BIOL 373 midterm 2 correctly solved
exam questions and answers {100%
correct} 2025|2026
Why not only filter the 1% of filtrate that needs to be excreted? CORRECT ANSWERS
filtering all then excreting selected solutes is easier because there isn't a need for
specific transport mechanisms
-able to happen quickly
Why are the roles of the kidneys? CORRECT ANSWERS 1) regulation of ECF volume
and blood pressure
2) regulates plasma osmolarity (Na+,CL-)
3) regulates ion balances
4) excretion of waste
5) regulates plasma pH
6) endocrine
Describe the urinary tract pathway CORRECT ANSWERS 1. fluid moves from plasma
into nephrons (hollow tubules) in the kidneys
2. nephrons modify the composition of the fluid as it passes through
3. modified fluid leaves the kidneys and enters hollow tube called ureter
4. ureters lead from kidney to bladder
5. bladder fills and expands until it conracts and expels urine through a single tube
called urethra
What are the vascular elements of a nephron? CORRECT ANSWERS renal artery
smaller arteries
1) afferent arteriole
2) glomerulus (capillaries)
3) efferent arteriole
4) peritubular capillaries
5) vasa recta (juxtamedullary only)
What is contained in the cortex of the nephron? the medulla of the nephron? CORRECT
ANSWERS cortex:
-all Bowman's capsules
-PCTs
-DCTs
medulla:
-Loop of Henle
-collecting ducts
,What are the tubular elements of the nephron in order? CORRECT ANSWERS renal
corpuscle (Bowman's capsule + glomerulus)
proximal tubule
descending limb
Loop of Henle
ascending limb
distal tubule
collecting duct
to bladder
Describe renal circulation in general CORRECT ANSWERS artery -> capillary -> vein ->
capillary -> vein -> heart
nephrons have 2 capillary beds (glomerulus capillaries and pertitubular capillaries)
What is the difference between renal circulation in juxtaglomedullary nephrons and
corticol nephrons? CORRECT ANSWERS jutaglomerular nephrons go through vasa
recta
Describe the detailed pathway of renal circulation CORRECT ANSWERS abdominal
aorta -> renal artery -> branches of smaller arteries -> 1. afferent arterioles -> 2.
glomerulus (capillaries) -> 3. efferent arteriole -> 4. peritubular capillaries/ 5. vasa recta
-> venules -> veins -> renal vein -> vena cava
Overview of kidney function CORRECT ANSWERS -kidneys process over 180 L
plasma/day but only 1.5 L secreted - 99% of fluid is reabsorbed
1) filtration
2) reabsorption
3) secretion
What is filtration? CORRECT ANSWERS movement of water/solute from blood into
tubules
-occurs in renal corpuscles
-once in tubules, filtrate will be excreted if not reabsorbed
What is reabsorption? CORRECT ANSWERS movement of water/solute from filtrate
back into blood (peritubular capillaries)
What is secretion? CORRECT ANSWERS removing molecules from blood, adding
them to filtrate
-much more selective than filtration
Where does filtration occur? CORRECT ANSWERS only at the glomerulus
-blood to lumen
What does urinary excretion depend on? CORRECT ANSWERS filtration, reabsorption
and secretion
, amount of solute excreted = amount filtered - amount reabsorbed + amount secreted
filtrate at the renal corpuscle CORRECT ANSWERS -filtrate is almost identical to
plasma in composition (isoosmatic with plasma, Na+ Cl-)
-minus blood cells and most of the protein
Reabsorption and secretion in the nephron CORRECT ANSWERS -70% of filtrate and
solute is reabsorbed in proximal tubule (iso-osmotic reabsorption)
-fluid leaving ascending Loop of Henle is hypo-osmotic relative to plasma (at this point
90% of fluid has been reabsorbed)
-distal tubule/collecting duct: "fine tuning" of water-salt balance (endocrine control)
Filtration at the renal corpuscle CORRECT ANSWERS ~20% of the plasma moves out
of glomerular capillaries into tubules (the rest exits in the efferent arteriole)
What is filtration fraction? CORRECT ANSWERS % of total plasma volume that filters
into tubule
What is the function of the macula densa? CORRECT ANSWERS modifies tubular
epithelium
-macula densa cells release paracrine factors that act on smooth muscle of afferent
arteriole
What are the barriers to glomerular filtration? CORRECT ANSWERS 1) endothelium of
glomerular capillaries
-"fenestrated": allow most substances to pass
-exceptions: cells (too big) and most proteins (repelled by negatively charged proteins
on pore surfaces)
2) basement membrane
-layer of ECM between capilary endothelium and epithelium of Bowman's capsule
*collagens, other proteins (negatively charged)
*acts as a course sieve, keeping most proteins in plasma
3) epithelium of Bowman's capsule
-gaps between foot processes of podocytes leave narrow slits closed by semi-porous
membrane
What are the 3 types of capillaries? CORRECT ANSWERS 1) continuous
-most common
-muscle, neural tissue, connective tissue
-tight junctions, intracellular clefts
2) fenestrated
-kidney, intestine
-fenestrations, tight junctions
3) sinusoid
exam questions and answers {100%
correct} 2025|2026
Why not only filter the 1% of filtrate that needs to be excreted? CORRECT ANSWERS
filtering all then excreting selected solutes is easier because there isn't a need for
specific transport mechanisms
-able to happen quickly
Why are the roles of the kidneys? CORRECT ANSWERS 1) regulation of ECF volume
and blood pressure
2) regulates plasma osmolarity (Na+,CL-)
3) regulates ion balances
4) excretion of waste
5) regulates plasma pH
6) endocrine
Describe the urinary tract pathway CORRECT ANSWERS 1. fluid moves from plasma
into nephrons (hollow tubules) in the kidneys
2. nephrons modify the composition of the fluid as it passes through
3. modified fluid leaves the kidneys and enters hollow tube called ureter
4. ureters lead from kidney to bladder
5. bladder fills and expands until it conracts and expels urine through a single tube
called urethra
What are the vascular elements of a nephron? CORRECT ANSWERS renal artery
smaller arteries
1) afferent arteriole
2) glomerulus (capillaries)
3) efferent arteriole
4) peritubular capillaries
5) vasa recta (juxtamedullary only)
What is contained in the cortex of the nephron? the medulla of the nephron? CORRECT
ANSWERS cortex:
-all Bowman's capsules
-PCTs
-DCTs
medulla:
-Loop of Henle
-collecting ducts
,What are the tubular elements of the nephron in order? CORRECT ANSWERS renal
corpuscle (Bowman's capsule + glomerulus)
proximal tubule
descending limb
Loop of Henle
ascending limb
distal tubule
collecting duct
to bladder
Describe renal circulation in general CORRECT ANSWERS artery -> capillary -> vein ->
capillary -> vein -> heart
nephrons have 2 capillary beds (glomerulus capillaries and pertitubular capillaries)
What is the difference between renal circulation in juxtaglomedullary nephrons and
corticol nephrons? CORRECT ANSWERS jutaglomerular nephrons go through vasa
recta
Describe the detailed pathway of renal circulation CORRECT ANSWERS abdominal
aorta -> renal artery -> branches of smaller arteries -> 1. afferent arterioles -> 2.
glomerulus (capillaries) -> 3. efferent arteriole -> 4. peritubular capillaries/ 5. vasa recta
-> venules -> veins -> renal vein -> vena cava
Overview of kidney function CORRECT ANSWERS -kidneys process over 180 L
plasma/day but only 1.5 L secreted - 99% of fluid is reabsorbed
1) filtration
2) reabsorption
3) secretion
What is filtration? CORRECT ANSWERS movement of water/solute from blood into
tubules
-occurs in renal corpuscles
-once in tubules, filtrate will be excreted if not reabsorbed
What is reabsorption? CORRECT ANSWERS movement of water/solute from filtrate
back into blood (peritubular capillaries)
What is secretion? CORRECT ANSWERS removing molecules from blood, adding
them to filtrate
-much more selective than filtration
Where does filtration occur? CORRECT ANSWERS only at the glomerulus
-blood to lumen
What does urinary excretion depend on? CORRECT ANSWERS filtration, reabsorption
and secretion
, amount of solute excreted = amount filtered - amount reabsorbed + amount secreted
filtrate at the renal corpuscle CORRECT ANSWERS -filtrate is almost identical to
plasma in composition (isoosmatic with plasma, Na+ Cl-)
-minus blood cells and most of the protein
Reabsorption and secretion in the nephron CORRECT ANSWERS -70% of filtrate and
solute is reabsorbed in proximal tubule (iso-osmotic reabsorption)
-fluid leaving ascending Loop of Henle is hypo-osmotic relative to plasma (at this point
90% of fluid has been reabsorbed)
-distal tubule/collecting duct: "fine tuning" of water-salt balance (endocrine control)
Filtration at the renal corpuscle CORRECT ANSWERS ~20% of the plasma moves out
of glomerular capillaries into tubules (the rest exits in the efferent arteriole)
What is filtration fraction? CORRECT ANSWERS % of total plasma volume that filters
into tubule
What is the function of the macula densa? CORRECT ANSWERS modifies tubular
epithelium
-macula densa cells release paracrine factors that act on smooth muscle of afferent
arteriole
What are the barriers to glomerular filtration? CORRECT ANSWERS 1) endothelium of
glomerular capillaries
-"fenestrated": allow most substances to pass
-exceptions: cells (too big) and most proteins (repelled by negatively charged proteins
on pore surfaces)
2) basement membrane
-layer of ECM between capilary endothelium and epithelium of Bowman's capsule
*collagens, other proteins (negatively charged)
*acts as a course sieve, keeping most proteins in plasma
3) epithelium of Bowman's capsule
-gaps between foot processes of podocytes leave narrow slits closed by semi-porous
membrane
What are the 3 types of capillaries? CORRECT ANSWERS 1) continuous
-most common
-muscle, neural tissue, connective tissue
-tight junctions, intracellular clefts
2) fenestrated
-kidney, intestine
-fenestrations, tight junctions
3) sinusoid
