Unit 6:
1. List the structures of the renal system including location in the body and primary function.
1. Kidneys
• Location:
• Retroperitoneal space on either side of the spine.
• Situated between the T12-L3 vertebrae, with the right kidney slightly lower due to the liver.
• Primary Function:
• Filter blood to remove waste products (e.g., urea, creatinine).
• Regulate fluid and electrolyte balance (e.g., sodium, potassium, and water).
• Maintain acid-base balance.
• Produce hormones:
• Erythropoietin (stimulates red blood cell production).
• Renin (regulates blood pressure via the renin-angiotensin-aldosterone system).
• Active vitamin D (calcium homeostasis).
2. Ureters
• Location:
• Muscular tubes extending from the renal pelvis of each kidney to the bladder.
• Approximately 25–30 cm long, descending retroperitoneally.
• Primary Function:
• Transport urine from the kidneys to the bladder via peristaltic contractions.
3. Urinary Bladder
• Location:
• Located in the pelvic cavity, posterior to the pubic symphysis.
• In females: Positioned anterior to the uterus and vagina.
• In males: Positioned anterior to the rectum and superior to the prostate gland.
• Primary Function:
• Temporarily store urine until voluntary excretion.
• Can hold 300–500 mL of urine under normal circumstances.
,4. Urethra
• Location:
• Females: Short tube (~3–4 cm), extending from the bladder to the external urethral orifice (located anterior
to the vaginal opening).
• Males: Longer (~18–20 cm), passing through the prostate and penis, divided into prostatic, membranous, and
spongy portions.
• Primary Function:
• Conveys urine from the bladder to the external environment.
• In males, also functions as part of the reproductive system, carrying semen during ejaculation.
5. Nephrons (Functional Unit of the Kidney)
• Location:
• Found within the renal cortex and renal medulla of the kidneys.
• Primary Function:
• Filter blood to form urine through three main processes:
• Filtration (in the glomerulus).
• Reabsorption (in the proximal tubule, loop of Henle, and distal tubule).
• Secretion (in the distal tubule and collecting duct).
6. Renal Cortex
• Location:
• Outer region of the kidney, surrounding the renal medulla.
• Primary Function:
• Contains glomeruli and parts of the nephron (proximal/distal tubules).
• Site of blood filtration and initial urine formation.
7. Renal Medulla
• Location:
• Inner portion of the kidney, consisting of renal pyramids.
• Primary Function:
, • Concentrates urine by creating a gradient for water reabsorption.
• Contains loops of Henle and collecting ducts.
8. Renal Pelvis
• Location:
• Funnel-shaped structure located at the center of the kidney, connecting to the ureters.
• Primary Function:
• Collects urine from the calyces and directs it into the ureters.
9. Renal Arteries and Veins
• Location:
• Renal arteries branch off the abdominal aorta to supply blood to the kidneys.
• Renal veins drain blood from the kidneys into the inferior vena cava.
• Primary Function:
• Renal Arteries: Deliver oxygenated blood for filtration.
• Renal Veins: Remove filtered, deoxygenated blood.
10. Adrenal Glands (Associated with Renal System)
• Location:
• Sit atop each kidney.
• Primary Function:
• Produce hormones such as aldosterone, which regulates sodium and water balance, indirectly impacting
kidney function.
2. Describe the pathophysiology of the autoregulation of renal blood flow.
1. Myogenic Mechanism:
• Stimulus: Changes in arterial blood pressure.
• Process:
• Increased blood pressure → Stretch of the afferent arteriole → Smooth muscle contraction
(vasoconstriction) → Limits blood flow to maintain constant GFR.
• Decreased blood pressure → Reduced stretch → Smooth muscle relaxation (vasodilation) → Increases
blood flow to sustain GFR.
• Outcome: Stabilizes RBF by modulating afferent arteriole diameter.
, 2. Tubuloglomerular Feedback:
• Stimulus: Changes in sodium chloride (NaCl) delivery to the macula densa in the distal tubule.
• Process:
• Increased NaCl delivery (e.g., high GFR) → Macula densa releases adenosine → Afferent arteriole
constriction → Decreases GFR to normal levels.
• Decreased NaCl delivery (e.g., low GFR) → Macula densa signals the release of renin from
juxtaglomerular cells → Activates the renin-angiotensin-aldosterone system (RAAS) → Increases systemic
blood pressure and GFR.
• Outcome: Adjusts GFR by modulating afferent/efferent arteriole tone and systemic blood pressure.
3. Limits of Autoregulation:
• Effective within a systemic blood pressure range of 80–180 mmHg.
• Outside this range, autoregulation fails, and renal function may be compromised.
Key Regulators:
• Nitric Oxide: Promotes vasodilation of arterioles.
• Prostaglandins: Protect renal blood flow during stress (e.g., hypotension).
• Angiotensin II: Preferentially constricts the efferent arteriole, helping maintain GFR during low perfusion states.
Clinical Relevance:
• Impaired autoregulation can lead to acute kidney injury or chronic kidney disease in conditions such as
hypertension, diabetes, or renal artery stenosis.
• Certain medications (e.g., NSAIDs or ACE inhibitors) can disrupt autoregulation by affecting prostaglandins or the
RAAS pathway.
3. Differentiate between the processes of glomerular filtration, tubular reabsorption, and tubular secretion and excretion.
1. Glomerular Filtration
• Definition: Movement of fluid and solutes from the blood in the glomerular capillaries into the Bowman’s capsule
to form filtrate.
• Process:
• Driven by hydrostatic pressure (blood pressure) in the glomerulus.
• Opposed by oncotic pressure and capsular hydrostatic pressure.
• The glomerular filtration rate (GFR) is the volume of filtrate formed per minute (~125 mL/min in adults).
• Filtered Substances: Water, electrolytes, glucose, amino acids, urea, and small solutes (not proteins or cells).
• Clinical Relevance: Altered in conditions like glomerulonephritis or renal artery stenosis.
2. Tubular Reabsorption
• Definition: Movement of substances from the filtrate in the renal tubules back into the bloodstream in the
peritubular capillaries.
• Purpose: Conserves essential substances.
• Key Substances Reabsorbed:
• Proximal Tubule: Majority of water, sodium (Na⁺), glucose, and amino acids.
• Loop of Henle: Reabsorbs water (descending limb) and sodium (ascending limb).
1. List the structures of the renal system including location in the body and primary function.
1. Kidneys
• Location:
• Retroperitoneal space on either side of the spine.
• Situated between the T12-L3 vertebrae, with the right kidney slightly lower due to the liver.
• Primary Function:
• Filter blood to remove waste products (e.g., urea, creatinine).
• Regulate fluid and electrolyte balance (e.g., sodium, potassium, and water).
• Maintain acid-base balance.
• Produce hormones:
• Erythropoietin (stimulates red blood cell production).
• Renin (regulates blood pressure via the renin-angiotensin-aldosterone system).
• Active vitamin D (calcium homeostasis).
2. Ureters
• Location:
• Muscular tubes extending from the renal pelvis of each kidney to the bladder.
• Approximately 25–30 cm long, descending retroperitoneally.
• Primary Function:
• Transport urine from the kidneys to the bladder via peristaltic contractions.
3. Urinary Bladder
• Location:
• Located in the pelvic cavity, posterior to the pubic symphysis.
• In females: Positioned anterior to the uterus and vagina.
• In males: Positioned anterior to the rectum and superior to the prostate gland.
• Primary Function:
• Temporarily store urine until voluntary excretion.
• Can hold 300–500 mL of urine under normal circumstances.
,4. Urethra
• Location:
• Females: Short tube (~3–4 cm), extending from the bladder to the external urethral orifice (located anterior
to the vaginal opening).
• Males: Longer (~18–20 cm), passing through the prostate and penis, divided into prostatic, membranous, and
spongy portions.
• Primary Function:
• Conveys urine from the bladder to the external environment.
• In males, also functions as part of the reproductive system, carrying semen during ejaculation.
5. Nephrons (Functional Unit of the Kidney)
• Location:
• Found within the renal cortex and renal medulla of the kidneys.
• Primary Function:
• Filter blood to form urine through three main processes:
• Filtration (in the glomerulus).
• Reabsorption (in the proximal tubule, loop of Henle, and distal tubule).
• Secretion (in the distal tubule and collecting duct).
6. Renal Cortex
• Location:
• Outer region of the kidney, surrounding the renal medulla.
• Primary Function:
• Contains glomeruli and parts of the nephron (proximal/distal tubules).
• Site of blood filtration and initial urine formation.
7. Renal Medulla
• Location:
• Inner portion of the kidney, consisting of renal pyramids.
• Primary Function:
, • Concentrates urine by creating a gradient for water reabsorption.
• Contains loops of Henle and collecting ducts.
8. Renal Pelvis
• Location:
• Funnel-shaped structure located at the center of the kidney, connecting to the ureters.
• Primary Function:
• Collects urine from the calyces and directs it into the ureters.
9. Renal Arteries and Veins
• Location:
• Renal arteries branch off the abdominal aorta to supply blood to the kidneys.
• Renal veins drain blood from the kidneys into the inferior vena cava.
• Primary Function:
• Renal Arteries: Deliver oxygenated blood for filtration.
• Renal Veins: Remove filtered, deoxygenated blood.
10. Adrenal Glands (Associated with Renal System)
• Location:
• Sit atop each kidney.
• Primary Function:
• Produce hormones such as aldosterone, which regulates sodium and water balance, indirectly impacting
kidney function.
2. Describe the pathophysiology of the autoregulation of renal blood flow.
1. Myogenic Mechanism:
• Stimulus: Changes in arterial blood pressure.
• Process:
• Increased blood pressure → Stretch of the afferent arteriole → Smooth muscle contraction
(vasoconstriction) → Limits blood flow to maintain constant GFR.
• Decreased blood pressure → Reduced stretch → Smooth muscle relaxation (vasodilation) → Increases
blood flow to sustain GFR.
• Outcome: Stabilizes RBF by modulating afferent arteriole diameter.
, 2. Tubuloglomerular Feedback:
• Stimulus: Changes in sodium chloride (NaCl) delivery to the macula densa in the distal tubule.
• Process:
• Increased NaCl delivery (e.g., high GFR) → Macula densa releases adenosine → Afferent arteriole
constriction → Decreases GFR to normal levels.
• Decreased NaCl delivery (e.g., low GFR) → Macula densa signals the release of renin from
juxtaglomerular cells → Activates the renin-angiotensin-aldosterone system (RAAS) → Increases systemic
blood pressure and GFR.
• Outcome: Adjusts GFR by modulating afferent/efferent arteriole tone and systemic blood pressure.
3. Limits of Autoregulation:
• Effective within a systemic blood pressure range of 80–180 mmHg.
• Outside this range, autoregulation fails, and renal function may be compromised.
Key Regulators:
• Nitric Oxide: Promotes vasodilation of arterioles.
• Prostaglandins: Protect renal blood flow during stress (e.g., hypotension).
• Angiotensin II: Preferentially constricts the efferent arteriole, helping maintain GFR during low perfusion states.
Clinical Relevance:
• Impaired autoregulation can lead to acute kidney injury or chronic kidney disease in conditions such as
hypertension, diabetes, or renal artery stenosis.
• Certain medications (e.g., NSAIDs or ACE inhibitors) can disrupt autoregulation by affecting prostaglandins or the
RAAS pathway.
3. Differentiate between the processes of glomerular filtration, tubular reabsorption, and tubular secretion and excretion.
1. Glomerular Filtration
• Definition: Movement of fluid and solutes from the blood in the glomerular capillaries into the Bowman’s capsule
to form filtrate.
• Process:
• Driven by hydrostatic pressure (blood pressure) in the glomerulus.
• Opposed by oncotic pressure and capsular hydrostatic pressure.
• The glomerular filtration rate (GFR) is the volume of filtrate formed per minute (~125 mL/min in adults).
• Filtered Substances: Water, electrolytes, glucose, amino acids, urea, and small solutes (not proteins or cells).
• Clinical Relevance: Altered in conditions like glomerulonephritis or renal artery stenosis.
2. Tubular Reabsorption
• Definition: Movement of substances from the filtrate in the renal tubules back into the bloodstream in the
peritubular capillaries.
• Purpose: Conserves essential substances.
• Key Substances Reabsorbed:
• Proximal Tubule: Majority of water, sodium (Na⁺), glucose, and amino acids.
• Loop of Henle: Reabsorbs water (descending limb) and sodium (ascending limb).
