urinary system Flashcards
what are the organs for the urinary system
bladder, kidneys, ureters and urethra
How do kidneys control ions in the blood
electrolyte homeostasis
sodium, potassium, calcium, chloride and phosphate ions back into body or excreted
- filtration = blood enters through renal arteries in glomeruli
- reabsorption = of ions like sodium, calcium etc which is regulated by hormones like aldosterone and parathyroid hormones
- secretion = kidneys secrete ions into tubular fluid to be excreted to maintain a balance
- excretion = excreted ions that are not needed
what are glomeruli
tiny ball shaped structures in kidney which filters blood
- network of capillaries encased in bowmans capsule
- blood flows into capillaries and water small ions pass through and large molecules do not
- travels to renal tubules where nutrients reabsorbed into blood and waste excreted as urine
function of bowmans capsule
- surrounds the glomerulus forming a cup like sac
- collects filtrate produced i.e. water ions etc
- filtrate then moves to renal tubules
main ions in blood for kidneys
- Na + sodium
- K+ potassium
- Ca2+ calcium
- Cl- chloride
- HPO4 2- phosphate
how do the kidneys maintain the pH balance
- bicarbonate reabsorption from filtrate back to bloodstream, acts as buffer
- hydrogen ions, kidneys secret into tubular fluids to reduce acidity
- ammonia = combines with hydrogen to make ammonium
- phosphate buffer system = forms dihydrogen phosphate with hydrogen
- h plus ions increase pH
how do kidneys maintain blood volume
- filtration and reabsorption
- Renin angiotensin aldosterone system = blood volume or pressure low kidneys release enzyme called renin which triggers cascade of reactions that produce angiotensin II which constricts blood vessels and stimulates aldosterone release from adrenal glands, this increases sodium and water reabsorption in kidneys, raising blood volume and pressure
- ADH = hypothalamus detects chnag in volume and signals pituatary gland to release, increases water reabsorption in kidneys reducing urine, increasing blood volume
- ANP = heart releases which reduces sodium reabsorption in kidneys, increased urine production and decrease blood volume
how does blood control blood osmolarity
- filtration
- reabsorption and secretion
- ADH = hypothalamus signals pituitary gland to increase water reabsorption and reduce urine output
- thirst mechanism = drink more water impulse reduces osmolarity
- aldosterone = hormone from adrenal glands, promotes sodium reabsorption in kidneys, water follows sodium
how do the kidneys help with blood pressure
- Renin Angiotensin aldosterone system RAAS = when blood pressure low kidney release renin which converts angiotensinogen into angiotensin I which is then converted to angiotensin II by enzyme in lungs, constricts blood vessels increasing blood pressure and stimulates release of aldosterone from adrenal glands which increases sodium and water reabsorption in kidneys raising water reabsorption
- regulation of blood volume = adjust sodium and water excreted and kidneys control blood volume that leads to increased blood pressure
- ADH = osmolarity is high or blood pressure low hypothalamus triggers pituitary gland to release to increase water reabsorption in kidneys reducing urine
- ANP = blood pressure high the heart releases which reduced sodium reabsorption in kidneys and leads to increase urine
how do the kidneys help excrete
Filtration: Blood is filtered in the glomeruli, removing water, ions, and waste products to form filtrate.
Reabsorption: Essential substances like glucose, amino acids, and certain ions are reabsorbed back into the bloodstream from the filtrate.
Secretion: Additional waste products and excess ions are secreted into the tubular fluid.
Formation of Urine: The remaining fluid, now called urine, contains waste products like urea and creatinine.
Excretion: Urine is transported from the kidneys to the bladder via the ureters and is excreted from the body through the urethra during urination
how are the kidneys involved in hormone production
rythropoietin (EPO):
Stimulates the production of red blood cells in the bone marrow.
Released in response to low oxygen levels in the blood.
Renin:
Part of the renin-angiotensin-aldosterone system (RAAS).
Helps regulate blood pressure and fluid balance.
Calcitriol (Active Vitamin D):
Produced from vitamin D in the kidneys.
Helps regulate calcium and phosphate levels, promoting bone health.
how do the kidneys help maintain blood glucose levels
Glucose Reabsorption:
In the proximal tubules of the kidneys, glucose is reabsorbed from the filtrate back into the bloodstream.
This process ensures that glucose is conserved and not lost in urine.
Renal Threshold for Glucose:
The kidneys have a renal threshold for glucose, typically around 180 mg/dL.
If blood glucose levels exceed this threshold, glucose appears in the urine (glycosuria).
Gluconeogenesis:
The kidneys can produce glucose from non-carbohydrate sources (amino acids, lactate) during prolonged fasting or starvation.
This process helps maintain blood glucose levels when dietary intake is low.
where are the kidneys located
retroperitoneal partly protected by lower ribs
what is the hilum
part of kidney where structures enter and leave
- renal artery
- renal vein
- ureter
- nerves and lymphatics
renal capsule
membrane surrounding outer surface of kidney, tough fibres of collagen and elastin to support and protect
cortex
outer layer of kidney which is involved in filtration of blood, reabsorption. where nephrons start and creates EPO hormone which helps make rbcs in bone marrow
medulla
inner part of kidney that consists of medullary collecting ducts, loops of henle and interstitium that regulates concentration of urine
renal artery
supplies oxygenated blood to the kidneys
renal vein
carries blood from kidney and ureter to inferior vena cava
renal pelvis
area at centre of kidney where urine collects and funelled into ureter
ureter
narrow tube that carries urine from kidney to bladder
calyx
- minor calyx = surround renal papillae of each pryamid and collects urine
- major = urine flows into renal pelvis and then ureter
3 processes to form urine
1) filtration = blood to nephron
2) reabsorption = filtrate to blood
3) secretion = blood to filtrate
how does the renal corpuscle help glomerular filtration
- podocytes = modified squamous epithelial cells
- folded up to increase sa for capillaries
- thin filtration membrane and leaky capillaries
- glomerular pressure is high - every 30 mins amount of blood passing through can equal total blood volume of plasma in body
99% of all blood plasma is reabsorbed
renal corpuscle features
- podocyte have foot like structures where bottom lies on basment membrane
- forms filtration membrane
- holes called fenestrations make endothelial leaky
- basal lamina lies between endothelim and podocytes and excludes large plasma proteins
- slit membrane which occurs between podocyte extensions, small diameter so small plasma proteins can pass through and larger molecules cannot
glomerular filtration
- occurs due to high pressure
of afferent arteriole, has large diameter so large volume - pushed into thin capillaries in glomeruls to increase pressure
- glomerular blood hydrostatic pressure = pressure that forces water and solutes through filtrationmembrane
- capsular hydrostatic presssure is back pressure or resisitance
- blood colloid osmotic pressure is pressure from proteins in capilklaries ie.albumins
net filtartion pressure calc
GBHP-CHP-BCOP
gomerular filtration rate and controlled by
m= 125ml/min
f= 105ml/min
homeostatis regulates to prevent loss substances
controlled by adjusted bloodflow and altering glomerular capillary surface area
three parts of renal tubule
- proximal convulted tubule
-nephron loop = descending and ascending loop
-distal convoluted tubule
