Urinary Anatomy

Question 1

Where are the kidneys locate?

Answer 1

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

Question 2

What do the pronephros, mesonephros, and metanephros do and what do they develop into?

Answer 2

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

Question 3

What does the nephron develop from?

Answer 3

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

Question 4

Where is the best place to transplant a kidney?

Answer 4

R iliac fossa
- blood vessels are attaches to the external iliac and the ureter is shorter

Question 5

What does the hilus in the kidney contain?

Answer 5

renal artery and vein
ureter

Question 6

What does the renal sinus contain?

Answer 6

minor and major calyces
renal pelvis - where major calyces come together
adipose tissue in renal sinus

Question 7

What is the difference between the juxtamedullary nephron and cortical nephron?

Answer 7

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

Question 8

describe the blood flow from the renal artery to peritubular capillaries

Answer 8

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

Question 9

What is cap bed 1 and cap bed 2 in the renal system?

Answer 9

Cap bed 1 - glomerulus
- blood from afferent arteriole

Cap bed 2 - peritubular capillaries
- blood from efferent arterioles
- important for secretion and reabsorption

Question 10

There are two fates of the efferent arteriole. What are they and where are they located?

Answer 10

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

Question 11

How do the arterioles, glomeruli affect pressure of the kidneys?

Answer 11

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

Question 12

Describe the filtration membrane of the kidney. What is is made of? How do these structures filter the filtrate?

Answer 12

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

Question 13

Describe the proximal convoluted tubule. What kind of ET does it have? Describe its folding and how it helps its function

Answer 13

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

Question 14

How can you tell the difference between the collecting duct and distal tubule histology?

Answer 14

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

Question 15

What are the structures that are only found in the cortex?

Answer 15

blood vessels:
cortical radiate
afferent arteriole
efferent arteriole
glomerulus
peritubular capillaries

nephron/collecting duct:
Bowman’s capsule
proximal convoluted tubular
distal convoluted tubule

Question 16

What are the structures that are found in the medulla only?

Answer 16

blood vessels
- interlobar arteries
- vasa recta

nerphon/collecting duct:
papillary ducts - located at tips of medullary period

Question 17

What structures are i both the cortex and the medulla?

Answer 17

arcuate artery - in between, but no other vessel is shared

collecting ducts

nephron loops: long nerphon loops

Question 18

What happens at these different points of the nephron: proximal convoluted tubule, nephrons loop, distal convoluted tubule, collecting ducts

Answer 18

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

Question 19

Where is the first place of filtrate? What structures are involved?

Answer 19

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

Question 20

What are the structures in the filtration membrane that filter particles out of the filtrate?

Answer 20

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

Question 21

What are the pressures that determine filtration pressure? How does that affect glomerular filtration rate?

Answer 21

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

Question 22

How does dilating/construction of the afferent and efferent arteriole affect GFR?

Answer 22

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

Question 23

What is the myogenic response in renal blood flow?

Answer 23

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

Question 24

What are juxtaglomerular cells? Where are they located? What does it release?

Answer 24

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

Question 25

What is the macula densa? Where is it located? What does it release?

Answer 25

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

Question 26

What is int he juxtaglomerular capsule? What are the extraglomerular meseangeal cells? Where are the located?

Answer 26

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

Question 27

What are the intraglomerular mesangial cells? How do they regulate filtration rate?

Answer 27

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

Question 28

Describe the MOA for renin.

Answer 28

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

Question 29

How does atrial naturietic peptide and brain naturietic peptide affect afferent arteriole hydrostatic pressure?

Answer 29

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

Question 30

Where does reabsorption occur? What kind of cells does this structure have? What features of this cell help its function?

Answer 30

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

Question 31

Describe how glucose and amino acidsreabsorption occurs. What kind of transport does it require?

Answer 31

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-

Question 32

How does K affect reabsorption?

Answer 32

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

Question 32

How does water and urea leave the filtrate?

Answer 32

water - moves through aquaporins depending on concentration gradient urea - leaves filtrate and is soluble in plasma membrane

Question 33

What is secretion in the PCT? What gets secreted?

Answer 33

peritubular capillary to filtrate - urea, uric acid, bile acids, catecholamines, some creatinine - drugs PCT can only SECRETE H and can only REABSORB HCO3-

Question 34

What happens to glutamine when it is in the PCT tubule cells?

Answer 34

enters cuboidal cell and gets deaminated, oxidized and acidified to create: NH4 (ammonia): added to filtrate HCO3-: returns to capillary via secondary active transport

Question 35

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?

Answer 35

BOTH have simple squamous descending loop: highly permeable to WATER ascending loop: impermeable to water - moderate permeability of urea and sodium

Question 36

Describe the thick segment of the ascending limb. What role does it play in creation of the extracellular osmotic gradient?

Answer 36

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

Question 37

How does the vasa recta relate to the nephron loop and how does it contribute to the cellular osmotic gradient?

Answer 37

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

Question 38

Compare the osmolality of the descending limb and the ascending limb of the loop of henle

Answer 38

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

Question 39

Once the filtrate reaches the collecting duct, what happens? What is the osmolality of the filtrate?

Answer 39

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

Question 40

Describe the effects of the following hormones and where they affect reabsorption: aldosterone, ADH, parathyroid hormone, calcitriol

Answer 40

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

Question 41

What are principle cells? Where are they located? What are they sensitive to? When these hormones bind, what happens?

Answer 41

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

Question 42

Describe aldosterone release. What regulates it?

Answer 42

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

Question 43

Describe how aldosterone gets into the cell. How does it make more Na channels?

Answer 43

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

Question 44

Describe intercalated cells A and B. Where are they found?

Answer 44

alpha cells: distal convoluted tubule and collecting duct - secrete H - reabsorb HCO3- beta cells: distal convoluted tubule - reabsorb H - secrete HCO3-