
-collecting duct
-responsible for excretion and producing urine
vascular components of the nephron
- afferent arteriole
-glomerulus
-efferent arteriole
-peritubular capillaries - vasa recta form when peritubular capillaries are wrapped around the juxtamedullary nephrons
-responsible for supplying the kidney with blood for the process
why is the nephron surrounded by the peritubular capillary network?
- The close proximity of the kidney nephron tubules and peritubular capillaries allows fluid transfer between the fluid inside the tubules and the blood within the peritubular capillaries.
renal reabsorption pathway
- substances need to cross:
-the luminal membrane of the tubular cells
-the cytosol of the tubular cells
-the basolateral membrane of the tubular cells
-the intenstital fluid through diffusion
-capillary wall to get into the blood
glomerular filtration process
- afferent arteriole carries the blood plasma to the capillaries of the glomerulus
-pressure forces the plasma from capillaries into the bowman’s capsule Most proteins are removed from selective filtration
-filtered plasma enters the proximal tubule
role of podocytes
- specialised epithelial cells which surrounds the glomerulus and regulate glomerulus filtration via selective permeability
glomerular filtration rate (GFR)
- a measure of the kidney function/health
-represents the flow of plasma from the glomerulus into Bowmans space over a specified time period (ml/min)
-only twenty percent of plasma that enters the glomerulus is filtered the 80% that is not filtered leaves through the efferent arrteriole.
-active Na+ reabsorption
-throughout most of the tubule Na+ is reabsorbed except the descending loop of Henle
-uses 80% of the energy requirements of the kidneys
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go back to end of lecturen one for reabsorption and secretionn
reabsorption at the descending limb of the loop of henle
-water reabsorbed only and nothing is secreted
reabsorption at the ascending limb of the loop of henle
- solute ions reabsorbed only and nothing secreted
vertical osmotic gradient in the renal medulla
-in the cortex the concentration of solutes is isotonic meaning they are the same concentration everywhere else in the body around three hundred mOsm
-in the medulla the deeper you go the concentration in the medulla increases
- the gradient enables the kidney to produce urine that ranges in concentration
-mediated by the hormone ADH
regulation of sodium readsorption
Na+ reabsorption is subject to hormonal control and is inversely dependent on the total amount of Na+ in the body fluids
-High [Na+] =no reabsorption =Na+ excreted in urine. -
-Low [Na+] =Na+ is reabsorbed in the bloodstream
The role of ADH (vasopressin)
ADH (Antidiuretic Hormone) is a substance which made in in the hypothalamus but it’s released into the bloodstream from the posterior pituitary.
When ADH is released, it tells the kidneys to put more water back into the bloodstream. It does this by making special channels called aquaporins move to the surface of kidney cells.
These aquaporins act like gates, allowing more water to flow back into the kidney cells from the urine passing through them. This makes the urine more concentrated because more water is being taken out of it and put back into the body.
As a result, the body can maintain the right balance of water and minerals in the bloodstream and throughout the body
Nephrogenic diabete
-deficiency of ADH or aquaporins can’t fuse with the membrane which leads to excessive excretion of dilute urine leading to dehydration and thirst which can lead to serious health problems
what does long-term hormonal regulation of arterial blood pressure depend on ?
-Renin-angiotensin-aldosterone system
Juxtaglomerular apparatus
origin of the hormone renin
granular cells
secrete an hormone called renin
-Function as intrarenal baroreceptors. If blood pressure (BP) is low within the afferent arteriole, the granular cells will secrete more renin
- They are also innervated by sympathetic nervous system. When systemic BP low sympathetic activity increases that stimulates the granular cells to secrete more renin
-The macula densa senses [Na+] & [Cl-] passing through the distal tubule. If [Na+] & [Cl-] decreases, the macula densa cells stimulate the granular cells to secrete more renin
Renin-angiotensin-aldosterone system(RAA system)
- involves the liver,kidney,lungs,adrenal cortex
-the liver produces angiotensinogen in the bloodstream the kidney produces renin which converts the angiotensinogen into angiotensin 1. - a converting enzyme produced by the lungs then converts it into angiotension 2. -the adrenal cortex converts in into aldosterone which acs on the kidneys
roles of aldosterone in the kidney
-Aldosterone increases Na+ reabsorption by the distal tubules and collecting duct by…
-Insertion of additional Na+ channels (Enac) in the luminal membrane of tubular cells
-Cl- follows passivelythrough different typesof transporters(to re-establish the charge equilibrium)
-Increase of [Na+] & [Cl-] in bloodstream and tissues leading to ECF rises as H2O follows [Na+] & [Cl-] to re-establish the isotonic equilibrium
role of angiotensin 2
- increases ADH/vasopressin secretion= low BP sensed by stretch receptors in heart and artery walls also leads to increased secretion of ADH
- increased water reabsorption by kidney tubules
how does the Renin-angiotensin-aldosterone system ultimately increased blood pressure
-leads to an increase in NA+ and CL- concentration which increases the extracellular fluid volume which leads to an increase in the arterial blood pressure.
chronic kidney disease
-lasting 3moths or more and cannot be prevented by vaccines or cured by medication or disappear
what can cause chronic kidney diseases?
- genetics, cancer,polycycstic kidney disease or can be a secondary disease e.g. diabetes cause it
why is chronic kidney disease common?
- because the kidney is able to compensate for a loss of function, therefore the symptoms only appear after the disease is well advanced
chronic kidney disease symptoms
- dehydration and thirst
-electrolyte imbalance
-acid-base disturbance
-weakened muscles and bones due to calcium and other mineral imbalances
-anaemia
treatments for chronic kidney disease as there is no cure
-kidney transplant
-dialysis=prolongs patents life while they wait for transplant
-use a semipermeable membrane to allow small solutes to exchange freely between the blood and a dialysing solution(eliminate contaminants from the blood, e.g. excess of solutes, metabolites)
-2 types of dialysis:-haemodialysis (haemodialysis system/artificial kidney)- peritoneal dialysis (uses the peritoneum which surrounds the interbal organs and the abdominal wall as a dialysis membrane)
storage of urine into the bladder
- it is eliminated by the collecting duct and is collected by the renal pelvis and then leaves the kidney through the ureter and is stored into the bladder
reflec control of urine secretion
-usually in infants
-bladder fills which activate the stretch receptors in the bladder walls are activatedwhich sends impulses to the spinal cord which in return activates the parasympathetic system and then activates the bladder to contract
-the internal and external urethral spincter opens causing urination
voluntary control of urine secretion
- the cerebral cortex is involved which gives us a perception of how full the bladder us before the sphincter relaxes therefore overrides the reflec pathway
-inhibts motor neurones to the external spincter so it does not open
