Week 11 Flashcards
What does the kidneys excrete?
Metabolic waste products and foreign chemicals
What do the kidneys regulate?
Water and electrolyte balance
Body fluid osmolarity
Acid base balance
RBC production
BP
What kind of gland does the kidney act as?
Endocrine gland
What percent of cardiac output do kidneys receive?
25%
What are the 2 main regions of the kidney?
Cortex and medulla
What is the cortex of the kidney?
Outer region (just under the capsule)
What is the medulla of the kidney?
Central region (divided into outer and inner medulla)
How many nephrons does each kidney contain?
.8-1.2 million
When does the number of nephrons start to decline?
At age 40 by 10% every 10 years
What are 20-30% of nephrons that have glomeruli deep in the renal cortex called?
Juxtamedullary nephrons
What are the 70-80% of nephrons that have glomeruli located in the outer cortex called?
Cortical nephrons
What do principle cells play an important role in?
Reabsorption of NaCl and secretion of K+
What do intercalated cells play an important role in?
Regulating acid base balance
What processes are the sum of urine formation?
Glomerular filtration
Reabsorption
Secretion
What does the urinary excretion rate equal?
Filtration - Reabsorption + secretion
What 3 main layers make up the filtration barrier?
Endothelium
Basement membrane
Podocytes (epithelial cells)
What is the endothelium permeable to?
Water or small solutes (not to RBC, WBC, or platelets)
What is the basement membrane made out of?
Porous matrix of negatively charged proteins
What does the basement membrane serve as?
Charge selective barrier to plasma proteins
What do Podocytes form?
Filtration slits
What do Podocytes function as?
Size selective filter
What does the mesangium consist of?
Mesangial cells and mesangial matrix
What do mesangial cells have properties of?
Smooth muscle cells
What do mesangial cells provide?
Structural support to glomerular capillaries
What do mesangial cells secrete?
Extracellular matrix
Prostaglandins
Pro inflammatory cytokines
What do mesangial cells have?
Phagocytic activity
What are mesangial cells located outside the glomerulus between afferent and efferent arterioles called?
Extraglomerular mesangial cells
What are mesangial cells involved in?
Immune complex mediated glomerular disease
What is the concept of renal clearance based on?
Fick principle
What does the principle of renal clearance emphasize?
Excretory function of the kidneys
What does the renal clearance consider?
Only the rate at which a substance is excreted into urine
What is the urinary excretion rate of substance proportional to?
Plasma concentration of substance
What is the clearance rate?
Volume of plasma completely cleared of a substance by the kidneys per unit time
What can renal clearance vary from?
0-600 ml/min
Inulin
Fructose polymer
Freely filtered
Neither reabsorbed or secreted
C inulin= GFR
Inulin is a glomerular marker
What’s the first step in urine formation?
Glomerular filtration
How does blood come in to the glomerular?
Afferent arteriole
How does blood come out of the glomerular?
Efferent arteriole
Most filtrate in the glomerular is reabsorbed so how much is excreted a day?
1 L
What is the sum of the filtration rates of all functioning nephrons?
GFR
What does filtration fraction equal?
GFR/RPF
How many times is plasma volume filtered per day?
60 times
How much is filtered in GFR?
125 ml/min or 180 liters/day
How is GFR measured?
Clearance of a glomerular marker
What is the gold standard glomerular marker?
Inulin
What can a glomerular marker not do when it’s infused?
Alter the GFR
What can the glomerular marker freely filter across?
Glomerular capillaries
What can the glomerular marker not be reabsorbed or secreted by?
Renal tubule
What is creatinine a byproduct of?
Normal skeletal muscle metabolism
Where is creatinine freely filtered across?
Glomerulus into bowman’s space
What is creatinine secreted by?
Renal tubules
What are the two main factors in determinants of GFR?
Filtration coefficient
Net filtration pressure
What is the pressure of the glomerular capillary determined by?
Arterial pressure
Afferent arteriolar resistance
Efferent arteriolar resistance
What is usually the result of changes to Kf?
Reduction in GFR
What does RBF equal?
Change in pressure/ Resistance
What do myogenic mechanisms respond to?
Changes in arterial pressure
What do tubuloglomerular feedback respond to?
Changes in NaCl in tubular fluid
What happens when renal artery BP increases?
Both RBF and GFR increase
What results in an increase delivery of water and solute to the macula densa?
Increase GFR
What type of feedback is the macula densa?
Negative feedback
What does autoregulation of RBF and GFR allow for?
Uncoupling renal function from blood pressure
When is autoregulation absent?
When BP is less than 90 mmHg
When do neurohormonal mechanisms play a key role in regulating RBF bad GFR?
When ECF volume changes
What are neurohormonal mechanisms?
SNS activity
Circulating catecholamines
Angiotensin 2
ANP
Prostaglandins
Nitric oxide
Endothelin
Between afferent and efferent arterioles who has more a1 receptors?
Afferent
What are more sensitive to angiotensin 2?
Efferent arterioles
What does ANP cause?
Dilation of afferent and constriction of efferent
When is ANP released?
When ECFV increases
What do prostaglandins cause?
Vasodilation of efferent and afferent
What is nitric oxide?
Vasodilator
What is endothelin?
Vasoconstrictor
Endothelin is released by endothelial cells in response to what?
Ang 2
Bradykinin
Epi
What does SNS activity do the GFR and RBF?
Decreases
What does angiotensin 2 do the GFR and RBF?
Low levels increase GFR and decrease RBF
High levels decrease both
What does ANP do the GFR and RBF?
Increases
What does nitric oxide do the GFR and RBF?
Increases
What does endothelin do the GFR and RBF?
Decreases
What does fever do the GFR?
Increases
What do glucorticoids do to GFR?
Increass
What does aging do the GFR?
Decreases by 10%
What does hyperglycemia do to GFR?
Increases
What does high protein do to GFR?
Increases
What is the amount of substance filtered into bowman’s space per unit time?
Filtered load
What is the fluid inside the lumen of the nephron?
Tubular fluid
Where are water and many solutes reabsorbed from the tubular fluid into?
Particular capillary
