introduction to kidney & renal function

Question 1

what are the 2 functions of the urinary system?

Answer 1

1) excretion

2) elimination

Question 2

what is excretion?

Answer 2

the removal of organic waste products from body fluids

Question 3

what is elimination?

Answer 3

the discharge of waste products into the environment

Question 4

what are the essential renal functions?

Answer 4

• excretion
• homeostasis
• regulation

Question 5

what is excreted from the renal system?

Answer 5

endogenous waste products, drugs and their metabolites

Question 6

what is regulated by homeostasis in the renal system?

Answer 6

• water and electrolyte balance

- acid-base balance

Question 7

what is produced in the renal system by an essential function?

Answer 7

hormones (erythropoietin, renin…)

Question 8

what happens in renal dysfunction (failure)?

Answer 8

• reduction in renal excretory function (uraemia, azotaemia)
• reduction in renal excretory function (drug toxicity)
• inability to maintain salt and water balance and acid-base balance (metabolic consequences)
• compromised hormone function (anaemia, hypertension…)

Question 9

what type of renal failure accounts for 10% of renal failure?

Answer 9

acute kidney injury (AKI) - rapid

Question 10

what type of renal failure accounts for 90% of renal failure?

Answer 10

chronic kidney disease (CKD) - months or years to develop

Question 11

where are the kidneys located?

Answer 11

on the posterior wall of the abdomen behind the peritoneum on either side of the vertebral kidney

Question 12

roughly how much does an adult human kidney weigh?

Answer 12

120-170g

Question 13

what is the average size of a kidney?

Answer 13

11cm long, 6cm wide, 3cm thick

Question 14

where is the kidney joined?

Answer 14

at the medial side to the renal artery and vein, nerves and ureter

Question 15

what are the 2 major layers of the kidney?

Answer 15

• cortex (outer layer)

- medulla (middle layer)

Question 16

how many nephrons make up the cortex?

Answer 16

approximately 1.25 million

Question 17

what is a nephron?

Answer 17

the functional unit of the kidney responsible for urine formation and composition

Question 18

what is the structure of the medulla like?

Answer 18

pyramids that drain into the pelvis which drains into the ureters

Question 19

what are the 5 distinct sections of the nephron?

Answer 19

1) glomerulus (renal corpuscle)
2) proximal tubule (PT)
3) loop of Henle (LOH)
4) distal tubule (DT)
5) collecting duct (CD)

Question 20

what are the 2 types of nephron?

Answer 20

• cortical nephrons

- juxtamedullary nephrons

Question 21

how many of the nephrons in the kidney are cortical and juxtamedullary?

Answer 21

• cortical = 70-80%

- juxtamedullary = 20-30%

Question 22

where are the cortical nephrons found?

Answer 22

located in the cortex

Question 23

what is the loop of Henle like in cortical nephrons?

Answer 23

short into the medulla

Question 24

where are the juxtamedullary nephrons found?

Answer 24

situated closer to the medulla

Question 25

what is the loop of Henle like in juxtamedullary nephrons?

Answer 25

loop of Henle extends deep into the renal pyramids

Question 26

how much of the cardiac output does the kidney receive?

Answer 26

20%

Question 27

what are the nerves supplying the kidney?

Answer 27

• sympathetic postganglionic fibres from sympathetic chain and fibres from coeliac gangion
• parasympathetic efferent supply from vagus nerve: ganglion in hilum

Question 28

what blood vessels surround the cortical nephron’s loop of Henle?

Answer 28

peritubular capillaries

Question 29

what blood vessels surround the juxtamedullary’s loop of Henle?

Answer 29

vasa recta

Question 30

what is the function of the sympathetic postgangionic supply of the kidney?

Answer 30

• supplies arteries, afferent and efferent articles and granular cells
• reduces blood supply to the kidney during stress

Question 31

what is the function of the parasympathetic efferent supply of the kidney?

Answer 31

• may control tone of efferent arterioles

- may modify glomerular filtrate rate (GFR) and renal blood flow (RBF)

Question 32

what are the 3 major functions of the nephron?

Answer 32

1) filtration of blood to produce filtrate
2) reabsorption of water, ions and organic nutrients from filtrate
3) secretion of waste products into tubular fluid

Question 33

what is transcellular transport?

Answer 33

movement through cells

Question 34

what is paracellular transport?

Answer 34

movement between cells

Question 35

where does filtration occur?

Answer 35

at the glomerulus

Question 36

what small molecules are filtered during filtration?

Answer 36

• electrolytes
• amino acids
• glucose
• metabolic waste
• some drugs, metabolites

Question 37

what cells and large molecules remain in the blood during filtration?

Answer 37

• red blood cells
• lipids
• proteins
• most drugs, metabolites

Question 38

what is tubular reabsorption and its key stages?

Answer 38

• more than 99% of filtered water, electrolytes and nutrients are reabsorbed back into the blood
• some solutes are reabsorbed down concentration and/or electrochemical gradients
• other molecules can undergo co-transport
• water follows passively along the osmotic gradient created by solute reuptake via aquaporins
• reabsorption of solutes requires energy in the form of ATP which drives Na+ reabsorption via the Na+/K+/ATPase transporter

Question 39

what is tubular secretion and its key stages?

Answer 39

• some endogenous substances and drugs cannot be filtered at the glomerulus which may be due to their size or due to protein binding
• specialised pumps in the PT can transport compounds from the plasma into the nephron for excretion
• uses 2 pumps

Question 40

what are the 2 pumps in tubular secretion?

Answer 40

1) for organic acids or drugs

2) for organic bases or drugs