Body Fluids & Blood

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

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

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

4. Source of daily waternormal conditions University of Jordan

5. Renal excretion of water is regulated

6. 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 University of Jordan

7. 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

8. 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 NatruiticPeptideANP: 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

9. 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

10. 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

12. Distribution of some cations and anions in extracellular and intracellular fluid

13. University of Jordan

14. University of Jordan

15. 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

16. 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

17. 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

18. 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

19. 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+ ATPasepumps play major role in keeping K+ high inside cells and Na+ high outside cell University of Jordan

20. 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

21. Chloride Cl- • 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

22. 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

23. 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

24. 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

25. 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

26. 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