CFB L7 - Factors affetcing filtration

Question 1

Glomerular Filtration

Answer 1

100% = vol of plasma in afferent arteriole

20% passes through filter membrane to form initial filtrate

19% reabsorbed therefore, vol of urine lower than 99%

Question 2

State the 4 renal functional stages

Answer 2

• Filtration of blood
  -Selective reabsoroption
  -Secretion as required
  -Reabsorption of water

Question 3

Descibe the blood supply to the glomerulus

Answer 3

Oyxygenated blood from the aorta enters glomerulus by afferent arteriole

A mena arterial pressure of 60mmHg or higher is required for filtration to take place

20% of blood volume passes into Bowman’s capsule

Question 4

Kidney anatomy

Answer 4

1. Ureter
2. Renal Pelvis
3. Major calyx
4. Minor Calyx
5. Renal Medulla
6. 10-18 Renal pyramids
7. Renal cortex:
   outercortical zone
   Inner juxtamedullary zone
8. Renal column - seperate renal pyramids
9. Renal lobe

Question 5

Renal blood supply

Answer 5

BLOOD FROM AORTA TO RIGHT RENAL ARTERY:

Renal Artery (DIVIDIES INTO…)
Segmental arteries
Interlobar arteries - passs by renal columns
Arcuate arteries - go over bases of renal pyramids
Cortical Radiate arteries - which supply the cortex - continue to divide forming afferent arterioles which lead to the glomerulus (small bundle of capillaries) where blood filtration starts

Afferent Arteriole

Glomerulus

Once blood leaves gloerulus, does NOT enter VENULE instead…

Efferent arteriole - perilobular capillaries (the efferent arteriole divide to form perilobular capillaries)

Perilobular capillaries reuinte to become cortical radiate veins which lead to arcuate veins which lead to interlobular veins and eventually, left renal vein

Letft + right renal veins connect to inferior vena cava

Question 6

Nephrons DIAGRAM

Answer 6

1. Epithelium
2. Basement Membrane
3. Endothelium
4. Podocytes (wrap around basement membrane)

Each nephron is made of:

1. Renal corpuscle
2. Renal Tubule

Renal Corpuscle:
-Where blood filtration starts
Contains
Glomerulus
Bowman’s capsule

Filtration slits - between podocytes
Allow passage of SMALL PARTICLES:
-Water
-Glucose
-Ionic Salts
BUT NOT
-RBC
-Large particles

Question 7

Renal Tubule

Answer 7

PCT
Loop of Henle - Descending limb, ascending limb
DCT
Collecting duct (send urine to minor calysces)

Here, filtarte fine tuned based on body needs

Water + solutes passed back and forward between filtrate in renal tubules and blood in peritubilar capillaries

Question 8

What are the 3 layers of the filtration membrane / 3 filtration membranes

Answer 8

Endothelium

Basement Membrane

Epithelium

Question 9

Juxta Glomerular Complex

Answer 9

Helps regulation of BP + GFR

DIAGRAM:

1. Afferent Arteriole
2. Distal Convoluted Tubule
3. Macula Densa Cells (in DCT) - Sense low sodium and chloride levels (when hypovolemia, hypotension) and signal the…
4. Extraglomerular Mesangial Cells (help in signalling…)
5. Juxtaglomerular cells
   -Recieve signal
   -Sense low BP
   -Secrete renin

Question 10

What is the GFR

Answer 10

Amount of blood that passes through glomeruli / min

125/min = 180L/day

Used by doctors to work out kidney / renal function

Question 11

State the functions of renin

Answer 11

Increases blood vessel constriction
Therefore, higher bp
Increases Na+ reabsorption, which increases blood vol

Question 12

Fenestrated Endothelium

Answer 12

Lines inside of blood vessel
Fenestrated - has holes, at glomerulus, only lets in substances which are 70-100 nm or less
No cells e.g. red blood cells
Lets through glucose, proteins, ions, fluids etc

CELL MEMBRANE

Question 13

Basement membrane / Basal lamina of glomerulus

Answer 13

Connective tissue
-ve charged because filled with collagen
proteins also -ve charged, therefore, they repel each other stops them from entering

PROTEIN MEMBRANE, prevents filtration of large proteins

Question 14

Epithelium / Slit membrane between pedicels

Answer 14

Prevents filtration of medium sized proteins

Lined by podocytes
Stops cells, proteins which have made it through

Question 15

What are pedicels?

Answer 15

Fingere like projections of podocytes

Question 16

Diagram of filter between glomerular blood and filtrate

Answer 16

pay attention to

filtration slits
pedicel
podocytes
Fenestrated endothelium
Basal membrane
Epithelium
Fenestrations
Capillary

Mesangial cells, also present in filtration membrane

Answer 17

Plasma volume entering afferent arteriole = 100%

20% filtered into nephron

Therefore, 80% still in arteriole

19% of the 20% that is filtered is reabsorbed by blood, therefore, 99% of plasma returns to systemic circulation from entering afferent arteriole , less than 1% of plasma vol excreted

Mesangial cells - alter blood flow via contractile activity

Positively and negatively charged large molecules cannot pass through filter

Medium positively charged molecules can pass through filter

Very small molecules with negative charge can pass

Role of proteoglycans is to cause a negative charge and repel negatively charged molecules

The principal force favouring filtration out of capillary (into nephron) is Glomerular Hydrostatic Pressure, which has a pressure of 60 mm Hg

Opposing this are two pressures:
1.Bowman’s capsule pressure (16 mmHg)
2. Glomerular colloid osmotic pressure (13 mmHg)

Question 18

Net Filtration Pressure

Answer 18

Pressure causing filtration - pressure opposing filtration

60-50 = 10 mm Hg

Question 19

How can the kidney reduce the amount of filtrate produced?

Answer 19

Increase pressure in afferent arteriole

Question 20

How can the kidneys increase the amount of filtrate produced?

Answer 20

Inrease pressure in efferent arteriole