Question

Blood plasma has an osmolality of about \(300 \mathrm{mOsm}\). The osmolality of isotonic saline is equal to a. \(150 \mathrm{mOsm}\). b. \(300 \mathrm{mOsm}\). c. \(600 \mathrm{mOsm}\). d. none of these.

Short answer

The osmolality of isotonic saline is equal to \(300 \mathrm{mOsm}\), which matches the osmolality of blood plasma. Therefore, the correct answer is option b. \(300 \mathrm{mOsm}\).

Step-by-step solution

Review the given information

The osmolality of blood plasma is about \(300 \mathrm{mOsm}\).

Compare the osmolality of blood plasma to the answer options

Now, let's compare the osmolality of blood plasma to each of the options provided: a. \(150 \mathrm{mOsm}\) b. \(300 \mathrm{mOsm}\) c. \(600 \mathrm{mOsm}\) d. none of these

Identify isotonic saline osmolality

Since isotonic saline has the same osmolality as blood plasma, we should choose the option that is equal to \(300 \mathrm{mOsm}\). In this case, the answer is: b. \(300 \mathrm{mOsm}\)

Key concepts

Blood Plasma

Blood plasma is an essential component of our circulatory system. It is the liquid part of blood, making up about 55% of the total blood volume. Plasma serves many functions, including transporting nutrients, hormones, and proteins to where they are needed in the body.
One of the major characteristics of blood plasma is its osmolality. Osmolality is a measure of the concentration of solutes such as electrolytes in the plasma. This concentration influences many physiological functions because it helps maintain the balance of fluids in the body’s cells and tissues.
Typically, blood plasma has an osmolality of approximately 300 milliosmoles per kilogram (mOsm/kg). This balance is crucial for normal cell function and overall homeostasis. If the osmolality shifts significantly, it can lead to conditions such as dehydration or overhydration. Understanding the osmolality of blood plasma is vital for medical professionals when administering intravenous fluids to patients, ensuring the fluids are properly balanced to maintain or restore health.

Isotonic Saline

Isotonic saline, often referred to as normal saline, is a commonly used intravenous solution in medical settings. It consists of water mixed with sodium chloride (salt) to create a solution that matches the osmolality of human blood plasma.
The osmolality of isotonic saline is approximately 300 mOsm, which is nearly identical to that of blood plasma. This similarity allows isotonic saline to effectively maintain the osmotic balance when administered into the bloodstream.
Using an isotonic solution like saline helps prevent fluid shifts between compartments in the body, ensuring that cells neither swell nor shrink dramatically. This makes isotonic saline an ideal choice for fluid replacement, maintaining hydration, or rapidly increasing the blood volume in situations like dehydration or shock. It is important for healthcare providers to understand this property to ensure safe and effective treatment in clinical scenarios.

Osmolarity

Osmolarity refers to the concentration of solute particles in a solution, expressed as osmoles per liter (Osm/L). While osmolality and osmolarity are closely related, they measure concentration slightly differently: osmolality is based on weight (osmoles per kilogram), while osmolarity is based on volume (osmoles per liter).
Despite these differences, both concepts are crucial in understanding how solutions interact with biological tissues. When referring to solutions like blood plasma or isotonic saline, the terms are often used interchangeably because their values are similar in normal physiological conditions.
Osmolarity is important in medical and biological contexts because it helps predict how water will move across cell membranes. For instance, if a solution has higher osmolarity than a cell's interior, water will move out of the cell to balance the concentration. This movement can affect cell size and function. Therefore, knowledge of osmolarity is essential in fields like medicine and physiology, aiding in the understanding and management of fluid balance within the body.