Body Water Content and Fluid Compartments Quiz

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Questions and Answers

What is the approximate body water content in elderly individuals?

45% (correct)

70%

60%

50%

What percentage of body water is found in skeletal muscle?

20%

50%

75% (correct)

60%

Which compartment contains the majority of body water?

Extracellular fluid

Intracellular fluid (correct)

Interstitial fluid

Plasma

Which of the following types of fluid is considered a component of extracellular fluid?

Plasma Signup and view all the answers

What is the percentage of body water content in young women?

50% Signup and view all the answers

Which statement accurately describes nonelectrolytes?

They do not produce charged species in solution. Signup and view all the answers

What is a characteristic of electrolytes?

They can dissociate into ions in water. Signup and view all the answers

Which compartment contains high concentrations of sodium and chloride?

Blood plasma Signup and view all the answers

Which of the following is a primary route for water exit from the body?

Urination Signup and view all the answers

What happens to a cell placed in a hypertonic solution?

Water moves out of the cell causing it to shrink. Signup and view all the answers

What regulates the concentration of sodium in the extracellular fluid?

Renin-angiotensin-aldosterone system Signup and view all the answers

What is the pH level of arterial blood typically supposed to be?

7.4 Signup and view all the answers

Which process occurs when the intracellular environment has a higher concentration of solutes than the external environment?

Osmosis Signup and view all the answers

Which ion is recognized as the most abundant cation in extracellular fluid?

Sodium Signup and view all the answers

How are normal physiological pH levels primarily maintained?

Chemical buffers in the blood Signup and view all the answers

What is the primary role of NaHCO3 in the body?

Regulation of blood pH Signup and view all the answers

What causes obligatory water losses in the body?

Cellular waste elimination Signup and view all the answers

When a strong base is introduced to the body, what occurs in buffer systems?

It becomes a weak base. Signup and view all the answers

Why is water and sodium related in their balance within the body?

Sodium acts as a ‘water magnet’. Signup and view all the answers

Study Notes

Body Water Content and Fluid Compartments

Body water content varies based on age, sex, and body fat. Infants have ~70%, elderly ~45%, young men ~60%, young women ~50%.
Adipose tissue has the lowest water content (up to 20%), skeletal muscle has the highest (75%).
Total body water is approximately 60% of body weight and is roughly 40 liters.
Intracellular fluid (ICF) is inside cells and accounts for 40% of body weight (approx. 25 liters)
Interstitial fluid (IF) exists between cells and accounts for 80% of extracellular fluid, roughly 12 liters.
Extracellular fluid (ECF) is outside cells and accounts for 20% of body weight (approx. 15 liters). Plasma, roughly 3 liters, is the fluid portion of blood, constituting approximately 20% of the ECF.

Two Classifications of Solutes

Electrolytes dissociate into ions in water, conducting electrical current, like salts, acids and some proteins.
Nonelectrolytes do not dissociate into ions when in solution, such as glucose. They have a significantly lower osmotic pressure than electrolytes.

Composition of Body Fluids

Electrolytes have a much higher osmotic power than nonelectrolytes, due to dissociation into more than one ion.
Examples of electrolytes: sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3-), chloride (Cl-), hydrogen phosphate (HPO42-), and sulfate (SO42-). (There are concentration percentages which can be found via tables within the provided scans.)
Non-electrolytes include glucose and other organic molecules.

Comparison of ECF vs ICF

Sodium (Na+) concentration is higher in extracellular fluid (ECF) while potassium (K+) concentration is higher in intracellular fluid (ICF).
These ion concentration differences are crucial for maintaining the resting membrane potential of cells, facilitated by Na+/K+ pumps.

Exchanges Between Fluid Compartments

Water molecules easily move between the compartments, maintaining a constant osmolality.
Substances need to pass through plasma and interstitial fluid to reach intracellular fluid.
Plasma carries materials throughout the body.
Fluid exchanges occur across capillary walls between plasma and interstitial fluid, and between interstitial fluid and intracellular fluid via plasma membranes.

Water Intake and Output

Water intake varies greatly among individuals. Intake can come from metabolism, food, and beverages.
Water exits the body through excretion (urine, feces), perspiration, and vaporization from lungs (insensible water loss).
Water and sodium are tightly linked; sodium can be viewed as a "water magnet".

Regulation of Water Output

Obligatory water loss is approximately 500 mL of urine per day.
Kidneys need to flush out waste products alongside water loss.
Factors affecting water output include intake, diet, and perspiration.

Disturbances in Water Balance

If the environment outside a cell has a higher solute concentration (hypertonic) than inside the cell, water moves out of the cell, causing it to shrink.
Conversely, if the environment has a lower solute concentration (hypotonic) than inside the cell, water moves into the cell, causing it to swell potentially burst.

Regulation of Sodium

Although sodium is essential for water balance, there is no identified sodium receptor.
Increased ECF potassium concentration triggers the renin-angiotensin-aldosterone system, increasing blood volume and sodium reabsorption in kidneys.

Regulation of Physiological pH

pH is critical for many biochemical reactions within the body.
Normal arterial blood pH is around 7.4.
Many factors, including metabolic waste and breathing, contribute to pH variations in blood.
Chemical buffers (e.g., bicarbonate, phosphate) help regulate the body's pH.

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Description

Explore the intricate details of body water content, fluid compartments, and classifications of solutes. This quiz covers variations in water content based on age and body composition, as well as the roles of electrolytes and nonelectrolytes. Test your understanding of these fundamental concepts in human physiology.