S2 L1 Glomerulus

Question 1

• *Kidney:**
• what ions/substances are filtered in the kidney?
• what ions/substances are reabsorbed in the kidney?
• What is ultrafiltrate?
• What substances are in the ultra filtrate?
• How much is filtered per day, how much is reabsorbed per day, how much is excreted?

Answer 1

Question 2

Recap - Body Compartments and there water content

Answer 2

Question 3

• *Electrolytes:**
• Intra and extra cellular fluids has different electrolyte composition, state electrolyte composition of intracellularly and extracellularly
• How is this maintained?
• Problems if electrolytes are not controlled

Answer 3

Question 4

• *Water and Osmotic force:**
• Does water cross cell membranes freely?
• What is movement of water driven by?
• Define: Osmolality, osmolarity, oncotic

Answer 4

Question 5

• *Essential terms:**
• What happens in the glomerulus and bowman’s capsule
• Aim of glomerulus
• Define: Renal blood flow, Renal plasma flow, equation for renal plasma flow, Hmt, Glomerular filtration rate, filtration fraction

Answer 5

Found only in the cortex
• The normal total glomerular filtrate per day is 140 – 180 L /day (~125 ml/min) (GFR)
• Renal plasma flow ~ 600 mL/min
• The filtration fraction (F/F), therefore, represents the proportion of the fluid reaching the kidneys that passes into the renal tubules. It is normally about 20%.
• FF= GFR/RPF
• 20% of blood from renal artery is filtered at any one time
• 80% blood arriving exits via efferent arteriole (unfiltered)
• Always the same despite two types of kidney nephrons: Cortical, Juxtamedullary

Question 6

Glomerular Filtration rate (GFR):
- Glomerular filtrate normally contains… doesn’t contain… composed of…

Answer 6

The glomerular filtrate normally:
• Contains no blood cells or platelets
• Contains virtually no proteins
• Is composed of mostly organic solutes with a low molecular weight and inorganic ions

Question 7

Renal corpuscle:

• How to tell the difference between DCT and PCT
• Why this difference?
• How to describe the relationship between glomerulus and DCT

Answer 7

Question 8

Compare plasma to ultra-filtrate:

• Glucose level
• Na+ level
• Urea level
• Creatinine level

Answer 8

Question 9

Glomerular capillary membrane

• State what this ‘looks’ like, cells involved
• How is albumin not filtered out of the glomerular (2 reasons)

Answer 9

• Filtration slits in the podocyte

Question 10

Selectivity of the barrier (basement membrane)

• What molecules can be filtered? Which can’t?
• What is haematuria?
• What is proteinuria?

Answer 10

Question 11

Which 3 forces determine how much plasma is filtered?
- Where is the net movement?

Answer 11

Question 12

S______ F_____ govern movement:
- Explain the movement and forces in the first part of the afferent arteriole, middle part and last part of the glomerulus

Answer 12

Question 13

S______ F______ govern movement:
- Talk about these forces in 3 parts of the glomerulus (first bit, middle, end)

Answer 13

• Hydrostatic (due to water)
• Colloid osmotic (oncotic) pressure (due to protein)
• Net Filtration = PGC – (PBS + !BS) = 50 – (12 + 25)
• Net Filtration = 13mmHg

Question 14

How does the regulation of renal blood flow and GFR occur?
- 2 ways

Answer 14

Question 15

Myogenic regulation (P_GC is regulated by myogenic…)

• Describe 4 ‘ways’
• Where does it occur most in the kidney

Answer 15

Arterial smooth muscle responds to increases and decreases in vascular wall tension
• It contributes to total auto- regulatory mechanism
• Occurs rapidly (3-10 s )
• It is a property predominantly of the preglomerular resistance vessels: Accurate, Interlobular, Afferent arteriole

Question 16

Summary of: Myogenic Mechanism

Answer 16

Question 17

Autoregulation - Further regulation of P_GC by Tubular Glomerular feedback (TG-feedback)
- 3 main cells involved and what they do (their role)

Answer 17

Question 18

Tumbuloglomerular feedback mechanism - High Tubular Flow

Answer 18

Question 19

Tumbuloglomerular feedback mechanism - Low BP

Answer 19

How to remember - Renin is released by juxtaglomerular cells, in response to the three S’s…
STIMULI: S S S

• Stretch afferent decrease
• Sympathetic
• Signals decreased from macula denSa cells due to decreased NaCl

Question 20

REALLY IMPORTANT BITS/CLEAR UP STUFF:
Important bits from group work:
- When have systemic low blood pressure, what happens to GFR?
- What would happen to GFR is there was an increase in renal blood flow?
- Which vessels cause the main change to GFR?
- Summarise the role of renin and angiotensin II?

Answer 20

• *When have systemic low blood pressure, what happens to GFR?**
• Immediately effect GFR
• Then auto regulation kicks in, GFR then stays the same
• GFR is then affected again if really low blood pressure e.g. septic shock

What would happen to GFR is there was an increase in renal blood flow?
Increase, as more filtrate enters the Bowman’s capsule, so more blood is cleared (as nearly all moves back into blood again)

What would happen to GFR is there was an decrease in renal blood flow?
Decrease GFR, as less capillary hydrostatic pressure, less blood passes into the Bowman’s capsule, so less is cleared (as more stays in the blood)
Which vessels cause the main change to GFR?
Within the afferent arteriole
Summarise the role of renin and angiotensin II?
- Macula densa cells lead to juxtaglomerular cells releasing renin, this leads to systemic vasoconstriction
- Macula densa cells also release prostaglandins, this antagonises receptors on afferent arterioles to stop constricting

Question 21

CHANGES IN AFFERENT ARTERIOLE - NOT EFFERENT ARTERIOLE