Renal system

Question 1

What is the function of the kidneys?

Answer 1

Excretery organs - process blood and rid the body of the waste products of metabolism via urine

Question 2

What do the kidneys maintain homeostasis of?

Answer 2

Fluid
Electrolytes (sodium/potassium)
Acid/base
Blood pressure
Calcium/vitamin D
Erythropoietin

Question 3

What are the components of the urinary system?

Answer 3

Two kidneys (produce urine)
Ureters (Convey urine)
Bladder (stored)
Urethra (void urine)

Question 4

What are the three distinct parts of the kidney?

Answer 4

• Cortex - 85% of nephrons
• Medulla - urine is concentrated, prevents excessive water loss
• Pelvis - collection area for urine which is funneled into ureter

Question 5

What are the blood vessels of the kidney?

Answer 5

Renal artery delivers blood from abdominal aorta

Renal artery
Segmental arteries
Lobar arteries
Interlobar arteries
Arcuate arteries
Interlobular arteries

Question 6

How does blood move from the interlobular arteries to the interlobular veins?

Answer 6

Blood travels through afferent arterioles to the glomerular capillaries and then out via efferent arterioles to peritubular capillaries and finally interlobular veins

Question 7

What are the veins of the kidney?

Answer 7

Interlobular veins
Arcuate veins
Lobar veins
Segmental veins
Renal vein
Inferior vena cava

Question 8

What is a nephron?

Answer 8

A structure optimally evolved to filter blood plasma

and excrete waste products of metabolism in urine

Question 9

What are the two types of nephrons?

Answer 9

Cortical

Juxtamedullary

Question 10

What is the renal corpuscle?

Answer 10

The blood filtering component of the nephron

Consists of:
Glomerulus
Bowmans capsule

Question 11

What is the renal tubule?

Answer 11

The renal tubule is the part of the nephron involved in reabsorption and secretion.

It consist of:

• PCT
• Loop of Henle
• DCT

After passing through the renal tubule, the filtrate continues to the collecting duct system.

Question 12

What is the glomerulus?

Answer 12

A network of fine capillaries

Single layer of endothelial cells surrounded by basement membrane

Enables rapid filtration of blood plasma

Surrounded by bowmans capsule

Question 13

What is the bowmans capsule?

Answer 13

A cuplike structure surrounding the glomerulus

Parietal (outer) layer
Visceral (inner) layer comprised of specialised epithelium - Podocytes

Question 14

What forms the filtration barrier in the renal corpuscle?

Answer 14

The glomerular endothelium, basement membrane and pedicels of the podocytes

Filtration barrier freely permeable to water and small molecules but NOT large protein or cells

Question 15

How is filtration controlled in the filtration membrane?

Answer 15

Filtration is facilitated by a pressure gradient - hydrostatic pressure

Question 16

What is filtered from the plasma?

Answer 16

Sodium
Chloride
Calcium
Phosphate
Potassium
Bicarbonate
Water 
Glucose
Amino acids
Urea
Creatinine

Question 17

What is not filtered in glomerulus?

Answer 17

Cells
Large proteins (haemoglobin)
Negatively charged proteins (albumin)

Question 18

What is the glomerular filtration rate?

Answer 18

The rate at which blood is filtered through the glomerulus into the Bowmans capsule

Question 19

What drives GFR?

Answer 19

Glomerular hydrostatic pressure

Question 20

What counteracts GFR?

Answer 20

Hydrostatic pressure in bowmans capsule or glomerular osmotic pressure

Question 21

What factors can influence GFR?

Answer 21

• Hydrostatic pressure
• Osmotic pressure
• Systemic blood pressure
• Renin-angiotensin system
• Disease

Normal healthy GFR = 125ml/min

Question 22

What does a reduced GFR result in?

Answer 22

Inefficient blood clearance and waste removal

Question 23

What can be used to estimate GFR?

Answer 23

Serum creatinine (and urea) measurements

Question 24

What GFR is indicative of kidney failure?

Answer 24

Less than 15%

Question 25

What facilitates reasborption?

Answer 25

Sodium transport facilitates reabsorption of nutrients, water and ions

Question 26

What facilitates secretion?

Answer 26

Sodium transport facilitates secretion of H_ (and waste)

Question 27

Where does reabsorption occur?

Answer 27

Within the renal tubule 65% in PCT 25% in ascending LofH 8% reabsorbed in DCT

Question 28

How much sodium is reabsorbed?

Answer 28

98%

Question 29

How does water move?

Answer 29

Via aquaporins

Question 30

How do glucose and amino acids move?

Answer 30

Via sodium cotransporters

Question 31

How does reabsorption occur in the PCT?

Answer 31

``` Sodium/potassium pump 3 na out/2 k in Na moves against conc gradient Everything (almost) follows Na - Water - Glucose and amino acids co-transported with Na - Chloride ``` Remaining filtrate continues to LofH

Question 32

What features of the nephron lie in the cortex?

Answer 32

PCT DCT Renal corpuscle

Question 33

What features of the nephron lie in the medulla?

Answer 33

Loop of Henle | collecting duct too but not part of nephron technically

Question 34

Is the descending limb of the LofH thin or thick?

Answer 34

Thin - freely permeable to water

Question 35

Is the ascending limb of the LofH thin or thick?

Answer 35

Both - has two sections Thin part impermeable to water but permeable to ions Thick part impermeable to water Actively pumps na, cl, and k into interstitium Interstitium becomes 'salty' Generates osmotic gradient Facilitates water reabsorption from thin ascending limb

Question 36

What is the vasa recta?

Answer 36

It maintains the concentration gradient of the medulla

Question 37

What is the concentration of solutes in the plasma?

Answer 37

Approx 300 mosm/kg

Question 38

How is the 200 mOsm/L difference between interstitual fluid and the ascending limb created?

Answer 38

Movement of sodium ions out

Question 39

Does the osmolarity increase or decrease due to a loss in sodium?

Answer 39

Decreases

Question 40

What happens after sodium is pumped out of the thick ascending limb?

Answer 40

After 200 mOsm/L gradient established, water moves passively out of the thin descending limb until equilibrium reached between interstitial fluid and filtate. Water moving out descending limb doesn't affect ISF osmolarity but lowers the filtrate osmolarity.

Question 41

What is the maximum osmolarity?

Answer 41

1200 mOsm/L

Question 42

Tubule fluid entering the distal convoluted tubule is?

Answer 42

Hypotonic with the interstitium

Question 43

What is the purpose of distal convoluted tubule?

Answer 43

Fine-tuning - site of fluid volume and electrolyte regulation Sodium and water reasbsorption hormonally regulated - ADH - increases water reasborption - Aldosterone - Increases Na reabsorption - Atrial natiuretic hormone (ANH) - Promotes Na secretion

Question 44

What are the juxta-glomerular apparatus and what is their function?

Answer 44

Macula densa - detects sodium conc Juxtaglomerular cells - adjust the diameter of the afferent arteriole

Question 45

What occurs in normal homeostatic blood pressure?

Answer 45

GFR in normal limits as is sodium conc Macula dens detects this and does not pass signal to juxtaglomerular cells thus large diameter of afferent arteriole and thus GFR is maintained

Question 46

What occurs from elevated BP in tubuloglomerular feedback?

Answer 46

Elevated systemic BP leads to elevated glomerular hydrostatic pressure increasing GFR and sodium conc in DCT, detected by macula densa which signals to juxtaglomerular cells to constrict via release of adenosine - lowers GFR by reducing blood flow

Question 47

What occurs from decreased BP in tubuloglomerular feedback?

Answer 47

Macula densa detects drop in sodium conc and releases prostaglandins which act on juxtaglomerular cells to cause dilation of afferent arterioles, only has marginal effect Main response - release of RENIN from juxtaglomerular cells in response to prostaglandins

Question 48

How does the renin angiotensinogen-system work?

Answer 48

Angiotensinogen released into circulation Renin converts angiotensinogen to Angiotensin 1 Angiotensinogen coverting enzyme converts angiotensin 1 into angiotensin 2 Angiotensin 2 is a potent vasoconstrictor - rapidly increases blood pressure

Question 49

What is Angiontensin 2 detected by?

Answer 49

Adrenal medulla- release of aldosterone | Hypothalamus - release of ADH

Question 50

What does Atrial Natriueretic peptide do?

Answer 50

Helps to return an elevated blood pressure to homeostasis by inhibiting the action of renin, aldosterone and ADH. Promotes water and sodium excretion

Question 51

How does RAAS raise blood pressure?

Answer 51

Via Angiotensin II

Question 52

How does RAAS raise blood volume?

Answer 52

Via aldosterone and ADH

Question 53

What are the symptoms of chronic kidney disease?

Answer 53

``` Nausea Oedema Blood/protein in urine Anaemia Weak/painful bones ```

Question 54

What are the causes of CDK?

Answer 54

Hypertension Diabetes High cholesterol Long term use of NSAIDs

Question 55

How do you regulate hypertension?

Answer 55

Diet Diuretics ACE inhbitors inhibit angiontensin II Beta-blockers block SNS by stress hormones

Question 56

What receptor facilitates sodium reabsoprtion of apical membrane?

Answer 56

NKCC2

Question 57

What is dialysis and what are the two types?

Answer 57

Dialysis is the artifical removal of wastes, solutes, water and toxins from blood Haemodialysis Peritoneal dialysis Required in stage 5 (kidney failure)