WGU D236 – PATHOPHYSIOLOGY | STUDY GUIDE 2025-2026 150
QUESTIONS AND CORRECT ANSWERS | STARLING’S LAW, RAAS
SYSTEM & EDEMA EXPLAINED
This guide simplifies complex cardiovascular and renal physiology by
explaining how capillary forces (hydrostatic vs. oncotic pressure)
influence fluid movement—and how imbalances, like low protein in
malnourished children, can lead to edema. It also provides a step-by-
step breakdown of the RAAS system, showing how it reacts to
hypotension by triggering renin release, vasoconstriction, and fluid
retention to raise blood pressure. Ideal for nursing students aiming to
understand the "why" behind patient symptoms, this study resource
makes WGU D236 content clear, memorable, and clinically relevant.
How does this explain why a nutritionally deficient child would have edema? - CORRECT ANSWER-
Starling's Law describes how fluids move across the capillary membrane. There are two major
opposing forces that act to balance each other, hydrostatic pressure (pushing water out of the
capillaries) and osmotic pressure (including oncontic pressure, which pushes fluid into the
capillaries).
Both electrolytes and proteins (oncontic pressure) in the blood affect osmotic pressure, high
electrolyte and protein concentrations in the blood would cause water to leave the cells and
interstitial space and enter the blood stream to dilute the high concentrations.
On, the other hand, low electrolyte and protein concentrations (as seen in a nutritionally deficient
child) would cause water to leave the capillaries and enter the cells and interstitial fluid which can
lead to edema.
How does the RAAS (Renin-Angiotensin-Aldosterone System) result in increased blood volume and
increased blood pressure? - CORRECT ANSWER-A drop in blood pressure is sensed by the kidneys
by low perfusion, which in turn begins to secrete renin.
Renin then triggers the liver to produce angiotensinogen, which is converted to Angiotensin I in the
lungs and then angiotensin II by the enzyme
Angiotensin-converting enzyme (ACE). Angiotensin II stimulates peripheral arterial vasoconstriction
which raises BP.
Angiotensin II is also stimulating the adrenal gland to release aldosterone, which acts to increase
sodium and water reabsorption increasing blood volume, while also increased potassium secretion
in urine.
,How can hyperkalemia lead to cardiac arrest? - CORRECT ANSWER-Normal levels of potassium are
between 3.5 and 5.2 mEq/dL. Hyperkalemia refers to potassium levels higher that 5.2 mEq/dL.
A major function of potassium is to conduct nerve impulses in muscles. Too low and muscle
weakness occurs and too much can cause muscle spasms.
This is especially dangerous in the heart muscle and an irregular heartbeat can cause a heart attack
The body uses the Protein Buffering System, Phosphate Buffering System, and Carbonic Acid-
Bicarbonate System to regulate and maintain homeostatic pH, what is the consequence of a pH
imbalance - CORRECT ANSWER-Proteins contain many acidic and basic group that can be affected
by pH changes. Any increase or decrease in blood pH can alter the structure of the protein
(denature), thereby affecting its function as well
Describe the laboratory findings associated with metabolic acidosis, metabolic alkalosis, respiratory
acidosis and respiratory alkalosis. (ie relative pH and CO2 levels). - CORRECT ANSWER-Normal ABGs
(Arterial Blood Gases) Blood pH: 7.35-7.45 PCO2: 35-45 mm Hg PO2: 90-100 mm Hg HCO3-: 22-26
mEq/L SaO2: 95-100%
Respiratory acidosis and alkalosis are marked by changes in PCO2. Higher = acidosis and lower =
alkalosis
Metabolic acidosis and alkalosis are caused by something other than abnormal CO2 levels. This could
include toxicity, diabetes, renal failure or excessive GI losses.
Here are the rules to follow to determine if is respiratory or metabolic in nature. -If pH and PCO2 are
moving in opposite directions, then it is the pCO2 levels that are causing the imbalance and it is
respiratory in nature.
-If PCO2 is normal or is moving in the same direction as the pH, then the imbalance is metabolic in
nature.
The anion gap is the difference between measured cations (Na+ and K+) and measured anions (Cl-
and HCO3-), this calculation can be useful in determining the cause of metabolic acidosis.
Why would an increased anion gap be observed in diabetic ketoacidosis or lactic acidosis? -
CORRECT ANSWER-The anion gap is the calculation of unmeasured anions in the blood.
Lactic acid and ketones both lead to the production of unmeasured anions, which remove HCO3- (a
measured anion) due to buffering of the excess H+ and therefore leads to an increase in the AG.
Why is it important to maintain a homeostatic balance of glucose in the blood (ie describe the
pathogenesis of diabetes)? - CORRECT ANSWER-Insulin is the hormone responsible for initiating
the uptake of glucose by the cells. Cells use glucose to produce energy (ATP).
,In a normal individual, when blood glucose increases, the pancreas is signaled to produced in insulin,
which binds to insulin receptors on a cells surface and initiates the uptake of glucose.
Glucose is a very reactive molecule and if left in the blood, it can start to bind to other proteins and
lipids, which can lead to loss of function.
AGEs are advanced glycation end products that are a result of glucose reacting with the endothelial
lining, which can lead to damage in the heart and kidneys.
Compare and contrast Type I and Type II Diabetes - CORRECT ANSWER-Type I diabetes is caused by
lack of insulin. With out insulin signaling, glucose will not be taken into the cell and leads to high
blood glucose (hyperglycemia). Type I is usually treated with insulin injections.
Type II diabetes is caused by a desensitization to insulin signaling. The insulin receptors are no longer
responding to insulin, which also leads to hyperglycemia.
Type II is usually treated with drugs to increase the sensitization to insulin (metformin), dietary and
life-style changes or insulin injections.
Describe some reasons for a patient needing dialysis - CORRECT ANSWER-AEIOU-acidosis.
Electrolytes, Intoxication/Ingestion, overload, uremia. Patients with kidney or heart failure.
A build up of phosphates, urea and magnesium are removed from the blood using a semi-permeable
membrane and dialysate.
AEIOU:
A—acidosis;
E—electrolytes principally hyperkalemia;
I—ingestions or overdose of medications/drugs;
O—overload of fluid causing heart failure;
U—uremia leading to encephalitis/pericarditis
Compare and contrast hemodialysis and peritoneal dialysis.
What are some reasons for a patient choosing one over the other? - CORRECT ANSWER-
Hemodialysis uses a machine to pump blood from the body in one tube while dialysate (made of
water, electrolytes and salts) is pumped in the separate tube in the opposite direction. Waste from
the blood diffuses through the semipermeable membrane separating the blood from the dialysate.
Peritoneal Dialysis does not use a machine, but instead injects a solution of water and glucose into
the abdominal cavity. The peritoneum acts as the membrane instead of dialysis tubing. The waste
products diffuse into the abdominal cavity and the waste solution is then drained from the body.
, Peritoneal dialysis offers continuous filtration and is less disruption to the patient's daily routines.
However, it does require some training of the patient and is not recommended for individuals who
are overweight or have severe kidney failure.
Hemodialysis provides medical care, but 3 times a week for several hours sitting at a hospital or
clinic. Individuals with acute kidney failure are recommended to use hemodialysis.
How does homeostasis and maintaining optimal physiological health impact your wellbeing? -
CORRECT ANSWER-Homeostasis acts to create a constant and stable environment in the body
despite internal and external changes. Proteins and other cellular processes require optimal
conditions in order to carry out their functions.
Alterations in pH, salt concentration, temperature, glucose levels, etc. can have negative effects on
health, so it is vital for mechanisms that regulate homeostasis to function properly for maintaining
good health
Differentiate between Innate Immunity and Adaptive Immunity ? - CORRECT ANSWER-The innate
immune system encompasses physical barriers and chemical and cellular defenses. Physical barriers
protect the body from invasion. These include things like the skin and eyelashes. Chemical barriers
are defense mechanisms that can destroy harmful agent. Examples include tears, mucous, and
stomach acid.
Cellular defenses of the innate immune response are non-specific. These cellular defenses identify
pathogens and substances that are potentially dangerous and takes steps to neutralize or destroy
them.
Adaptive immunity is an organism's acquired immunity to a specific pathogen. As such, it's also
referred to as acquired immunity. Adaptive immunity is not immediate, nor does it always last
throughout an organism's entire lifespan, although it can.
The adaptive immune response is marked by clonal expansion of T and B lymphocytes, releasing
many antibody copies to neutralize or destroy their target antigen
What is a way that Adaptive Immunity can recruit innate immunity? - CORRECT ANSWER-The
innate immune response to microbes stimulates adaptive immune responses and influences the
nature of the adaptive responses.
Conversely, adaptive immune responses often work by enhancing the protective mechanisms of
innate immunity, making them more capable of effectively combating pathogenic microbes
Why are some infections harder on children while other infections are harder on the elderly? -
CORRECT ANSWER-Children have not been exposed to many pathogens yet, so they lack memory
cells and have not built-up immunity yet.
The elderly have a depleted naïve T cell population from years of battling infections, so the
likelihood of getting a match is less.
QUESTIONS AND CORRECT ANSWERS | STARLING’S LAW, RAAS
SYSTEM & EDEMA EXPLAINED
This guide simplifies complex cardiovascular and renal physiology by
explaining how capillary forces (hydrostatic vs. oncotic pressure)
influence fluid movement—and how imbalances, like low protein in
malnourished children, can lead to edema. It also provides a step-by-
step breakdown of the RAAS system, showing how it reacts to
hypotension by triggering renin release, vasoconstriction, and fluid
retention to raise blood pressure. Ideal for nursing students aiming to
understand the "why" behind patient symptoms, this study resource
makes WGU D236 content clear, memorable, and clinically relevant.
How does this explain why a nutritionally deficient child would have edema? - CORRECT ANSWER-
Starling's Law describes how fluids move across the capillary membrane. There are two major
opposing forces that act to balance each other, hydrostatic pressure (pushing water out of the
capillaries) and osmotic pressure (including oncontic pressure, which pushes fluid into the
capillaries).
Both electrolytes and proteins (oncontic pressure) in the blood affect osmotic pressure, high
electrolyte and protein concentrations in the blood would cause water to leave the cells and
interstitial space and enter the blood stream to dilute the high concentrations.
On, the other hand, low electrolyte and protein concentrations (as seen in a nutritionally deficient
child) would cause water to leave the capillaries and enter the cells and interstitial fluid which can
lead to edema.
How does the RAAS (Renin-Angiotensin-Aldosterone System) result in increased blood volume and
increased blood pressure? - CORRECT ANSWER-A drop in blood pressure is sensed by the kidneys
by low perfusion, which in turn begins to secrete renin.
Renin then triggers the liver to produce angiotensinogen, which is converted to Angiotensin I in the
lungs and then angiotensin II by the enzyme
Angiotensin-converting enzyme (ACE). Angiotensin II stimulates peripheral arterial vasoconstriction
which raises BP.
Angiotensin II is also stimulating the adrenal gland to release aldosterone, which acts to increase
sodium and water reabsorption increasing blood volume, while also increased potassium secretion
in urine.
,How can hyperkalemia lead to cardiac arrest? - CORRECT ANSWER-Normal levels of potassium are
between 3.5 and 5.2 mEq/dL. Hyperkalemia refers to potassium levels higher that 5.2 mEq/dL.
A major function of potassium is to conduct nerve impulses in muscles. Too low and muscle
weakness occurs and too much can cause muscle spasms.
This is especially dangerous in the heart muscle and an irregular heartbeat can cause a heart attack
The body uses the Protein Buffering System, Phosphate Buffering System, and Carbonic Acid-
Bicarbonate System to regulate and maintain homeostatic pH, what is the consequence of a pH
imbalance - CORRECT ANSWER-Proteins contain many acidic and basic group that can be affected
by pH changes. Any increase or decrease in blood pH can alter the structure of the protein
(denature), thereby affecting its function as well
Describe the laboratory findings associated with metabolic acidosis, metabolic alkalosis, respiratory
acidosis and respiratory alkalosis. (ie relative pH and CO2 levels). - CORRECT ANSWER-Normal ABGs
(Arterial Blood Gases) Blood pH: 7.35-7.45 PCO2: 35-45 mm Hg PO2: 90-100 mm Hg HCO3-: 22-26
mEq/L SaO2: 95-100%
Respiratory acidosis and alkalosis are marked by changes in PCO2. Higher = acidosis and lower =
alkalosis
Metabolic acidosis and alkalosis are caused by something other than abnormal CO2 levels. This could
include toxicity, diabetes, renal failure or excessive GI losses.
Here are the rules to follow to determine if is respiratory or metabolic in nature. -If pH and PCO2 are
moving in opposite directions, then it is the pCO2 levels that are causing the imbalance and it is
respiratory in nature.
-If PCO2 is normal or is moving in the same direction as the pH, then the imbalance is metabolic in
nature.
The anion gap is the difference between measured cations (Na+ and K+) and measured anions (Cl-
and HCO3-), this calculation can be useful in determining the cause of metabolic acidosis.
Why would an increased anion gap be observed in diabetic ketoacidosis or lactic acidosis? -
CORRECT ANSWER-The anion gap is the calculation of unmeasured anions in the blood.
Lactic acid and ketones both lead to the production of unmeasured anions, which remove HCO3- (a
measured anion) due to buffering of the excess H+ and therefore leads to an increase in the AG.
Why is it important to maintain a homeostatic balance of glucose in the blood (ie describe the
pathogenesis of diabetes)? - CORRECT ANSWER-Insulin is the hormone responsible for initiating
the uptake of glucose by the cells. Cells use glucose to produce energy (ATP).
,In a normal individual, when blood glucose increases, the pancreas is signaled to produced in insulin,
which binds to insulin receptors on a cells surface and initiates the uptake of glucose.
Glucose is a very reactive molecule and if left in the blood, it can start to bind to other proteins and
lipids, which can lead to loss of function.
AGEs are advanced glycation end products that are a result of glucose reacting with the endothelial
lining, which can lead to damage in the heart and kidneys.
Compare and contrast Type I and Type II Diabetes - CORRECT ANSWER-Type I diabetes is caused by
lack of insulin. With out insulin signaling, glucose will not be taken into the cell and leads to high
blood glucose (hyperglycemia). Type I is usually treated with insulin injections.
Type II diabetes is caused by a desensitization to insulin signaling. The insulin receptors are no longer
responding to insulin, which also leads to hyperglycemia.
Type II is usually treated with drugs to increase the sensitization to insulin (metformin), dietary and
life-style changes or insulin injections.
Describe some reasons for a patient needing dialysis - CORRECT ANSWER-AEIOU-acidosis.
Electrolytes, Intoxication/Ingestion, overload, uremia. Patients with kidney or heart failure.
A build up of phosphates, urea and magnesium are removed from the blood using a semi-permeable
membrane and dialysate.
AEIOU:
A—acidosis;
E—electrolytes principally hyperkalemia;
I—ingestions or overdose of medications/drugs;
O—overload of fluid causing heart failure;
U—uremia leading to encephalitis/pericarditis
Compare and contrast hemodialysis and peritoneal dialysis.
What are some reasons for a patient choosing one over the other? - CORRECT ANSWER-
Hemodialysis uses a machine to pump blood from the body in one tube while dialysate (made of
water, electrolytes and salts) is pumped in the separate tube in the opposite direction. Waste from
the blood diffuses through the semipermeable membrane separating the blood from the dialysate.
Peritoneal Dialysis does not use a machine, but instead injects a solution of water and glucose into
the abdominal cavity. The peritoneum acts as the membrane instead of dialysis tubing. The waste
products diffuse into the abdominal cavity and the waste solution is then drained from the body.
, Peritoneal dialysis offers continuous filtration and is less disruption to the patient's daily routines.
However, it does require some training of the patient and is not recommended for individuals who
are overweight or have severe kidney failure.
Hemodialysis provides medical care, but 3 times a week for several hours sitting at a hospital or
clinic. Individuals with acute kidney failure are recommended to use hemodialysis.
How does homeostasis and maintaining optimal physiological health impact your wellbeing? -
CORRECT ANSWER-Homeostasis acts to create a constant and stable environment in the body
despite internal and external changes. Proteins and other cellular processes require optimal
conditions in order to carry out their functions.
Alterations in pH, salt concentration, temperature, glucose levels, etc. can have negative effects on
health, so it is vital for mechanisms that regulate homeostasis to function properly for maintaining
good health
Differentiate between Innate Immunity and Adaptive Immunity ? - CORRECT ANSWER-The innate
immune system encompasses physical barriers and chemical and cellular defenses. Physical barriers
protect the body from invasion. These include things like the skin and eyelashes. Chemical barriers
are defense mechanisms that can destroy harmful agent. Examples include tears, mucous, and
stomach acid.
Cellular defenses of the innate immune response are non-specific. These cellular defenses identify
pathogens and substances that are potentially dangerous and takes steps to neutralize or destroy
them.
Adaptive immunity is an organism's acquired immunity to a specific pathogen. As such, it's also
referred to as acquired immunity. Adaptive immunity is not immediate, nor does it always last
throughout an organism's entire lifespan, although it can.
The adaptive immune response is marked by clonal expansion of T and B lymphocytes, releasing
many antibody copies to neutralize or destroy their target antigen
What is a way that Adaptive Immunity can recruit innate immunity? - CORRECT ANSWER-The
innate immune response to microbes stimulates adaptive immune responses and influences the
nature of the adaptive responses.
Conversely, adaptive immune responses often work by enhancing the protective mechanisms of
innate immunity, making them more capable of effectively combating pathogenic microbes
Why are some infections harder on children while other infections are harder on the elderly? -
CORRECT ANSWER-Children have not been exposed to many pathogens yet, so they lack memory
cells and have not built-up immunity yet.
The elderly have a depleted naïve T cell population from years of battling infections, so the
likelihood of getting a match is less.
