Kidneys Flashcards
What are the 4 metabolic products not needed in the body that are excreted by the kidney
Urea
Creatinine
End product of hemoglobin breakdown
Metabolites of various hormones
How long would it take the kidneys to adjust to a 10 fold increase in sodium
2-3 days until a new balanced sodium excretion rate was met
How do the kidneys regulate arterial pressure
-By excreting variable amounts of sodium and water
-Renin forming angiotensin II
How do the kidneys regulate acid-base balance
-Excreting acids
-regulation of bicarb
How do the kidneys regulate erythrocyte production
Secrete erythropoietin in hypoxia situations
What are the 7 key functions of the kidneys
- Excretion of metabolic waste products and foreign chemicals
- Regulation of water and electrolyte balance
- Regulation of body fluid osmolality and electrolyte concentrations
- regulation of arterial pressure
- regulation of acid-base balance
- regulation of erythrocyte production
- secretion, metabolism, and excretions of hormones
Where is the kidney located within the body
The posterior wall of the abdomen outside the peritoneal cavity
What is contained within the medial side of the kidney
- indented region called hilum
-renal artery and vein
- lymphatics
- nerve supply
- ureter
What is contained in the inner medulla of the kidney
8-10 renal pyramids
- they terminate in the papilla
What is contained in the renal pelvis
- funnel shaped continuation of the upper end of the ureter
- outer end of the bored splits in major and then minor calyx
How many nephron are within each kidney
1 million
Which area of the kidney needs to be VERY salty
Renal medulla (between each renal pelvis)
What is contained in the outer cortex
The start of the nephron (then dips below outer cortex and into the renal pyramid)
What percent of cardiac output do the kidneys receive
22% of blood flow (most blood for organ based on size)
What is the rate of blood flow to the kidneys
1100 ml/min (1L/min)
What is the path of the Renal artery when it arrives at the kidney
Renal artery > segmental arteries > Interlobar arteries > arcuate arteries > afferent arterioles > glomerulus > efferent arterioles > peritubular capillaries
What is the function of the efferent and afferent arterioles
dilation and construction to alter the hydrostatic pressure in both the glomerular and peritubular capillaries
- changes the rate of glomerular filtration, tubular reabsorption or both
What type of of pressure causes rapid fluid filtration the the glomerular capillaries
High hydrostatic pressure
What type of pressure causes rapid fluid reabsorption at the peritubular capillaries
Low hydrostatic pressure
What separates the glomerular capillaries from the peritubular capillaries
Efferent arterioles
What percent fewer nephrons will you have at age 80
40% fewer
What is the high hydrostatic pressure of the glomerular capillaries
60 mmHg
What type of cells cover glomerular capillaries
Epithelial cells
What incases the glomerulus
The bowman’s capsule
Flow of travel of fluid from the glomerular capillaries
Into the bowman’s capsule > proximal tubule (in the cortex of the kidney) > loop of Henle (dips into medulla) > back to cortex
What specialized epithelial cell is located at the top of thorp of the thick ascending tubule and what is its purpose
The macula densa, regulates blood pressure
What are the two types of nephrons
Cortical nephrons, juxttamedullary nephrons
What makes cortical nephrons unique from juxtamedullary nephrons
- glomeruli located in outer cortex
- loops on Henle go only a little into medulla
- entire tubular system is surrounded by extensive network of peritubular capillaries
What makes juxtamedullary nephrons unique from cortical nephrons
- 20-30 percent of nephrons have glomerular that are deep in the renal cortex near the medulla
Jux
- long efferent arterioles extend from the glomeruli down into the outer medulla and divide into peritubular capillaries called vasa recta
- plays essential role in forming concentrated urine
What is urine fluid free of
Protein
What are the 4 steps of urine formation
- Filtration (glomerular capillaries into bowman’s capsule)
- Reabsorption (Water and solutes back into blood)
- Secretion (substances from peritubular capillaries into the blood)
- Excretion
What are the 4 possible routes of substances through the kidneys
A - no reabsorption or secretion
- Creatine, GFR
B - Filtration with reabsorption
- Electrolytes such as sodium, chloride, Uria
C - freely filtered but not excreted
- glucose
D - Freely filtered + secreted from peritubular capillary blood
- Organic acids and bases, rapid clearance
Is reabsorption of tubular secretion more important
Reabsorption
What is the important role of secretion
Determining the amount of K+ and H+ excreted into the urine
What 3 bodily substances are poorly reabsorption and have large amounts in urine
Urea, creatinine, Uric acid
(Certain foreign substances and drugs are also poorly reabsorbed + secreted into the tubules)
Are electrolytes highly or poorly reabsorbed, name 3
Highly
Sodium ions, chloride ions, bicarbonate ions (only small amounts in urine)
Two nutritional substances that are completely reabsorbed from the tubules and don not appear in urine
Glucose and amino acids
(Even though large amounts are filtered by glomerular capillaries)
What does High GFR allow
- More rapid removal of waste
- allows all body fluids to be filtered and processed by kidneys many times a day
- plasma is 3 liters
- GFR = 180L/day
Plasma is filtered 60 times a day
What are the glomerular capillaries impermeable to, what is filtrate called
Proteins, glomerular filtrate
- no RBC’s
- calcium and fatty acids
- 50% of calcium is bound to proteins
GFR is what % of renal plasma flow
20%
What 2 things determine GFR
- balance of hydrostatic and colloid osmotic forces acting across a capillary membrane
- Capillary filtration coefficient (Kf)
- product of the permeability and filtering surface area of the capillaries
What is unique about the Glomerular capillary membrane
- filters several hundred times as much water and solutes as the usual capillary membrane
- 3 layers involved
- each has strong negative charge to hinder passage of plasma proteins
- membrane is more permeable but thicker, filtration of any substance depends on its size and electrical charge
What 3 layers make up the filtration barrier of the glomerular capillary membrane, what makes each one unique
- Endothelium
-fenestrated- negative charges hinder plasma proteins
- basement membrane
- mesh work of collagen
- large spaces for water a solute filtration
- epithelial cells (podocytes)
- line the outside of glomerulus
- long foot like processes ( prodocytes) not continuous because gaps called slit pores that filtration moves through
What is the filterability of solutes
Inverse to their size
1 = filtered as freely as water
.75 = filtered 75% as rabidly as water
How to find net filtration pressure
- sum of hydrostatic pressure and colloid osmotic forces across glomerular membrane
Net filtration pressure (10) = hydrostatic pressure (60) - bowman’s capsule pressure (18) - colloid osmotic pressure (32)
What is the effect of Kf (filtration coefficient) on GFR
What diseases commonly affect it
Increase in Kf raises GFR
Decrease in Kf reduces GRF
- kidney disease lowers Kf / decreases surface area
- hypertension and diabetes also lower Kf by increasing membrane thickness
What is the Kidney stone affect
- increased bowman’s capsule hydrostactc pressure decreases GFR
- can be caused by obstruction fo of the urinary tract
How does blood flow into glomerulus affect GFR
High blood flow increases GFR
Low blood flow decreases GFR
what is the standard glomerular capillary hydrostatic pressure?
What do changes to this pressure mean
60 mmHg
Means physiologic regulation of GFR
What 3 things is glomerular capillary hydrostatic pressure regulated by
- increased arterial pressure = increased (gchp) and GFR
- resistance of afferent arteriolar resistance = reduced (gchp and GFR)
- constricted efferent arteriolar (resistance to outflow) = increased GFR
- constricted too much can cause the reverse affect
What is renal artery pressure about equal to
What is it determined by?
Systemic arterial pressure
Total vascular resistance through kidneys - SNS
Big three
What do the kidneys have to maintain renal blood flow
AUTO__REGULATION SYSTEM to maintain renal blood flow and GFR between 80 and 170 mmHg
Important to know about Physiologic control of GFR and blood flow
SNS controlled
- all kidney vessels are SNS innervated
- strong stimulation causes constriction of arerioles and decreases flood and GFR
- moderate stimulation does very little
- can be uses in defense of severe hemorrhage
- does very little at rest
Effect of Hormone and autacoid on renal blood vessels
Norepinephrine, Epinephrine, and endothelin constrict renal blood vessels and decrease GFR in extreme conditions
- endothelin = peptide released by damage vascular endothelial cells
Function of Angiotensin ll on kidneys
- powerful vasoconstrictor
- locally produced autocoid because produced in kidneys
- receptors in all kidney arteries EXCEPT preglomerular arteries = afferent arterioles (protected by NO)
- Efferent arterioles are highly sensitive, restriction raises glomerular hydrostatic pressure and reduces renal blood flow
- angiotensin ll keeps GFR high through restricted efferent arterioles (causes greater reabsorption of NA and K)
Factors that decrease FGR
What is tubuloglomerular feedback and auto regulation of GFR
Feedback mechanism that links changes in sodium chloride concentration at macula densa with control of renal arteriolar resistance
- regulates renal blood flow and GFR
What are the two tubuloglomerular feedback and auto regulation of GFR mechanisms
What do they rely on
- Afferent arteriolar feedback mechanism
- Efferent arteriolar feedback mechanism
Special anatomical arrangement of the juxtaglomerular complex
2 feedback components of juxtaglomerular complex to control GFR
- Macula densa cells ( group of epithelial cells in distal tubules)
- Juxtaglomerular cells (walls of the afferent and efferent arterioles)
What does decreased macula dens sodium chloride cause
Dilation of afferent arterioles and increase rennin release
How does the macula densa work
Senses change in volume delivery to the distal tubule, by sensing reduction of sodium and chloride in tubule
- a decrease in GFR cause in increase in sodium and chloride reabsorption
What are the two effects of the macula densa
- Decrease. Resistance to blood flow in the afferent arterioles
- raise glomerular hydrostatic pressure
- return GFR to normal - Increase renin release from the juxtaglomerular cells of the afferent and efferent arerioles (major storage sites for renin)
- increases glomerular hydrostatic pressure
Juxtaglomerular complex provide auto regulation
- GFR changes only a few percentage points even with large arterial pressure fluctuations
Explain using diagram on slide 37
What are the affects of ACE inhibitors on kidneys
Prevents formation of Ang ll and reductions in GFR
Complications:
Renal artery stenosis
Decreased GFR
Sudden renal failure
