Renal Flashcards
What are the three basic functions of the kidney?
-Homeostatis
-Excretion
-Production
True/False: kidneys are important in regulating total body water?
true
What is the main ion regulating blood volume?
Na
List 5 metabolic waste products removed from the blood
Urea, creatinine, uric acid, allantoin, bilirubin
Under what conditions is renin released?
low arterial blood pressure
What cells release renin?
juxtamedullary
Why is it not uncommon for CKD patients to be anemic as well?
because the kidney releases erythropoietin
What is the preferred substrate for gluconeogenesis in the kidney?
glutamine
Where does gluconeogenesis occur in the kidney?
proximal tubule epithelial cells
What is the body mass: cardiac output ratio of the kidney
<1% body mass to 20% CO
Why does the kidney receive so much of the cardiac output?
because all of the blood needs to be processed by the kidney
What structures are included in the nephron?
renal corpuscle (glomerulus and bowman’s capsule) and the tubules
What is the macula densa, what is its function, where is it located?
a group of cells located in the wall of the distal tubule and its main function is to monitor the amount of NA in the blood, regulate flow rate and blood flow through afferent arteriole
Describe the path blood takes through the kidney
renal artery, afferent arteriole, glomerular capillaries, efferent arteriole, peritubular capillaries (vasa recta), renal vein
What cells make up the tubular system?
a single layer of epithelial cells
True/False: the glomerulus is a high pressure capillary bed
true
What type of capillaries are in the glomerulus?
fenestrated
what can leave fenestrated capillaries?
most solutes and limited amounts of small peptides
What are the 4 main steps of urine formation?
-filtration
-selective reabsorption from filtrate
-selective secretion into filtrate
-excretion of final product=urine
what percent of plasma moves into filtrate?
20%
True/False: kidney osmolarity is higher than plasma? why?
true because the kidney usually reabsorbs more water than dissolved substances
what is the main difference between cortical and justamedullary nephrons
renal corpuscle sits at junction between cortex and medulla and they have longer loops of henle that extend into the medulla
what percent of the blood that goes to the glomerulus gets filtered?
25%
Why can glomerular capillaries have high pressures?
because the goal is filtration of plasma (starlings forces)
Why do peritubular capillaries have low pressure?
because the goal is reabsorption of a large percentage of the filtrate (starlings forces)
True/False: ultrafiltrate contains proteins and blood celss
false. Ultrafiltrate contains water and all the small solutes of blood, but does not have proteins and blood cells
What are the three main layers of glomerular filtration
fenestrated endothelium, basement membrane (basal lamina), podocyte foot processes
What is the purpose of the podocyte foot process?
there are filtration slits that are bridged by nephrin which result in a charged barrier
What is the charge of the barrier created by the glomerular wall?
negative
Describe what will and will not pass the glomerular filtration barrier
-small and/or positively charged particles pass freely
-large and/or negatively charged particles are excluded
What are the roles of mesangial cells
-surround capillary endothelial cells and exhibit contractile characteristics similar to muscle cells
-phagocytic functions
Where does the majority of reabsorption take place?
prox tubule
True/False: proteinurea can be indicative of glomerulus disease
true
Define GFR
the volume of fluid filtered per minute from the glomerular capillaries into bowman’s space
Filtration coefficient is determined by what two factors
permeability and surface area
What two things are true of glomerular capillaries that is not true of capillaries in the rest of the body
-pressure declines only marginally along the length of the glomerular capillary due to flow into a high resistance efferent arteriole
-oncotic pressure increases as more plasma is filtered since protein is left behind
What is the main regulation of GFR
autoregulation which acts on afferent and efferent arterioles
What are the 3 main auto regulation controls
-Myogenic control
-Pressure diuresis
-Tubuloglomerular feedback
Describe myogenic auto regulation
increase in afferent arterial pressure should increase GFR but the myogenic response tempers this response
Describe pressure diuresis auto regulation
increase urine output and Na excretion as a result of an increase in arterial blood pressure which in turn reduces blood pressure and blood volume
Describe tubuloglomerular feedback auto regulation
mediated by the macula densa which senses a flow of filtrate and NaCl in distal tubule, signals juxtamedullary cells to release renin and decreases GFR and RBF`
What factors stimulate renin release?
-drop in blood pressure
-reduced GFR
-reduced concentration of Na and Cl in tubules of kidney
-SNS input to the kidney and circulation catecholamines
Think hemorrhage or dehydration
What are the effects of angeotensin II on GFR and RBF? at high levels vs low levels
- AngII can act on both efferent and afferent arterioles but to different ends whether it is at low levels or high levels
-At low levels preferentially constricts EA
-At high levels constricts AA and EA trying to maintain GFR which results in a small decrease of GFR and RBF, this also leads to a decrease in hydrostatic pressure in peritubular capillaries facilitating reabsorption of ions/ water and maintenance of ECF
What are the factors that inhibit renin release? (7)
-Ang II
-Aldostrone
-ADH
-Renal hypertension
-increased Na or Cl in the distal tubule filtrate
-increased GFR
-ANP
What is the gold standard for GFR measurement?
inulin
What is PAH clearance used to measure?
Measuring of the effective renal plasma flow