Pharmacology · chapter 33 · Introduction to the Renal and Urinary Systems
Introduction to the Renal System
The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.
Key points
Three main kidney functions
The kidneys have three main functions: filtration, reabsorption, and secretion. The kidneys filter 200 liters of fluid daily to remove waste products that exit the body in the urine.
Sympathetic stimulation and renin
Sympathetic stimulation results in constriction of the renal vessels and the release of renin.
Erythropoietin
The EPO stimulates the production of red blood cells by the bone marrow (Schoener Borger, 2022).
Kidneys activate vitamin D
Deficient vitamin D levels are associated with altered calcium balance and bone metabolism (Kim et al., 2021).
Normal GFR
The normal glomerular filtration rate is 120–125 mL per minute (Ogobuiro Tuma, 2022). This value is influenced by the client’s age, weight, and muscle mass.
Limits of the myogenic response
The myogenic response rapidly addresses alterations in the GFR; however, the response only occurs when the systolic blood pressure is 80–180 mm Hg.
What angiotensin II does
Angiotensin II constricts systemic and renal efferent arterioles; prompts reabsorption of sodium, chloride, and water by osmosis from the proximal tubule; releases aldosterone, which further increases sodium ion and water reabsorption in the distal tubule; and stimulates the thirst response.
High sympathetic stimulation lowers GFR
Conversely, when sympathetic stimulation is high due to blood loss or strenuous physical activity, large amounts of angiotensin II are secreted, constricting both the afferent and efferent arterioles, which decreases the GFR. This response protects the circulating blood volume.
Most reabsorption is in the proximal tubule
Approximately 65% of the filtrate is reabsorbed in the proximal tubule.
Aldosterone
Aldosterone, released by the adrenal cortex, increases cellular permeability to sodium and increases the number of sodium and potassium pumps, which increases sodium reabsorption from the filtrate.
ADH
ADH is released from the posterior pituitary gland and facilitates water reabsorption by opening the aquaporins in the tubular cells. These cells are impermeable to water when ADH is absent, resulting in large volumes of water in the urine.
Drugs are secreted by the proximal tubules
The proximal tubules secrete nitrogenous waste products such as urea, ammonia, and creatinine; excess hydrogen ions; and toxic substances including many protein-bound drugs that do not cross the glomerular basement membrane.
Catheter-associated infections
Infections associated with indwelling urinary catheters are common in hospitalized clients, and these infections can progress to chronic renal failure in susceptible clients.
Preventing kidney stones
Preventive measures include maintaining oral fluid intake at 64–96 fluid ounces per day (or approximately 2–3 liters), avoiding additional calcium intake, and limiting dietary sodium and protein (National Kidney Foundation, 2019).
Terms to know
- hilum
- The renal artery divides into anterior and posterior branches before entering the kidney at the hilum, an indentation on the medial side of the organ that allows blood vessels, lymphatic vessels, and nerves to enter and exit the kidney.
- glomerulus
- The glomerulus is a tufted structure of fenestrated capillaries essential to filtration.
- Tubular secretion
- Tubular secretion is the movement of substances from the peritubular vessels into the tubular lumen to be excreted in the urine.
- Glomerulopathies
- Glomerulopathies are disorders of the glomerular capillaries. These disorders can be due to systemic, autoimmune, or intrinsic renal alterations.
- renal corpuscle
- Blood is filtered by the globe-shaped renal corpuscle, which contains the glomerulus and Bowman’s capsule.
Practice questions
Stuck on select-all-that-apply? How to take them one option at a time.
The graded version needs JavaScript. Every question is below anyway, with the answer and why.
Every question here, with the answer
A client with recurrent kidney stones asks how to prevent new ones. Which advice is supported by the section?
- Take extra calcium supplements.
- Restrict fluids to concentrate the urine.
- Drink about 2–3 liters of fluid per day and limit dietary sodium and protein.
- Increase red meat intake.
Answer: Drink about 2–3 liters of fluid per day and limit dietary sodium and protein.
Prevention includes oral fluid intake of 64–96 ounces (about 2–3 liters) daily, avoiding additional calcium, and limiting sodium and protein. Extra calcium goes against that advice, and red meat ingestion is a listed risk factor.
A hospitalized client has had an indwelling urinary catheter for several days. Why does the nurse monitor closely for infection?
- Catheter-associated infections are common and can progress to chronic renal failure in susceptible clients.
- Catheters lower the GFR to zero.
- Catheters cause kidney stones in every client.
- Catheters increase erythropoietin production.
Answer: Catheter-associated infections are common and can progress to chronic renal failure in susceptible clients.
Infections associated with indwelling urinary catheters are common in hospitalized clients and can progress to chronic renal failure in susceptible clients. The other statements are not supported by the section.
A client with low oxygen levels in the blood asks how the body responds. Which substance released by the kidneys stimulates red blood cell production?
- Bile
- Erythropoietin
- Insulin
- Renin
Answer: Erythropoietin
When blood oxygen falls, the kidney releases erythropoietin, which stimulates red blood cell production by the bone marrow. Renin is part of blood pressure control, bile comes from the liver, and insulin from the pancreas.
Which are effects of angiotensin II described in the section? Select all that apply.
- Prompts reabsorption of sodium and water
- Releases aldosterone
- Stimulates the thirst response
- Increases urine output by blocking ADH
- Constricts systemic and renal efferent arterioles
Answer: Prompts reabsorption of sodium and water, Releases aldosterone, Stimulates the thirst response, Constricts systemic and renal efferent arterioles
Angiotensin II constricts systemic and efferent arterioles, promotes sodium, chloride and water reabsorption, releases aldosterone, and stimulates thirst. It conserves fluid rather than increasing urine output.
A client asks what the kidneys do besides making urine. Which functions should the nurse include? Select all that apply.
- Maintenance of systemic blood pressure
- Erythropoietin secretion
- Regulation of electrolytes and fluid
- Production of bile
- Acid–base balance regulation
Answer: Maintenance of systemic blood pressure, Erythropoietin secretion, Regulation of electrolytes and fluid, Acid–base balance regulation
The kidneys regulate electrolytes and fluid, acid–base balance and blood pressure, and secrete erythropoietin, among other functions. Bile is made by the liver.
A client's lab report lists a GFR. What is the normal glomerular filtration rate?
- 20–25 mL per minute
- 120–125 mL per minute
- 200–250 mL per minute
- 60–65 mL per minute
Answer: 120–125 mL per minute
The normal glomerular filtration rate is 120–125 mL per minute, influenced by age, weight and muscle mass. The other values fall outside that range.
Where every quote comes from
Section 33.1 Introduction to the Renal System of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.
The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.