Kidney Function I: Filtration, Reabsorption, Secretion and Clearance Flashcards
1
Q
What are the 3 main functions of the kidney?
A
- EXCRETION OF METABOLITES OR INGESTED SUBSTANCES
- CONTROL OF BODY FLUID COMPOSITION
- ENDOCRINE
2
Q
List 5 examples of metabolites/ingested sub excreted by kidney and their origin
A
- Urea from protein catabolism
- Uric acid from nucleic acid breakdown
- Creatinine from muscle creatine
- End products of haemoglobin breakdown
- Foreign chemicals eg. drugs, pesticides
3
Q
Why are metabolites/ingested sub excreted from kidney?
A
Prevent acc in body and toxicity
4
Q
How is the kidney involved in control of body fluid comp?
A
- directly control plasma composition
– indirectly controls comp of interstitial fluid and then intracellular fluid comp - Volume Regulation i.e. linked to sodium concentration in plasma
- Osmoregulation i.e. water balance – reg osmolarity of plasma
- pH regulation of plasma
5
Q
Name 5 hormones that act on kidney
A
- ADH
- Aldosterone
- Natriuretic peptides
- Parathyroid hormone
- Fibroblast growth factor 23
6
Q
What is origin, location of action on kidney and function of ADH?
A
- secreted by pos pit gland
- CD
- cause water reabsorption
7
Q
What is origin, location of action on kidney and function of aldosterone?
A
- secreted by adrenal cortex
- CD
- cause Na+ reabsorption
8
Q
What is location of action on kidney and functions of natriuretic peptides?
A
- CD
- cause Na+ excretion
- syn + secrete cardiac cells
9
Q
What is origin and functions of parathyroid hormone?
A
- secreted by parathyroid gland
– involved in Ca2+ reabsorption, phosphate excretion and vit D production
10
Q
What is origin and functions of FGF23?
A
- secreted by both osteocytes
– involved in inhibiting vit D production and causing phosphate excretion
11
Q
Name 4 hormones produced by the kidney
A
- renin
- vit D
- erythropoietin
- prostaglandins
12
Q
What is function of renin?
A
controls Na+ conc in plasma
13
Q
What is function of vit D?
A
acts at gut to cause Ca2+ + phosphate absorption
14
Q
What is function of erythropoietin?
A
- syn in response to hypoxia (deficiency in amount of O2 reaching tissues)
- stimulates bone marrow to inc production of RBCs
15
Q
What is function of prostaglandins?
A
control vascular tone
16
Q
Where are the kidneys located and what’s the diff between the R + L?
A
- Kidneys between T12 + L3 vertebrae
- R slightly lower than left due to liver
17
Q
Approx how many nephrons are in kidneys?
A
> 1 million/kidney
18
Q
What is main structure of nephron?
A
- Renal corpuscle
2. Tubule
19
Q
What is function of efferent arteriole?
A
where blood leaves glom
20
Q
What is function of afferent arteriole?
A
supplies glom with blood
21
Q
What happens to plasma in glom and how?
A
- Blood enters through afferent arteriole and 20% of plasma leaves glom + filtered into Bowman’s space
- 80% of plasma that’s entered A arteriole leaves through E arteriole
22
Q
What are 3 layers of renal corpuscle?
A
- Capillary endo
- Basement mem
- Tubular epithelium (podocytes)
23
Q
What is structure of capillary endo and how does it relate to its function?
A
- pores (100nm)
– means its highly perm
24
Q
What is charge and main structure of BM?
A
- has –ve charged sites
- 3 layers
25
What is main structure of tubular epithelium (podocytes)?
have filtration slits (8nm)
26
What are important filtration slit proteins in podocytes?
- Nephrin
| - podocin
27
What are the 4 main regions of renal tubule?
1. Proximal tubule
2. Loop of Henle
3. Distal convoluted tubule
4. Collecting duct
28
Name the 2 sections the PT is split into
1. Proximal convoluted tubule
| 2. Proximal straight tubule
29
Name the 3 sections the LOH is split into
1. Thin descending limb
2. Thin ascending limb
3. Thick ascending limb
30
Name the 2 sections the CD is split into
1. Cortical CD
| 2. Medullary CD
31
Name the 2 sections the renal corpuscle consists of
1. Glomerulus/glomerular capillaries
| 2. Bowman's capsule (Bowman's space)
32
List all 11 features of the nepron from start to finish
1. Glom
2. BC
3. PCT
4. PST
5. Thin DL
6. Thin AL
7. Thick AL
8. DCT
9. Cortical CD
10. Medullary CD
11. Renal pelvis
33
At what level do nephrons merge?
CD
34
Name the 2 types of nephron and % they make up in kidneys
1. Cortical (85%)
| 2. Juxtamedullary (15%)
35
Where are cortical nephrons located and how does their structure and function differentiate them from juxt nephrons?
- outer 2/3 of cortex.
- short Loop of Henle
- producing dilute urine
36
Where are juxt nephrons located and how does their structure and function differentiate them from cortical nephrons?
- inner 1/3 cortex
- long Loop of Henle
- producing concentrated urine
37
Where does glom filtration occur?
at renal corpuscle
38
Where is renal corpuscle located?
Renal cortex
39
What is the juxtaglomerular apparatus?
structure formed by the distal convoluted tubule and the glomerular afferent arteriole and consists of 3 main cells.
40
What are the 3 main cell types of JA?
1. Juxtaglomerular cells
2. Macula densa
3. Mesengial cells
41
What is function of juxtglom cells?
secrete renin into blood
42
What is function of macula densa?
involved in control of Na+ conc in plasma
43
What is function of mesengial cells?
lie over glom capillaries + contain smooth muscle
44
What is the blood supply to the nephrons?
- 2 sets of arterioles (afferent and efferent)
- 2 sets of capillary beds (glomeruli and peritubular) in series (peritubular capillaries called vasa recta when they surround LOH)
45
What are the 4 basic renal processes?
1. Glomerular Filtration
2. Tubular Reabsorption
3. Tubular Secretion
4. Metabolism
46
What is glomerular filtration?
The movement of fluid and solutes from the glomerular capillaries into Bowman’s space.
47
What % of plasma that enters the glomerulus filtered into BS?
20%
48
What type of process is glomerular filtration and what does that mean?
Non-selective process = no specific protein involved – body able to excrete waste products without having a specific transporter/selective protein
49
What is the filtrate produced from glomerular filtration and what its comp like?
Ultrafiltrate – has same comp of plasma except for some stuff
50
What is tubular secretion?
The secretion of solutes from the peritubular capillaries into the tubules. Secretion of mol directly from walls of tubule.
51
What mol are syn in tubule epi?
- H+
- HCO3-
- NH4+
52
What is tubular reabsorption?
The movement of materials from the filtrate in the tubules into the peritubular capillaries.
53
Do all the basic renal process have to happen in order?
No - tubular secretion may not occur before tubular reabsorption
54
How can u determine the amount excreted in the urine?
Amount filtered + amount secreted - amount reabsorbed
55
What renal processes occur in case of glucose?
filtered and completely reabsorbed but never secreted + not normally in urine
56
What renal processes occur in case of toxic sub, PAH?
filtered and secreted but not reabsorbed
57
What renal processes occur in case of H2O and most electrolytes?
filtered and some of it is reabsorbed + little bit in urine.
58
How does the kidney perform metabolism?
metabolises sub and eliminates them from body e.g. glutamine met in walls of tubule
59
What gets through the glom filtrate barrier?
Ultrafiltrate
60
What is ultrafiltrate?
Normally all plasma constituents MINUS proteins
61
What doesn't get through glom filtrate barrier and why?
large proteins - not able to cross filtration barrier.
+ve and –ve charged mol bind to proteins – can’t be filtered and won’t pass into BS e.g. 40% of Ca2+ binds to proteins – not able to be filtered
62
What is one function of plasma proteins?
bind many drugs
63
What is function of albumin?
binds acidic drugs
64
What is function of α1-acid glycoprotein?
binds basic drugs
65
How does size of mol smaller than 7kDa affect glom filtration and 2 examples?
- small and can be freely filtered - have conc in ultrafiltrate that’s same as plasma
- glucose, inulin
66
How does size of mol larger than 7kDa affect glom filtration and 2 examples?
- too large to freely filtrate across barrier - lower conc in filtrate –
- larger proteins e.g. albumin, myoglobin
67
How does charge of mol affect glom filtration?
- Large +ve mol cross filtration barrier to greater extent compared to uncharged mol and –ve mol bcos BM has –ve charges
68
What does infection, damage to glomerulus, very high
| blood-pressure result in?
- protein in urine (proteinuria)
- haemoglobin in urine (haemoglobinuria)
- red cells in urine (haematuria)
69
What is glomerular filtration rate?
volume of fluid filtered from the glomeruli per minute (ml/min).
70
What does GFR depend on?
combination of:
1. Starling forces
2. Hydraulic permeability (which is high in this capillary bed)
3. Surface area
71
How is GFR regulated?
neural and hormonal input
72
Which 3 forces are involved in filtration?
1. Starling forces (opposing)
2. Hydrostatic pressure - capillary bp opposed by water – fluid in BS
3. Osmotic/Oncotic
73
How is net glomerular filtration pressure calculated?
Diff in pressure between Hydrostatic pressure in capillary lumen and capsular pressure in capsular space minus diff in oncotic pressure in capillary lumen and capsular space = 16mmHg
74
What does diff in hydrostatic and capsular pressures cause?
higher pressure in capillary lumen cause movement of fluid from plasma to space
75
What does diff in oncotic pressures in capillary lumen and capsular space cause?
lower pressure in space cause movement of fluid from space to plasma
76
What does net glom filtration pressure show?
Overall movement of fluid from plasma to space (greater hydrostatic/capsular pressure diff)
77
Why is oncotic pressure in BS considered to be zero?
protein concentration in Bowman’s space filtrate is so low
78
What causes decreased GFR?
- Constrict AA/dilate EA
- restrict hydrostatic pressure/bp
- Red driving force of filtration
79
What causes decreased GFR?
- Constrict EA/dilate AA
- inc hydrostatic pressure/bp
- inc driving force of filtration
