PSC1002/L11 Renal System

Question 1

What is the functional unit of the kidney?

Answer 1

Nephron

Question 2

What are juxtamedullary nephrons involved in?

Answer 2

Making concentrated urine

Question 3

Describe the structure of a nephron. (6)

Answer 3

Bowman’s capsule into proximal convoluted tubule
Descending limb
Loop of Henle
Ascending limb
Distal convoluted tubule
Collecting tubules/duct

Question 4

What is the approximate renal blood supply?

Answer 4

1.2 L/min

Question 5

Describe the vascular supply to nephrons. (5)

Answer 5

Afferent arterioles feed into glomeruli
Efferent arterioles leave glomeruli and wrap around nephron
Peritubular capillaries or vasa recta
Renal veins
Inferior vena cava

Question 6

What can be inferred from the fact that an arteriole leaves the capillary bed of the nephron?

Answer 6

Role is not to supply oxygen but for reabsorption

Question 7

Give 3 functions of the kidney.

Answer 7

Homeostatic regulation of water and ion content of blood
Excretion of metabolic waste products and foreign substances
Production of hormones

Question 8

Give 3 hormones produced by the kidney.

Answer 8

Erythropoietin
Renin
Bone prostaglandins & kinins

Question 9

What 3 processes occur in the kidney?

Answer 9

Glomerular filtration
Tubular reabsorption
Tubular secretion

Question 10

What is glomerular filtration and where does it occur?

Answer 10

Blood filtered at glomerulus
Renal corpuscle

Question 11

What is tubular reabsorption?

Answer 11

Fluid and solutes are reabsorbed from the filtrate and returned to the blood

Question 12

What is tubular secretion?

Answer 12

Substances are secreted from blood into filtrate

Question 13

What is filtered in the kidneys?

Answer 13

All plasma constituents except proteins >67kDa

Question 14

How does the filtration barrier restrict solute movement? (2)

Answer 14

On size and charge

Question 15

What is the average glomerular filtration rate (GFR)?

Answer 15

180 L/day
Total plasma filtered 2.5x per hour

Question 16

What are fenestration pores?

Answer 16

Small spaces within the endothelial cell layer of filtration barrier

Question 17

What is a podocyte?

Answer 17

Modified epithelial cells of the capsular epithelium and renal glomerulus

Question 18

Name 4 substances that get filtered in the kidneys.

Answer 18

H2O
Na+
K+
Ca2+
Cl-
Glucose
NH4+
Creatinine
Uric acid

Question 19

What 3 pressures contribute to filtration?

Answer 19

Hydrostatic pressure of blood in glomerular capillaries (P(H))
Colloid osmotic pressure (Pi)
Hydrostatic pressure of fluid in Bowman’s space (Pfluid)

Question 20

What is the equation for net filtration pressure? Give an approximation.

Answer 20

NFP = P(H) - Pi - Pfluid
55 - 30 - 15 = 10 mmHg

Question 21

How would an increase in resistance of afferent arteriole affect renal blood flow? (2)

Answer 21

Decrease hydrostatic pressure
Decrease GFR

Question 22

How would an increase in resistance in the efferent arteriole affect renal blood flow?

Answer 22

Decreases blood flow out of glomerulus
Increases pressure in glomerulus

Question 23

What mechanisms maintain RBF and GFR within narrow limits?

Answer 23

Myogenic response
Tubuloglomerular feedback

Question 24

Describe the myogenic response. (5)

Answer 24

Increased BP
Stretch of SMC
Vasoconstriction
Decreased RBF
Decreased PH & GFR

Question 25

Define tubuloglomerular feedback.

Answer 25

Fluid flow through tubule influences arteriole resistance and GFR

Question 26

Explain how tubuloglomerular feedback works. (8)

Answer 26

GFR increases
Flow through tubule increases
Flow past macula densa increases (sensed ions)
Paracrine factors released from macula densa (Adenosine, ATP, NO)
Afferent arteriole constricts
Resistance in afferent arteriole increases
Hydrostatic pressure in glomerulus decreases
GFR decreases