Excretion - kidney Flashcards
(123 cards)
1
Q
main function?
A
produce urine. they do this thru filtering the blood
2
Q
2 main purposes of kidneys?
A
filtering the blood and controlling the water potential in the body
3
Q
why is the kidney an excretory organ?
A
- the blood needs to be cleaned bc of the build up of toxic urea
- this is excreted as urine
4
Q
How can the kidney regulate the water potential of the blood?
A
by controlling how much water is in the urine
5
Q
cortex means?
A
Bark, the kidney cortex is the bark of the kidney
6
Q
the interior of the cortex is?
A
the medulla, which is a darker colour than the cortex
7
Q
there are pale branches of the medulla called the?
A
they are together called the renal pelvis. These collect urine and funnel it into the ureter
8
Q
the renal pelvis drains together ?
A
into a tube called the ureter, each kidney has its own ureter
9
Q
what does the ureter do?
A
Tube which carries urine to the bladder
10
Q
how is the kidney separated from other organs and protected from mechanical forces?
A
By a layer called the fibrous capsule
11
Q
what r nephrons?
A
messy tubes. MILLIONS in the kidney!!
12
Q
the Bowman’s capsule is what shape?
A
cup shaped
13
Q
how to remember PCT and DCT?
A
P in PCT means proximal so close to glomerulus, D in DCT means distal meaning far away
14
Q
ultrafiltration definition?
A
the filtration of blood at the molecular level under a high pressure
15
Q
blood supply to the glomerulus?
A
blood is supplied to the glom by the afferent arteriole
16
Q
blood leaves the glomerulus from the?
A
efferent arteriole (eff off = go away)
17
Q
after the glomerulus?
A
The efferent arteriole forms blood capillaries that surround the tubules of the kidney nephron -vasa recta
18
Q
the afferent arteriole is a branch of the?
A
renal artery
19
Q
feature of the efferent arteriole?
A
- smaller diameter than the afferent arteriole (smaller lumen)
- this means that the blood in the glomerulus is at a high HP
- so filtrate is ‘pushed’ into the Bowman’s capsule
20
Q
hydrostatic pressure is ?
A
the pressure that the blood exerts on the wall of the vessel
21
Q
The 3 major causes of kidney failure?
A
- diabetes
- hypertension
- infection
22
Q
what happens when kidneys fail?
A
- Can’t make excess fluids, can’t remove waaste products from blood - urea, excess salts e.g.
23
Q
any condition that lasts over 6 months is typically ?
A
chronic, acute is fast acting
24
Q
symptoms of kidney failure?
A
- urea accumulation - uremic frost
- low vol of urine production
- K+ accumulation - can lead to heart failure
- electrolyte imbalance
- TF accumulation - oedema
- Acidosis
25
what causes AKD?
injury, infection, necrosis of tissue, blockage of ureterer
26
what causes CKD?
diabetes, hypertension, inflammation of glommeruli - nephritis
27
treatments for kidney diease?
- dialysis
| - transplant
28
2 types of dialysis?
- Hameodialysis
| - peritoneal dialysis
29
Kidney transplant?
- old left in
- new ones connected to blood supply + bladder
- cure - no more dialysis
- lasts 10 -15 years
- but, immunosupressants for life, leaves open to infection
- long waiting lists
30
advantages of dialysis
- more available than transplants
- patioent can walk around
- can be done at home (PD)
31
disadvantages of dialysis
- incovenient - 3-4x a week
| - for life, not a cure
32
advantages of transplant
- cure
| - 10 -15 years
33
disadvantages of transplant
- immunosuppresants for life
- chance of organ rejection
- long waiting lists
34
dialysis: background?
- both types rely on allowing the patient's blood to come close to dialysis fluid, seperated by a partially permeable membrane
- allows substances to diffuse across the membrane from blood to dialysis fluid and VV
35
Haemodialysis?
- location
- where taken
- what's added
- temp
- happens oustide body, in machine
- bloodtaken from a vein/ small artery/ fistula
- runs through the machine (artifical membrane)
- hepatin added - anticoagulant/ thinner
- thermostatically controlled @ around 37 deg
36
Why is HD thermostatically controlled?
- blood cools dwn when out of the body - would give patient hypothermia
37
HD
- bubbles
- mechanism
- at home?
- bubbles removed then goes back into body
- 3-4x per week (3-4 hrs)
- counter current mechanism of blood and dialysis fluid - maintains steep CG
- can get take at home one but still heavy
38
mor protein in diet =
more dialysis needed
39
Peritoneal dialysis?
- location
- procedure
- happens inside body, inside perironeal cavity
- peritoeum - own abdominal membrane - contains guts so v good blood supply
- surgeon implants permanent tube into abdomen
- dialysis fluid poured into the tube, where it fills the space between the abdomen wall and organs
- fluid fills the peritoneal cavity
40
PD 2
- sessions
- mobility
- tie
- convience
- several sessions/ day
- patient can walk
- every day/ night, 4-6 times a day, 2.5 litres
- no needles needed, can be done at home
- not 'hooked up' to machine when fluid isn't being drained in and out
- temp kept constant, but less liquid so easier
- catheter hygiene
41
how are renal problems diagnosed?
GFR - glomerular filtration rate
Blood sample is analysed and the conc of creatinine is measured.
when [createnine] is high, GFR is low
when GFR is high, [creatinine] is low
42
what is creatinine?
- natural breakdown product of muscle protein - usually excreted in the urine
43
what does the GFR tell us?
- if GFR is high, the glomerulus is working properly
- will be a low [creatinine] in the blood as it's excreted in the urine
- vice versa
- more creatinine in the blood = worse kidneys
- this relationship can be used to estimate GFR in cm3min-1
44
GFR reduces with ?
age
45
What the GFR values actually mean?
- if GFR is , <60cm3min-1 for > 3 months = severe chronic kidney disease
- if GFR is < 15cm3mil-1 = kidney failure
46
hCG?
- hormome produced by a very early stage embryo - indicates pregnancy
- used in pregnancy tests
47
what do pregnancy tests rely on?
rely on specificity of antibodies
48
Things on a pregnancy test?
- immobilised Ab specific to AB/ pigment complex
- mobilised antibody/ pigment complex specific to hCG
- AB pigment/ hcG complex
- immobilised antibody spec yo Ab/ pigment/ hCG complex
49
+ pregnancy test
2 lines - in patient test region and procedural control region
50
- test ?
1 line in PCR
51
False +s?
- bc a n embryo may be big enough to show + (hCG is secreted) but that pregnancy might not work (might be in the wrong place)
52
false -s?
- too early in preg so embryo doesn't produce enough hCG
53
some tests can also?
- estimate the number of days since conception that the preg is
- hCG conc inc until 10th week, the conc of hCG varies depending on the week so the conc of measured to estimate the number of days
54
How are monoclonal antibodies made?
- antigen injected into mouse
- detected by B lymphocytes, plasma B cells formed
- Ab secreted
- Plasma cells can't /
- so plasma cells fused with myeloma cells
- these hybrid cells can secrete ABs and rapidly /
55
what happens after MAB are made?
- cloned, all cells produced secrere same ABs
| - the cells form a self renewing stock where all of the cells keep secreting the AB
56
anabolic sterioids background?
- cholesterol derived
- all sex hormones are ^
- are all lipid soluble - can diffuse directly into cells through plasma membrane
57
effect of steroids on cells?
- inc rate of protein synthesis
- leads to build up of tissue, espec muscles (muscle fibres get bigger: don't make more)
- decrease recovery time
58
side effects of steroids?
- body can shut down
- development of breast tissue due to high levels of testosterone
- agression
- inhibits IS
- liver damage
- acne
- balding
59
EPO?
- hormone that signals greater production of erythrocytes
- happens naturally at high altitudes
- Atheletes do this to inc erythrocyte count - altitude training
- made commercially
60
Anabolic steroids ?
detected using GS of urine/ mass spec
61
x40 mag =
250 um (graticule units)
62
x 400 mag =
25 um
63
x 600 mag =
17 um
64
How do preg tests work?
- hCG binds to mobile antibody/ pigment complex which is specific to hCG
- these complexes move upwards and bind to immobilised antibodies specific to AB/ pigment, hCG complex
- causes line in patient test region (+ result)
- these procedural control region contains immobilsed ABs which are spec to Ab/ pigment complex not hCG
- so line always present even if - result
mobile antibody pigment complexes bind here
65
Kidneys location?
* 2 kidneys,
* situated at the back of the abdomen, behind the digestive system and liver, just in front of the lower ribs.
* On top of each kidney is an adrenal gland
66
Input and output of blood in the kidneys ?
Input: renal artery
Output: renal vein
67
Kidneys and urine!
* Produce urine
* out of the ureters, and into the urinary bladder.
* Urine exits the bladder via the urethra during urination.
68
Overall function of kidneys?
* filter the blood, removing excess water, ions and urea.
* Urine is produced allowing these substances to be excreted.
* Useful substances like glucose and amino acids are reabsorbed back into the blood and not excreted.
69
renal =
kidney related
70
RA is a branch of the ?
aorta
71
renal vein is a branch of the ?
vena cava
72
cortex of kidney?
outer layer of tissue
73
medulla of kidney?
middle layer of tissue
74
capsule of kidney?
fibrous, tough, outer layer
75
medulla pyramid of kidney?
striations showing collecting ducts of nephrons and loops of Henle
76
in the middle of the kidney is?
pelvis which goes into ureter
77
What is a nephron?
the functional unit of the kidney - around 1x10^^ in each kidney
78
How many main regions in a nephron?
5
79
Region 1 - BC
• The Bowman’s capsule, containing the glomerulus, a ‘knot’ of capillaries - ultrafiltration
80
Region 2 - P
* PCT
| * Selective reabsorption
81
R3 : loop
The loop of Henlé - production of Na+ / Cl- conc. gradient from cortex to medulla.
82
R4: D
• The distal convoluted tubule (DCT) - blood ion regulation.
83
R5: duct
The collecting duct - production of a concentrated urine, and osmoregulation.
84
inside the nephron there is a liquid called?
* renal filtrate, which is formed in the Bowman’s capsule,
| * and eventually becomes urine at the end of the collecting duct.
85
what is the nephron closely associated with?
Closely associated with the nephron is a network of capillaries called the vasa recta.
86
glomerulus?
capillary bed
87
What is key in order for ultrafiltration to happen in the glomerulus?
* The afferent arteriole carrying blood into the Bowman’s capsule has a larger diameter than
* the efferent arteriole, carrying blood out of the capsule.
* This means there is a high hydrostatic pressure in the glomerulus, allowing ultrafiltration to happen.
88
loop of henle has 2 limbs...
ascending and descending
89
Ultrafiltration?
Substances in the blood that are small enough are forced by the high hydrostatic pressure in the glomerulus through 3 filtration layers, to form filtrate in the Bowman’s capsule.
90
⭐ substances in suspension?
* e.g. erythrocytes, leucocytes, platelets
* don’t contribute to blood water potential.
* Only solutes in solution contribute to water potential.
91
The 3 filtration layers of the Bowman's capsule?
1. capillary endothelium
2. basement membrane
3. podocytes
92
Capillary endothelium?
* formed from the squamous epithelial cells of the walls of the capillaries of the glomerulus.
* There are quite large gaps between these cells - fenestrations
* This layer stops cells and platelets, and allows everything else through.
93
Basement membrane?
* a ‘molecular mesh’, mainly of collagen fibres.
| * This layer has the smallest pores - stops everything bigger than plasma proteins Mr > 69,000
94
Podocytes?
* - the inner layer of epithelial cells lining the Bowman’s capsule.
* These cells have ‘foot processes’ that wrap around the capillaries of the glomerulus, forming filtration slits that allow filtrate into the Bowman’s capsule from the blood
95
outside to inside of BC?
* Outside: endothelium
| * inside: in contact w G, podocytes
96
podocytes don't stop
anything, they allow filtrate to form
97
Ultrafiltration: filtration pressure?
* There is a high hydrostatic pressure in the glomerulus, and a lower hydrostatic pressure in the Bowman’s capsule.
* This steep hydrostatic pressure gradient ‘forces’ filtrate through the filtration layers into the Bowman’s capsule.
* from filtrate to blood is the oncotic pressure gradient
* Large plasma proteins remain in the blood, and don’t enter the filtrate.
* This means the water potential of the blood is lower than the filtrate, causing an osmotic (or oncotic) pressure gradient from the filtrate into the blood
* filtration is a result of these 2 opposing gradients
98
filtration pressure signs
+ number indicates gradient from blood to filtrate
| - number indicates gradient from filtrate into blood
99
What is selective reabsorbtion?
useful substances are reabsorbed back into the blood from the filtrate, and substances that need to be excreted are not reabsorbed, and continue on to be excreted in the urine.
100
PCT cells?
* The epithelial cells lining the PCT are highly specialised for absorption.
* The membrane in contact with the filtrate is folded into structures called microvilli, increasing surface area.
* These cells also have many mitochondria, suggesting they are very metabolically active
101
co-transporter proteins are a ?
type of carrier protein.
102
(ultrafiltration) Why is there a high HP in the glomerulus?
* afferent arteriole from renal artery relatively wide
* blood leaves through narrower efferent arteriole
* this forces the blood through the fenestrated capillary wall
103
Cotransport?
first substance is AT out of cell, both diffuse in (facilitated diffusion) together through co-transporter protein
104
Which substances are not reabsorbed - ARE excreted?
* excess water
* excess ions
* urea
105
which substances are reabsorbed?
* Water that is not in excess.
* Ions that are not in excess
* Small plasma proteins Mr < 69,000 (eg enzymes, some clotting factors)
* Products of digestion eg glucose, amino acids, vitamins
* Hormones
106
SR: why is urea reabsorbed?
* water moving from filtrate into PCT by osmosis
* so [urea] (& everything else in the filtrate) ⬆
* so higher [urea] in filtrate than in PCT epithelial cells
* some urea moves (50%) by diffusion into epithelial cells - reabsorbed into blood
107
Why is the relationship between glucose conc and BC filtrate GC linear?
* the more glucose there is in the renal artery blood (going into BC)
* the more glucose there will be in BC filtrate
108
Renal threshold?
* as you ⬆ [glucose] in the RA, no glucose appears in urine bc of SR
* but, as [glucose] ⬆ more, cells in PCT cannot reabsorb all glucose in the filtrate as conc inc
* cells have reached their threshold
* as no further glucose molecules can be reabsorbed, glucose will appear in urine
* at renal threshold, glucose just starts to appear in urine
109
What does the loop of Henle do?
* Produces a concentration gradient of Na+ / Cl- ions in the tissue fluid (TF) from cortex to medulla.
* So there is a water potential gradient from filtrate to TF along the whole length of the collecting duct,
* enabling water to move out of the collecting duct by osmosis, resulting in a small volume of concentrated urine
110
general principle of loop of Henle?
* Na+ / Cl- ions are actively transported from the ascending limb into the TF.
* This lowers the water potential of the TF…
* so water moves by osmosis from the descending limb into the TF.
* This happens in a countercurrent mechanism along the whole length of the Loop of Henlé, producing a concentration gradient of Na+ / Cl- ions in the TF from cortex to medulla.
111
Ascending and descending limbs key point?
* the ascending limb is impermeable to water
| * the descending limb is permeable to water.
112
DCT structure?
* Lined with cuboidal epithelial cells but no microvilli.
| * These cells have many mitochondria to aid with the active transport of ions.
113
DCT: ions and hormone effects?
* In the DCT, ion content of the blood is regulated by removing ions from and / or adding ions to the blood.
* The main ions that are regulated are: K+, Na+, Cl-, Ca2+, H+ (ie blood pH).
* Aldosterone, a hormone produced by the adrenal cortex, controls Na+ and K+ reabsorption by acting here.
* ADH also has an effect here - same as collecting duct - increasing the reabsorption of water.
114
What happens along the collecting duct?
* Water is reabsorbed from the filtrate into the blood along the whole length of the CD, resulting in a small volume of concentrated urine.
* This can happen because the Ψ of the TF from cortex to medulla is always lower than the Ψ of the filtrate in the CD - that’s what the LoH achieved
* The volume of water reabsorbed is regulated by the presence of ADH
115
effect of ADH?
More ADH increases the permeability of the CD walls to water, so more water is reabsorbed - osmoregulaion
116
filtrate in CD Ψ compared to TF Ψ?
* filtrate in CD always has a higher Ψ than TF
| * so water is reabsorbed into blood
117
secretion if ADH?
* secreted by neurosecretory cells into blood of capillaries in the posterior pituitary gland
* pituitary gland situated just below hypothalamus
118
if someone is dehydrated...
* ψ of blood would start to fall
* Sensory receptor cells in the hypothalamus called osmoreceptors detect the ↓ of blood ψ
* osmoreceptors generate action potentials which stimulate neurosecretory cells to release ADH into the capillaries of the posterior pituitary gland.
* The ADH then enters the bloodstream and has its effect at epithelial cells of CD
119
ADH secretion process?
1. Osmoreceptors detect lower Ψ of blood in capillaries flowing through hypothalamus, generate APs
2. which move along axon of osmoreceptor & stimulate neurosecretory cell
3. NSC generates APs which move along axon and then stimulate the movement of vesicles containing ADH towards plasma membrane of the cell
4. vesicle fuses, ADH secreted in posterior pituitary gland
5. ADH released into capillaries that r carrying blood through the pituitary gland
120
effect of ADH on CD epithelial cells?
• ADH binds to receptors in the membranes of collecting duct epithelial cells.
• This binding triggers a second messenger system
which causes vesicles in the cytoplasm of the cells to move to and fuse with the membrane of the cells in contact with the filtrate.
• These vesicles have aquaporins in their membranes, which are then inserted into the membranes of the CD epithelial cells.
• Water now enters these cells more easily, and the permeability of the walls of the CD to water is increased, • so more water is reabsorbed from filtrate into blood.
• Less water is lost in the urine, and the blood water potential increases.
121
ADH is secreted in response to ?
low water potential of blood
122
when ADH stops being secreted?
the whole process is reversed
123
As filtrate moves down the collecting duct, what happens to its composition?
becomes more conc bc WP gradient exists between TF and filtrate in CD so water moves out of CD by osmosis producing a small volume of conc urine
