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Questions and Answers
What is the primary function of the kidneys in regulating blood pressure?
Which of the following ions is NOT regulated by the urinary system?
What is the function of the enzyme renin in the kidneys?
What is the role of the kidneys in maintaining normal body fluid levels?
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What is the term for the functional unit of the kidney?
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What percentage of resting cardiac output does the kidneys receive?
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What is the name of the space where water and solutes in blood plasma are filtered through the capillary walls?
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What is the term for the fluid that enters the capsular space?
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What does an increase in GFR typically indicate?
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Which of the following is a way the body regulates GFR?
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What happens to the afferent arteriole when there is an increase in BP?
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What is the function of angiotensin II in regulating GFR?
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Which hormone increases the reabsorption of calcium?
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What is the primary function of the angiotensin-converting enzyme (ACE)?
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What is the result of increased blood volume on the glomerular filtration rate (GFR)?
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What is the role of the ureter in the urinary system?
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Which of the following is a result of the micturition reflex?
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What is the effect of aging on the kidneys?
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Study Notes
Structures of the Urinary System
- Comprises kidneys (2), ureters (2), bladder, and urethra.
- Kidneys are retroperitoneal and located between T12 and L3, partially protected by ribs 11 and 12.
- The renal cortex is the outer layer, and the renal medulla is the inner portion.
- Nephrons are the functional units of the kidney, consisting of the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
Functions of the Urinary System
- Regulates volume and composition of body fluids to maintain normal cell volume and cardiovascular function.
- Manages electrolyte/ion balance for several ions such as sodium (Na+), potassium (K+), and calcium (Ca2+).
- Maintains acid-base (pH) balance by excreting hydrogen ions (H+) and reabsorbing bicarbonate.
- Produces hormones including erythropoietin (stimulates red blood cell production) and calcitriol (active vitamin D).
- Excretes waste materials such as urea, ammonia, and uric acid.
- Regulates blood glucose levels by producing glucose during hypoglycemia.
Urine Production and Flow
- Blood enters the kidney via the renal artery, branching into smaller vessels leading to the glomerulus.
- The glomerulus filters water and solutes from the blood plasma into the Bowman’s capsule, forming glomerular filtrate.
- As this filtrate moves along the renal tubule, most useful solutes and water are reabsorbed.
- Wastes are secreted from the peritubular capillaries into the tubular fluid for elimination.
Glomerular Filtration Rate (GFR)
- GFR measures the volume of filtrate produced per minute, indicating kidney function.
- Regulated through adjusting blood flow and the capillary surface area for filtration.
- Increased GFR leads to increased urine production; decreased GFR results in reduced urine production.
Regulation of GFR
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Renal Auto-Regulation: Adjusts blood pressure and flow via:
- Myogenic mechanism: Increased blood pressure triggers vessel constriction to maintain normal GFR.
- Tubuloglomerular feedback: Increased tubular fluid causes vascular response to regulate blood flow.
- Neural Regulation: Sympathetic nervous system activation leads to decreased GFR through vasoconstriction of arterioles.
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Hormonal Regulation: Various hormones influence GFR:
- Angiotensin II acts as a vasoconstrictor, reducing GFR.
- Atrial natriuretic peptide (ANP) increases GFR by promoting excretion of sodium and water.
Hormonal Regulation of Reabsorption & Secretion
- Reabsorption and secretion mechanisms are influenced by hormones such as:
- Angiotensin II: Reduces GFR, promotes sodium and water reabsorption.
- Aldosterone: Increases reabsorption of sodium and water.
- Antidiuretic Hormone (ADH): Enhances water reabsorption in renal tubules.
- Parathyroid Hormone (PTH): Promotes calcium reabsorption.
Ureters, Bladder, and Urethra
- Ureters transport urine from the kidneys to the bladder via peristaltic contractions.
- The bladder is a muscular organ located behind the pubic symphysis; it stores urine.
- Internal and external urethral sphincters control urine flow from the bladder and out of the body.
Elimination and the Micturition Reflex
- Micturition is triggered by bladder pressure stimulating stretch receptors, leading to bladder contraction and relaxation of sphincters.
- Incontinence refers to the involuntary loss of urine control due to stress, nerve damage, or aging.
Aging and the Urinary System
- Kidney size decreases, renal blood flow and GFR decline with age.
- Reduced functional glomeruli and increased incidence of kidney diseases may occur.
Diuretics and Dialysis
- Diuretics are substances that reduce water reabsorption, used in medications and certain foods.
- Dialysis is a medical procedure that cleanses blood artificially when kidneys are unable to function.
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Description
Test your knowledge of the urinary system's structures and functions, including the regulation of body fluids, electrolyte balance, and waste excretion. Learn about the kidneys, ureters, bladder, and urethra.
