Urinary Anatomy Flashcards
Where are the kidneys locate?
retroperitoneal
superior portion is protected by the 11th and 12th ribs
lie anterior to the quadratus lumborum and psoas major muscles
- QL - moves pelvis, deeper
- PM - moves thigh, more superficial
What do the pronephros, mesonephros, and metanephros do and what do they develop into?
pronephros - similar arrangement but does not filter blood
- disappears as mesonephros develops
- pronephric ducts connect to cloaca
mesonephros - where 1st filtration occurs
- mesonephric tubules grow and fuse with pronephric ducts
- branches from aorta grow into mesonephric tubules to form glomeruli
Metanephros - develops from mass of unorganized mesoderm
- metaneprhic diverticulum: develops into calyces and collecting ducts
- mesonephros + metanephros = nephron
What does the nephron develop from?
metanephrogenic blastema - becomes the nephrotic vessel that associates with glomerulus
metanephric diverticulum develops into calyces and collecting ducts
renal ducts develop into Bowman’s capsule, proximal convoluted tubule, loop of Henle, and distal convoluted tubule
Where is the best place to transplant a kidney?
R iliac fossa
- blood vessels are attaches to the external iliac and the ureter is shorter
What does the hilus in the kidney contain?
renal artery and vein
ureter
What does the renal sinus contain?
minor and major calyces
renal pelvis - where major calyces come together
adipose tissue in renal sinus
What is the difference between the juxtamedullary nephron and cortical nephron?
juxtamedullary - nephron that starts in the cortex and dips into the medulla
cortical - nephron that starts in the cortex but does not go into medulla
describe the blood flow from the renal artery to peritubular capillaries
renal after - segmental artery - interlobar artery - arcuate artery - interlobular artery (cortical radiate) - afferent arteriole - glomerulus - efferent arteriole - peritubular capillaries
when going back to veins, enters venules and descends via complementary structures starting with the interlobular veins besides segmental
What is cap bed 1 and cap bed 2 in the renal system?
Cap bed 1 - glomerulus
- blood from afferent arteriole
Cap bed 2 - peritubular capillaries
- blood from efferent arterioles
- important for secretion and reabsorption
There are two fates of the efferent arteriole. What are they and where are they located?
peritubular capillary - spans the cortex
vasa recta - if efferent arteriole is near the arcuate, it can drop into the medullary pyramids
- next to the juxtramedullary nephron
How do the arterioles, glomeruli affect pressure of the kidneys?
smooth muscles on afferent and efferent arterioles allow them to control blood pressure
no smooth muscle on glomeruli - requires pressure from the arterioles
to increase filtration pressure, efferent dilates
to decrease filtration pressure, efferent constricts
Describe the filtration membrane of the kidney. What is is made of? How do these structures filter the filtrate?
SSET sandwich made from parietal layer of Bowman’s capsule and glomerular capillaries
capillaries - contain fenestra that allow passage of small proteins ions, NO cells
- basal lamina layer from capillaries
reticular lamina - made from the epithelium of the capillary, thicker, in between basal laminas
- basement membrane with the basal and reticular lamina does most filtration
Bowman’s capsule - basal lamina layer that meets the reticular lamina
- contain PODOCYTES - cells that have PEDICELS that interdigitate
- pedicels form filtration slits
- filtration slits contain slit diaphragms - a small negative protein membrane that helps repels AA
Describe the proximal convoluted tubule. What kind of ET does it have? Describe its folding and how it helps its function
closest tubule to the Bowman’s capsule
- major site of water and solute reabsorption
- site of H ion and detoxified drug secretion
ET: simple cuboidal with microvilli that increases SA
- microvilli on filtrate side
contains lateral and basal infolding that helps increase surface area
contains lots of mitochondria at basal infolding
- close to peritubular capillaries for active transport
How can you tell the difference between the collecting duct and distal tubule histology?
both do not have microvilli (cancels proximal tubule)
distal tubule - nuclei tend to bulge near surface
- carries filtrate back towards glomerulus - straight tubule
collecting duct - nuclei towards bottom
- found in both cortex and medulla
What are the structures that are only found in the cortex?
blood vessels:
cortical radiate
afferent arteriole
efferent arteriole
glomerulus
peritubular capillaries
nephron/collecting duct:
Bowman’s capsule
proximal convoluted tubular
distal convoluted tubule
What are the structures that are found in the medulla only?
blood vessels
- interlobar arteries
- vasa recta
nerphon/collecting duct:
papillary ducts - located at tips of medullary period
What structures are i both the cortex and the medulla?
arcuate artery - in between, but no other vessel is shared
collecting ducts
nephron loops: long nerphon loops
What happens at these different points of the nephron: proximal convoluted tubule, nephrons loop, distal convoluted tubule, collecting ducts
proximal convoluted tubule - major site of water and solute reabsorption
- site of H+ and drug secretion
nephron loops - site of concentration gradient formation
distal convoluted tubules - site of REGULATED solute reabsorption
collecting ducts - site of REGULATED water reaborption
Where is the first place of filtrate? What structures are involved?
first place of filtrate - capsular space
structures - filtration membrane formed between:
- glomerular capillaries - no smooth muscle, crosses epithelium into glomerular capsule and into capsular space
- capsule - visceral layer of capsule is where filtration occurs, contains podocytes
What are the structures in the filtration membrane that filter particles out of the filtrate?
visceral capsule later - podocytes
- pedicels interdigitate to make filtration slits
- slit diaphragm - nephrin - zipper appearance, podocin
fenestra of SSET - visceral capsule and glomerular capillaries
- 50-70 nm, small proteins can pass
basement membrane - visceral capsule and glomerular capillaries
- reticular lamina sandwiched between basal lamina
- where most filtration occurs via collagen fibers
general negative charges from: glycocalyx on capillary, basement membrane, slit diaphragm to prevent proteins from passing
What are the pressures that determine filtration pressure? How does that affect glomerular filtration rate?
glomerular filtration rate - how much fluid moving across filtration membrane
- 100 mL blood = 1 mL fluid into nephron
determined by:
blood pressure from the afferent arteriole - into capsule
capillary osmotic pressure - colloid pressure
- albumin cannot cross, attracts water back into the arteriole
capillary hydrostatic pressure - capsule expands and resists additional fluid
How does dilating/construction of the afferent and efferent arteriole affect GFR?
Afferent:
- dilation: increases volume = increase in hydrostatic pressure = increase in flow of fluid through nephron
- construction: reduces fluid flow, decreases hydrostatic P and flow of fluid through nephron
Efferent:
- dilation: more fluid out of glomeruli, less hydrostatic pressure lower filtration rate
- constriction increases hydrostatic pressure and increases filtration rate
What is the myogenic response in renal blood flow?
when there is increased blood flow in the afferent arteriole, it stretches the tunica media (smooth muscle) in wall and causes it to contract
- protects glomerular capsule from hypertension
- does not require hormones/molecule/innervation
low blood flow - blood vessels collapse
- responds with vasodilation
What are juxtaglomerular cells? Where are they located? What does it release?
specialized granular cells in the smooth muscle of the afferent arteriole
- baroreceptors - sensitive to low hydrostatic pressure and release renin
- sympathetic stimulation: sympathetic neurons release NE that bind to B1 receptors and cause renin to be released
- can be stimulated by prostaglandins released by macula densa cells
What is the macula densa? Where is it located? What does it release?
macula densa - specialized cells in the in the distal tubule near the Bowman’s capsule
- chemoreceptors sensitive to low [Na] in filtrate
- triggers dilation of the afferent arteriole when Na in filtrate low
releases:
- prostaglandins - in response to low Na in filtrate (low BP), stimulates renin release
- adenosine - in response to high Na (high BP) - causes afferent arterioles to constrict, also stops renin release
What is int he juxtaglomerular capsule? What are the extraglomerular meseangeal cells? Where are the located?
juxtaglomerular cells, macula densa, extraglomerular mesangial cells
located between the afferent and efferent arterioles in the juxtaglomerular capsule
- type of smooth muscles cells involved in auto regulation of GFR
What are the intraglomerular mesangial cells? How do they regulate filtration rate?
modified smooth muscle cells that are wrapped on the outside of podocytes
- when they contract the decrease the surface area of the basement membrane and DECREASE filtration rate
- does not effect glomerular pressure
Describe the MOA for renin.
renin - enzyme made by juxtaglomerular cells in kidney
angiotensinogen - protein made by liver
- gets converted into angiotensin I by renin
angiotensin I goes to lungs and angiotensin converting enzyme (ACE, made in lungs) converts AGI into AGII
angiotensin II effects:
- efferent arterioles constrict
- renal glands to secrete aldosterone for Na/H2O retention
CNS effects:
- increases thirst to increase blood volume
- stimulates ADH secretion - water reabsorption
- sympathetic stimulation - increased cardiac output and vasoconstriction
How does atrial naturietic peptide and brain naturietic peptide affect afferent arteriole hydrostatic pressure?
increases afferent arteriole hydrostatic pressure
- stretching of atria of heart and ventricles of the brain
ANP/BNP cause:
- dilation of the afferent arterioles
- constriction of the efferent arterioles
- increased Na reabsorption by proximal (1*) and distal tubules
Where does reabsorption occur? What kind of cells does this structure have? What features of this cell help its function?
reabsorption occurs at the proximal convoluted tubule
simple cuboidal cells with tall microvilli
- contains basal and lateral infolding for increased surface area
- contains lots of mitochondria on the basal surface for active transport
- basal membrane against peritubular capillary, apical surface facing filtrate
Describe how glucose and amino acidsreabsorption occurs. What kind of transport does it require?
crossing apical membrane of PCT
- secondary active transport with Na into the cell
crossing basal membrane of the PCT
- glucose transporter - facilitated diffusion
- AA transporter - fascinated diffusion
Na/K active transport pumps (basal membrane) remove and create an Na gradient that allows symptort movement of other molecules with Na
- important for reabsorption of glucose, AA, K, Cl, HCO3-
How does K affect reabsorption?
K pumped into the cell via Na/K pumps
K simply diffuses out of leak channel
helps create Na gradient needed for secondary active transport for reabsorption
How does water and urea leave the filtrate?
water - moves through aquaporins depending on concentration gradient
urea - leaves filtrate and is soluble in plasma membrane
What is secretion in the PCT? What gets secreted?
peritubular capillary to filtrate
- urea, uric acid, bile acids, catecholamines, some creatinine
- drugs
PCT can only SECRETE H and can only REABSORB HCO3-
What happens to glutamine when it is in the PCT tubule cells?
enters cuboidal cell and gets deaminated, oxidized and acidified to create:
NH4 (ammonia): added to filtrate
HCO3-: returns to capillary via secondary active transport
Describe the thin segment of the descending limb and ascending limb of the nephron loop. What are these areas permeable to and what kind of ET do they have?
BOTH have simple squamous
descending loop: highly permeable to WATER
ascending loop: impermeable to water
- moderate permeability of urea and sodium
Describe the thick segment of the ascending limb. What role does it play in creation of the extracellular osmotic gradient?
simple cuboidal ET
- impermeable to H2O, urea
contains active transport pumps for Na
pumps Na out of loop and into extracellular space, but does not pump water out with it
- creates a 200 mosm/liter gradient
- ascending limb becomes hypotonic
- extracellular fluid is hypertonic - causes water to leak out of descending loop
continuous cycle to increase osmolality of extracellular and descending loop
How does the vasa recta relate to the nephron loop and how does it contribute to the cellular osmotic gradient?
Vasa recta - has ascending and descending loop similar to loop of henle
- blood in vasa recta flows in opposite direction
descending limb - absorbs solutes
ascending limb - absorbs water
instead of water from the descending limb going into the extracellular space, it goes into the vasa recta and allows the gradient to continue forming
Compare the osmolality of the descending limb and the ascending limb of the loop of henle
descending limb: 200 mosm/L more than ascending limb
- hyper osmotic
- water being pumped out increases concentration of solutes in limb
ascending limb - hypo osmotic
- filtrate leaving ascending limb to distal tubule becomes less concentrated
Once the filtrate reaches the collecting duct, what happens? What is the osmolality of the filtrate?
osmolality of filtrate as it enters the collecting duct is 100 mosm/L
can continue into calyces as is
if body needs to increase blood volume, ADH is released
- causes aquaporins to be inserted into the wall of the collecting duct
- water moves out into the of the collecting duct and into intracellular space until concentration matches extracellular fluid
Describe the effects of the following hormones and where they affect reabsorption: aldosterone, ADH, parathyroid hormone, calcitriol
aldosterone: mostly DCT, some collecting duct
- increases synthesis of Na transport proteins in the cell for reabsorption
ADH - collecting duct
- adds aquaporins to the membrane for water reabsorption
parathyroid hormone: increases Ca absorption
- receptors found in DTC
calcirtiol - synthesized by kidneys to increase Ca reabsorption in kidneys and small intestine
What are principle cells? Where are they located? What are they sensitive to? When these hormones bind, what happens?
found in the DCT and the collecting duct
- contain receptors for aldosterone and ADH
when bound, increases synthesis of:
- NaK pumps for NaCl reabsorption: Na pumped out into peritubular, more Na in through apical membrane leak channels
- aquaporins for water reabsorption
Describe aldosterone release. What regulates it?
angiotensin II stimulates release of aldosterone from the adrenal cortex - made from cholesterol
juxtaglomerular cells release renin in response to:
- drop in BP - sympathetic NS releases NE, binds B1 to release renin
- drop in BP - less stretch in afferent arteriole - stimulates release
- decrease in Na in distal tubule filtrate triggers macula densa to release prostaglandins - release renin
Describe how aldosterone gets into the cell. How does it make more Na channels?
aldosterone - cholesterol derivative - can pass through membrane
- receptor in cytoplasm: moves into the nucleus to stimulate transcription of genes to make more Na, K channels and Na/K pump
mostly occurs in the distal convoluted tubules
allows Na to move first and water follows
Describe intercalated cells A and B. Where are they found?
alpha cells: distal convoluted tubule and collecting duct
- secrete H
- reabsorb HCO3-
beta cells: distal convoluted tubule
- reabsorb H
- secrete HCO3-
