Renal Function
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1
What is the approximate weight of a kidney?
150 g
2
What are the approximate dimensions of a kidney?
12.5 cm × 6 cm × 2.5 cm (length × width × depth)
3
What is the approximate length of a ureter?
25 cm
4
At approximately what urine volume in the bladder is a nerve reflex initiated?
150 mL
5
What is the approximate length of the female urethra?
4 cm
6
What is the approximate length of the male urethra?
24 cm
7
How often do the ureters empty small amounts of urine into the bladder?
Every 10–15 seconds
8
What is urine considered in relation to the kidney?
A fluid biopsy of the kidney
9
What is the basic structural and functional unit of the kidney?
Nephron
10
How many nephrons are present in each kidney?
Approximately 1–1.5 million
11
What are the two main components of a nephron?
Glomerulus and renal tubules
12
How much of the total cardiac output do the kidneys receive?
Approximately 25%
13
Enumerate the pathway of renal blood flow in the correct order.
Renal artery → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries → vasa recta → renal vein
14
What does the afferent arteriole mean?
Approaching the glomerulus
15
What does the efferent arteriole mean?
Exiting the glomerulus
16
What is the function or location of the peritubular capillaries?
They surround the renal tubules
17
Which blood vessel brings blood into the kidney?
Renal artery
18
Which vessel carries blood away from the glomerulus?
Efferent arteriole
19
Which blood vessel carries blood out of the kidney?
Renal vein
20
What is the total renal blood flow?
Approximately 1,200 mL/min
21
What is the total renal plasma flow?
Approximately 600–700 mL/min
22
What is glomerular filtration?
The process of filtering plasma substances through the glomerulus
23
What is considered the working portion of the kidney?
Glomerulus
24
What is the glomerulus composed of?
A coil of approximately 8 capillary lobes forming a capillary tuft
25
Where is the glomerulus located?
Within the Bowman's capsule
26
What epithelial cells are attached to the glomerular basement membrane?
Podocytes
27
What does the glomerulus resemble?
A sieve
28
What type of filter is the glomerulus?
A non-selective filter of plasma substances with molecular weights below 70,000 daltons
29
What is the molecular weight limit for substances filtered by the glomerulus according to the notes?
Less than 70,000 daltons or 70 kDa
30
Enumerate the substances with molecular weights below 70 kDa that can pass through the glomerulus.
Salts, water, amino acids, glucose, and urea
31
What is the specific gravity of glomerular filtrate?
1.010
32
What prevents albumin from passing through the glomerular filtration barrier despite being small enough?
The negatively charged filtration barrier repels negatively charged albumin at physiological pH
33
What is the electrical charge of albumin at physiological pH?
Negative
34
Why can albumin not normally pass through the glomerular filtration barrier?
Similar negative charges repel each other
35
At what pH does albumin become positively charged according to the notes?
pH 4.9
36
Why is albumin becoming positively charged at pH 4.9 not physiologically practical?
The patient would have to be in an extremely acidotic state that is impossible or deadly
37
What percentage of filtered plasma volume is actually excreted as urine?
Approximately 1%
38
What are the three components of the glomerular filtration barrier?
Capillary endothelium, trilayer basement membrane, and filtration diaphragm
39
What is the first layer of the glomerular filtration barrier?
Capillary endothelium with large open pores
40
What are the three layers of the glomerular basement membrane?
Lamina rara interna, lamina densa, and lamina rara externa
41
Where is the filtration diaphragm located?
Between the podocytes of Bowman's space
42
What is the first renal function affected in renal disease?
Tubular reabsorption
43
What happens when the plasma concentration of a normally completely reabsorbed substance becomes abnormally high?
The filtrate concentration exceeds the tubules' maximal reabsorptive capacity (Tm), causing the substance to appear in the urine
44
What does Tm mean in tubular reabsorption?
Maximal reabsorptive capacity of the tubules
45
What is the renal threshold?
The plasma concentration at which active transport stops
46
What is the renal threshold for glucose?
160–180 mg/dL
47
What percentage of filtered substances is reabsorbed in the proximal convoluted tubule (PCT)?
Approximately 65%
48
What substances are reabsorbed in the PCT?
Salts, water, amino acids, glucose, and urea
49
What is active transport?
Movement of a substance across cell membranes into the bloodstream using electrochemical energy
50
Which substances undergo active transport in the PCT?
Glucose, amino acids, and salts
51
Action of RAAs
o Dilates the afferent arteriole & constricts the efferent arteriole
o Stimulates sodium reabsorption in the PCT
o Triggers the adrenal cortex to release aldosterone to cause sodium
reabsorption & potassium excretion in the DCT and CD
o Triggers release of anti-diuretic hormone by the hypothalamus to stimulate
water reabsorption in the CD
o Stimulates sodium reabsorption in the PCT
o Triggers the adrenal cortex to release aldosterone to cause sodium
reabsorption & potassium excretion in the DCT and CD
o Triggers release of anti-diuretic hormone by the hypothalamus to stimulate
water reabsorption in the CD
52
What are the two major functions of tubular secretion?
Regulation of acid-base balance through hydrogen ion secretion and elimination of waste products not filtered by the glomerulus
53
Which ions are secreted to regulate acid-base balance?
Hydrogen ions in the form of NH₄⁺ and H₂PO₄⁻
54
What is the major site for removal of nonfiltered substances?
Proximal convoluted tubule (PCT)
55
What happens to hydrogen ions and sodium ions in the PCT during tubular secretion?
H⁺ ions are secreted in exchange for Na⁺ ions
56
What happens to the reabsorbed sodium ions in the PCT?
They are reabsorbed with HCO₃⁻ into the plasma
57
What is renal tubular acidosis (RTA)?
Failure to produce acidic urine due to the inability to secrete hydrogen ions
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