Lecture 16 - Introduction to the Kidney

Question 1

What % of blood flow does the kidney receive?

Answer 1

25%

Question 2

Why does the kidney recieve a lot of blood?

Answer 2

Due to their important role in homeostasis - the kidney has regulation of composition and volume of body fluids.

Question 3

How does the kidney control the composition and volume of bodily fluids?

Answer 3

They do this by filtering the blood and controlling what substances (including water) are excreted from the body.

Question 4

What are the overall functions of the kidney? (5)

Answer 4

• Regulation of water and ion balance (body pH
• Excretion of metabolic wastes
• Excretion of foreign chemicals
• Endocrine functions (calcitriol, EPO, renin)
• Gluconeogenesis

Question 5

How are toxins and (most) drugs removed by the body?

Answer 5

In the kidney by target proteins along the nephron.

Question 6

How much plasma does the kidney filter per day?

Answer 6

180 L

Question 7

What percentage of filtrate is reabsorbed?

Answer 7

99%

Question 8

What is the basic anatomy of the kidney?

Answer 8

Cortex
Medulla
Pyramid
Capsule
Pelvis

Question 9

What are the pyramids in the kidney?

Answer 9

Medullar pyramids - accumulated areas of nephrons

Question 10

What is the blood supply of the kidney?

Answer 10

The kidney is supplied by the renal arteries

Question 10

How does the renal artery divide in the kidney?

Answer 10

The renal artery divides to form small capillary structures which lead to the formation of the glomerulus capillaries, peritubular capillaries and vasa recta, which all surround the nephron

Question 11

Which of the following statements is true?
A. The kidney filters about 200 litres of plasma per day.
B. The kidneys do not produce hormones.
C. The Urinary system has three ureters.
D. The kidneys excrete foreign chemicals.

Answer 11

D. The kidneys excrete foreign chemicals.

Question 12

What is the nephron?

Answer 12

The smallest functional unit of the kidney

Question 13

What are the two types of nephron?

Answer 13

Nephrons can either be superficial (cortical) or juxtamedullary

Question 14

Where do the juxtamedullary nephrons expand?

Answer 14

The cortex and the medulla

Question 15

Where do the superficial (cortical) nephrons expand?

Answer 15

Contained in the cortex

Question 16

What are the components of the nephron? (7)

Answer 16

The nephron consists of the glomerulus, bowman’s capsule, proximal tubule, loop of Henle, distal tubule, and collecting duct.

Question 17

Where is glucose reabsorbed in the nephron?

Answer 17

The proximal tubule

Question 18

What are the two ways in which material can move from the blood to the lumen of the nephron?

Answer 18

Glomerular filtration or tubular secretion

Question 19

Which of the following statements is false?
A. The Nephron is the smallest functional unit of the kidney.
B. The afferent arteriole branches to make the glomerulus.
C. Each kidney contains more that 1 million nephrons.
D. Reabsorption of material is from the blood to the lumen of the nephron.

Answer 19

Reabsorption of material is from the blood to the lumen of the nephron - filtration of blood occurs at nephron, not reabsorption

Question 20

What is Glomerular Filtration (Ultrafiltration)?

Answer 20

The bulk flow of protein-free plasma into the Bowman’s space which forms the filtrate

Question 21

What is filtrate composed of?

Answer 21

The filtrate contains everything in plasma except RBC and proteins

Question 22

What are the structures of the Renal Corpuscle

Answer 22

Glomerulus (capillaries)
Bowman’s capsule - outer epithelium
(Podocytes - inner epithelium)

Question 23

What is the glomerulus made up of?

Answer 23

Endothelium (capillary tuft) fenestrated with basement membrane - for sieve action

Question 24

Describe the podocytes

Answer 24

Specialised epithelial cells of Bowman’s capsule. Podocytes have finger like structures (pedicels) which enhance filtration barrier - Filters small things

Question 25

What is the filtration system composed of?

Answer 25

Macula densa (MD)
Granular cells (G)
Pedicels - Podocyte foot processes (FP)
Podocyte (P)
Endothelium (EN)
Basement membrane (BM)

Question 26

What are the macula densa?

Answer 26

Series of cells in thick ascending limb which monitors the level of sodium - osmotically involved

Question 27

What are the granular cells?

Answer 27

Cells the produce renin

Question 28

Why is renin important?

Answer 28

For Na+/water balance

Question 29

What forms the filtration barrier?

Answer 29

Together the endothelial cells of the glomerular capillaries, the basement membrane and the podocytes form the filtration barrier

Question 30

What is the fenestrated endothelium permeable to?

Answer 30

Freely permeable to water, ions, and small solutes but not cells

Question 31

What is the basement membrane in the filtration barrier?

Answer 31

Matrix of negatively charged proteins which acts as a charged-based filtration barrier to proteins

Question 32

What is nephrotic syndrome?

Answer 32

The break down of the filtration barrier so we have less filtration and increase protein excretion - Inability to concentrate urine, low plasma proteins can lead to oedema

Question 33

Which of the following statements is false?
A. The renal corpusle contains the glomerulus and the Bowman’s capsule.
B. Podocytes do not aid with filtration.
C. The basement membrane is negatively charged to assist filtration.
D. Jonah Lomu died from nephrotic syndrome.

Answer 33

B. Podocytes do not aid with filtration.

Question 34

What are the pressures (forces) that make up the Glomerular Ultrafiltration Pressures?

Answer 34

Pressure Favouring filtration:
Glomerular capillary hydrostatic pressure (PGC) - Blood pressure
Pressures Opposing filtration:
Hydrostatic pressure – Bowman’s space (PBS)
Oncotic pressure due to proteins in the glomerular capillary (πGC)

Question 35

What is the equation for the net glomerular ultrafiltration pressure?

Answer 35

(PUF) = PGC - PBS - πGC

Question 36

What is Glomerular capillary hydrostatic pressure (PGC)?

Answer 36

Pressure that pushes fluid from the lumen into bowman’s capsule (high pressure in glomerular capillary wants to move fluid out)

Question 37

What is Hydrostatic pressure – Bowman’s space (PBS)?

Answer 37

Pressure that opposes the movement of water from blood to LS (Bowman’s space pressure wants to move fluid out)

Question 38

What is πGC?

Answer 38

Osmotic pressure (opposing filtration due to proteins in the glomerular capillary)