11/28: Urinary System II Flashcards
What is the first segment of the renal tubule?
Proximal convoluted tubule
Where does the proximal convoluted tubule begin?
At the urinary pole of the glomerulus
Where is a majority of the glomerular filtrate reabsorbed?
PCT (70%)
What is the loop of henle continuous with?
PCT in cortex
Where does the loop of henle travel?
Into the medulla, then back to the cortex
Where does the loop of hele empty into?
Distal convoluted tubule (DCT)
What does the loop of henle form?
A hair-pin structure that dips down into the medulla
What 4 segments are contained in the loop of henle?
Pars recta (straight/thick descending limb of proximal tubule)
Thin descending limb
Thin ascending limb
Thick ascending limb
What do the thick and thin segments denote?
Epithelial change (cuboidal to squamous) in both the descending and ascending limbs
Where does the turn of the loop of henle occur?
In the thin segment within the medulla
Where does the tubule ascend after the turn in the loop of henle?
Towards the cortex parallel to the descending limb
What does the end of the loop of henle become?
The distal convoluted tubule near its original glomerulus
What is the area in the loop of henle where it runs parallel into capillary loops known as?
Vasa recta
What does the loop of henle serve to create?
High oscmotic pressure in the renal medulla via the counter-current multiplier system
What is high osmotic pressure important for?
Reabsorption of water in the later segments of the renal tubule, helps create hypertonic urine (excretion of excess solutes)
Where does the bulk of the loop of henle extend into?
Medulla; variable length
Describe the length of thin limbs
Long in juxtamedullary nephrons
Short in cortical nephrons
What kind of epithelium does thin limb have?
Simple squamous
What kind of epithelium does thick limb have?
Simple cuboidal epithelium
What does the pars recta have?
Brush border of apical microvilli (like PCT)
What is the loop of henle surrounded by?
Peritubular capillary network, vasa recta
What does the countercurrent multiplier function to generate?
High osmotic pressure in ECF of renal medulla via Na-K pumps in thick ascending limb of loop of henle
Where is extracellular Na quantities higher?
Medulla combined with water resorption by proximal convoluted tubule in cortex (cortico-medullary interstitial gradient)
What does counter current (exchange) multiple system of urine concentration result in?
Production of hypertonic urine
What is the loop of henle’s vascular component?
Vasa recta
What does the vasa recta arise from?
Efferent arterioles of juxtamedullary nephrons
What surrounds all loops of henle (regardless of whether cortical or juxtamedullary nephrons)?
Vasa recta
What has the concentration of the interstitium?
Loop of henle
What is a continuation of thick ascending limb of loop of henle; present within cortex?
Distal convoluted tubulel
What epithelium is the DCT?
Simple cuboidal epithelium with short apical microvilli
What does the DCT lack?
Distinct brush border
What is the DCT responsible for?
Active resorption of Na and Cl secretion of H & K ions
What two cell types is the DCT controlled by?
Principal cells
Intercalated cells
What is the function of principal cells?
Resorb - Na and water
Secrete - K
What is the function of intercalated cells?
Resorb- K, Cl
Secrete - H, HCO3-
What is important regualtors of acid-base balance?
Intercalated cells
What is the DCT controlled by?
Aldosterone (adrenal mineralcorticoid)
What receptors make up the juxtaglomerular appratus (JGA)?
Baroreceptor (pressure)
Chemoreceptor (Ion)
The JGA (juxtaglomerular apparatus) has specialized areas of?
Afferent arteriole and distal convoluted tubule
The JGA is used for what?
Regulate systemic blood pressure via renin-angiotensin-aldosterone system (RAAS)
What are the three components of the JGA?
Macula densa
juxtaglomerular cells
Extraglomerular mesangial cells
What is a thickened region on one side of the distal convoluted tubule?
Macula densa
What kind of epithelial cells does the macula densa contain?
Densely packed cuboidal to columnar epithelial cells
What kind of receptor does the macula densa contain?
Chemoreceptor sensitive to changes in [Na] in filtrate
What does a decrease in systemic BP cause?
Decrease in filtrate -> decrease [Na]
What are modified smooth mm cells in wall of afferent arteriole?
Juxtaglomerula cells
What do juxtaglomerular cells act as?
Baroreceptors; detect changes in blood pressure
What do juxtaglomerular cells produce?
Renin in response to decrease in blood pressure
What do juxtaglomerular cells convert?
Angiotensinogen to angiotensin I
What are flattened cells surrounding afferent and efferent arterioles?
Extraglomerular mesangial cells (lacis or polkissen cells)
What is the function of Extraglomerular mesangial cells (lacis or polkissen cells)?
Exact function is unclear; provide structural support & phagocytosis
What kind of feedback can extraglomerular mesangial cells assist in?
Tubular glomerular feedback (by transmitting signals from cells of macula densa to intraglomerular mesangial cells) whose contraction/relaxation may change glomerular filtration rate
What does the macula densa act as?
Sensor, regulating juxtaglomerular
function by monitoring Na+ &
Cl- levels in the DCT
A decrease in blood volume/pressure elicits…
secretion of renin by JG cells
Angiotensinogen ->
Active angiotensin
What does angiotensin cause?
Suprarenal glands to secrete aldosterone
What inhibitors are used for the treatment of hypertension (high bp)?
Angiotensin-convertinge nzyme (ACE) inhibitors
What pathway do Angiotensin-convertinge nzyme (ACE) inhibitors take to treat chronic hypertension?
Prohibit angiotensin I from converting to angiotensin II
What and where do collecting tubules receive liquid from?
Isotonic urine from DCT
What and where do collecting ducts receive liquid from?
Isotonic urine from collecting tubules
Where do collecting ducts leave the cortex?
In medullary rays and enter medulla
Where do collecting ducts open at?
papilla into minor calyx
What do collecting ducts play an important role in?
Final concentration of urine (interstitium and vasa recta)
What do lining cells in collecting tubules/ducts have?
Distinct intercellular borders
What shape are lining cells?
Cuboidal (smaller tubules) to columnar (larger ducts)
What is responsibe to antidiuretic hormone (ADH,vasopressin) and what is it released by?
Epithelium; posterior pituitary
What do epithelial cells contain?
Awuaporin 2 (AQP-2) transmembrane proteins
What regulates collecting ducts?
ADH
What are mutations in AQP-2 (do not respond to ADH) linked to?
Congenital nephrogenic diabetes inspidius
What causes hypertonic urine?
ADH - water lost from collecting ducts
What causes iso-/hypotonic urine?
Without ADH - ducts remain impermeable to water
What are collecting ducts/tubules lined by?
Cuboidal epithelium, cells have distinct borders and stain poorly
Describe the 4 steps towards the ureter?
Minor calyces -> major calyces -> renal pelvis -> ureter
What is the structure of the ureter?
Hollow tube with muscular walls
What is the ureter lined by?
Transitional epithelium
What is the ureter designed to be?
Distensible; withstand contact with fluid containing toxic substances
What does the ureter wall consist of?
Mucosa (epithelium and underlying CT)
Muscularis
Adventitia
What is the urinary bladder lined by?
Stratified urothelium
What is the surface layer of balloon cells linked by?
Desmosomes and tight junctions
What does the surface area of balloon cells have?
Deep clefts and vesicles that may increase surface area with distention
