Renal Physiology Flashcards
What is intracellular fluid
The largest compartment of the body (a virtual compartment)
How much of male and female bodies are made up of intracellular fluid
Females = 27%, males = 33%
What is the composition of intracellular fluid
Contains high K+ and Mg2+. Low in Na+ and Cl-. Also contains lots of negatively charged proteins
What does the negative charge of intracellular fluid do
Exerts a primary osmotic pressure
What are the two subdivisions of intracellular fluid
Plasma and interstitial fluid
Describe plasma
4.5% of body weight in males and females. Contains no proteins so exerts osmotic pressure
Describe interstitial fluid
18% of body weight in females, 21.5% in males. Contains high Na+, Cl-, HCO3(-). Has few proteins
What is plasma
The whole blood minus RBCs, WBCs and platelets
How much of plasma is water
90%
What is the remainder or plasma
Mineral ions: Na+, K+, Cl-, HCO3(-). Small organic molecules: amino acids, fatty acids and glucose. Plasma proteins: albumin, fibrinogen, globulins
What determines extracellular fluid volume
The concentration of Na+
What happens if there is an increase in the total body of Na+
The volume of plasma will increase
What are the main functions of the kidneys Unicorns Whisper Cunt Everyday
- Clear the body of urea and other metabolic waste 2. To control the amount of water in the body 3. To regulate the composition of ECF 4. To produce erythropoietin and renin (regulates erythropoiesis and BP)
By forming urine what 3 important functions does the kidney perfom ERM
1.) Excretes waste products of metabolism. 2.) Regulates the body’s water, sodium and potassium content. 3.) Maintains the appropriate acid-base balance of plasma
What are the kidneys innervated by
The sympathetic postganglionic fibres and vagal parasympathetic fibres
Where is the kidney located
High in the abdomen
How long and wide is the kidney
11cm long and 3cm wide
What is the hilum
Where water comes out of the kidney
Which two vessels is the hilum close to
Vena cava and aorta
What percentage of resting cardiac output do the kidneys receive
25%
What is renal blood flow
1.25L/min
Label this cross section of the kidney
Labelled diagram Hilum, ureter, renal cortex, renal medulla
What does a nephron consist of
Cortex and medulla; glomerulus and bowman’s capsule; proximal convoluted tubule; loop of Henle; distal convoluted tubule; collecting duct
What are the two types of nephrons
Cortical nephrons and juxtamedullary nephrons
Describe cortical nephrons
Around 85% of all nephrons, located in the cortex
Describe juxtamedullary nephrons
Closer to renal medulla, loops of Henle extend deep into renal pyramids
Describe the juxtaglomerular apparatus
The ascending loop of Henle/ DCT makes contact with the afferent arteriole
Describe the mascula densa
Cells are more dense and sensitive to Na+ conc
Describe the juxtaglomerular cells
Modified cells of the afferent arteriole which release renin
Through which 3 processes does the nephron regulate plasma conposition
Filtration, reasbsorption and secretion
What is filtration
The movement of water and solutes across the filtration membrane
Where does filtration occur
In the renal corpuscle
What is reabsorption
Returning water and desirable solutes back to the body
Where does reabsorption occur
Primarily in the proximal convoluted tubule
What is secretion
Transport of undesirable material missed by filtration (waste, drugs, excess ions) from the blood into tubular fluid
Where does secretion occur
In the distal convoluted tubule
Describe ultrafiltration
Pressure in the glomerular capillaries forces a portion of plasma into the Bowman’s space
What is able to pass during ultrafiltration
Plasma minus large proteins
Which cells are responsible for filtering the blood
Podocyte cells
What is glomerular filtration rate regulated by
Renal autoregulation, hormonal regulation and neural regulation
What is the amount of filtrate formed in the kidneys every minute
105-125ml/min
How much of the filtrate leaves the body
1%
Describe reabsorption that occurs in the PCT
~65% of water and 70% of Na+. Also potassium, cholride, bicarbonate, calcium, magnesium
In normal circumstances what does tubular reabsorption remove
All filtered glucose, lactate and amino acids
What does tubular reabsorption do
Reclaims useful substances from tubular fluid whilst simultaneously allowing waste products to be excreted
By which three mechanisms does absorption occur
Osmosis (water), active transport (Na+/ K+ ATPases), secondary active transport (glucose and amino acids coupled to sodium reabsorption)
How much of the filtered sodium, chloride and water are reabsorbed by the loop of Henle
20%
What happens as the filtrate moves down the loop of Henle
It becomes increasingly hypertonic as a result of passive movement of water out of the tubule
What is the only substance the descending loop is permeable to
Water
Where does osmolarity peak
At the hair pin bend
What happens as the filtrate moves up the ascending loop
Becomes increasingly hypotonic as a result of the pumping out of Na+, K+ and Cl-
What happens in the distal convoluted tubule
Sodium and chloride reabsorption; potassium and hydrogen secretion; calcium and magnesium handling
What is the unique capacity of the DCT
It can adapt to changes in hormonal stimuli
What are the functions of the collecting system
Adjusts final filtrate composition; determines final osmotic concentration; dtermines final volume of urine; permeable to urea
Only one DCT empties into one collecting duct- true/false
FALSE. Many DCTs empty into one collecting duct
What happens once the filtrate enters the minor calyx
The fluid is now called urine. concentration and Composition vary based on metabolic and hormonal activities
What 3 hormones act on the kidneys
Angiotensin II, Aldosterone and ADH
What does Angiotensin II do
In response to low sodium and low tubular flow juxtaglomerular cells produce renin. Renin cleaves angiotensin I from angiotensin which is converted to angiotensin II by enzymes from the lungs. Angiotensin II directly stimulates Na+ reabsorption in the PCT. Also stimulates vasocontriction of the afferent and efferent arterioles decreasing the GFR
What does a decrease in GFR simulate
The secretion of aldosterone
What part of the kidney does angiotensin II act on
Afferent and efferent arterioles and PCT
What does aldosterone do
Raises BP by stimulating kidneys to retain water and Na+ (increasing blood volume). Leads to production of Na+ channels and promotes Na+ reabsoprtion. Na+ reabsorption leads to water retention and limits unrianry losses
What part of the kidney does aldosterone affect
DCT and collecting ducnt
What does ADH do
Raises BP by stimulating kidneys to retain water (increasing blood volume). Increase in plasma osmolarity or decrease in blood volume causes the release of ADH from the posterior pituitary gland. ADH increases aquaporins in the renal collecting ducts
Where does ADH affect
Collecting duct
What are the most common causes of chronic renal failure
Diabetes and long term uncontrolled hypertension
When does CRF occur
When more than 3/4 of the functional renal tissue is lost
What happens during CRF
- Glomerular filtration rate falls substantially.
- Concentration of urea in blood rises (uraemia).
- Impaired tubular function leads to failure of normal ionic regulation, acidosis and accumulation of metabolites.
- Accumulation of metabolites and disturbance of ionic balance will lead to CNS depression, coma and eventually death
