lecture 15 and 16: the renal system Flashcards
1
Q
main parts of renal system
A
kidneys
ureters
bladder
prostate
urethra
2
Q
kidney function
A
-blood vol+electrolytes
-remove urea from blood
-conserve nutrients
-regulate BP
regulate AB balance
-calcium homeostatsis
-production of erthropoietin and renin
3
Q
what passes through the middle of the kidneys
A
vena cava and aorta which splits into renal artery and renal vein
4
Q
what sits at the top of the kidneys
A
adrenal gland
5
Q
what is the glomerulus
A
special capillary bed adapted for filtration
6
Q
what does the wide afferent arteriole do
A
supplies each glomerulus
7
Q
what does the narrow efferent arteriole do
A
drains each glomerulus
8
Q
how much blood passes through glomeruli each min
A
1200ml (650 is plasma)
9
Q
how much blood forced into renal tubules
A
120-125ml
10
Q
how much blood reabsorbed
A
119-124ml
11
Q
what is the urine path
A
glomerulus, bowman’s capsule, PCT, loop of Henle, DCT, collecting tubule, collecting ducts, calyces, renal pelvis, ureter, urinary bladder, urethra
12
Q
what are the 3 jobs of the nephron
A
- glomerular filtration
- tubular reabsorption
- tubular secretion
13
Q
what’s glomerular filtration
A
passively dumping all blood nutrients and ions
14
Q
what’s tubular reabsorption
A
actively taking back required nutrients and ions
15
Q
what’s tubular secretion
A
actievly dumping selective nutrients
16
Q
2 structures involved in glomerular filtration
A
- endothelial fenestrations (50-100nm)
- slit diaphragm, glomerular basement membrane and glycocalyx
17
Q
what do endothelial fenestrations do
A
lets through everything but cells
18
Q
what do slit diaphragm, glomerular basement membrane and glycocalyx do
A
lets through everything but protein
19
Q
what is glomerular filtrate
A
plasma without protein (mainly albumin) or cells
20
Q
GFR
A
120-125ml per min forced into renal tubules in both kidneys
21
Q
what is GFR controlled by
A
- vasoconstriction of arterioles
- contraction state of glomerular mesangial cells (more membrane to filter through)
- filtration membrane permeability (podocytes)
22
Q
which processes are passive and which are active
A
filtration- passive
reabsorption- active
Na+ conc- active
secretion- active
water reabsorption- active
23
Q
what kind of organ is the kidney
A
multilobed and retroperitoneal
24
Q
what do the medulla and cortex regions do
A
contain and support structure of nephrons
25
why are the kidneys heavily vasculated
max filtration at nephron
26
what do nephrons consists of
glomerular (bowmans) capsule, PCT, loop of Henle, DCT, collecting ducts
27
what does bowmans capsule contain
the process of passive blood filtration
28
what does the rest of the nephron do
supports active tubular reabsorption and secretion
29
how longs are the ureters
approx 20cm, either side of vertebral column
30
what happens as urine enters renal pelvis
peristalitic waves initiated force urine into ureter
30
what do the ureters do
convey urine from kidneys to bladder
31
what stimulates contraction of the ureter
distension
32
what are the 3 wall layers of the ureter
inner mucosa, muscularis, outer adventitia
33
what do ureterovesical valves do
prevent urine from flowing back towards kidneys
34
how much urine can the baldder hold
500ml (max 1000ml)
35
bladder shape
-pyramid when empty
-pear shaped when full
36
3 layers of the bladder
1. mucosa with transitional epithelium
2. mucosal layer with longitudinal and circular muscles (elastic walls)
3. fibrous adventitia
37
internal urethral sphincter
-smooth muscle
-opens involunatrily when bladder reaches certain distension level
-opening resulting in needing to urinate
38
external urethral sphincter
-skeletal muscle
-voluntarily opened to allow urine to pass through urethra
-may be held closed to delay urination
39
what does the male prostate do
produces semen and controls switch between urination and ejaculation
40
what does the internal urethral sphincter in males do
stops semen entering bladder during ejaculation
41
what are the 3 parts of the external urethral sphincter
1. sphincter urethrae
2. urethrovaginal muscle
3. compressor urethrae
42
what is the spongy urethra
extended flexible section after the external sphincter
43
what does the SNS do
senses bladder stretch and relaxes bladder then internal sphincter
44
what does relaxation of internal sphincter do
sends signal to brain that you have to pee
45
what does the PNS do
controls external sphincter which automatically contracts bladder
46
what gives urine a yellow colour
urobilin/urochrome which is a pigment resulting from haemoglobin breakdown (microbiome degredation of bilirubin)
47
what are the 2 different circumstances for diuresis
water dieuresis and osmotic diuresis
48
water diuresis
more water ingested than body requires
49
osmotic diuresis
more soulte that normal excreted
50
what are diuretics
drugs that increase excretion of water and NaCl due to action on kidney
51
what do diuretics indirectly do
modify composition of filtered fluid (osmotic diuretics)
52
what do diuretics directly do
act of cells of nephron, esp those most involved in NaCl reabsorption (e.g. caffeine)
53
what is micturition
process of releasing urine from bladder through urethra
54
when does urination begin
when the muscles of the urethral sphincters relax, allowing urine to pass through urethra
55
what happens at the same time the sphincters relax
the smooth muscle in the walls of the bladder contract to expel urine from the bladder
56
what is urine made up of
mostly water with some ions, urea and uric acid
57
how can micturition be accelerated
through diuretics
58
how does the urinary system mainatin homeostasis of the organism
1. urea removal from bloodstream
2. control of water and ion balance in bloodstream
3. BP regulation
59
what causes changes in osmolarity
constant fluid loss and ion gain from food
60
which ions does the kidney control the excretion of into urine
potassium, sodium, calcium, magnesium, phosphate, chloride
61
how do the kidneys conserve ions
increase their reabsorption into blood during filtration
62
how do the kidneys control pH
monitor and regulation levels of H+ and bicarbonate ions in blood
63
H+
-metabolite of dietary protein
-excrete excess H+ in urine for elimination
64
bicarbonate ions
-conserved by kidneys
-important pH buffers in blood
65
what is the osmolarity of a solution
total number of dissolved particles in a solution
66
whats the standard body fluid osmolarity
280-200 mOsml/L
67
mOsmol/kg= mOsmol/L
n x mmol= n x mM
67
isotonic solution
ion control transporters tightly regulated and usually co-transport to maintain osmolarity
68
isosmotic solution
transporters generally want as much gluscose as possible (can be insulin induced)
69
what are 2 important regulatory cells
juxtaglomerular cells (granule cells)
macula densa cells
70
what are granule cells
smooth muscle cells surrounding the afferent and efferent arterioles- composed of granules containing renin
act as mechanoreceptors that sense the BP in the arteriole
71
what are macula densa cells
distal tubule cells that act as chemoreceptors or osmoreceptors that respond to changes in solute conc of filtrate in distal tubule
-sense low GFR, triggering renin-angiotensin-aldosterone system
72
what is GFR interlinked with
BP
73
why is constant GFR important
allows kidneys to make filtrate and maintain extracellular homeostasis
74
what does increased GFR do
causes increased urine output which lowers BP and vice versa
75
what are extrinsic controls
NS and endocrine mechanisms
76
what are intrinsic controls
myogenic mechanism and tubuloglomerular feedback mechanism
77
what are the 4 GFR mechanisms for homeostasis
1. myogenic mechanism
2. tubuloglomerular feedback mechanism
3. renin-angiotensin-aldosterone mechanism
78
myogenic mechanism
-decreased BP causes dilation of afferent arterioles
-increased BP causes muscle to stretch, leading to constriction of afferent arterioles
-restricts blood flow into glomerulus
-protects glomeruli from damaging high BP
-both help maintain normal GFR despite normal fluctuations in BP
79
tubuloglomerular mechanism
-flow-dependent mechanism directed by macula densa cells
-respond to filtrate’s NaCl increases
-if GFR increases, filtrate flow increases
-leads to decreased reabsorption time, causing high NaCl levels in filtrate
-feedback mechanism causes constriction of afferent arteriole, which lowers NFP and GFR, allowing more time for NaCl reabsorption
-opposite mechanism for decreased GFR
80
reinin-angiotensin-aldosterone mechanism
main mechanism for increasing BP
3 pathways to renin release by granular cells
1. direct stimulation of granular cells by SNS
2. stimulation by activated macula densa cells when filtrate NaCl conc is low
3. reduced stretch of granular cells
81
osmotic homeostasis to incream BP
ADH (aka vasopressin) produced by hypothalamus and released from pituitary gland in response to:
-hyperosmolarity sensed by hypothalamus (too much fluid in blood)
-angiotensin II (peptide that increases BP)
release is stopped by high BP (-ve feedback)
82
how is BP increased
1. increasing water reabsorption of collecting ducts
2. increases urea reabsorption in collecting ducts
3. increase in sodium absorption in ascending loop of Henle
-also vasoconstricts blood vessels- stops sweating etc.
83
when do osmoreceptors in hypothalamus become more active
when water levels fall
84
whats ADH
hormone released to prevent excess water loss in urine by causing duct cells to reabsorb more water
