the kidneys, regulators, producers and excretory Flashcards
what is renal perfusion and why is this important
Renal perfusion, defined as the blood flow that passes through a unit mass of renal tissue within a given time
- necessary to maintain normal urine output
what are the 4 kidney function in terms of regulation
- fluid and electrolyte balance
- plasma volume
- excreting end products of metabolism (urine)
- help maintain proper blood pH
what 3 things does the kidney produce to maintain homeostasis
- erythropoietin
- renin
- calcitrol
nephron is a renal unit, what are the 2 types of nephrons in the kidney and what percentage of kidney nephrons do they make
cortical nephron (80%)
juxtamedullary nephron (20%)
what is the difference between a cortical and juxtamedullay nephron
Cortical nephrons contain a short loop of Henle. (mantel in cortex)
Juxtamedullary nephron contains a long loop of Henle that extend deep into the medulla
what is the function of the cortical nephron
- clean blood going thru kidney
- remove excess water, drugs etc
- forming urine
1 million nephrons in one kidney
1m of nephrons on each side
no of nephrons decreases gradually with renal injury, disease or aging
what are the 9 structures forming a nephron (including vessels)
- afferent / efferent arteriole
- glomerulus
- bowman capsule
- proximal / distal convoluted tubule
- loop of henle (ascending and descending)
- peritubular capillaries / vasa recta
- collecting duct
what do you call the tubular area that marks the transition from the ascending loop of Henle to the distal tubule
macula densa
what are the 4 steps of nephron function
- filtration
- reabsorption
- secretion
- excretion
note the blood filtered in the kidneys returns to the venous system
how much filtration is done by the glomerular per min / per day
125ml per min
180l per day
what is the average plasma volume
2.75L
How much of the 180 L of plasma filtration is reabsorbed per day
178.5 L
list some of the excretion products from the nephron after filtration
- urea
- uric acid
- creatinine
- end products of haemoglobin
- metabolites of hormones
- foreign substances e.g drugs
explain what happens during glomerular filtration
- high pressure in the glomerular due to the diameter difference of the afferent and efferent arteriole causes ultrafiltration
- urea, glucose, water and salt is forced out and into the bowmans capsule
what are the 3 major layers within the glomerular capillary
- endothelium
- basement membrane ( scaffold that supports the physiological function of the glomerular endothelium and podocyte)
- podocytes
what role do podocytes play in the golmerular capillaries
preventing plasma proteins from entering the urinary ultrafiltrate
- prevent RBC for exiting
what does Kf represent and how does this relate to glomerular filtration rate
glomerular capillary filtration coefficient
- increased Kf = Increased glomerular filtration rate vice versa
how does chronic hypertension or diabetes mellitus cause damage to the glomerular capillary
- it gradually increases the thickness of the basement membrane
filterability of solutes is related to their size
most salts and organic molecules are filtered
protein and rbc aren’t normally filtered
what is ABP
ambulatory blood pressure
(mean ABP is 80-160 mm Hg)
renal blood flow depends of RENAL VASCULAR RESISTANCE and the difference between renal artery and renal vein hydrostatic pressure.
how does the diameter of the afferent and efferent arteriole affect glomerular capillary pressure (Pgc), glomerular filtration rate (GFR) and renal blood flow (RBF) in the following scenarios:
- thinner afferent arteriole vs wider efferent arteriole (average glomerulus)
- wider afferent arteriole vs thin efferent arteriole (average glomerulus)
- thin afferent arteriole, slightly wider glomerulus, even wider efferent arteriole
- low capillary pressure, low GFR, low RBF
- high capillary pressure, high GFR, low RBF
- low pressure, low GFR, high RBF
describe how reabsorption happens at the proximal convoluted tubule
- active transport allows glucose, water and salt back into blood capillary from the filtrate
- ions are also reabsorbed
- excess water, excess salt, urea and other waste substances remain
what are the 5 ions reabsorbed at the proximal convoluted tubule
- Na+
- K+
- Ca2+
- Cl-
- Mg2+
explain the process of reabsorption and secretion through out the nephron and its ending products found in urine etc
what are the 2 main hormones that control the rate of water excretion in the nephron and where are they secreted
- aldosterone (distal convoluted tubule)
- ADH (posterior pituitary gland)
what is the role of aldosterone in the distal convoluted tubue
- increases rate of water reabsorption
what is the role of ADH in nephron function
- causes more water to be reabsoped by the collecting duct
note that any damage to the glomerulus e.g high bp, autoimmune disease or diabetes will affect filtration, reabsorption and excrretion
renin is released by the endocrine system of kidney, what does it do and where is it released from
- enzyme
- central hormone in controlling bp
- released from granular cells with the juxtagglomerula apparatus
what is the juxtaglomerular apparatus
consisting of the glomerular afferent and efferent arterioles and the specialized tubular epithelial cells called the macula densa,
- plays a central role in the regulation of glomerular hemodynamics and renin release.
what system does renin trigger
RAAS
- renin angiotensin aldosterone system
below what bp is renin triggered to release at
80mmHg
explain how blood loss causes secretion of renin
- baroreceptor in aorta senses decrease in blood low
- sends signals to medulla oblongata which sends beta receptors to the juxtaglomerular apparatus
- here renin is triggered to be released
the kidneys release erythropoietin, what does this do
stimulate production of RBC
the kidneys release calcitrol, what does this do
promoting renal tubular reabsorption of calcium in the kidneys
assessment of renal function involve :
- clearance methods (time urine collection and measuring serum level)
- modification of diet in renal disease formula (accounting body SA, age, sex, race, levels of creatinine)
what is MDRD and what is its purpose
modification of diet in renal disease
- investigated whether protein restriction and control of blood pressure had an effect on the progression of chronic kidney disease
how does a UTI affect renal function
- infection (pyelonephritis) can spread to blood
- may progress to form pocket of infection (difficult to cure with antibiotics alone)
- urine flow is significantly reduced
- scaring causes decreased renal function and atrophy to cortex, renal pelvis may be distended
what can be done to drain the pocket of infection in the kidney or treat ureter blocked by stone
- nephrostomy, a tube placed thru skin into kidney and connected to either external drainage bag or bladder
- stent into ureter
back pressure on kidney can lead to kidney failure or infection
how does contrast cause renal failure/ contrast induced nephopahty
- increased conc of contrast in collecting duct
- increased viscosity of tubular fluid
- tubular obstruction
- increased tubular pressure and infrarenal tissue pressure
- decreased renal perfusion pressure
- hypoxic injury (a condition of insufficient supply of oxygen to cells and tissues)
which vitamin production is regulated by the kidney
vitamin D3
what substance is used to assess renal function
creatinine
- compares the creatinine level in urine with the creatinine level in blood
the kidneys synthesise glucose from amino acids during prolonged fasting through what process
gluconeogenesis
main role of juxtamedullary nephron?
maintaining vertical osmotic gradient
filtration takes place in the renal corpuscle, what structure are found here
- glomerulus
- bowman capsule
- afferent/efferent arterial
- start of PCT
what percentage of filtered electrolytes is reabsorbed in the proximal tubule
65%
out of 100% filtered Na+ how much is reabsorbed
99%
what part of the nephron is impermeable to water
ascending loop of henle
in a severely burned patient, glomerular capillary colloid osmotic pressure will decrease
how is Cl- transported in ascending loop of henle
secondary active transport with Na+ and K+
when blood pressure decreases in urine more or less concentrated
more
sodium and water excretion is promoted by ?
atrial natriuretic peptide