renal system Flashcards
what are the functions of the kidney
excretion
- the formation of urine - this is its aim function
- excrete waste products of metabolism and excess inorganic substances from diet
homeostatic regulation
- electrolyte homeostasis
- water homeostatsis
- acid and base balance
endocrine function
- synthesis of hormones
- target site for hormones
structure of the kidney
- bean shaped organ, the size of. a fist
- contains the renal cortex - this contains many capillaries
- medulla
- renal pyramid which are steps related by renal columns
- pyramid contain minor calyces - these form major calyces - and then these form renal pelvis
- the renal pelvis collects urine and transports urine to ureters
what is the structure of the nephrons
nephrite’s are the urine forming units of the kidney
there are about 1 million in each kidney
there are two types
- cortical nephron
these form 85% of all the nephrons, they are shorter in length
they are located in the cortex
they perform most of the re absorption and secretory functions of the kidney
- juxtamedullary nephron
these are longer in length, they run through the medulla and the concerntrate the urine
how does the nephron work
- glomerular capsule ( bowman’s capsule)
2. proximal tubule nacl nutrients
3. loop of henle
4. descending loop of henle
5. thick segment of ascending limb
6 . distal tubule
7. collecting duct
what is the structure and function of the glomerular capsule
strcuturew
- located in the context and encloses the glomerulus
- the glomerular capillaries are fenetstrated ( they have small openings or pores because exchange occurs)
they have endothelium with larger diameter pores
function
- cells called MACULA DENSA detect the levels of chloride and sodium ions reaching the DCT distal tubule
- this then makes the JUXTAGLOMERULAR CELLS release renin - this is a hormone which controls the levels of chloride and sodium
what is the structure and function of proximal convoluted tubule
function
- 60 to 70% of glomerular filtrate is reabsoprted by the PCT
they absorb substances like
- organic nutrients = glucose, amino acids
- ions - na+- this requires active reabsorption, cl - passive reabsoption and water - by osmosis because of the increased solute concerntration
how is an+ reabsoption
1. diffusion through sodium leak channels
2. sodium linked cotransport of glucose and amino acids
3. countertransport with H+ where it then leaves the cells through the sodium potassium pump
what is the structure of the loop of henle both the ascending and the descending
- descending
- the cells of the descending limb are flat with no microvilli and few mitochondria - so the cels are not specialised for transport
2 . ascending
however the cells of the ascending are specialised
the cells are cuboidal with lots of mitochondria- so they are specialised for transport
this ascending section of the loop of henle is the thick segments
what us the fusion of the descending loop of henle
- the kidney is able to produce urine of different concerntratetion because of the loop of henle due to its - COUNTERCURRENT
- counter current is the exchange that occurs between the fluids moving in opposite direction
the descending loop is permeable to water but not Na and Cl
what is the function of the ascending loop
- it is permeable to Na amd Cl but not water
Na+, K+ and Cl- are transported out of the tubular fluid - this is through active transport through the use of transporters - k+ and Cl- are pumped into the pertubular fluid
- then Na is pumped out in exchange K+ through an exchange pump
- then K+ diffuse back into the lumen of the tubule through leak channels
- so Na and Cl are lost into the peritubukar fluid
how does countercurrent work to help the transport of fluid
- the forcing out of the Na and Cl ions from the ascending limb of the loop of henle elevates the osmotic concerntration of the peritubular fluid
this facilitates the osmostic flow of water from the descending limb into the peritubular fluid
what is the structure and function of the distal convoluted tubule dct
structure
- cuboidal epithelia cells
- fewer microvilli
- abundant mitochondria
function
this is involved with the reabsorption of water, Na+ and Ca ions from the tubular fluid
Na and cl are actively transported across the dct - where na is reabsobed in exchange for K by the pump
this pump is controlled by ALDOSTERONE
this stimulates the synthesis and incoporation of pump into the membrane and it favours the reabsorption of filtered sodium
however prolonged ALDOSTERONE stimulation can cause hypokalemia
what is the structure and function of the collecting dust
function
- has connecting tubules, which connect each nephron to a collecting duct
- several collecting ducts empty into a large papillary duct
- simple cuboidal cells line connecting tubules
- columnar epithelium lines collecting and papillary ducts
function
- it is impermeable to water in the absconded of the hormone ADH ( this lowers the osmolality both intra and extracellular)
- it reabsorbes Na+ and HCO3- , the cortical region contains aldosterone sensitive na/k pumps
- also involved in the secretion of h+ and HCO3+ = h+ ions secreted into the tubular fluid from the peritubular fluid when the Ph of the peritubular fluid drops - then HCO3+ is reabsobed, when the pH increases H+ ions are reabsorved
what is glomerular filtration dependant on
- the net filtration pressure is dependant on
- glomerular blood
- hydrostatic pressure
- capsular hydrostatic pressure
- blood colloid osmotic pressure
how is an edema caused - swelling
in some kidney diseases the glomerular capillaries are damaged
the plasma protein enter the glomerular filtatrate and reduce the blood colloid osmotic pressure
more fluid then move into the tissues
this causes an edema
what is GFR
this is the glomerular filtration rate
if the gfr is too high then the needed substances are not reabsorbed and are lost in the urine
if it is tool low then everything is reabsobed including waste
