Renal physiology No.1

Question 1

What hormones do the Kidneys produce ?

Answer 1

• Erythropoietin
• Calcitriol

Question 2

What is the process in which blood filters into the bowman’s capsule ?

Answer 2

Ultrafiltration.

Question 3

Ultrafiltration is, simply put, filtration that occurs under pressure. What is responsible for maintaining the pressure in this process?

Answer 3

• The afferent and efferent arterioles.
• The afferent arteriole (proximal glomerulus) dilates, while the efferent arteriole (distal glomerulus) constricts. This creates a pressure gradient throughout the glomerulus, causing filtration under pressure.

Question 4

What is the Triad of symptoms of nephrotic syndrome?

Answer 4

• Proteinuria
• Hypoalbuminemia
• Oedema

Question 5

What are the 4 basic steps of the nephron.

Answer 5

1- Filtration

2- Reabsorption

3- Secretion

4 - excretion

Question 6

Cortical vs Juxtamedullary neprhons

What is the difference ?

Answer 6

Cortical nephrons perform the excretory and regulatory functions of a kidney.

Juxtamedullary nephron is involved in concentrating or diluting urea.

Question 7

What happens at the proximal convoluted tubule?

Answer 7

Reabsorption

Question 8

What two cells are present within the collecting duct ?

Answer 8

• Intercalated cells
• Principles cells

Question 9

What are the layers of the filtration Barrier ?

Answer 9

1- Endothelial cells of glomerular capillaries - This has many perforations called fenestrae which prevents the filtration of RBC.

2—Glomerular basement membrane—This has a glycocalyx consisting of negatively charged ions and, therefore, prevents the filtration of negative ions.

3- Epithelial cells of Bowman’s Capsule (podocytes) - Prevents large molecules such as proteins being filtered out.

Question 10

What cell prevents the filtration of large molecules such as proteins?

Answer 10

Podocytes

Question 11

Anything that has a lower molecular mass than what number can pass through the filtration membrane ?

Answer 11

68KD

Question 12

What can pass through the filtration membrane of the glomerulous during ultrafiltration?

Answer 12

H20
NA
K
CL
Glucose
Urea
Creatinine

Question 13

What can not pass through the filtration membrane of the golmerulous during ultrafiltration ?

Answer 13

Proteins > 68KDa
Immunoglobulins
Ferritin
Blood cells

Question 14

What is the force in favour of filtration?

What is its value ?

Answer 14

Glomerular blood hydrostatic pressure (GBHP) 60 mmHg

High due to resistant of afferent arteriole

Question 15

What are the two forces opposing filtration and what are their values ?

Answer 15

Capsular Hydrostatic Pressure (CHP) - 15mmHg due to accumulated fluid in the capsule.

Blood colloid osmotic pressure (BCOP) - 30 mmHg due to proteins such as albumin and fibrinogen in the plasma.

Question 16

What is the pressure of the glomerular blood hydrostatic pressure (GBHP) ?

Answer 16

60 mmHg

Question 17

What is the Capsular Hydrostatic Pressure (CHP)?

Answer 17

15 mmHg

Question 18

What is the Blood Colloid Osmotic Pressure (BCOP)?

Answer 18

30 mmHg

Question 19

What are the three main regulatory mechanisms that maintain the GFR ?

Answer 19

1- Autoregulation (myogenic, intra-renal baroreceptors mechanism, and macula denser sense).

2- Neural regulation - -Sympaethic and parasympathetic nervous system, e.g. vasoconstriction or dilation.

3- Hormonal regulation

Question 20

What are the steps of autoregulation of ultrafiltration ?

Answer 20

• Myogenic - Increase stretch of smooth muscle in afferent arteriole walls - Reflex constrictions of arteriole smooth muscle.
• Intra-renal baroreceptor mechanism
• Macula densa sensor - Renin secretion is inversely proportional to the amount of NA and CL entering the distal renal tubules from the loop of henle.

Question 21

What part of the nephron is CLOSELY located to the bowman’s capsule?

Answer 21

Distal convoluted tubule

Question 22

What cells are in the first segment of the DCT and are essential for tubuloglomerular feedback?

Answer 22

Macula densa cells

Question 23

What cells produce renin ?

Answer 23

Juxtaglomerular cells

Question 24

What is used to estimate EGFR?

Answer 24

Creatinine clearance

Question 25

What type of nephron is responsible for the medullary osmotic gradient?

Answer 25

Juxtamedullary nephron

This type of nephron has—a LONG loop of henle.

Question 26

What is normal blood osmolarity?

Answer 26

300

Question 27

What happens in the descending loop of henle ?

Answer 27

• This is highly permeable to water
• Reabsorption happens passively by aquaporin channels.

Question 28

What happens at the thin ascending loop of henle ?

Answer 28

• This part if impermeable to water as it has NO aquaporin channels.
• NA reabsorption occurs passively.
• CL- is absorbed using CL- channels.

Question 29

What happens at the thick ascending loop of Henle?

Answer 29

The primary site of sodium reabsorption by the Na+/K+ ATPase on the basolateral membrane which actively pumps 3 Na+ ions out of the cell and 2 potassium (K+) ions into the cell. So by creating a low intracellular concentration of sodium, the inside of the cell becomes negatively charged, creating an electrochemical gradient.

This section is impermeable to water.

Removal of Na+ whilst retaining water in the tubules – this leads to a hypotonic solution arriving at the DCT.
Pumping Na+ into the interstitial space – this contributes to a hyperosmotic environment in the kidney medulla

THIS SECTION IS HYPOTONIC REMEMBER THIS !