2. Diaphragm
Functions Adrenal
T11
T12 Renal
artery
gland Renal
• Primary Function is: vein
– Regulation of volume and
composition of plasma and
interstitial Fluid
Left
• Kidneys Right
filter the blood
kidney
kidney
• Remove water-soluble Aorta
wastes
Inferior
• Help control blood pressure Ureter
and composition vena cava
• Help maintain red blood cell
levels
Bladder
5. Filtration Happens in the Glomerulus
Proximal
tubule
Efferent
arteriole
Bowman’s
space
Afferent
arteriole
6. Glomerular Filtration
• Glomerular capillary cells sit along
a basement membrane
• Bowman’s capsule epithelium cells
sit along the same basement
membrane
• They stand up away from the
membrane on pseudopods
• Fluid filters across the basement
membrane and between the
pseudopods
7. Glomerular Filtration Rate
Glomerular filtration rate = 125 mL/min
Discussion:
• How would it change if you:
– Constricted the efferent arterioles?
– Constricted the afferent arterioles?
– Decreased the blood pressure?
• Which of the following will increase GFR?
– Epinephrine – Prostaglandins
– NO – Endothelin
8. If 125 mL of Ultrafiltrate Is Formed Each
Minute, How Much Is Formed in a Day?
• Actual urine excretion is 1.5 L a day
• Proximal convoluted tubule reabsorbs about 60% of nutrients
and ions in the urine
– Absorbs at an automatic rate
– The amount of a solute it can reabsorb is the transport
maximum
– Nutrients not reabsorbed pass out in the urine
• Water follows the solutes back into the blood
9. Question
Tell whether the following statement is true or
false.
If GFR increases, urine output (UO) will
decrease.
10. False Answer
Rationale: If GFR increases, it means that fluid is
moving more quickly across the basement
membrane/through the pseudopods. This
means that more fluid will become filtrate and
less fluid will be reabsorbed into the blood. If
less fluid is reabsorbed, more fluid is left to be
excreted (increasing UO).
11. When Urine Reaches Distal Tubule
• Juxtaglomerular cells
measure blood flow in
the afferent arteriole
and urine flow and
composition
Juxtaglomerular
cells • They can release renin
(Image modified from Bowne, P.S. [2004]. Kidneys tutorial. Used with
author’s permission.)
12. Renin Starts the RAA Pathway
• Which turns on
the Na+/K+
ATPase in the
distal tubule
• Na+ and water
Juxtaglomerular
cells
are reabsorbed
• K+ is secreted
(Image modified from Bowne, P.S. [2004]. Kidneys tutorial. Used with author’s permission.)
13. Renin-Angiotensin-Aldosterone
•
System tubule
Turns on the Na /K ATPase in the distal
+ +
• Na+ and water are reabsorbed
– Raises blood volume
– Does not change blood osmolarity
• K+ is secreted
– Lowers blood K+
14. Discussion
What changes in these variables would turn on the RAA
system?
• Blood volume
• Blood K+
• Urine volume
• Urine Na+
15. Reabsorbing Water
Alone to Reduce Blood
Osmolality
• This happens
in the inner
layer of the
kidney, the
medulla
• The loop of
Henle contains
ion pumps
16. Osmolality
(cont.)
•The NaCl pumped
into the medulla
makes it salty
•It is hypertonic to
the urine in the
collecting duct
• Water moves from
the collecting duct
into the salty
medulla and enters
the blood
18. a. Collecting duct Answer
Rationale: Reabsorption of water occurs in the
medulla (the inner layer of the kidney). Na+Cl-
leaves the loop of Henle, which makes it
hypertonic to the urine in the collecting duct.
Water moves from the collecting duct into
the blood (reabsorption).
19. Amount of Water
Absorbed
•Depends on
how much can
move out of the
collecting duct
•Antidiuretic
hormone makes
the duct
permeable to
water
20. Antidiuretic Hormone (ADH)
• Makes collecting duct more permeable to water
• More water can be reabsorbed from the urine into the
blood
• Blood osmolarity decreases
21. Question
Tell whether the following statement is true or
false.
Increased ADH decreases urine output (UO).
22. True Answer
Rationale: ADH makes the collecting duct more
permeable to water, so that more water can
leave the duct and be reabsorbed into the
blood. More reabsorption means that there is
less fluid to be excreted (↓ UO).
23. Scenario
A man was given a drug that stopped the ion
pumps in the loop of Henle.
Question:
• What happened to:
– Medulla osmolarity?
– Na+ levels in the distal convoluted tubule?
– Amount of water reabsorbed from the collecting
duct?
– Renin levels?
– Blood K+?
24. Removing NaCl and Water From
Your Blood
• Atrial natriuretic peptide and B-type natriuretic
peptide
– ANP is made by overstretched atria
– BNP is made by overworked ventricles
º Both cause the kidneys to stop reabsorbing NaCl
º The NaCl and water are lost in the urine, reducing blood
volume and decreasing the stretch and workload of the
heart
25. Discussion
• What will happen to urine if:
– Aldosterone is given?
– ADH levels are high?
– BNP levels are elevated?
26. Discussion
A man has severe renal disease.
Question:
• Why does he develop:
– Anemia?
– Weak bones?
27. Question
What hormone secreted by the kidneys
stimulates RBC formation in the bone
marrow?
b. Renin
c. Erythropoietin
d. Aldosterone
e. Angiotensin
28. a. Erythropoietin Answer
Rationale: Erythropoietin literally means
“producing erythrocytes/RBCs.” Decreased
levels of this hormone lead to anemia;
increased levels lead to polycythemia.
29. Kidney Functions
• The kidneys clear wastes out of the blood
• Renal clearance is a measurement of how much
blood the kidneys clean in a minute
– If the blood contains 1 mg waste/100 mL blood
– If the person produces 1 mL urine per minute
– And if the urine contains 1 mg waste/mL
Question
• How much blood did the kidney clean in one
minute?
30. Kidney Functions (cont.)
• If the kidneys fail, waste builds up in the blood
What is the percent of kidney
function when serum creatinine is:
2 mg/dL?
3 mg/dL?
10 mg/dL?
31. Kidney Functions (cont.)
• If the kidneys fail, waste builds up in the blood
Kidney function = Normal serum creatinine
Current serum creatinine
32. Discussion
What would each of these test results indicate?
• Severe proteinuria
• Casts with red blood cells in them
• Low specific gravity
• Serum creatinine = 6 mg/dL
• BUN = 35 mg/dL, serum creatinine = 1.2 mg/dL
