Tortora, Ebaa M Alzayadneh, DDS, PhD Body Fluids & Blood Tortora, Ebaa M Alzayadneh, DDS, PhD University of Jordan

Body Fluid Compartments Barriers 1-plasma membrane 2- blood vessel wall 1L- has a mass of 1kg 40% 20%

Q? Calculate volume of blood plasma in a lean 60 kg female? University of Jordan

Source of daily water normal conditions University of Jordan

Renal excretion of water is regulated Route ml/day Water intake Fluid In food Metabolic product Total Water output Insensible Sweat Feces Urine 1200 1000 300 2500 700 100 200 1500 Water loss Normal temp. Hot weather Prolonged exercise Insensible loss Skin Lungs Sweat Feces Urine Total loss Intake 350 100 200 1500 2500 250 1400 1200 3400 650 5000 500 6700

Regulation of water gain (Intake) Metabolic water volume : depends on level of aerobic cellular respiration (ATP demand). Mainly; water intake (drinking): Thirst center in the hypothalamus is stimulated by Blood high osmolality (Osmoreceptors) neurons in the mouth Baroreceptors in the heart and blood vessels Dehydration occurs when water loss is greater than water intake. Decline in blood pressure stimulates RAS (Renin Angiotensin System) Angiotensin II RAS: Renin Angiotensin System University of Jordan

Regulation of water and solute loss Although loss of water by sweat and exhalation is increased during exercise, elimination of excess water and solutes is mainly controlled by urine output. The main factor that determines body fluids volume is the extent of urinary NaCl loss (Water follows solutes). Variable NaCl intake- variable urinary NaCl loss to maintain homeostasis. University of Jordan

Regulation of water and solute loss increased NaCl intake leads to increased blood volume by increased water movement from intracellular to ICF. The three most important hormones that regulate Na and Cl excretion are Angiotensin II, Aldosterone and ANP. Ang II : increases NaCl reabsorption in the kidney, water follows. Aldosterone: increases NaCl reabsorption in the kidney, water follows. Atrial Natruitic PeptideANP: decreases NaCl and water reabsorption; thus decrease blood volume. (Natriuresis) The main hormone that regulate water loss is antidiuretic hormone (ADH) which decreases water loss from kidney. University of Jordan

Effective Osmoles #Na concentration and it’s attendants (such as Cl-) is the major determinant of the osmolality of the ECF. You can estimate ECF osmolality by doubling the concentration of Na+. #Na and Cl in the ECF are considered effective osmoles as they can cause water to move into or out of the cells. #Glucose and urea can move freely through the cellular membrane so they don’t cause water to move in or out so they are considered ineffective osmoles. # In contrast to the ECF, content of Na+ in the ICF is very low and K is the predominant cation of the ICF. #This difference between the 2 compartments in Na and K content is due to Na+-K+ ATPase channel. University of Jordan

Osmole Measure of solution’s ability to create osmotic pressure & thus affect movement of water Proportional to the number of osmotic particles formed in solution 1 mole of nonionizable substance= 1 osmole. 1mole of glucose forms a 1 osmolar solution in 1L water 1mole of NaCl forms a 2 osmolar solution in 1L water 1mole of CaCl2 forms a 3 osmolar solution in 1L water Osmolality When the concentration of a solution is expressed in osmoles per kilogram of water, the osmolar concentration of a solution is referred to as its osmolality. 1 osmoles/kg H2O=1 osmoles/L = 1000 milliosmoles/L= 1000 mOSM =1000mmol/L

hypotonic isotonic hypertonic Particle concentration compared with intracellular fluid fewer same more Osmolality (mmol/L) <280 280-310 >310 Representative solution 0.45% NaCl 0.9% NaCl 3% NaCl Distilled water 5% glucose 20% glucose Response of cell placed in solution Swell & burst no alteration wrinkle or shrivel

Distribution of some cations and anions in extracellular and intracellular fluid ECF 280-295 mOsm/kgH2O ICF Na+ 145 mEq/L 12 mEq/L K+ 4 150 Ca++ 5 0.001 Cl- 105 HCO3- 25 12 Inorganic phosphate (Pi)+ 2 100 pH 7.4 7.1 #Na concentration and it’s attendants (such as Cl-) is the major determinant of the osmolality of the ECF. You can estimate ECF osmolality by doubling the Concentration of Na+. #Na and Cl in the ECF are considered effective osmoles as they can cause water to move into or out of the cells. #Glucose and urea can move freely through the cellular membrane so they don’t cause water to move in or out so they are considered ineffective osmoles. # In contrast to the ECF, content of Na+ in the ICF is very low and K is the predominant cation of the ICF. #This difference between the 2 compartments in Na and K content is due to Na+-K+ ATPase channel.

University of Jordan

University of Jordan

Movement of water between compartments Normally, cells neither shrink or swell because intracellular and interstitial fluids have the same osmolarity. Increasing osmolarity of interstitial fluid draws water out of cells and cells shrink Decreasing osmolarity of interstitial fluid causes cells to swell Changes in osmolarity most often result from changes in Na+ concentration Water intoxication – drinking water faster than the kidneys can excrete it Can lead to convulsions, coma or death University of Jordan

Electrolytes in body fluids Ions form when electrolytes dissolve and dissociate To compare the charge carried by ions in different solutions, the conc. of ions(cations or anions) is expressed in milliequivalents per liter (mEq/L); one thousandth of amount of charge in one mole of H+. for single positive or negative charge = mEq/L = number in mmol/L Na+ or Cl- number of mEq/liter = mmol/liter Ca2+ or HPO42- number of mEq/liter = 2 x mmol/liter Functions of electrolytes Control osmosis of water between body fluid compartments Help maintain the acid-base balance Carry electrical current Serve as cofactors University of Jordan

Concentrations in body fluids Concentration of ions typically expressed in milliequivalents per liter (mEq/liter) Na+ or Cl- number of mEq/liter = mmol/liter Ca2+ or HPO42- number of mEq/liter = 2 x mmol/liter Chief difference between 2 ECF compartments (plasma and interstitial fluid) is plasma contains many more protein anions Largely responsible for blood colloid osmotic pressure University of Jordan

Differences between plasma and interstitial fluids Chief difference between the two ECF compartments (plasma and interstitial fluid) is that plasma contains many more protein anions. Largely responsible for blood colloid osmotic (oncotic) pressure University of Jordan

ICF differs considerably from ECF ECF most abundant cation is Na+, anion is Cl- ICF most abundant cation is K+, anions are mostly proteins and phosphates (HPO42-) Na+ /K+ ATPase pumps play major role in keeping K+ high inside cells and Na+ high outside cell University of Jordan

Sodium Na+ Most abundant ion in ECF 90% of extracellular cations Plays key role in fluid and electrolytes balance because it account for almost half of the osmolarity of ECF. Hypernatremia, hyponatremia and natriuresis ( urinary excretion of Na). Level in blood controlled by AngII Aldosternone – increases renal reabsorption of Sodium (Na+ ) ADH – low sodium, inhibits ADH release Atrial natriuretic peptide – increases renal excretion of Sodium (Na+) natriuresis University of Jordan

Chloride Cl- Gastric juice Most prevalent anions in ECF Moves relatively easily between ECF and ICF because most plasma membranes contain Cl- leakage channels and antiporters. Can help balance levels of anions in different fluids Chloride shift in RBCs Gastric juice Regulated by ADH – governs extent of water loss in urine Processes that increase or decrease renal reabsorption of Na+ also affect reabsorption of Cl- University of Jordan

Potassium K+ Most abundant cations in ICF Key role in establishing resting membrane potential in neurons and muscle fibers and repolarization. Also helps maintain normal ICF fluid volume Helps regulate pH of body fluids when exchanged for H+ Controlled by aldosterone – ( under high K+ plasma conc) aldosterone stimulates principal cells in renal collecting ducts to secrete excess K+ . abnormal K levels can be lethal. hyperkalemia – ventricular fibrillation and death. University of Jordan

Bicarbonate HCO3- Second most prevalent extracellular anion Concentration increases in blood passing through systemic capillaries picking up carbon dioxide Carbon dioxide combines with water to form carbonic acid which dissociates Drops in pulmonary capillaries when carbon dioxide exhaled Chloride shift helps maintain correct balance of anions in ECF and ICF Kidneys are main regulators of blood HCO3- Can form and release HCO3- when low or excrete excess University of Jordan

Calcium Ca2+ Most abundant mineral in body 98% of calcium in adults in skeleton and teeth In body fluids mainly an extracellular cation Contributes to hardness of teeth and bones Plays important roles in blood clotting, neurotransmitter release, muscle tone, and excitability of nervous and muscle tissue Regulated by parathyroid hormone Stimulates osteoclasts to release calcium from bone – resorption Also enhances reabsorption from glomerular filtrate Increases production of calcitrol to increase absorption for GI tract Calcitonin lowers blood calcium levels University of Jordan

Phosphate About 85% in adults present as calcium phosphate salts in bone and teeth Remaining 15% ionized – H2PO4-, HPO42-, and PO43- are important intracellular anions HPO42- important buffer of H+ in body fluids and urine Same hormones governing calcium homeostasis also regulate HPO42- in blood Parathyroid hormone – stimulates resorption of bone by osteoclasts releasing calcium and phosphate but inhibits reabsorption of phosphate ions in kidneys Calcitrol promotes absorption of phosphates and calcium from GI tract University of Jordan

Magnesium In adults, about 54% of total body magnesium is part of bone as magnesium salts Remaining 46% as Mg2+ in ICF (45%) or ECF (1%) Second most common intracellular cation Cofactor for certain enzymes and sodium-potassium pump Essential for normal neuromuscular activity, synaptic transmission, and myocardial function Secretion of parathyroid hormone depends on Mg2+ Regulated in blood plasma by varying rate excreted in urine University of Jordan