Urinary System - Part 1 Flashcards
1
Q
what does the urinary system consist of?
A
- paired kidneys and ureters
- unpaired bladder and urethra
2
Q
functions of urinary system
A
- produces and excretes urine
- regulates electrolyte levels in extracellular fluid
- blood pressure regulation
- endocrine fxn
3
Q
how does the urinary system regulate blood pressure?
A
JG cells synthesize renin - initiates conversion of angiotensinogen to angiotensin 1
4
Q
endocrine fxn of urinary system?
A
peritubular capillary endothelial cells and interstitial cells (fibroblasts) in cortex and medulla synthesize erythropoietin
5
Q
describe capsule of kidney
A
thin CT w/ 2 layers:
- inner layer of myofibroblasts
- dense irregular CT
6
Q
what part of the kidney receives most of the blood supply?
A
cortex - 90%
7
Q
functional unit of the kidney
A
nephron + collecting tubule = uriniferous tubule
8
Q
how many nephrons in kidney?
A
~2 million
9
Q
how much of the cardiac output do kidneys receive?
A
20-25%
10
Q
hilum of kidney
A
concave region where renal pelvis is located - contains arteries, veins, lymphatics, nerves
11
Q
pelvis of kidney
A
cone-shaped expansion of the upper end of the ureter continuous w/ major renal calyces
12
Q
contents of renal cortex
A
mostly:
- renal corpuscles
- convoluted tubules (mostly PCT)
13
Q
renal column
A
extensions of cortical tissue that run b/w adjacent renal pyramids
14
Q
medullary rays
A
groups of straight tubules that extend from the base of each renal pyramid into the cortex
15
Q
renal/medullary pyramids
A
- pyramidal structures that make up most of renal medulla
- 10-18 renal pyramids/kidney
- consist primarily of thin limbs of Henle and collecting tubules
16
Q
renal papilla
A
- at apex of each renal pyramid
- perforated tip projects into minor calyx lumen
- lined by transitional epithelium
17
Q
what is the perforated tip of the renal papilla called?
A
area cribrosa
18
Q
renal interstitium
A
- sparse (extravascular-intertubuler spaces)
- mostly fibroblasts and mononuclear cells
19
Q
what do fibroblasts near peritubular capillaries produce?
A
erythropoietin
20
Q
what renal interstitium cells are found along blood vessels supplying loops of Henle?
A
pericytes
21
Q
what renal interstitium cells are found b/w loops of Henle and collecting ducts and vasa recta
A
interstitial cells
22
Q
describe interstitial cells
A
- elongated nuclei with lipid droplets
- may synthesize medullipin I
23
Q
medullipin I
A
vasodilator converted to medullipin II in the liver
24
Q
renal lobule
A
area of cortex bounded on either side by an interlobular artery - all nephrons in each lobule drain to same collecting duct
25
what do nephrons consist of?
- renal corpuscle
- PCT
- LOH
- DCT
26
two classifications of nephron
cortical or juxtamedullary (depends on renal corpuscle location)
27
cortical nephron
- in outer part of cortex
| - short LOH, peritubular capillaries
28
juxtamedullary nephron
-long LOH that run w/ vasa recta far down into medulla
29
what are juxtamedullary nephrons responsible for?
establishing the interstitial concentration gradient in the medulla
30
outer zone of medulla
- outer stripe: thick limbs, collecting ducts
| - inner stripe: thick and thin limbs, collecting ducts + hairpin turns of cortical nephrons
31
inner zone of medulla
all thin limbs and collecting ducts
32
how quickly does all the blood in the body pass through the kidneys?
4-5 minutes
33
blood circulation in the kidneys (pathway)
renal artery enters in hilum -> interlobar a. b/w renal pyramids -> arcuate a. along the corticomedullary jxn -> interlobular a. that enter cortical tissue and travel b/w medullary rays -> afferent/glomerular arterioles -> glomerulus -> efferent arterioles
34
what defines the boundaries of a renal lobule?
adjacent interlobular arteries
35
how does kidney blood circulation differ from normal circulation?
typical: arteriole -> capillary -> venule
kidney: afferent arteriole -> capillaries of glomerulus -> efferent arteriole -> capillary network -> venule
36
what do afferent arterioles supply?
glomerular capillaries
37
what do efferent arterioles associated with cortical and midcortical nephrons give rise to?
extensive peritubular capillary network high in cortex and vasa recta near the corticomedullary jxn
38
describe anastamoses b/w interlobar arteries
there are none - blood cannot shunt around an infarct -> focal necrosis
39
what do vasa recta arise from?
efferent arterioles supplying juxtamedullary nephrons
40
describe vasa recta
long, thin vessels that follow straight path in medulla and renal papilla -> form capillaries -> loop back -> increase in diameter toward the corticomedullary boundary
-closely associated w/ LOH
41
fxn of vasa recta
- supply nutrients and oxygen
| - COUNTERCURRENT EXCHANGE w/ interstitium
42
what do stellate veins drain
formed by convergence of superficial cortical veins which drain the outermost cortex layers
43
what do deep cortical veins drain
drain the deeper regions in the cortex
44
what do interlobular veins drain
- receive both stellate and deep cortical veins
| - join arcuate veins -> interlobar veins -> renal vein in hilum of kidney
45
what does a renal corpuscle consist of?
glomerulus and bowman's capsule
46
bowman's capsule layers
- parietal layer: simple squamous epithelium on outer wall
| - visceral layer: modified simple squamous epithelium of podocytes covering glomerular capillaries
47
what is the space in b/w the visceral and parietal layers of bowman's capsule?
bowman's space aka urinary space
48
what is the vascular pole of bowman's capsule?
where afferent and efferent glomerular arterioles enter and leave the glomerulus
49
what is the urinary pole of bowman's capsule?
where urinary space becomes continuous w/ PCT lumen
50
what is the renal glomerulus?
capillary tuft that extends into bowman's capsule
51
describe glomerulus endothelium and basal lamina
fenestrated endothelium with thick basal lamina shared with podocytes
52
what makes up the interstitial tissue b/w glomerular capillaries on inside of bowman's capsule?
mesangial cells and amorphous extracellular matrix
53
5 functions of mesangial cells
1. mechanical support for capillaries
2. TURNOVER OF GLOMERULAR BASEMENT MEMBRANE
3. regulare blood flow (contractile) - decrease filtration SA
4. source of prostaglandins and endothelins (constriction of afferent and efferent arterioles)
5. respond to angiotensin II and atrial natriuretic peptide
54
how can mesangial cells contribute to immune response?
can proliferate and synthesize matrix material and collagen -> Ig's and complement can enter mesangial matrix and induce cytokine production by mesangial cells -> triggers immune response
55
what are podocytes?
modified epithelial cells - have primary and secondary processes - that form visceral layer of bowman's capsule
56
pedicels
secondary processes that wrap around glomerular capillaries and interdigitate w/ pedicels from other primary processes
57
what is the transmembrane protein in pedicels?
podocalyxin - transmembrane sialoglycoprotein that extends into glycocalyx coating
58
function of podocalyxin?
contributes to negative charge in glomerular epithelium
59
what does the renal filtration barrier consist of?
- glomerular capillary fenestrated epithelium
- basal lamina
- filtration slits w/ diaphragms b/w pedicels
60
filtration slits
-nephrin anchored to actin filaments in pedicels
61
what type of protein is nephrin?
member of Ig superfamily
62
what anchors nephrin to actin filaments in pedicels?
protein CD2AP
63
describe basement membrane of filtration slit
negatively charged due to GAGs - repels negatively charged proteins
64
what can and cannot pass from blood into the urinary space?
- can: water, ions, small molecules (< 3.5 nm)
| - canNOT: large or negative proteins
65
what is urine?
an ultrafiltrate of blood plasma?
66
PCT
- drain bowman's space at urinary pole
- lined by simple cuboidal epithelium
- microvillus brush border
- pinocytotic vesicles
- abundant lysosomes (acid phosphatase)
- many infoldings of plasma membrane near base of cell
67
function of brush border, pinocytotic vesicles, and lysosomes in PCT
uptake and breakdown of peptides to aa's
68
fxn of PCT (3)
- reabsorb all glucose, aa's, small proteins, 80% of NaCL and water from filtrate
- secrete organic acids (creatinine) and bases, some foreign substances
- exchanges H+ ions in the interstitium for HCO3- in the filtrate
69
what establishes the osmotic gradient for water absorption in PCT?
transport of NaCl and glucose
70
describe osmolarity changes in ultrafiltrate in PCT
no change
71
describe descending thick limb of LOH
- proximal tubule straight portion (pars recta)
- simple cuboidal epithelium
- less lysosomes
- smaller mitochondria
- prominent brush border similar to PCT
72
what is absorbed in descending thick limb?
water (NaCl NOT absorbed)
73
describe thin limb of LOH in JM nephrons vs. cortical nephrons
JM: descending segment, loop, ascending segment
cortical: may only have a thin descending segment
74
lining of thin limb of LOH
simple squamous epithelium - cells bulge into lumen
75
describe permeability of descending thin limb
permeable to water - ultrafiltrate will equilibrate w/ renal interstitium
76
describe permeability of ascending thin limb
impermeable to water - Na-K ATPase pump reabsorbs NaCl
77
fxn of diuretics (ex: furosamide)
inhibit reabsorption of NaCl -> increase excretion of NaCl and water
78
describe ascending thick limb of LOH
- straight portion of distal tubule
- cuboidal epithelial cells w/ apical nucleus
- mitochondria comparmentalized w/i basal plasma membrane infoldings
- returns to renal corpuscle of origin
79
what is different about the area of the ascending thick limb near the afferent and efferent arterioles?
becomes modified to form the macula densa - part of juxtaglomerular apparatus
