Renal 1 Flashcards
What does Renal artery do ?
what does Renal vein do?
Renal artery: blood and nutrients into the kidney
Renal vein: takes the blood out of the kidney into the body
what consists in the waste products (in the form of urine) ?
excess water
urea
excess nutrients
what are capillary beds and their roles?
renal arteries connect to the renal vein by capillary beds
- vasa recta
- peritubular capillaries
what are the three parts of a nephron?
1) renal corpuscle
2) Renal tubules
3) capillary network
what forms renal corpsucle?
- afferent arteriole
- glomerulus
- efferent arteriole
- bowman capsule
what forms renal tubules?
Proximal convoluted tubule
loop of henle - ascending and descending
distal convoluted tubules
collecting duct
what forms the capillary network and where are they found ?
- vasa recta - found interwining/surrounds the loop of henle
- peritubular capillaries - surrounds pct and dct
what are the 3 processes which occur in a nephron?
1) filtration
2) reabsorption
3) secretion
what happens in the process of filtration (nephron)
- occurs in the glomerulus & Bowman’s capsule
- blood enters the glomerulus under a really high pressure
- constituents from the blood leave the glomerulus and enter the nephron via the Bowman’s capsule
- this forms the filtrate. As it enters the tubules it is referred to as tubular fluid.
- complex process then takes place as the tubular fluid passes through the nephrons. End product = urine
- key relationship between molecular mass and filtration at this stage
in the process of filtration what is its relationship with molecular mass
The blood is arriving from the afferent arterioles contain RBCs, WBCs, water, really big proteins, amino acids (smaller proteins), glucose, waste products
The walls of the arterioles consists multiple layers which allow smaller molecules to pass through, but excluding larger molecules such as proteins
- only lets small molecules enter and pass into the nephron
- the larger molecules will stay in the blood - therefore it never enters the kidney
what is size of the molecules which is most appropriate to cross into the glomerulus and form a filtrate?
Substances that are up to 5000 Da flow freely across the glomerulus and into the Bowman’s capsule to form the filtrate
Substances above 5000 Da are less likely to cross from the glomerulus into the Bowman’s capsule
what happens in the process of reabsorption in the nephron?
- movement of constituents from the tubular fluid back into the blood
- this is aided by the existence of peritubular capillaries/vasa recta
- the body is reclaiming these constituents before they are excreted in the form of urine
- e.g. the reabsorption of water is one of the key regulators of blood pressure
- can be transcellular of paracellular
what happens in the process of secretion?
- movement of constituents from the blood into the tubular fluid
- this is aided by the existence of peritubular capillaries/vasa recta
- the body is removing these constituents so that they are excreted in the form of urine
- can be transcellular or paracellular
what does the reabsorption of water regulate
blood pressure
what are the functions of a kidney?
- Homeostasis
- PRODUCE an active form of vitamin D that promotes strong, healthy bones
- Control the PRODUCTION of RED BLOOD CELL
- Remove drugs from the body
what are the roles of homeostasis within the kidney?
- Removing waste products from the body
- Regulating the pH of your blood
- Regulating the blood pressure by regulating inorganic ions
- Regulating water balance to maintain osmolality
- Releasing hormones that influence water balance and regulate blood pressure
waste removal (homeostasis) - what products?
The kidneys are filtering devices for the blood
Remove the waste products of metabolic processes
- urea - uric acid - creatinine
- what is the main component of urine?
- how can you determine if the kidney is not functioning correctly?
- urine
- if there is high levels of urea, uric acid or creatine in the plasma then the kidney is not functioning correctly
how can inorganic ions effect blood pressure (homeostasis):
- hc03
- ph of blood vs urine
- ammonia
Due to their low molecular mass, all inorganic ions present in the blood are filtered into the Bowman’s capsule to form the filtrate
These ions are then reabsorbed into the blood at various points along the nephron
60-70% of Na+ and 90% of HCO3- is reabsorbed in the PCT
Bicarbonate (HCO3-)
- Alkaline; important function in maintaining acid-base balance in the blood
- Completely reabsorbed by the kidneys
pH
- pH of urine is much lower than that of plasma
- Acidic waste is removed by the kidneys
- Serious medical conditions can occur if the blood plasma is too acidic
Ammonium (NH4+)
- Almost all ammonium in the blood is removed by the kidneys
Excess sodium, potassium, calcium, phosphate and chloride are also removed by the kidneys
Inorganic ions: reabsorption into the blood
PCT
Within the cortex
Na/K pumps transporters.
Sodium is actively pumped out of the tubular fluid back into the peri-tubular capillaries
Inorganic ions: reabsorption into the blood
Descending limb
Within the medulla
IMpermeable to ION
Inorganic ions: reabsorption into the blood
Ascending limb
Makes medulla very salty
Within the medulla
Na/K pumps
Na/K/Cl transporters
End result is having Na, Cl and K ions leaving the tubular fluid via the vasa recta
Inorganic ions: reabsorption into the blood
DCT
Na/K and Na/Ca pumps
End result is having Na and Ca ions leaving the tubular fluid into the peri-tubular capillaries
Helps to pick more of the important nutrients to retain in the body
How does regulation of water balance work?
homeostasis
They control how much water is removed from the blood stream and excreted as urine
- central role in the regulation of blood pressure
Reabsorption of water takes place in the tubules of the nephrons
Reabsorption of water can occur either of two ways:
- Along an osmotic gradient (passive) - By the release of hormones from the kidneys (active)
where ever sodium goes…
water goes aswell
PCT, ascending limb, descending limb, DCT and collecting duct and its relationship with water and sodium
PCT – the majority of water is reabsorbed here because the majority of sodium is reabsorbed here
Ascending limb – the high sodium content being reabsorbed drives the reabsorption of water in the descending limb. Not permeable to water.
Descending limb – impermeable to ions but permeable to water
DCT - reabsorbs a little bit more water
Collecting duct – re-absorbs some urea and water
what hormones are released which regulates blood pressure
Renin-Angiotensin-Aldosterone System (RAAS)
Anti-diuretic hormone (ADH)
what is the role juxtaglomerlus apparatus
where is it found
intercession where DCT passes through efferent and afferent arteriole
-picks up when the BP is low so that the kidney can release hormones
what cells are consisted in DCT?
macular densa cells - only found in dct where it intercepts the efferent and afferent arterioles
-role with regulating blood pressure = water balance
where are juxtaglomerlus cells found?
afferent arteriole
where is the mesangial cells found and what is its role
- keep the structure of afferent and efferent arteriole
where are sympthatic nerves found
sitting ontop of juxtaglomerlus cells in the afferent arteriole
sympathetic nerves have nerve endings which are sitting in the juxtaglomerlus cells
which hormone does juxtaglomerlus cells contain?
Renin
when is renin released from juxtaglomerlus cell and what happens
- when blood pressure is low
- the renin is released and enters the afferent arteriole which enters into the blood stream
what are the triggers for renin release into the bloodstream
a) Low blood pressure
b) Sympathetic nerves
c) Low sodium levels picked up by the macular densa cells
how can low blood pressure trigger renin
- when blood pressure is low it means the pressure of the blood entering the glomerlus via the afferent arteriole is low
- this is sensed by the ENDOTHELIAL cells
- the endothelial cells give a nudge to juxtaglomerlus cells to release renin
- allow renin to enter blood stream
how can sympathetic nerves trigger renin
- the nerve ends sit into the juxtaglomerlus cells
- when there is low blood pressure it is picked up by the sympathetic nerve along the afferent arteriole
- when this is picked up the nerve endings which sit in the juxtaglomerlus cells starts firing
- cause the release of renin from the JC.
how does low levels of sodium picked up by macular densa cells trigger renin release
- mucular densa cells has all the tubular fluid flowing through it
- mucular densa cells are like tasting cells - they taste the amount of sodium are flowing through them
- when sodium levels are low its telling macular densa cells that blood pressure is low
- when sodium is low the macular densa cells release their own hormones
- the hormone is called prostagladin
- these travel to the juxtglomerlus cells to release renin
what does renin do after it reaches the blood stream
- Liver contains angiotensinogen = an inactive hormone
- Renin + angiotensinogen = angiotensin 1 (converted)
(angiotensin 1 floating around the blood)
Endothelial cells within the tiny capillaries contain Angiotensin Converting Enzyme (ACE)
ACE + angiotensin 1 = angiotensin 2
Angiotensin 2 will now go on to perform various functions in response to low blood pressure
what is the 4 things angiotensin 2 do to increase blood pressure?
travels to Smooth muscle cells: cause vasoconstriction (blood vessel smaller) = increased resistance (rapid response) ( in efferent as-well - concentrate blood in glomerulus therefore more blood to filter and deliver more oxygen)
Kidneys: signal to the cells to re-absorb more Na+ = more H20 reabsorption
Pituitary gland: signal to release Anti-diuretic Hormone (ADH) = vasoconstriction of smooth muscle + water reabsorption in collecting duct of nephron
goes to Adrenal gland: signal to release aldosterone = (goes to nephron) Na + reabsorption = more H20 reabsorption
VASOCONSTRICTION + INCREASED BLOOD VOLUME = INCREASED BLOOD PRESSURE!
what is ADH and its role?
-where is it released from?
Released from the pituitary gland with the aim of reabsorbing more water. It’s release is triggered by…
Angiotensin 2 (RAAS system – we know this already!)
Osmoreceptors: they can detect higher concentration of blood (blood is thicker) = higher osmolarity (not very dilute) = trigger ADH release
Low blood volume: sympathetic nerve endings in the VEINS of the heart will sense this - signal to pituitary gland to release ADH
Low blood pressure: sympathetic nerve endings in the ARTERIES of the heart will sense this - signal to pituitary gland to release ADH
what is Diabetes insipidus and its causes and what can go wrong
types
- kidneys are unable to conserve water = pale, water urine; increased frequency of urination (every 15-20 minutes!); increased thirst; always feeling ‘dry’
- Two types of diabetes insipidus…
1) Cranial diabetes insipidus
2) Nephrogenic diabetes insipidus
- Two types of diabetes insipidus…
cranial :
Brain tumour damaging the hypothalamus or pituitary gland
Severe head injury damaging the hypothalamus or pituitary gland
Complications that occur during brain or pituitary surgery
nephrogenic :
Nephrons unable to respond to ADH
Congenital (i.e. genetic)
Acquired e.g. use of longterm lithium for bipolar disease or other causes such as hypercalcaemia or obstruction of the ureters
what hormone does adrenal gland produce?
and its role
goes to Adrenal gland: signal to release aldosterone = (goes to nephron) Na + reabsorption = more H20 reabsorption
