Week 3 (Body Fluids)

Question 1

Body Fluids

Answer 1

A dilute solution of various solutes in water, distributed in different compartments in the body. The volume, distribution, composition, and osmolarity of body fluids are crucial for normal cell metabolism and organ function.

Question 2

Body Fluids & Gender

Answer 2

Males: Body fluids account for 60% of total body mass.

Females: Body fluids account for 55% of total body mass due to higher body fat and less skeletal muscle compared to males.

Body water content varies with age, sex, body mass, and body fat percentage.

Question 3

Key Components of Body Fluids

Answer 3

-Water: Universal solvent

-Solutes: Include electrolytes and nonelectrolytes

*Electrolytes: Sodium (Na⁺), Potassium (K⁺), Chloride (Cl⁻)
*Nonelectrolytes: Proteins, oxygen (O₂), glucose

Question 4

Body fluids are divided into 2 main compartments

Answer 4

Intracellular Fluid (ICF)
Extracellular Fluid (ECF)

Question 5

Intracellular Fluid (ICF)

Answer 5

-Makes up ⅔ of total body fluid.

-Largest percentage of water in the body is found here.

Question 6

Extracellular Fluid (ECF)

Answer 6

-Makes up ⅓ of total body fluid.

*Interstitial Fluid (80% of ECF)

*Plasma (20% of ECF)
-also called intravascular fluid

*Transcellular Fluid: Includes lymph, cerebrospinal fluid, synovial fluid, aqueous humor, and fluids in the pleural, pericardial, and peritoneal cavities.

Question 7

60-40-20 Rule:

Answer 7

60% of body weight is total body water 40% of body weight is intracellular fluid 20% of body weight is extracellular fluid

Question 8

Extracellular Fluids (ECF) Compositions

Answer 8

*Sodium (Na⁺) is the most abundant cation.
*Chloride (Cl⁻) is the most abundant anion.

Plasma contains a higher protein content than interstitial fluid.

Question 9

Intracellular Fluids (ICF) Compositions

Answer 9

*Potassium (K⁺) is the most abundant cation
*Phosphate (PO₄³⁻) is the most abundant anion.

Low in sodium (Na⁺) and chloride (Cl⁻).

Question 10

Body Fluids and Electrolyte Balance

Answer 10

Maintaining homeostasis of water and electrolytes is crucial for normal cell function.

Movement of water and electrolytes between compartments is regulated to ensure stability in:
*Total volume
*Distribution
*Solute concentration and pH

Question 11

Two Barriers Separate Fluid Compartments

Answer 11

Cell Membrane – Separates intracellular fluid from interstitial fluid.

Blood Vessel Walls – Separate plasma from interstitial fluid.

Question 12

Fluid movement is regulated by

Answer 12

Osmotic Pressure
Hydrostatic Pressure

Question 13

Mechanisms of Movement

Answer 13

Osmosis
Diffusion
Filtration
Reabsorption

Nutrients, respiratory gases, and wastes move unidirectionally.

Plasma is the only fluid that circulates throughout the body, linking internal and external environments.

Question 14

Regulation of Water Intake

Answer 14

Thirst Mechanism: Primary regulator of fluid intake.

Dehydration stimulates the thirst center in the hypothalamus.
*Dehydration = Water loss > Water gain

Results in decreased volume and increased osmolarity of body fluids.

Question 15

Regulation of Water and NaCl Loss

Answer 15

Key Hormones:
*Antidiuretic Hormone (ADH) (also called vasopressin)
-Increases water permeability in the nephron.
-Produces concentrated urine.

*Atrial Natriuretic Peptide (ANP)
-Promotes excretion of Na⁺ and Cl⁻, followed by water excretion to decrease blood volume.