Week 1 - Anatomy of the Urinary System

Question 1

Outline some functions of the urinary system.

Answer 1

1. Controls concentration of key substances in extracellular fluid and thus regulate plasma osmolarity
2. Excretion: excretes waste products
3. Endocrine: Synthesis of renin, erythropoietin, and prostaglandins
4. Metabolism: Activation of vitamin D, catabolism of insulin, PTH, Calcitonin
5. Control plasma volume
6. Regulate pH of the plasma by controlling number of bicarbonate ions in plasma

Question 2

Outline approximate values for the fluid composition of body compartments.

Answer 2

Intracellular fluid/cytosol = 28 L
Extracellular fluid = 14 L, Interstitial fluid = 11 L, Intravascular (Plasma) = 3 L, Lymph, Transcellular, synovial, intestinal, CSF, Sweat, Urine, Pleural, peritoneal, pericardial and intraocular fluids

Question 3

Define osmolality.

Answer 3

Is the solute per kilogram of solvent

Question 4

Define osmolarity.

Answer 4

Number of osmoles of solute per litre

Question 5

What is the osmolality of plasma under normal conditions?

Answer 5

Plasma osmolality = Interstitial fluid = Intracellular fluid osmolality = 280-310 mOsm/kg

Question 6

How can serum osmolality be estimated in clinical conditions?

Answer 6

By doubling serum sodium

Na+ and Cl- = 80%: ECF

Question 7

Describe the main ions present in intracellular and extracellular fluids.

Answer 7

Intracellular fluid: High K+, low Na+, many large organic anions

Extracellular fluid: Low K+, high Na+, main anion: Cl- and HCO3-

Question 8

What percentage of cardiac output do the kidneys typically require?

Answer 8

22%

Question 9

What is the typical value for glomerular filtration rate?

Answer 9

125 ml/min or 180 L/day

Question 10

What is the main function of the Loop of Henle?

Answer 10

To create a gradient of increasing osmolarity in the medulla by counter-current multiplication

Question 11

What is the main electrolyte composition of extracellular fluid?

Answer 11

1. Low K+
2. High Na+
3. Main anions - HCO3- and Cl-

Question 12

What is the ultra filtrate composed of?

Answer 12

1. Water
2. Ions
3. All small molecules

Question 13

What is the average filtration rate by the kidney?

Answer 13

180 L/day

Question 14

What is the average amount of urine produced per day?

Answer 14

1.5 L per day of urine

Question 15

What percentage of cardiac output goes to the kidneys at rest?

Answer 15

22%

Question 16

What blood flow is required by the kidneys?

Answer 16

4 ml/g/min

Question 17

What is the glomerular filtration rate?

Answer 17

125 ml/min or 180 L/day

Question 18

What percentage of sodium and water is reabsorbed in the PCT?

Answer 18

60-70%

Question 19

What percentage of potassium is reabsorbed in the PCT?

Answer 19

80-90%

Question 20

What percentage of bicarbonate is reabsorbed in the PCT?

Answer 20

90%

Question 21

Is the fluid leaving the loop of Henle hypotonic or hypertonic?

Answer 21

Hypotonic

Question 22

At what vertebral level do the renal arteries arise?

Answer 22

L1-L2

Question 23

Outline the course of the ureters.

Answer 23

1. Arise from the renal pelvis
2. Pass anterior to psoas major
3. Cross the pelvic brim at the bifurcation of the iliac arteries
4. Under the uterine artery/ductus deferens - inserts into the posterior wall of the bladder

Question 24

What is the most common form of hypertension?

Answer 24

Essential hypertension

Question 25

What three components make up the juxtaglomerular apparatus?

Answer 25

1. Macula densa
2. Extraglomerular mesangial cells (Lacis cells)
3. Juxtaglomerular cells (granulated cells)

Question 26

What causes renal agenesis?

Answer 26

Failure of ureteric bud to interact with intermediate mesoderm

Question 27

Which pathological state commonly causes increased compliance of the lungs?

Answer 27

Emphysema