W - PHGY209 - 1.Body Fluids

Q1: What is total body water (TBW)?

A1: The total amount of fluid in the body; ~45–75% of body weight.

Q2: How does body fat affect TBW?

A2: Inversely; more fat = less TBW %.

Q3: Which tissues have the highest water percentage?

A3: Muscle (75%), liver (70–80%), skin (70%).

Q4: What are other factors affecting TBW?

A4: Age (↓ with age), gender (females ↓), weight, ethnicity.

Q6: Formula: Drug concentration (mg/mL)?

Q7: Negative water balance examples?

A7: Desert (↓ intake), marathon (↑ sweat), altitude (↑ expiration), shellfish (↑ GI loss).

Q8: What causes water intoxication?

A8: Drinking excessive water or renal failure.

Q9: How do we gain water?

A9: Food, liquids, nutrient oxidation.

Q10: How do we lose water?

A10: Obligatory (urine, stool, insensible) and facultative losses.

Q11: What are insensible losses?

A11: Water lost via skin/respiratory lining (not sweat).

Q12: Difference: Insensible perspiration vs sweating?

A12: Insensible: water only, passive, whole skin;
Sweating: water + electrolytes, active, sweat glands.

Q13: What is the final concentration of 200 mg drug in 55 kg woman (50% TBW)?

Q14: Who has lowest drug concentration from 100 mg?

A14: 80 kg male with 50% TBW (highest volume).

Q15: Which statement is FALSE?

A15: B. "Insensible losses include sweating" (FALSE — not sweat).

Q16: What is the 60-40-20 rule?

A16: TBW = 60% of BW, ICF = 40%, ECF = 20%.

Q17: What separates ICF and ECF?

A17: Cellular membranes.

Q18: ECF split into what subcompartments?

A18: ISF (15%), Plasma (5%).

Q19: What is plasma?

A19: Aqueous fluid with blood cells suspended; 55% of blood volume.

Q20: What is serum?

A20: Plasma minus clotting factors.

Q21: What is hematocrit?

A21: % of blood volume as red blood cells.

Q22: What is interstitial fluid (ISF)?

A22: Ultrafiltrate of plasma (minus proteins + cells).

Q23: Minor ECF compartments?

A23: Transcellular fluid, lymph.

Q24: What is transcellular fluid?

A24: Small volumes secreted into body cavities (e.g., joints, lungs).

Q25: What is lymph?

A25: ISF that enters the lymphatic system to return to circulation.

Q26: Indicator for TBW?

A26: Antipyrine, D₂O, or T₂O.

Q27: Indicator for ECF?

A27: Inulin, sucrose, mannitol.

Q28: Indicator for plasma?

A28: Evan’s Blue or I¹³¹-Albumin.

Q29: Indicator dilution formula?

Q30: Formula: TBW = ?

A30: ICF + ECF = ICF + (ISF + Plasma)

Q31: Which subcompartment takes up ~15% of ECF?

A31: ISF.

Q32: Which is a FALSE statement?

A32: A. "Lymph and transcellular fluid are ICF" (they’re ECF).

Q33: Are solute compositions uniform in ICF and ECF?

A33: No, they differ significantly.

Q34: Key ECF ions?

A34: Na⁺, Cl⁻, HCO₃⁻.

Q35: Key ICF ions?

A35: K⁺, PO₄³⁻, proteins.

Q36: Osmolarity in both compartments?

A36: ~290 mOsm/L.

Q37: pH in ECF vs ICF?

A37: ECF: 7.4, ICF: 7.1.

Q38: Molarity formula?

Q39: Equivalent formula?

A39: Molarity × valence.

Q40: Osmolarity formula?

A40: Molarity × particles dissociated.

Q41: % wt/vol formula?

Q42: Hematocrit formula?

Q43: CaCl₂: # of equivalents for Ca²⁺ and Cl⁻?

A43: 1 mol → 2 Eq of Cl⁻, 2 Eq of Ca²⁺.

Q44: CaCl₂ osmolarity in 1 L?

A44: 3 Osm (1 Ca²⁺ + 2 Cl⁻).

Q45: Mg²⁺ (48.6g, MW=24.3) in 1L: what concentration?

A45: 2 M, 4 Eq/L, 4 Osm/L, 4.86% wt/vol.

Q46: ECF vs ICF: What does ECF have more of?

A46: Na⁺, Cl⁻; less proteins, PO₄³⁻.