Download Module 4: Genetics

Module 11:
Human Health and Physiology
II
11.3 The Kidney
11.3.1 Define excretion.
Excretion is the
removal of waste
products of cell
reactions/metabolic
pathways
11.3.2 Draw and label the structure of the kidney
Renal
Renal pelvis
11.3.3 Annotate a diagram of a glomerulus and
associated nephron to show the function of each part.
The functional
unit of the
kidneys is the
nephron
11.3.4 Explain the process of ultrafiltration, including
blood pressure, fenestrated blood capillaries and
basement membrane.
The afferent arteriole brings in
unfiltered blood into the
glomerulus. Unlike other
capillary beds, it has
fenestrations that open
when blood pressure is high.
The pressure is maintained
due to the fact that the
efferent arteriole has a
smaller diameter than the
afferent arteriole. This is
called ultrafiltration.
Basement
membrane
Explain the process of ultrafiltration [2
marks]
blood (in the glomerulus) under high
pressure caused by difference
in diameter of (afferent and efferent)
arterioles;
fluid plasma and small molecules forced into
kidney tubule/
Bowman’s capsule/through
fenestrations/basal membrane;
which prevent larger molecules/blood cells
from passing through;
11.3.5 Define osmoregulation.
Osmoregulation is the homeostatic control of the water balance
of the blood, tissue or cytoplasm of a living cell/organism
Quick review…
 What structure is responsible for
ultrafiltration?
 How is the high blood pressure generated
in the glomerulus?
What are fenestrations?
What kind of molecules cannot pass
through the basement/basal membrane?
What happens to these molecules?
11.3.6 Explain the reabsorption of glucose, water and
salts in the proximal convoluted tubule, including the
roles of microvilli, osmosis and active transport.
There are many useful substances left in the filtrate once it
enters the proximal convoluted tubule. This is where
reabsorption occurs. These substances are returned back to
the blood using the peritublar capillary bed.
11.3.6 Explain the reabsorption of glucose, water and
salts in the proximal convoluted tubule, including the
roles of microvilli, osmosis and active transport.
.
1) Glucose is actively transported from the filtrate into the cells
of the proximal convoluted tubule wall to the peritubular
capillary bed
2) Salt ions (Na+, K-, Cl-) are actively transported into tubule
cells and then to the intercellular fluid outside the tubule
before entering the peritublar capillary bed
3) Water follows the flow of salt ions and leaves the filtrate to
enter the tubule cells  intercellular fluid  peritubular
capillary bed through osmosis
11.3.7 Explain the roles of the loop of Henle, medulla,
collecting duct and ADH in maintaining the water
balance of the blood.
The loop of Henle makes a hypertonic environment in the medulla
Descending portion: permeable to
water; impermeable to salt
Ascending portion: permeable to
salt; impermeable to water
11.3.7 Explain the roles of the loop of Henle, medulla,
collecting duct and ADH in maintaining the water
balance of the blood.
The hypertonic environment of the
medulla draws out water from the
collecting duct via osmosis.
ADH increases the permeability of
the DCT and the collecting duct by
opening pores called aquaporins.
If there is no ADH, water content in
filtrate remains high and is excreted
in urine
11.3.8 Explain the differences in the concentration of
proteins, glucose and urea between blood plasma,
glomerular filtrate and urine.
Molecule
Amount in
blood plasma
(mg 100 ml-1)
Amount in
glomerular
filtrate (mg 100
ml-1)
Amount in urine
(mg 100 ml-1)
Proteins
>700
0
0
Glucose
>90
>90
0
Urea
30
30
>1800
• Proteins are too large to pass through the basement
membrane into the filtrate
• Glucose is actively transported back into the peritubular
capillary (even though it makes it to the filtrate)
• High concentration of urea is due to reabsorption of water
11.3.9 Explain the presence of glucose in the urine of
untreated diabetic patients.
Blood glucose is so high that the maximum rate of active
transport of glucose is exceeded. As a result, glucose is left in
the filtrate.
Explain why diabetes could be detected
through the analysis of urine [8 marks]
urine of diabetics contains glucose;
whereas urine of non-diabetics contains no glucose;
glomerular filtrate contains glucose / glucose filtered out;
glucose (normally) reabsorbed from filtrate/into blood;
through wall of / in the proximal convoluted tubules;
blood glucose concentration higher than normal in diabetics;
reabsorption not completed / pumps cannot reabsorb all glucose
in
diabetics;
glucose in urine can be detected using test strips;
type I diabetes is lack of insulin secretion / lack of β cells;
type II diabetes is body cells not responding to insulin / not
absorbing glucose; 8 max