Renal Conditions Flashcards
What is the main function of the kidneys?
To regulate the extracellular fluid environment which is an important aspect of homeostasis.
What is extracellular fluid?
Fluid which exists outside of the body cells.
What is the role of extracellular fluid?
To supply body cells with nutrients such as oxygen, proteins and amino acids and removing wastes from body cells such as carbon dioxide and urea.
What is the optimum pH for extracellular fluid?
7.35-7.45
Which fluid is a major component of extracellular fluid?
Interstitial fluid
What does interstitial mean?
Between the cells
As well as interstitial fluid, what is the other major component of extracellular fluid?
The plasma in the blood.
At the arteriole end of capillary beds, which three things are squeezed out of the plasma to become interstitial fluid?
Water, electrolytes and nutrients.
At the venous ends of capillary beds which three things return to the plasma?
Water, electrolytes and waste metabolites.
Which term refers to the concentration of osmotically active particles in the plasma?
Serum osmolality
What is the main osmotically active particle in the blood?
Sodium
Which principle acts to keep sodium out of the cells?
The sodium potassium pump.
What are the risks of water entering or leaving the cell by osmosis?
Cell shrinkage or cell enlargement (swelling).
What is the key osmolality range which must be adhered to in order to prevent water from leaving or entering the cells? How is this managed by the kidneys?
275-295mmol/kg.
The kidney regulates this by excreting more or less water.
What is the average blood volume in adults?
3L
Why must blood volume be carefully regulated by the kidneys?
In order to maintain a normal blood pressure to keep blood circulating at an adequate rate.
What is blood volume determined by?
The amount of water and sodium ingested (from the diet) and the amount lost from the body (through urine).
Name three hormones produced by the kidneys?
Erythropoietin, renin and active vitamin D.
Name the 5 key functions of the kidneys:
- Produce hormones (renin, vitamin D and erythropoietin)
- Reglulation of electrolyte levels in the plasma
- Maintain blood volumes
- Maintain blood acid base balance (pH)
- Excretion of waste
- Regulation of the osmolality of the plasma
Name the 4 main componants of the renal system and their primary functions:
The kidneys: filter blood removing waste products
The bladder: stores urine prior to micturation
2x ureters: collect urine from the kidneys and convey it to the bladder
The urethra:takes urine from the bladder to outside the body
Which arteries supply the kidneys?
The renal arteries
The renal arteries are a direct branch of the…
Abdominal aorta
What are the outer and inner parts of the kidneys called?
Outer cortex
Inner medulla
Filtration is carried out by microscopic tubules called:
Nephrons
The filtrate is modified as it travels down the nephron by two processes called:
- Tubular reabsorbtion: returns substances to the plasma including water, nutrients and electrolytes
- Tubular secretion: waste products such as toxins are passed to the bladder as urine to be removed from the body
What are the four sections of the nephron in the kidney?
- Bowmans capsule
- Proximal tubule
- Loop of henle
- Distal tubule and collecting ducts
What is the role of the Bowmans Capsule within the kidneys?
To filter the plasma
What is the role of the proximal tubule in the kidneys?
The site of tubular reabsorbtion
What is the role of the loop of henle i the kidneys?
Site of further water and sodium reabsorbtion and formation of a ‘salt’ gradient in the medulla. (This gradient is essential for water conservation in the collecting ducts).
What is the role of the proximal tubules and collecting ducts within the kidneys?
‘Fine tuning’ of the filtrate occurs. The collecting duct drains into the renal pelvis.
What is the name of the knot of capillaries which is located adjacent to the kidneys?
The glomerulus
How does blood enter and leave the glomerulus?
Enters via the afferent arteriole and leaves via the efferent arteriole.
What does the efferent arteriole branch to form?
The peritubular capillaries.
What is glomerular filtration?
The filtration of plasma in the glomerulus
Is pressure in the glomerulus high or low?
The pressure in the glomerulus must be high in order to filter the blood.
What can and cannot pass through the filtration barrier of the glomerulus into the Bowmans Capsule?
Can: water, solutes from the plasma, glucose, electrolytes (small particles)
Cannot: plasma proteins and blood cells
How can the filter barrier between the glomerulus and the bowmans capsule become damaged and what happens when this occurs?
A high blood pressure can cause damage to the fragile filtration barrier. This causes larger protein particles to pass through the barrier and end up in the urine.
What is autoregulation in relation to management of the blood supply to the kidneys?
Refers to the widening/narrowing of the afferent and efferent arterioles to manage pressure of blood travelling through the kidneys.
What is GFR?
The glomerular filtration rate- rate at which the fluid is filtered from the blood into the Bowmans capsule.
What average percentage of water and solutes are returned to the systemic circulation through tubular reabsorbtion in a healthy adult?
99%
Tubular processing refers to which two processes?
Reabsorbtion and secretion
Following filtration in the Bowmans capsule, most of the elctrolytes, nutrients and water are reabsorbed in the….
Proximal tubule
Which process drives the reabsorbtion of electrolytes and nutrients such as glucose and amino acids?
Which process drives the reabsorbtion of water?
Electrolytes and nutrients: active transport (sodium potassium pump)
Water: osmosis
The high osmolality in the medulla enables what to be produced?
A concentrated urine because water is reabsorbed by osmosis from the collecting ducts
The ascending loop, distal tubule and collecting ducts are normally impermeable or permeable to water? What causes this to change?
They are normally impermeable however the hormone ADH (antidiuretic hormone) causes them to become permeable.
What doe the impermeability of the ascending loop, distal tubule and collecting ducts lead to?
A dilute urine due to presence of water and removal of sodium.
In the presence of ADH, a ………………. urine is produced?
Concentrated
What is the release of ADH dependant on?
The osmilarity of the plasma
How does ADH work to regulate the osmilarity of the plasma?
By regulating the volume of water lost from the kidneys.
Where is ADH synthesised and released from?
Synthesised in the hypothalamus and released from the posterior pituitary gland.
What are the specialist water channels called which open to allow the collecting ducts to become permeable?
Aquaporins
Which receptors located in the hypothalamus detect a rise in plasma osmilarity?
Osmoreceptors
Which other two factors (symptoms/condition) can cause a raised plasma osmilarity and thus stimulate the release of ADH?
Thirst and dehydration
Blood volume is regulated by adjusting what within the body?
The bodies sodium content
How do the kidneys manage the bodies sodium content?
They alter how much sodium is excreted in the urine
Sodium is the main contributor to plasma osmolality- true or false?
TRUE
Will the reabsorbtion of more sodium by the kidneys increase or decrease the osmolality of the blood plasma?
Increase
If less sodium is reabsorbed by the kidneys, plasma osmolality will increase or decrease?
Decrease
What does RAAS stand for?
The renin-angiotensin-aldosterone system
What does the RAAS moderate?
Blood pressure
Where is renin released from?
The kidneys
Renin is an enzyme which converts angiotensinogen into:
Antiogensin 1
Angiotensin 1 is converted into angiotensin 2 by an angiotensin converting hormone. Angiotensin 2 has a range of functions which aim to increase blood pressure and/or blood volume including (4 things):
- Increased ADH secretion
- Increased sodium reabsorbtion
- Aldosterone secretion from the adrenal glands
- Widespread vasoconstriction
What is AKI defined as?
A sudden decrease in kidney function
What will positive AKI tests show? (3 things)
- A drop in glomerular filtration rate
- Increase of blood urea
- Increase in blood creatinine levels
What three groups are the causes of AKI classified into?
- Prerenal
- Intrarenal
- Postrenal
What are the prerenal causes of AKI?
Any causes which affect the blood supply to the kidneys leading to hypoxic cells which either become damaged or die all together.
What are the intrarenal causes of AKI?
Causes which actually damage the tissue of the kidneys such as ischaemic injury, vascular diseases or nephrotoxic injury.
What are the postrenal causes of AKI?
Abnormalities causing obstruction to the lower urinary tract such as tumours, blood clots, or an enlarged prostate in men leading to inability to ass urine or difficulty in passing urine.
What are clinical presentations of AKI?
Non specific symptoms such as nausea and lethargy combined with decreased urine output, potential fluid overload, electrolyte imbalances and build up of toxic substances.
What is chronic kidney disease?
A gradual and often progressive loss of renal functionality.
What are the three main causes of chronic kidney disease?
- Diabetes
- Hypertension
- Glomerulonephritis (glomeruli inflammation)
What are 5 risk factors for developing chronic kidney disease?
- diabetes
- hypertension
- cardiovascular diseases
- family history
- use of nephrotoxic drugs (such as lithium or NSAID’S)
What does an ACR blood test stand for and measure?
Albumin creatinine ratio measures levels of protein in the urine
How is chronic kidney disease diagnosed?
By noting a significant loss in kidney function and/or structural damage to the kidneys.
Does the glomerular filtration rate increase or decrease in chronic kidney disease?
Decrease to below 60ml per min
What symptoms are present in the early stages of chronic kidney disease?
Patients are normally asymptomatic during the early stages of the disease
As chronic kidney disease progresses, which non specific symptoms may occur?
Tiredness, lethargy, weight loss and nausea
A reduction in glomerular filtration rate can lead to which 3 things:
- Water and salt retention
- Acid retention
- Raised serum phosphate levels
What can sodium and water retention in chronic kidney disease lead to?
Oedema, hypertension and heart failure.
Why does chronic kidney disease often cause aneamia?
The kidneys synthesise erethropoietin which convert stem cells in the bone marrow into red blood cells. Damaged kidneys are unable to produce erethropoietin causing a reduction in red blood cells.
What normally happens to excess calcium which is not absorbed by bones?
It is excreted by the kidneys
Which two substances normally regulate plasma calcium and phosphate levels?
Parathyroid hormone and active vitamin D
What can decreased production of vitamin D cause?
Bone and mineral disease due to hypocalceamia.
