L1 Functional Microanatomy of the Kidney Flashcards
what’s homeostasis and what are its characteristics?
tendency to maintain relative constancy of physiological variables
- steady-state
- set-point
- negative & positive feedback
- error signal
- physiological range
what are the functions of the kidneys?
- regulation - homeostasis
- ECF volume and osmolality
- acid-base balance
- ECF K+ concentration
- divalent ion concentration
- blood pressure
- RBC mass
- skeletal integrity - excretion
- nitrogenous wastes
- dietary end products
- drugs and drug metabolites
- products of metabolism - endocrine function - hormone secretion
- erythropoietin (RBC synthesis)
- 1,25-OH vitamin D (active vitamin D for skeletal integrity)
- renin (catalyzes formation of angiotensin II) - metabolism
- ammonia synthesis from glutamine
- glucose synthesis from lactate
kidney gross anatomy
what are the major regions of the kidney?
- the cortex
- the medulla :
- outer medulla : outer and inner stripes
- inner medulla : papillary region and … - the calyces and pelvis : connect with the ureter
The kidney is covered by a ____ ____. The renal circulation is provided by the renal ____ and renal
____. The ____ ____ connects the kidney to the ureter, which ________________. The
renal ____, ____ and ____ join the kidney at the hilus.
The kidney is covered by a fibrous capsule. The renal circulation is provided by the renal artery and renal
vein. The renal pelvis connects the kidney to the ureter, which carries the putative urine to the bladder. The
renal artery, vein and pelvis join the kidney at the hilus.
what are the microvasculature steps?
blood comes in through renal artery → interlobar arteries → interlobular arteries → afferent arterioles (bigger than following) → efferent arterioles which can either become peritubular capillaries OR form the vasa recta
what are pericytes?
contractile cells at branch points that regulate blood flow through the capillaries
ultrafiltration occurs at ____ (located only in ____) passes along renal ____ → ____ ____ ____ → ____ ____ → ____ ____ → ____ ____ → ____ ____ → ____ ____
- walls of ____, ____ and ____ contain smooth muscle
- peristaltic contractions → help ________________ but cause ________________ → ________________
ultrafiltration occurs at glomeruli (located only in cortex) passes along renal tubule → loop of Henle → distal tubule → collecting duct → minor calyces → major calyx → renal pelvis
- walls of calyces, pelvis and ureter contain smooth muscle
- peristaltic contractions → help drive urine into and through ureter but cause some reflux of putative urine over epithelium that lines surface of papilla → further reabsorption
what are podocytes?
epithelial cells on the outside of the capillaries within the glomerulus - interdigitating foot processes ; form membranes which filter the plasma when under pressure
nephron (renal tubule) anatomy and main characteristics
- 1.2 million nephrons
- nephrons consist of 10+ cell types that form epithelial layer
- heterogeneity : superficial nephrons (90%, smaller glomeruli and shorter loop of Henle, lower single nephron glomerular filtration rate (SNGFR)) vs juxtamedullary nephrons (near junction of cortex + medulla) ; heterogeneity within each segment (different ultrastructures + transport activities)
glomerulus characteristics and function
- capillary tuft
- bowman’s capsule
function: ultrafiltration of large volumes of fluid (180 L/day)
proximal tubule characteristics and function
- convoluted part (early or S1 and late or S2)
- straight part (pars recta or S3)
function: reabsorption of most of the filtrate Na, K, Cl, urea, glucose, amino acids, acidification, secretion of organic acids + bases
loop of Henle characteristics and function
- thin descending limb
- thin ascending limb
- thick ascending limb (medullary = mTAL, cortical = cTAL)
function: dilutes urine + produces an osmotic driving force in the interstitium, which ultimately allows the concentration of urine
distal tubule characteristics and function
- convoluted part (early and late)
- connecting part
function: fine regulation of Na, K, Ca2-, and PO43- excretion; dilutes the urine
collecting duct characteristics and function
- cortical part (CCD)
- medullary part (outer OMCD + inner IMCD)
function: important site of regulated Na+ absorption, K+ and H+ secretion, site where osmotic concentration of final urine takes place
proximal tubule cell characteristics
- apical and basolateral surface has brush border → increases absorption
- interdigitate with neighboring cells
- segment is very active - many mitochondria
thick ascending limb characteristics
- where gradients are generated to concentrate urine
- many mitochondria
- suffers the most during kidney transplantation
collecting duct and main cells characteristics
- many different cell types
- principal cells : sodium absorption and water transport
- intercalated cells - acid-base balance (and K+)
practice question: the difference between superficial and juxtamedullary nephrons is that the former have their glomeruli in the cortex whereas the glomeruli of the latter arise in the medulla. True or False?
false all glomeruli are in the cortex.
