pathophysiology podacst ch8

Body fluid compartments

intracellular and extracellular fluid spaces in the body

Homeostatic balance

maintenance of proper fluid, electrolytes, and pH levels

Osmosis

movement of water across a semipermeable membrane from low to high solute concentration

Osmolarity

solute concentration per litre of solution

Isotonic solution

fluid with the same osmolarity as blood plasma

Hypotonic solution

lower osmolarity than plasma, causing water to enter cells

Hypertonic solution

higher osmolarity than plasma, causing water to exit cells

Hydrostatic pressure

pressure exerted by fluid against vessel walls

Oncotic pressure (colloid osmotic)

pressure due to protein concentration, mainly albumin, pulling water into vessels

Edema

accumulation of excess fluid in interstitial spaces

Causes of edema

increased hydrostatic pressure, decreased oncotic pressure, increased capillary permeability, lymphatic obstruction

Dehydration

loss of body water resulting in decreased volume and increased osmolarity

Electrolytes

charged ions essential for body functions (e.g., Na⁺, K⁺, Ca²⁺)

Sodium (Na⁺)

major extracellular cation important for fluid balance and nerve function

Hyponatremia

low serum sodium causing cellular swelling, CNS changes

Hypernatremia

high serum sodium causing cellular dehydration and neurological changes

Potassium (K⁺)

major intracellular cation key in cardiac and muscle function

Hypokalemia

low potassium causing muscle weakness, arrhythmias

Hyperkalemia

high potassium causing cardiac conduction problems

Calcium (Ca²⁺)

ion essential for bones, muscle contraction, coagulation, neurotransmission

Hypocalcemia

low calcium leading to neuromuscular excitability, tetany

Hypercalcemia

high calcium causing weakness, constipation, arrhythmias

Acid-base balance

regulation of hydrogen ion concentration to maintain pH 7.35–7.45

Acidemia

blood pH below 7.35

Alkalemia

blood pH above 7.45

Buffers

systems (bicarbonate, proteins, phosphates) that resist pH changes

Respiratory regulation

CO₂ elimination by lungs to control acid-base

Metabolic regulation

kidney excretion/reabsorption of bicarbonate to maintain pH

Respiratory acidosis

elevated CO₂ (hypoventilation) leading to acidemia

Respiratory alkalosis

low CO₂ (hyperventilation) leading to alkalemia

Metabolic acidosis

low bicarbonate (e.g., diarrhea, renal failure) causing acidemia

Metabolic alkalosis

high bicarbonate (e.g., vomiting, diuretics) causing alkalemia

Compensation

respiratory or renal adjustments to partially correct pH imbalances

Anion gap

measurement of unmeasured anions to identify metabolic acidosis origins