Lecture 16 - Body Fluids

Question 1

Differentiate osmolarity and osmolality.

L16 S5

Answer 1

Osmolarity:

• mOsm(milisomoles)/L
• concentration of particle per liter of fluid

Osmolality:

• mOsm/kg
• concentration of particles per kg of solvent

Question 2

What is an effective osmole?

L16 S6

Answer 2

• solute that does not easily cross a membrane and creates an osmotic force for water
• proteins are a good example

Question 3

List sources of fluid intake and loss.

L16 S7

Answer 3

Fluid intake (2300 mL/day):

• ingestion (2100 mL/day)
• metabolism (200 mL/day)

Fluid loss (2300 mL/day):

• evaporation through skin (350 mL/day)
• evaporation through lungs (350 mL/day)
• sweat (100 mL/day)
• feces (100 mL/day)
• urine (1400 mL/day)

Question 4

What are the components of a basic metabolic panel and their normal values?

(L16 S8)

Answer 4

Sodium:
-140 mEq/L

Chloride:
-104 mEq/L

Potassium:
-4 mEq/L

Hydrogen carbonate:
-24 mEq/L

BUN:
-15 mg/dL

Creatinine:
-1 mg/dL

Glucose:
-80 mg/dL

Question 5

What is osmolar gap and what is its normal value?

L16 S9

Answer 5

• difference between measured osmolarity and estimated osmolarity
• normal is less than or equal to 15

Question 6

What are common substances that elevate osmolar gap?

L16 S10

Answer 6

• ethanol
• methanol
• ethylene glycol
• acetone
• mannitol

Question 7

For each mOsm of concentration gradient of an impermeable solute __________ of osmotic pressure is exerted on the membrane.

(L16 S16)

Answer 7

19.3 mmHg

Question 8

What differentiates a isotonic, hypotonic, and hypertonic solutions?

(L16 S21-23)

Answer 8

Isotonic:

• extracellular volume increases
• Intracellular volume decreases
• fluids osmolarity is 282 mOsm/L
• 0.9% saline or 5% glucose

Hypertonic:

• extracellular volume increases
• Intracellular volume decreases
• fluids osmolarity is >282 mOsm/L

Hypotonic:

• extracellular and intracellular volume increases
• fluids osmolarity is <282 mOsm/L

Question 9

What is the anatomical organization of the kidney?

L16 S35

Answer 9

Capsule

Renal cortex:

• Bowman’s capsules
• proximal and distal convoluted tubules

Renal mendula:
-renal pyramids

Renal pelvis:
-major and minor calyces

Question 10

What is the path of blood flow to the kidney?

L16 S40

Answer 10

Renal artery

• > interlobar arteries
• > arcuate arteries
• > interlobular arteries
• > afferent arterioles
• > glomerular capillaries
• > efferent arterioles

Question 11

What is the path of blood flow from the kidney?

L16 S41

Answer 11

Peritubular capillaries

• > interlobular veins
• > arcuate veins
• > interlobar veins
• > renal vein

Question 12

What is the structure of a juxtamedullary nephron starting at the Bowman’s capsule and ending at the collecting tubule?
Differentiate if the structure is located in the cortex or the medulla.

(L16 S38)

Answer 12

Cortex:

• Bowman’s capsule
• > proximal tubule

Medulla:
-> loop of Henle (descending then ascending)

Cortex:

• > distal tubule
• > connecting tubule
• > collecting tubule

Question 13

Approximately __________ of the total cardiac output is received by the kidney.

(L16 S39)

Answer 13

22% (1100 mL/min)

Question 14

What effect does hydrostatic pressure have on kidney function?
What vessels are mostly responsible for this?

(L16 S39)

Answer 14

High hydrostatic pressure:

• ~60 mmHg
• rapid filtration

Low hydrostatic pressure:

• ~13 mmHg
• rapid fluid reabsorption

-efferent arterioles