Unit 7 - Urinary System Flashcards Preview

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Flashcards in Unit 7 - Urinary System Deck (56)
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functions of kidneys

1. clear blood of metabolic waste products
2. regulate fluid and electrolyte balance
3. produce renal erythropoietic factor and renin
4. hydroxylate vit D to active calcitriol


kidney location

retroperitoneally on posterior wall of abdominal cavity on either side of vertebral column


kidney hilus

concave medial border w/ ureter, nerves, blood, and lymphatic vessels


renal sinus

large cavity surrounded by kidney parenchyma
-contains renal pelvis, loose CT, adipose, blood vessels, and nerves


renal pelvis

expansion of upper end of ureter that subdivides into minor and major calyces


kidney capsule

consists of dense irregular cT


renal cortex

darker, granular tissue
-broad outer zone
-inward extensions (renal columns of Bertin)


minor VS major calyces

major: arise from renal pelvis
minor: arise from major


renal medulla

lighter, striated tissue
-made of renal pyramids and medullary rays


renal pyramids

in medulla
-apices (renal papillae) project into minor calyces
-tip is perforated by openings of collecting ducts (area cribosa)
-each pyramid together with its surrounding cortical tissue constitutes a renal lobe


renal lobe

renal pyramid + cortical tissue overlying its base and covering its sides
-each kidney contains 6 to 18 lobes


medullary rays

medullary tissue that projects up into cortex, consisting of collecting tubules and their accompanying proximal and distal tubules
-do NOT include renal corpuscles


renal lobule

medullary ray + surrounding cortical tissue



functional unit of kidney
-first part (Bowman's capsule to distal tubule) forms urine
-second part (collecting system) carries out final concentration of urinary solutes


components of nephron

1. Bowman's capsule
2. Proximal convoluted tubule
3. Loop of Henle
4. Distal convoluted tubule
5. Collecting tubules
6. Collecting ducts


Bowman's capsule components

thin-walled expansion at proximal end of nephron
-deeply indented by glomerulus
-visceral layer = podocytes and covers glomerular capillaries
-parietal layer = simple squamous epithelium
-urinary (capsular) space between both layers gets glomerular filtrate
-glomerular filtration barrier
-vascular pole = afferent arteriole enters, efferent arteriole leaves
-urinary pole = proximal tubule begins


components of glomerular filtration barrier

in Bowman's capsule
1. capillary endothelium (fenestrated, w/o diaphragms)
2. shared basement membrane (endothelium + podocytes)
3. filtration slits between secondary processes of podoccytes
4. produces glomerular filtrate (similar to blood, except little protein)


what is proteinuria caused by?

release of protein into urine due to defect in glomerular filtration barrier (usually doesn't let PRO in)


where is urinary space continuous with proximal tubule lumen?

at urinary pole of Bowman's capsule


proximal tubule composition

convoluted (close to renal corpuscle of origin) and straight part (enters medullary ray)
-lined by simple cuboidal epithelium with brush border
-eosinophilic cytoplasm
-extensive lateral extensions (cell boundaries indistinct b/c large cells)
-lumen has fine precipitated material


how many segments can the proximal tubule be subdivided into by electron microscopy?

can be subdivided into 3 segments by electron microscopy


loop of Henle composition

descending straight proximal (simple cuboidal epithelium with brush border, like convoluted), thin segment (simple squamous, like capillary w/o blood), and ascending straight distal
-located in medulla


distal tubule composition

ascending straight portion (last part of LoH), portion adjacent to renal corpuscle of origin, and convoluted part
-mainly in cortex
-simple cuboidal epithelium that lacks brush border
-cells smaller than proximal tubule, with apical nuclei
-less eosinophilic than proximal tubule
-no precipitate in lumen
-same extensive lateral extensions (indistinct boundaries) like in proximal


collecting tubules and ducts composition

tubules in cortex, and ducts in medulla
-cuboidal epithelium in tubules, columnar in ducts
-cells have clear, pale-staining cytoplasm
-intercellular boundaries are clearly visible
-largest ducts (papillary ducts) communicate with minor calyx at area cribosa)


3 types of nephrons

classified according to position of renal corpuscles in cortex
1. superficial (cortical) nephrons - short LoH that extend short distance into medulla
2. juxtamedullary nephrons - long LoH penetrate deep in medulla (most important for hypertonic urine)
3. intermediate (midcortical) nephrons have intermediate characteristics


what does the juxtaglomerular apparatus do? its components?

responsible for renin production
-located where distal tubule returns to its renal corpuscle of origin
--macula densa in wall of distal tubule
--juxtaglomerular cells: modified smooth muscle cells in tunica media of afferent arteriole
--extraglomerular mesangial cells (lacis cells): pale staining cells in angle between afferent and efferent arterioles


explain the renin-angiotensin system

regulates fluid and electrolyte balance and blood pressure
-when BP falls, juxtaglomerular cells release renin, that converts angiotensinogen (from liver) to AI to AII (by ACE in capillary endothelial cells of lungs)
-AII stimulates zona glomerulosa of adrenal cortex to make aldosterone to stimulate distal tubule to reabsorb Na and H2O
--reabsorption increases intravascular fluid volume, which raises blood pressure
--AII is also a vasoconstrictor
-renin also has localized effect on afferent arterioles (provides for single nephron GFR control)


what does the macula densa do?

senses changes in NaCl concentration in distal tubule
-high [NaCl] inhibits renin secretion
-low [NaCl] stimulates renin secretion


what are extraglomerular mesangial cells?

play a supportive role in the renin-angiotensin system
-may provide signal integrating system


how much of total cardiac output goes to kidneys?