The Urinary Stystem - Hormonal control, fluid and electrolyte balance, kidney disease

What is the main function of vasopressin?

Controlling water reabsorption in the collecting duct by increasing water permeability, helping maintain fluid balance and blood pressure

What triggers vasopressin release?

High blood osmolarity or low blood pressure triggers vasopressin release from posterior pituitary

What is the main function of vasopressin?

Controlling water reabsorption in the collecting duct by increasing water permeability, helping maintain fluid balance and blood pressure

What triggers vasopressin release?

High blood osmolarity or low blood pressure triggers vasopressin release from posterior pituitary

How does aldosterone affect sodium balance?

Increases sodium reabsorption in the distal tubule and collecting duct, helping maintain blood pressure and volume

What is the Renin-Angiotensin System (RAS)?

Hormone system that regulates blood pressure and fluid balance through angiotensin II production, which causes vasoconstriction and aldosterone release

What is the function of natriuretic peptides (ANP/BNP)?

They decrease blood pressure by promoting sodium and water excretion in urine

How do kidneys compensate for acidosis?

Kidneys secrete H+ (buffered by ammonia and phosphate), reabsorb bicarbonate to act as extracellular buffer.

What does presence of glucose in urine indicate?

Indicates Diabetes

What is diabetes insipidus?

Condition caused by poor secretion of or response to vasopressin, resulting in large volumes of dilute urine production

What causes diabetic nephropathy?

Complication of diabetes affecting 30-40% of type 1 and 10-20% of type 2 diabetes, causing progressive kidney damage

Why are women more prone to UTIs?

Women have shorter urethras (5cm vs 20cm in males) and closer proximity to the anus, allowing easier bacterial access

What is glomerulonephritis?

Inflammation of the glomeruli causing protein and blood cell leakage into urine, can be primary or secondary to other conditions

What causes kidney stones?

Often formed by crystals of inorganic ions, particularly due to hypercalciuria in urine

What is polycystic kidney disease?

Inherited condition affecting 1 in 600-1000 people, causing cyst formation in kidneys and progressive renal failure

What are the main features of chronic renal failure?

Progressive destruction of nephrons, reduced GFR, failure to remove toxins and disrupted ion balance

What is the difference between haemodialysis and peritoneal dialysis?

Haemodialysis is done 3x weekly for 4 hours at a clinic, while peritoneal dialysis is done daily at home using a permanent catheter

How do the kidneys maintain acid-base balance?

Through H+ secretion, HCO3- reabsorption and buffer systems using phosphate and ammonia

What does specific gravity in urinalysis indicate?

It shows how well kidneys adjust tonicity - high values may indicate dehydration or diabetes

What are the stages of diabetic nephropathy?

1. Increased glomerular filtration

2. Proteinuria

3. Reduced filtration rate due to mesangial cell growth

What is pyelonephritis?

Kidney infection that occurs when UTI bacteria migrate upward, particularly difficult to treat

What causes end-stage renal failure?

Destruction of nephrons due to chronic conditions like glomerulonephritis, pyelonephritis, diabetes or kidney stones

What is uraemia?

Condition in kidney failure where toxins build up in blood, accompanied by acidosis and hyperkalaemia

How does vasopressin affect the collecting duct?

It increases water permeability by inserting aquaporin channels allowing water reabsorption

What role do natriuretic peptides play in blood pressure?

They decrease blood pressure by promoting sodium excretion and reducing blood volume

What causes a hangover’s increased urination?

Alcohol inhibits vasopressin release, leading to increased water loss through urine

What triggers aldosterone release?

Angiotensin II and high blood potassium levels trigger aldosterone release from the adrenal cortex

What are signs of UTI in urinalysis?

Presence of nitrates/nitrites and white blood cells indicate urinary tract infection

How does fluid and electrolyte homeostasis work?

Through balanced intake and output of water and electrolytes, regulated by hormones and kidney function

What causes glomerular damage in diabetes?

High blood glucose causes abnormal mesangial cell growth, compressing glomerular capillaries

What is oliguria?

Decreased urine production, often seen in chronic renal failure

How does EPO deficiency affect kidney patients?

Reduced EPO production leads to chronic anaemia in kidney disease patients

What indicates kidney damage in urinalysis?

Presence of significant amounts of plasma protein or blood in urine

What are risk factors for diabetic nephropathy?

High blood pressure and tobacco use increase risk in diabetic patients

How do kidney stones cause damage?

Block ureters, causing back pressure and hydronephrosis, potentially leading to kidney failure

What is the inheritance pattern of polycystic kidney disease?

Autosomal dominant, linked to chromosome 16

What causes metabolic acidosis?

Accumulation of acid or loss of bicarbonate, often seen in kidney disease

How do kidneys regulate blood pressure?

Through RAS system, sodium balance, and fluid volume control

What causes proteinuria?

Damage to the glomerular filtration barrier allowing protein leakage into urine

What is the role of bicarbonate in acid-base balance?

Acts as a buffer in extracellular fluid to maintain pH balance

How does diabetes affect the kidneys?

High blood glucose damages blood vessels and filtration units, leading to nephropathy

What are symptoms of kidney stones?

Severe pain, blood in urine and possible urinary obstruction

What is RRT?

Renal Replacement Therapy - includes both dialysis and kidney transplantation

How does chronic kidney disease affect mineral balance?

Disrupts calcium, phosphate and other mineral homeostasis

What causes hydronephrosis?

Blockage of urine flow causing kidney swelling and potential damage

What is the main function of the collecting duct?

Fine-tuning of water reabsorption under vasopressin control

How do natriuretic peptides affect kidney function?

Increase sodium excretion and reduce water reabsorption

What causes secondary glomerulonephritis?

Develops as a result of other conditions like lupus or vasculitis

What are symptoms of polycystic kidney disease?

Hypertension, proteinuria and haematuria

How does RAS increase blood pressure?

Through vasoconstriction and increased sodium/water retention

What causes metabolic alkalosis?

Loss of acid or excess base, can occur with vomiting or certain medications

What are the main types of dialysis?

Haemodialysis (blood filtering through external machine) and peritoneal dialysis (using abdominal cavity as filter)

What is filtered load?

The amount of a substance filtered at the glomerulus per unit time, calculated by multiplying GFR by plasma concentration

What is the formula for clearance?

Clearance = (urine conc x urine flow rate) / plasma conc

What is the difference between active and passive transport in the nephron?

Active transport requires energy (ATP) and can move substances against concentration gradients, while passive transport occurs down concentration gradients without energy input

What is thee countercurrent multiplier system?

A mechanism in the loop of Henle that creates a concentration gradient in the medulla, essential for concentrating urine

What is the importance of GFR measurement?

GFR is the best measure of kidney function, indicating how well the kidneys filter blood. Normal values are approximately 120-125 mL/min

How do diuretics work?

Diuretics increase urine output by interfering with sodium reabsorption at different points in the nephron, leading to increased water excretion

What is tubuloglomerular feedback?

A mechanism where increased sodium delivery to the macula densa causes afferent arteriole constriction, reducing GFR as a protective mechanism

What is thee role of podocytes?

Form part of the glomerular filtration barrier, with their foot processes creating filtration slits that prevent protein loss

What causes acute kidney injury?

Can be pre-renal (reduced blood flow), intrinsic renal (damage to kidney tissue) or post-renal (urinary obstruction)

What is the significance of creatinine clearance?

Creatinine clearance is used to estimate GFR as creatinine is freely filtered but not reabsorbed or secreted significantly

What are the 2 main stimuli for vasopressin release?

1. Increased plasma osmolarity

2. Decreased blood pressure/blood volume

How does water move when ECF osmolarity increases?

Water moves out of cells into the ECF, causing cells to shrink

Why must serum K+ be monitored with aldosterone agonists?

Because aldosterone promotes K+ excretion, which could lead to dangerous hypokalemia

Name the main intracellular buffers in blood

1. Haemoglobin

2. Cellular proteins

3. Phosphate ions

What is the main trigger for ANP release?

Increased blood volume (causing stretch of atrial walls)

List three effects of ANP

1. Increases sodium and water excretion

2. Inhibits renin-angiotensin-aldosterone system

3. Decreases thirst and vasopressin secretion

Where is the final urine concentration determined?

In the collecting duct, under the influence of vasopressin

What are the three main stimuli for aldosterone release?

1. Decreased blood pressure

2. Increased plasma K+

3. Increased renin

What is the function of the vasa recta?

They are specialised medullary capillaries that maintain the concentration gradient through countercurrent exchange

How does eating salty food without water affect ECF initially?

Increases ECF osmolarity while initially not changing total fluid volume

What compensatory mechanisms occur after increased ECF osmolarity?

1. Increased thirst

2. Increased vasopressin release

3. Increased water retention by kidneys

What are the main functions of vasopressin?

1. Increases water reabsorption in collecting ducts

2. Causes vasoconstriction

3. Helps maintain blood pressure

Why is bicarbonate not considered an intracellular buffer?

Bicarbonate is the main extracellular buffer in blood, not intracellular

What happens to vasopressin release during blood volume depletion?

Vasopressin release increases to promote water retention and help restore blood volume

How does the collecting duct respond to vasopressin?

Vasopressin increases water permeability of the collecting duct by inserting aquaporin channels

What are the effects of aldosterone?

1. Increases Na+ reabsorption

2. Increases K+ excretion

3. Increases H+ excretion

4. Increases blood volume and pressure

How does the body detect changes in blood osmolarity?

Through osmoreceptors located in the hypothalamus

What is the relationship between ADH and urine concentration?

Higher ADH levels lead to more concentrated urine; lower levels produce dilute urine

What is the difference between intracellular and extracellular buffers?

Intracellular: haemoglobin, proteins, phosphate

Extracellular: mainly bicarbonate buffer system

How does the renin-angiotensin-aldosterone system respond to low blood pressure?

1. Increased renin release

2. Conversion of angiotensinogen to angiotensin II

3. Stimulation of aldosterone release

4. Increased Na+ and water retention

What role does the loop of Henle play in urine concentration?

It establishes the medullary concentration gradient needed for urine concentration but doesn’t determine final concentration

Where are the juxtaglomerular cells located and what do they produce?

Located in afferent arterioles; produce renin

What factors decrease vasopressin release?

1. Decreased plasma osmolarity

2. Increased blood volume

3. Increased blood pressure

How does potassium affect aldosterone release?

Increased plasma K+ directly stimulates aldosterone secretion from the adrenal cortex to promote K+ excretion

What is the difference between ANP and ADH responses to blood volume changes?

ANP increases with high blood volume and promotes fluid loss

ADH increases with low blood volume and promotes fluid retention