OSMOSIS
| A | 270 to 285 | |
| B |
300 to 320 |
|
| C |
350 to 375 |
|
| D |
200 to 250 |
The normal range of serum osmolality (in mOsm/L):
| A |
270 to 285 |
|
| B |
300 to 320 |
|
| C |
350 to 375 |
|
| D |
200 to 250 |
Normal serum osmolality ranges from 270-285 mOsm/L while in neonates, serum values as low as 266 mOsm/kg . And normal urine osmolality ranges from 40-1400 mOsm/L.
| A |
Bernoulli’s law |
|
| B |
Ohm’s law |
|
| C |
Van’t Hoff law |
|
| D |
Poiseuille’s law |
Van’t Hoff law is used for calculating osmotic pressure of a solution. Osmotic pressure of a solution depends upon the number of particles in the solution.
R = Gas constant
T = Absolute temperature
i = Number of ions
C = Molar concentration
| A |
Low molecular weight and high blood concentration |
|
| B |
Low molecular weight and low blood concentration |
|
| C |
High molecular weight and low blood concentration |
|
| D |
High molecular weight and high blood concentration. |
A i.e. Low molecular weight and high blood concentration
Osmotic pressure is determined by the number of particles in solution and not by the mass of the particle, that means 1 gm of a heavy molecular weight protein will contain a lesser no. of particles than 1 gm of a light molecular weight protein, & conse uentiv will have a lesser osmotic pressure
|
Plasma protein |
MW |
Concentration |
Contribution to plasma osmolality |
|
Albumin |
69,000 |
3.5-5 gm% |
80% |
|
Globulin |
1,40,000 |
2.0 gm% |
20% |
|
Fibrinogen |
4,00,000 |
0.3 gm% |
0% |
Of the there major types of plasma protein, albumin with minimum molecular weight contributes. max to plasma oncotic pressure.
| A | 6.5 atm. | |
| B |
22.4 atm. |
|
| C |
4 atm. |
|
| D |
2 atm. |
B i.e. 22.4
1 mol of an ideal solute dissolved in 1 kg (1000 gm) of water (i.e. 1 molal or M solution) at 1 atm pressure at 25°C yields a solution whose osmotic pressure relative to pure water is 22.4 atm.
The osmolality of plasma in a normal adult:
| A | 320-330 mOsm/L | |
| B |
300-310 mOsm/ L |
|
| C |
280-290 mOsm/ L |
|
| D |
260-270 mOsm/ L |
Ans. C: 280-290 mOsm/L
- Plasma osmolality is a measure of the concentration of substances such as sodium, chloride, potassium, urea, glucose, and other ions in blood
- Osmolal concencentration of plasma is 290 mOsm/L
- Osmolality of blood increases with dehydration and decreases with overhydration.
- In normal people, increased osmolality in the blood will stimulate secretion of antidiuretic hormone (ADH). This will result in increased water reabsorption, more concentrated urine, and less concentrated blood plasma.
- A low serum osmolality will suppress the release of ADH, resulting in decreased water reabsorption and more concentrated plasma.
March 2009
| A |
Sodium |
|
| B |
Potassium |
|
| C |
Glucose |
|
| D |
Calcium |
Ans. A: Sodium
Although the concentration of the plasma proteins is large when expressed in grams per liter, they normally contribute less than 2 mosm/ L because of their very high molecular weights.
The major nonelectrolytes of plasma are glucose and urea, which in the steady state are in equilibrium with cells. Their contributions to osmolality are normally about 5 mosm/L each but can become quite large in hyperglycemia or uremia.
The total plasma osmolality is important in assessing dehydration, overhydration, and other fluid and electrolyte abnormalities. Hyperosmolality can cause coma (hyperosmolar coma).
| A | Blood viscosity | |
| B |
Osmolarity |
|
| C |
Intra-ocular tension |
|
| D |
Intercranial tension |
Ans. is ‘b’ i.e., Omolarity
Which of the following statements is true about body fluid osmolarity?
| A |
Major contributor is proteins |
|
| B |
Major contributor is Na+ |
|
| C |
ECF osmolarity is 250 mOsm/L |
|
| D |
Measured by dilution method |
Ans. is ‘B’ i.e., Major contributor is Na+
- The osmolarity is the number of osmoles per liter of solution (eg. Plasma).
- Osmolarity is affected by the volume of the various solutes in the solution and the temperature.
- About 80% of the total osmolarity of the interstitial fluid and plasma is due to sodium and chloride ions, whereas for intracellular fluid almost half the osmolarity is due to potassium ions and the remainder is divided among many other intracellular substances.
