BODY FLUID COMPARTMENT👾

What percentage of total body weight (TBW) is body water in an average adult?

About 60% (≈42 L in a 70 kg adult).

Body water is divided into which two major compartments?

Intracellular fluid (ICF) and Extracellular fluid (ECF).

Which compartment contains the greatest volume of body water?

ICF 2/3~(28L)

Approximately how much of TBW is ECF?

1/3 (14L)

Name the three components of ECF.

Interstitial Fluids ~85%

Plasma Fluid ~15%

Transcellular Fluids ~ >1%

Which intracellular ions are present in high concentration besides potassium?

Magnesium (Mg²⁺) and phosphate (PO₄³⁻).

Which protein is abundant in plasma but scarce in interstitial fluid?

Albumin

Why does plasma retain water better than interstitial fluid?

Due to plasma proteins creating colloid osmotic pressure.

State one major function of intracellular potassium.

Electrical signaling and cellular metabolism.

State one major function of extracellular sodium

Fluid balance and nerve impulse conduction.

Which ion plays the major buffering role in ECF?

Bicarbonate (HCO₃⁻).

Total body water decreases with __________ and __________.

Age and increased body fat.

Which pump maintains Na⁺ and K⁺ concentration gradients?

Na⁺/K⁺-ATPase.

How many Na⁺ ions leave and K⁺ ions enter during one Na⁺/K⁺ pump cycle?

3 Na⁺ out, 2 K⁺ in.

Normal extracellular sodium concentration?

142 mEq/L

Normal intracellular potassium concentration

140 mEq/L

What is osmolality?

Concentration of osmotically active particles per kilogram of solvent.

Why is osmolality physiologically important?

It controls water movement across cell membranes.

Which method is used to determine body fluid compartment volumes?

Indicator dilution method.

Which indicator measures total body water?

Deuterium oxide (D₂O).

Which indicator measures ECF volume?

Inulin

Which indicator measures plasma volume?

Evans Blue dye

How is ICF volume calculated?

TBW − ECF

How is interstitial fluid volume calculated?

ECF − Plasma volume

Which hormone primarily regulates water reabsorption?

ADH (Vasopressin)

Which hormone mainly regulates sodium retention?

Aldosterone

Which organ is the major regulator of body fluid volume?

Kidneys

Which mechanism stimulates water intake during dehydration?

Thirst mechanism

Define edema.

Excess accumulation of fluid in interstitial tissues.

Name four causes of edema

Increased capillary hydrostatic pressure,

decreased plasma proteins,

inflammation,

lymphatic obstruction.

What is third spacing?

Movement of fluid from vascular space into non-functional interstitial spaces.

Give three conditions associated with third spacing.

Burns, sepsis and severe trauma.

Give one example of isotonic dehydration.

Hemorrhage

What happens to ICF during isotonic dehydration?

It remains essentially unchanged.

What is hyperosmotic (hypertonic) dehydration?

Water loss exceeds sodium loss.

Name two causes of hyperosmotic dehydration.

Excessive sweating and Diabetes Insipidus.

What happens to cells during hyperosmotic dehydration?

Cells shrink.

What is hypoosmotic dehydration?

Sodium loss exceeds water loss.

Give one disease causing hypoosmotic dehydration.

Addison’s disease.

Why does Addison’s disease cause hyponatremia?

Aldosterone deficiency causes excessive sodium loss.

Name two forms of Diabetes Insipidus.

Central and nephrogenic.

What causes brain edema in severe hyponatremia?

Water moves into brain cells causing swelling.

What is lymphedema?

Edema caused by impaired lymphatic drainage.

Why is D5W considered “free water” after metabolism?

Glucose is metabolized, leaving water to distribute throughout body compartments.

Why are 0.9% Normal Saline and Lactated Ringer’s preferred for hypovolemia?

They remain mainly in the ECF, expanding plasma volume and supporting blood circulation.