7.1 Body fluid and Electrolytes

What is the primary role of water in the body?

Water serves as a medium for metabolic reactions, a transporter for nutrients and waste, a lubricant, an insulator, a shock absorber, and helps regulate body temperature.

What percentage of body weight is typically composed of water?

50-60% of body weight is water.

How does age influence body water distribution?

Infants have a higher percentage of body fluid in extracellular fluid (ECF), making them more susceptible to fluid loss.

What is the percentage of body fluid in males compared to females?

Males typically have about 60% body fluid due to greater muscle mass, while females have about 50% due to higher adipose tissue.

What are the two major compartments of body fluids?

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

What is the function of intracellular fluid (ICF)?

ICF is vital for normal cell functioning and contains solutes like oxygen, electrolytes, and glucose.

What is the role of extracellular fluid (ECF)?

ECF serves as a transport system that carries oxygen and nutrients to cells and removes waste products.

What are the two main compartments of extracellular fluid (ECF)?

Intravascular fluid (plasma) and interstitial fluid.

What percentage of ECF is made up of intravascular fluid?

Approximately 1/3 of ECF is intravascular fluid.

What is insensible water loss?

Insensible water loss is the invisible vaporization of water from the lungs and skin, typically around 600 to 900 ml/day.

What mechanisms regulate fluid volume and electrolyte concentrations in the body?

Osmoreceptors, ADH (antidiuretic hormone), RAAS (renin-angiotensin-aldosterone system), and ANP (atrial natriuretic peptide).

What triggers the release of ADH?

Increased serum osmolality stimulates osmoreceptors in the hypothalamus to synthesize ADH.

What is osmosis?

Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

What is the difference between osmolality and osmolarity?

Osmolality measures the concentration of solutes per kilogram of solvent (mOsm/kg), while osmolarity measures solutes per liter of solution (mOsm/L).

What are Starling's Laws of Capillary Forces?

Starling's Laws describe the balance between hydrostatic pressure and osmotic pressure at capillary membranes, regulating fluid movement.

What is hydrostatic pressure?

Hydrostatic pressure is the pressure exerted by fluid on the walls of blood vessels, pushing fluid out of the capillary.

What is osmotic pressure?

Osmotic pressure is the pressure exerted by solutes in plasma, pulling fluid into the capillary from the interstitial fluid.

What can disturb the balance of body fluids and electrolytes?

Illness, excessive temperatures, vigorous activity, and therapeutic measures like diuretics or nasogastric suction can disturb this balance.

What is the average daily intake and output of water for healthy individuals?

The daily average intake and output of water are approximately equal.

What are some examples of transcellular fluids?

Cerebrospinal fluid, pericardial fluid, pancreatic fluid, pleural fluid, intraocular fluid, biliary fluid, peritoneal fluid, and synovial fluid.

What is colloid oncotic pressure?

Osmotic pressure exerted by albumin within the bloodstream.

What is diffusion?

Movement of particles from an area of higher concentration to lower concentration through a semipermeable membrane.

What factors affect the rate of diffusion?

Molecule size, concentration difference, and temperature.

What is facilitated diffusion?

Movement of molecules across a membrane with the help of a carrier molecule, e.g., insulin-glucose.

What is filtration in the context of body fluids?

Movement of both solute and solvent across a semipermeable membrane from an area of higher pressure to lower pressure.

What is active transport?

Movement of solute from lower concentration to higher concentration using energy (ATP), e.g., Na-K pump.

What are electrolytes?

Substances in body fluids that carry an electrical charge, including cations (+) and anions (-).

What are the major cations in body fluids?

Sodium, potassium, calcium, magnesium, and hydrogen ions.

What are the major anions in body fluids?

Chloride, bicarbonate, phosphate, sulfate, and negatively charged protein ions.

What are the functions of electrolytes in the body?

Promote neuromuscular irritability, maintain fluid volume and osmolality, distribute body water, and regulate acid-base balance.

What is the normal range for sodium (Na+) in ECF?

135-145 mEq/L (mmol/L).

What role does sodium (Na+) play in the body?

It is crucial for muscle contraction, nerve impulse transmission, and maintaining ECF osmolality and volume.

What regulates potassium (K+) levels in the body?

Aldosterone and hydrogen ions; aldosterone retains sodium and excretes potassium.

What is the normal range for potassium (K+) in ECF?

3.5-5.0 mEq/L (mmol/L).

What is the normal range for calcium (Ca++) in the blood?

8.8-10.5 mg/dl (2.25-2.75 mmol/L).

What are the two forms of calcium in the body?

Bound (attached to proteins) and unbound (ionized, active form).

What is phosphorus (P) and its normal range?

Major anion in ICF, normal range is 2.5-4.5 mg/dl (0.8-1.45 mmol/L).

What is the role of magnesium (Mg++) in the body?

It is involved in muscle contractions, ATP formation, and DNA synthesis.

What is the normal range for magnesium (Mg++) in the blood?

1.8-3.6 mg/dl (0.75-1.07 mmol/L).

What is the role of chloride (Cl-) in body fluids?

It helps maintain ECF osmotic pressure and is important in stomach acid formation.

What is tonicity in the context of body fluids?

It refers to the concentration of particles in a solution.

What is the normal tonicity of body fluids?

275-290 mOsm/L.

What defines isotonic fluids?

Fluids that have the same osmotic pressure as body fluids, comparable to 0.9% NaCl.

What are hypotonic fluids?

Fluids with a lower solute concentration than plasma.

What are hypertonic fluids?

Fluids with a higher solute concentration than plasma.