Renal Function Flashcards
Functions of the urinary system?
Maintain homeostasis of bodily fluids
Removal of metabolic wastes
Replacement of water, salts in blood
Regulation of blood volume and chemical composition
What does the urinary system consist of?
Kidneys, Bladder, Ureter, Urethra
Describe the anatomy of the kidney
Consists of outer cortex and inner medulla layer
Afferent arteriole flows into the Renal corpuscle that contains the glomerulus and Bowman’s capsule, exits via the efferent arteriole
Molecules approx 3nm in size flow down the proximal convoluted tubule
Down the thin descending limb of the Loop of Henle
Up the thick ascending limb of the Loop of Henle
Then the Distal convoluted tubule and then the collecting duct
Formula and definition of NFP
Net Filtration Pressure
Glomerular Hydrostatic Pressure - (Osmotic Pressure + Capsular Hydrostatic Pressure)
Define Glomerular Filtration Rate (GFR)
The volume of filtrate formed in both kidneys in 1 minute
How does the kidney auto-regulate?
It affects the diameter of the afferent arterioles, decrease in diameter decreases the blood flow, decreases pressure at glomerulus, less solute diffusion
Myogenic mechanism
Tubuloglomerular feedback
Define the Myogenic mechanism
A myocyte’s individual ability to respond to changes in pressure, to maintain constant pressure
tendency of vascular smooth muscle to
contract when it is stretched
Define Tubuloglomerular feedback
Involves the Macula Densa cells (chemoreceptors), specialised epithelial cells in the Distal convoluted tubule (that rest on the afferent arterioles) that regulate tubular flow by detecting filtrate osmolarity (or GFR) and commanding the dilation or contraction of the afferent arterioles.
What do the arterioles contain that help detect change in pressure
Juxtaglomerular cells, mechanoreceptors that produce and secrete renin
How is angiotensinogen converted into Angiotensin II ?
Renin acts on angiotensinogen to form Angiotensin I
Converted to Angiotensin II by Angiotensin converting enzyme
How do Macula Densa cells affect afferent arterioles?
They secrete Nitric acid (NO) which is a vasodilator
Na+ in the DCT inhibits NO, causing constriction, decreasing GFR
How do granular cells affect afferent arterioles?
Granular cells are juxtaglomerular cells within the afferent arterioles. They secrete renin which interacts with angiotensinogen, forming angiotensin I
Angiotensin converting enzyme converts this to Angiotensin II which is a vasoconstrictor
How is GFR affected extrinsically?
Sympathetic fibres release noradrenaline (a vasoconstrictor)
This constricts the afferent arterioles
What process results in the filtrate returning to the blood?
Tubular Reabsorption
How is the Proximal Convoluted Tubule’s structure fitted to it’s function?
It is layered with Microvilli, aiding in reabsorption
