1 Intro + lab equations Flashcards
Describe the location of the kidneys
Abdominal cavity, retroperitoneal (adjacent to the posterior abdominal wall) between T12-L3
**right kidney lower than the left because of liver
What makes up a renal lobe?
Macroscopic subdivision consisting of the medullary pyramid (striated) and the surrounding cortex (granular)
**indistinct in adult kidneys
List the course an RBC would take from the aorta to the glomerulus
- renal artery
- segmental artery
- interlobar artery
- arcuate artery
- interlobular artery (in cortex)
- afferent arteriole
List the course an RBC would take from the glomerulus to the IVC
- efferent arterioles
- peritubular capillaries
- vasa recta
- interlobular vein
- arcuate vein
- interlobar vein
- renal vein
What proportion of the total body weight are the kidneys? What percent of cardiac output do they receive?
1% of total body weight but receive 20-25% of cardiac output
What proportion of the population has an additional renal artery?
30%
Describe the innervation of the kidney
- parasympathetic
- kidneys and ureter= vagus
- ureter and urinary bladder= pelvic splanchnic nerves
- sympathetic
- kidney= T10-L1
- ureter= T11-L2
- urinary bladder= T11-L2
What are the 3 most common places where kidney stones get lodged?
- ureto-pelvic junction (where ureter leaves the kidney)
- where the ureter crosses the pelvic brim
- the angled entrance of the ureter into the urinary bladder
Where is referred pain from the kidney and ureter perceived?
T10-L2 spinal cord distribution
What are the functions of the kidney?
- excretory
- water, ions, drugs/toxins, metabolic breakdown products
- homeostatic
- regulate/maintain ECF volume and composition
- acid base balance (bicarb and H)
- endocrine
- monitoring O2 carrying capacity (erythropoietin)
- regulating blood pressure (RAAS)
Describe the renal medulla
- Striated appearance
- Consists of 6-18 renal pyramids
- Apex/tip called a renal papilla
Describe the renal cortex
Granular in appearance (homogenous consistency)
What is a Medullary ray?
Linear arrays of tubules extend into the cortex from the medulla
What is a renal lobule?
A microscopic subdivision consisting of a medullary ray and the cortical tissue (primarily nephrons*) on either side
*tubules of these nephrons connect with the collecting ducts within the medullary rays
What is the tubular plexus and vasa recta?
Capillary systems of the kidney…
- tubular plexus supplies tubules of cortical nephrons
- vasa recta (long) supplies tubules of juxtamedullary nephrons
What are the 4 components of the renal corpuscle?
- glomerulus
- visceral layer (Bowman’s)
- parietal layer
- mesangium
**only found in the kidney cortex
What is a renal corpuscle? Where are they found?
Spherical double layered sac surrounding a network of capillaries (glomerulus)
**renal corpuscles are found only in the kidney cortex
Compare the afferent and efferent arterioles
- afferent
- supplying arteriole
- larger diameter
- efferent
- draining arteriole
- smaller diameter
**difference in size creates a pressure differential that drives glomerular filtration
What are the portions of Bowman’s Capsule?
- parietal layer (simple squamous)
- visceral layer (simple squamous) composed of podocytes
- urinary space= space between parietal and visceral (continuous with the proximal tubule)
Describe the components that make up the filtration barrier of the kidney
- capillary endothelium (discontinuous, 70-100 nm pores)
**luminal surface= negative due to Heparan glycocalyx - basement membrane (primary barrier preventing protein from entering filtrate)
- podocytes (foot processes and filtration slits)
Describe the glomerular mesangium
- physically supports the glomerulus
- regulates glomerular blood flow
- ECM contains fibronectin and collagen
- specialized pericyte/smooth muscle cells
Describe the proximal tubule
- convoluted (cuboidal/columnar) portion
- straight (cuboidal) portion aka thick decending limb of henle
- glucose, AAs, and proteins reabsorbed through facilitated transport
- apical brush border with glycocalyx obscures the lumen and aids in absorption
- numerous mitochondria at base of cell provide energy for transport
What are the 4 parts of the loop of henle?
- striaght portion of the proximal tubule (thick descending limb)
- thin descending
- thin ascending
- straight portion of the distal tubule (thick ascending limb)
Describe the loop of henle
- located in the medulla
- length is determined by location of corpuscle
- cortical= short loops (only a descending thin limb)
- juxtamedullary= long loops (ascending and descending thin limbs)
- thick= cuboidal, thin= simple squamous
- thin ascending= impermeable to water
Describe countercurrent multiplier
- carried out through the loops of henle
- the process of urine concentration through differential reabsorption of water
- yields hypotonic fluid in the distal tubule (thin ascending limb is impermeable to water)
Describe countercurrent exchanger
- carried out by the vasa recta
- the process of maintaining the osmotic gradient established by countercurrent multiplier
- arterioles have continous endothelium and venules are fenestrated (preserve gradient while still supplying blood)
Describe the straight portion of the distal tubule
- aka the thick ascending limb of the loop of henle
- lined with cuboidal epithelium with scant microvilli and efficient tight junctions
- abundant mitochondria
- impermeable to water
- Na, Cl resorbed, H secreted
Describe the convoluted portion of the distal tubule
- aka early distal tubule
- lined with cuboidal epithelium with scant microvilli
- fewer basal interdigitaions and mitochondria
- Na, Cl resorbed, K secreted
Describe the collecting tubules
- aka late distal tubule (just before the collecting duct)
- cuboidal epithelium contains principle cells
- ADH dependent (Na reabsorbed, K secreted)
Describe the collecting duct
- distinct cell borders between cuboidal (or columnar) cells
- principal cells= light
- primary cilium (flow sensor)
- mediated by polycystin 1 and 2
- ADH sensitive aquaporins
- water flows out of duct into renal interstitium in the presence of ADH
- primary cilium (flow sensor)
- intercalated cells= dark
Describe the juxtaglomerular apparatus
- renin producing (JG) cells
- specialized smooth muscle in the wall of the afferent arteriole
- respond to macula densa signaling (alter filtration rate via RAAS)
- extraglomerular mesangial (lactis) cells
- connected to JG cells via gap junctions
- macula densa
- columnar cells in the distal convoluted tubule
- detect Na and Cl concentrations for JG cells
Describe the layers of the calyces/pelvis/ureters
mucosal layer:
- transitional epithelium
- lamina propria (abundant elastic tissue)
muscularis layer:
- smooth muscle
adventitia layer (fibrous connective tissue)
Describe the layers of the urinary bladder
Transitional epithelium + 3 layers of smooth muscle
(empty= thick, full= thin/stretched)
What is the calculation for renal clearance?
C= (U x UF)/P
**the volume of plasma that is completely cleared of the substance by kidneys per unit time (building/room analogy)
- C= clearance
- U= urine concentration
- UF= urine flow rate
- P= plasma concentration
What is the calculation for osmolar clearance?
Same as renal clearance, but looking at the clearance of all osmotically active substances (not just one specific one)
C(osm)= (Uosm x UF)/Posm
What is the calculation for free water clearance?
C(H2O)= UF - C(osm)
**the rate at which solute-free water is excreted by the kidneys (usually negative because urine osm is higher than plasma)
- C(H2O)= free water clearance
- UF= urine flow
- C(osm)= osmolar clearance
How can you quantify renal excretion?
Looking at the excretion rate of a specific substance:
Excretion= U x UF
(U= urine concentration, UF= urine flow)
What is fractional excretion?
FE=(U x UF)/(P x GFR)
**The percentage of a substance filtered by the kidney which is excreted in the urine
(helps us understand the tubular activity; damage can decrease reabsorption which would increase FE)
