part 2, body fluid, cations/anions

What percentage of body weight is water in adults?

Approximately 60%.

What is the average body water content for dogs?

534–660 mL/kg, similar in cats.

How does body water content differ in young animals?

Up to 80% due to less fat and more water.

What are the two major fluid compartments in the body?

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

What fraction of total body water (TBW) does ICF make up?

About two-thirds (⅔) of TBW.

What ions are rich in the intracellular fluid?

K⁺, Mg²⁺, and phosphates.

What is the main function of the ICF?

Site of metabolism, maintaining cell shape and concentration gradients.

What fraction of TBW is extracellular fluid?

About one-third (⅓) of TBW.

What are the subdivisions of the extracellular fluid?

Interstitial fluid, plasma, and transcellular fluids.

What proportion of ECF does interstitial fluid make up?

Around 80% of ECF.

What is the function of interstitial fluid?

Acts as a medium for nutrient and waste exchange between cells and blood.

What proportion of ECF is plasma?

About 20%.

What is the function of plasma?

Transports nutrients, gases, and hormones within the vascular system.

What are transcellular fluids and their examples?

Specialized fluids like cerebrospinal, synovial, pleural, peritoneal, ocular, and digestive fluids that provide lubrication and protection.

What barriers separate the body’s fluid compartments?

The plasma membrane separates ICF and ISF; the capillary wall separates ISF and plasma.

What are electrolytes?

Minerals that form ions in water and conduct electricity.

What are the major functions of electrolytes?

Nerve impulse transmission, muscle contraction, acid–base and osmotic balance, hydration, and enzyme activity.

List the major electrolytes.

Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃⁻, and PO₄³⁻.

What is the main extracellular cation?

Sodium (Na⁺).

How is sodium regulated in the body?

Through diet and renal excretion under aldosterone control.

How does aldosterone regulate sodium?

Low Na⁺ → increased aldosterone → Na⁺ reabsorption; high Na⁺ → decreased aldosterone → Na⁺ excretion.

What are common sodium requirements in animals?

Carnivores usually have adequate Na⁺, herbivores may need salt supplementation.

What is the main intracellular cation?

Potassium (K⁺).

What are the functions of potassium?

Nerve impulse conduction, muscle contraction, and cardiac rhythm maintenance.

How is potassium balance maintained?

By the Na⁺/K⁺ pump maintaining intracellular charge.

What are the effects of hyperkalemia?

Muscle paralysis, slow heart rate, and cardiac arrest.

What are the effects of hypokalemia?

Weakness, muscle cramps, thirst, and arrhythmias.

What are the main functions of calcium?

Bone and teeth formation, muscle contraction, nerve conduction, and blood clotting.

What hormones regulate calcium levels?

Parathyroid hormone (PTH) and Vitamin D.

What are the effects of hypercalcemia?

Kidney stones, arrhythmia, and fatigue.

What are the effects of hypocalcemia?

Tremors, spasms, and milk fever in cows.

What are the functions of magnesium?

Acts as an enzyme cofactor, aids nerve transmission and muscle relaxation, and works with Ca²⁺ and K⁺ in cardiac function.

What are the effects of hypomagnesemia?

Tremors, seizures, and grass tetany in ruminants.

What are the effects of hypermagnesemia?

Weak reflexes, hypotension, and cardiac arrest.

What is the main extracellular anion?

Chloride (Cl⁻).

What are the functions of chloride?

Forms HCl for digestion and follows sodium movement for osmotic balance.

What happens in hyperchloremia?

Acidosis causing fatigue and rapid breathing.

What happens in hypochloremia?

Alkalosis causing vomiting and muscle twitching.

What is the main buffer anion in plasma?

Bicarbonate (HCO₃⁻).

How is bicarbonate formed and regulated?

From CO₂ + H₂O → H₂CO₃ ↔ H⁺ + HCO₃⁻; regulated by lungs and kidneys.

Where is phosphate mainly found?

In intracellular fluid and bones.

What are the functions of phosphate?

ATP production, acid–base buffering, and bone formation.

What are the effects of hyperphosphatemia?

Occurs in renal failure, causes low Ca²⁺, bone pain, and itching.

What are the effects of hypophosphatemia?

Weakness, seizures, and respiratory failure.