Urinary System Flashcards
What are diuretics and how do they enhance urinary output?
chemicals that enhance urinary output by:
Inhibiting ADH (e.g., alcohol)
Inhibiting Na⁺ reabsorption, reducing H₂O reabsorption (e.g., caffeine, drugs for hypertension or edema)
Inhibiting the medullary gradient formation (loop diuretics)
Acting as osmotic diuretics, which are not reabsorbed, keeping water in the urine
What is urinalysis and what can it detect?
an examination of urine to detect signs of disease or illegal substances
How is renal function assessed?
Blood tests: Measure nitrogenous wastes in the blood
Urine tests: Required alongside blood tests to determine renal clearance
What is renal clearance, and why is it tested?
The rate at which a substance is removed from the plasma by the kidneys and excreted in urine.
Uses:
Determines Glomerular Filtration Rate (GFR).
Helps detect glomerular damage.
Monitors progression of renal disease.
What is Chronic Kidney Disease (CKD), and what are its effects?
Glomerular filtration rate < 60 ml/min for at least 3 months.
Effects:
Decreased filtrate formation.
Accumulation of nitrogenous wastes in the blood.
Blood pH becomes acidic.
Common Causes: Diabetes mellitus and hypertension
How is CKD severity classified based on GFR?
G1: ≥90 (Normal/High)
G2: 60-90 (Mildly decreased)
G3a: 45-59 (Mild to moderate decrease)
G3b: 30-44 (Moderate to severe decrease)
G4: 15-29 (Severely decreased)
G5: <15 (Kidney failure)
How is CKD severity classified based on albuminuria?
A1: Normal/mild increase (<30 mg/g)
A2: Moderate increase (30-299 mg/g)
A3: Severe increase (≥300 mg/g)
What is renal failure, and what are its effects?
GFR < 15 ml/min.
Causes:
Uremia: Ionic/hormonal imbalances, metabolic abnormalities, and toxic molecule accumulation.
Symptoms: Fatigue, anorexia, nausea, mental changes, cramps.
Treatment: Hemodialysis, Kidney transplant
What are the components of urine?
95% water and 5% solutes
Nitrogenous wastes:
Urea (from amino acid breakdown)
Uric acid (from nucleic acid metabolism).
Creatinine (metabolite of creatine phosphate).
What are some normal solutes found in urine?
Ions: Na⁺, K⁺, PO₄³⁻, SO₄²⁻, Ca²⁺, Mg²⁺, HCO₃⁻.
Note: Abnormally high concentrations of these or the presence of blood proteins, WBCs, or bile pigments may indicate pathology.
What do different urine colors indicate?
Clear: Normal, but cloudiness may indicate a UTI.
Pale to deep yellow: Normal due to urochrome/urobilin (pigment from hemoglobin breakdown).
Abnormal colors (pink, brown, smoky): May be caused by certain foods, bile pigments, blood, or drugs.
What factors influence urine odor?
Slightly aromatic when fresh
Ammonia odor develops as bacteria metabolize urea.
Odor changes can occur due to certain drugs or vegetables.
Diseases can alter smell:
Diabetes: Acetone smell in urine.
What are the normal pH and specific gravity ranges of urine?
pH: Slightly acidic (~6), but ranges from 4.5 to 8.0.
Lower pH: High-protein or whole-wheat diet.
Higher pH: Vegetarian diet, prolonged vomiting, UTIs.
Specific Gravity: 1.001 - 1.035 (higher than water due to solutes)
How does aging affect the urinary system?
Kidneys shrink, and nephrons decrease in size and number.
Tubule cells become less efficient.
GFR declines to half by age 80 (may be due to atherosclerosis of renal arteries)
Bladder shrinks, leading to:
Nocturia: Frequent urination at night.
Incontinence: Loss of bladder control.
What are some abnormal urinary constituents?
Glucose
Proteins
Ketone bodies
Haemoglobin
Bile pigments
Erythrocytes
Leukocytes
What is the possible cause and condition for the abnormal urinary constituent - glucose?
Condition- Glycosuria
Possible cause- Diabetes mellitus
What is the possible cause and condition for the abnormal urinary constituent - proteins?
Condition- Proteinuria/ Albuminuria
Possible cause- Excessive exertion, pregnancy, heart failure
What is the possible cause and condition for the abnormal urinary constituent - ketone bodies?
Condition- ketonuria
Possible cause- starvation, untreated diabetes mellitus
What is the possible cause and condition for the abnormal urinary constituent - haemoglobin?
Condition- haemoglobinuria
Possible cause- transfusion reaction, haemolytic anaemia, severe burns
What is the possible cause and condition for the abnormal urinary constituent - bile pigments?
Condition- Bilirubinuria
Possible cause- transfusion reaction, haemolytic anaemia, severe burns
What is the possible cause and condition for the abnormal urinary constituent - Erythrocytes
Condition- Hematuria
Possible causes- Bleeding urinary tract
What is the possible cause and condition for the abnormal urinary constituent - Leukocytes
Condition- Pyuria
Possible cause- Urinary tract infection
What are the key processes of urine formation in the nephron?
Filtration
Reabsorption
Secretion
Excretion
Filtration
Filtrate is forced into the Bowman’s capsule from glomerulus
No RBCs or large proteins.
Filtrate contains NaCl, K⁺, HCO₃⁻, H₂O, glucose, amino acids, creatinine, and urea.
Reabsorption
Takes place in the PCT, Loop of Henle, DCT
Loop of Henle: Descending limb reabsorbs H₂O; Ascending limb reabsorbs NaCl (impermeable to water).
DCT & Collecting Duct:
Aldosterone → ↑ Na⁺, H₂O reabsorption.
ADH → ↑ H₂O reabsorption.
Secretion
PCT<, DCT
Secretes uric acid, organic acids, H⁺, K⁺.
Excretion
Collecting Duct to bladder
H₂O, NaCl, K⁺, HCO₃⁻, creatinine, and urea are excreted
How is body water distributed among compartments?
Total Body Water: ~40L (~60% of body weight).
Intracellular Fluid (ICF): 25L (40% of body weight).
Extracellular Fluid (ECF): 15L (20% of body weight), includes:
Interstitial Fluid (IF): 12L (~80% of ECF).
Plasma: 3L (~20% of ECF).
How does body water content vary across age and sex?
Infants: ~73% water (low fat, low bone mass).
Adult Males: ~60% water.
Adult Females: ~50% water (higher fat, lower skeletal muscle).
Elderly: Water content declines by ~15% between ages 20-80.
How do electrolyte concentrations differ in body fluids?
Intracellular Fluid (ICF):
High in K⁺, HPO₄²⁻, protein anions.
Extracellular Fluid (ECF) (Plasma & IF):
High in Na⁺, Cl⁻, HCO₃⁻.
Plasma has more protein anions than IF.
How does water move between body compartments?
Osmotic & hydrostatic pressures regulate movement.
Water moves freely along osmotic gradients.
Changes in solute concentration cause net water flow:
↑ ECF osmolarity → Water leaves cells.
↓ ECF osmolarity → Water enters cells.
What are the daily water intake and output amounts?
Water intake = Water output (~2500 mL/day)
Intake sources: Beverages (60%), Food (30%), Metabolism (10%).
Output routes: Urine (60%), Insensible loss (28%), Sweat (8%), Feces (4%).
How does the body regulate water intake through thirst?
Stimuli for thirst:
↑ ECF osmolarity (detected by osmoreceptors in hypothalamus).
↓ Plasma volume (5-10%), leading to ↓ blood pressure.
Activation of Renin-Angiotensin-Aldosterone System (RAAS) → ↑ Angiotensin II → Stimulates thirst.
How does ADH regulate water balance?
Stimuli for ADH Release
↑ ECF osmolarity or Na⁺ concentration.
↓ Plasma volume (5-10%) → ↓ BP.
Detected by osmoreceptors in the hypothalamus & baroreceptors in large vessels.
ADH Release from Posterior Pituitary
Targets collecting ducts of the kidneys.
Increases water reabsorption → Scant, concentrated urine.
Restores plasma volume & osmolarity (negative feedback)
What is the cellular mechanism of ADH in the kidney?
ADH binds to ADH receptors on the basolateral membrane of collecting duct cells.
Activates G-protein → Adenylate cyclase → ↑ cAMP → Activates Protein Kinase A.
Aquaporin-2 channels inserted into the apical membrane → ↑ Water reabsorption from tubular fluid.
Water exits cell via Aquaporin-3 on the basolateral membrane, entering peritubular capillaries
What are the causes and symptoms of dehydration?
Causes:
ECF water loss due to hemorrhage, burns, vomiting, diarrhea, sweating, water deprivation, diuretics, endocrine disorders.
Symptoms:
Dry mouth, thirst, dry flushed skin, oliguria (low urine output).
Can lead to hypovolemic shock, fever, mental confusion, electrolyte loss.
What happens in hypotonic hydration (water intoxication)?
Causes: Renal insufficiency, excessive water intake.
Effects:
↓ ECF osmolarity → Hyponatremia.
Water shifts into cells, causing swelling.
Symptoms: Nausea, vomiting, muscle cramps, cerebral edema, possibly death.
What is edema and its effects?
Accumulation of interstitial fluid (not cell swelling).
Increases diffusion distance for oxygen/nutrients.
Caused by increased fluid movement out of blood and decreased fluid return to blood
How does sodium concentration affect fluid balance?
Na⁺ Concentration:
Determines ECF osmolarity & excites neurons/muscles.
Remains stable due to water shifts between ICF & ECF.
Na⁺ Content:
Determines ECF volume & blood pressure.
How is sodium regulated in the extra cellular fluid?
Regulated by osmoreceptors
Controlled by ADH & thirst
How is sodium regulated in the body?
Regulated by baroreceptors
Controlled by RAAS & ANP
What is the role of aldosterone in Na⁺ balance?
Aldosterone regulates Na⁺ reabsorption in the kidneys.
Regardless of aldosterone levels:
65% of Na⁺ is reabsorbed in the PCT.
25% is reabsorbed in the nephron loop.
Na⁺ is never secreted into the filtrate.
How does aldosterone concentration affect sodium reabsorption?
High aldosterone:
Na⁺ actively reabsorbed in DCT & collecting ducts → Water follows → ↑ ECF volume.
Low aldosterone:
Na⁺ not reabsorbed → Lost in urine with water.
What substances are filtered at the glomerulus?
Water, NaCl, K+, HCO3-, glucose, amino acids, creatinine, and urea
Red blood cells and large proteins
What percentage of NaCl, water, glucose, and amino acids are reabsorbed in the PCT?
65% of NaCl and water, 100% of glucose and amino acids
What occurs in the ascending and descending limbs of the Loop of Henle?
Descending limb: Water is reabsorbed; NaCl is NOT permeable.
Ascending limb: NaCl is actively reabsorbed; water is NOT permeable
How does aldosterone affect sodium and water reabsorption?
Aldosterone increases sodium (Na+) and water reabsorption in the distal convoluted tubule (DCT) and collecting duct, increasing blood volume and pressure.
How does ADH regulate water balance?
ADH binds to receptors in the collecting duct, increasing aquaporin channels to enhance water reabsorption and concentrate urine.
What are the major body fluid compartments?
Intracellular fluid (ICF): 40% of body weight (~25 L).
Extracellular fluid (ECF): 20% of body weight (~15 L), further divided into interstitial fluid (80% of ECF) and plasma (20% of ECF)
How does sodium (Na+) and potassium (K+) concentration differ in intracellular vs. extracellular fluids?
Extracellular fluid (ECF): High Na+, low K+.
Intracellular fluid (ICF): Low Na+, high K+.
How does a change in extracellular fluid (ECF) osmolarity affect water movement?
Increased ECF osmolarity → Water leaves the cell (cell shrinks).
Decreased ECF osmolarity → Water enters the cell (cell swells)
How much water is gained and lost per day on average?
Water intake (~2500 mL/day):
Beverages: 60%
Food: 30%
Metabolism: 10%
Water output (~2500 mL/day):
Urine: 60%
Skin/lungs: 28%
Sweat: 8%
Feces: 4%
What are the causes and symptoms of dehydration?
Causes: Hemorrhage, burns, diarrhea, excessive sweating, diuretic use.
Symptoms: Dry mouth, thirst, oliguria (low urine output), weight loss, fever, mental confusion.
What is hypotonic hydration, and what are its effects?
Excess water intake causes hyponatremia (low Na+ in ECF).
Water moves into cells, causing swelling.
Symptoms: Nausea, vomiting, cerebral edema, muscle cramps
How is sodium concentration different from sodium content?
Sodium concentration: Determines osmolarity and neuron excitability.
Sodium content: Determines blood volume and pressure.
What is the function of renin in sodium and water balance?
Renin is released in response to low blood pressure or Na+ levels.
Converts angiotensinogen to angiotensin I, which is then converted to angiotensin II.
Angiotensin II stimulates aldosterone release, increasing Na+ and water reabsorption.
How does ANP regulate blood pressure?
Released by atria in response to high blood pressure.
Inhibits ADH, renin, and aldosterone, promoting Na+ and water excretion.
Results in lower blood pressure and volume.
How does PTH regulate calcium levels?
Bones: Increases osteoclast activity, releasing Ca2+.
Kidneys: Increases Ca2+ reabsorption.
Intestines: Increases Ca2+ absorption (via vitamin D activation).5
What happens in Addison’s disease (hypoaldosteronism)?
Lack of aldosterone leads to excessive loss of Na+ and water in urine.
Risk of hypovolemia (low blood volume).
Requires increased salt and fluid intake to maintain balance.
How does fluid exchange occur between compartments?
Lungs: O₂ enters blood, CO₂ exits.
GI Tract: Nutrients, H₂O, ions absorbed into blood.
Kidneys: H₂O, ions reabsorbed; nitrogenous wastes excreted
