Problem 5 - Anatomy and Physiology of Animals

Question

Which of the following statements about blood is true? a. Blood is about 92 percent water. b. Blood is slightly more acidic than water. c. Blood is slightly more viscous than water. d. Blood is slightly more salty than seawater.

Step-by-Step Solution

Answer

Statements A and C are true.

Step 1: Analyzing Statement A

Statement A asserts that blood is about 92 percent water. This is indeed true, as plasma, which makes up about 55% of blood volume, is approximately 90-92% water. Hence, this statement is true.

Step 2: Analyzing Statement B

Statement B claims that blood is slightly more acidic than water. However, blood is typically slightly alkaline rather than acidic, with a pH level around 7.4, whereas pure water has a neutral pH of 7. This makes statement B false.

Step 3: Analyzing Statement C

Statement C suggests blood is slightly more viscous than water. Blood compromises several cells, proteins, and other components making it thicker and more viscous compared to water. Therefore, statement C is true.

Step 4: Analyzing Statement D

Statement D proposes that blood is slightly more salty than seawater. This is false, as seawater has a higher salt concentration than blood. Blood's salt concentration is about 0.9% compared to seawater's 3.5%. Thus, statement D is false.

Key Concepts

Blood Plasma

Blood plasma is the liquid component of blood, making up a significant portion of its overall volume. It comprises about 55% of total blood volume, and it holds various essential elements. One of the primary features of blood plasma is its water content.

• Plasma is around 90-92% water, making it the dominant constituent.
• Besides water, plasma contains proteins, electrolytes, hormones, waste products, and nutrients.

The presence of these components is crucial for the normal functioning of the body. Proteins such as albumin, globulins, and fibrinogen play important roles in maintaining blood pressure, immunity, and clotting.

The high water content in plasma facilitates efficient transport of cells, nutrients, and waste. This composition supports homeostasis by maintaining a stable internal environment.

Blood pH Level

The blood pH level is a measure of its acidity or alkalinity. In human bodies, maintaining a stable pH is vital for physiological processes. Blood is typically slightly alkaline, which is contrary to statement B in the exercise.

• The average pH level of blood is around 7.4, slightly above the neutral 7 of pure water.
• This alkalinity is tightly regulated through respiratory and kidney functions.

The importance of maintaining the correct pH level cannot be overstated as even small fluctuations can affect biological processes and enzyme activity. Thus, mechanisms like bicarbonate buffering systems exist in the body to stabilize pH levels.

Blood Viscosity

Blood viscosity refers to the thickness and stickiness of blood. It is an essential factor concerning blood flow and circulation. Compared to water, blood is slightly more viscous.

• This increased viscosity is due to the various cells (such as red and white blood cells) and proteins within the blood.
• Higher viscosity means that blood flows at slower rates than water.

However, this thickness is crucial for preventing quick leaks from vessels and maintaining adequate circulation and pressure in the body's system. The viscosity can be affected by several factors including temperature, hydration, and diseases such as scleroderma or increased protein levels.

Blood Salinity

Blood salinity refers to the salt concentration in blood. Contrary to statement D in the exercise, blood is less salty than seawater.

• Blood contains about 0.9% saline, significantly lower than seawater which has around 3.5% salt content.
• This saline concentration is essential for maintaining osmotic balance across cell membranes.

Osmotic balance helps in regulating fluid distribution and maintaining cell function. Imbalances can lead to conditions like dehydration or overhydration, impacting cell integrity and overall health. The body's mechanisms ensure that the salinity levels are just right to prevent such imbalances.