Body Fluid Compartments Lecture Notes PDF

PAGE 1 https://www.umfst.ro Lecture no 3 https://edu.umch.de Body fluid compartments. Plasma Lecturer Florina Gliga 2024 29th of April proteins Body fluid compartments...

PAGE 1 https://www.umfst.ro Lecture no 3 https://edu.umch.de Body fluid compartments. Plasma Lecturer Florina Gliga 2024 29th of April proteins Body fluid compartments PAGE 2 The maintenance of a relatively constant volume and a stable composition of the body fluids is essential for homeostasis. The relative constancy of the body fluids is remarkable because there is continuous exchange of fluid and solutes – with the external environment, – within the different body compartments. Some of the most common and important problems in clinical medicine arise because of abnormalities in the control systems that maintain this relative constancy of the body fluids.  Body fluid compartments PAGE 3 Total body water/fluid Depends on: – age: fetus ~ 80%, newborns ~ 75%, adult ~ 60%, elderly ~ 50% of body weight – sex: higher in men (larger muscle mass, less adipose tissue) – part of day: lower during the night (no water consumption) – season: lower during the summer (water loss due to sweating) – non-uniform distribution among the tissues: in some tissues less in the interstitial space accumulation of minerals (bones, teeth) in some tissues less in the cells –adipose tissue  Body fluid compartments PAGE 4 Water is added to the body by two major sources: – (1) it is ingested in the form of liquids or water in food, which together - 2000 ml/day – (2) it is synthesized in the body by oxidation of carbohydrates - 200 -400 ml/day. provide a total water intake of about 2300-2400 ml/day However, intake of water is highly variable among different people and even within the same person on different days, depending on – climate, – habits – level of physical activity. Body fluid compartments PAGE 5 Crash Course Anatomy and Physiology, 1, Copyright © 2019 Elsevier Limited. All rights reserved The Renal SystemMather, Amanda. © 2023. Body fluid compartments PAGE 6 Daily Loss of Body Water Insensible Water Loss. Some water losses cannot be precisely regulated - by evaporation from the respiratory tract and diffusion through the skin, which together account for about 700 ml/day of water loss under normal conditions. Insensible water loss: through the skin occurs independently of sweating; the average loss is 300 to 400 ml/day. through the respiratory tract averages about 300 to 400 ml/day. Air enters the respiratory tract, becomes saturated with moisture, before it is expelled. Body fluid compartments PAGE 7 Daily Loss of Body Water Fluid Loss in Sweat. The amount of water lost by sweating is highly variable, depending on physical activity environmental temperature. The volume of sweat normally is about 100 ml/day, but in very hot weather or during heavy exercise fluid loss in sweat occasionally increases to 1 to 2 L/hour. The body fluids depleted from the body will activate the thirst mechanism increasing the intake. Body fluid compartments PAGE 8 Daily Loss of Body Water Water Loss in Feces. Only a small amount of water (100 ml/day) normally is lost in the feces. This loss can increase to several liters a day in pathological states - severe diarrhea or vomiting. – For this reason, severe diarrhea can be life threatening if not corrected within a few days Body fluid compartments PAGE 9 Daily Loss of Body Water Water Loss by the Kidneys The most important mechanisms by which the body maintains a balance between water and electrolytes intake and output in the body are related to the kidney’s functions. The kidneys maintain the body’s osmotic balance by controlling the amount of water and electrolytes that is filtered out of the blood and excreted into urine: Intake - large amount of water → the kidneys reduce the reabsorption of water → excess water is excreted in urine → production of large, dilute, watery urine. Low intake - dehydration → the kidneys reabsorb as much water as possible → produce low volume, highly concentrated urine (ions and wastes). Body fluid compartments PAGE 10 Daily Loss of Body Water Water Loss by the Kidneys The changes in excretion of water are mainly controlled by the antidiuretic hormone (ADH or AVP). ADH is produced in the hypothalamus and released by the posterior pituitary gland; his action is to conserve the water in the body. intake >losses - positive water balance intake ˂losses - negative water balance Body fluid compartments PAGE 11 Daily Loss of Body Water AVP/ADH action on the Kidneys Berne and Levy Physiology, 35 Copyright © 2018 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 12 Normal Prolonged, Heavy Exercise Intake Fluids ingested 2000 ? From metabolism 400 ? Total intake 2400 ? Output Insensible: skin 350 - 400 350 Insensible: lungs 350 - 400 650 Sweat 100 5000 Feces 100 100 Urine 1400 500 Total output 2300- 2400 6600 Daily Intake and Output of Water (ml/day) Body fluid compartments PAGE 13 Body Water Netter's Essential Physiology, Chapter 1, Copyright © 2016 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 14 The total body fluid is distributed mainly between two compartments: the extracellular fluid and the intracellular fluid The extracellular fluid is divided into the interstitial fluid and the blood plasma. Guyton and Hall Textbook of Medical Physiology, Chapter 25, Copyright © 2016 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 15 Intracellular Fluid Compartment ICF About 28 of the 42 liters of fluid in the body are inside the cells and are collectively called the intracellular fluid. (about 40 % of the total body weight in an “average” person). Extracellular Fluid Compartment All the fluids outside the cells are collectively called the extracellular fluid - 20% of the body weight, or about 14 liters in a 70-kilogram man. The two largest compartments of the extracellular fluid are – the interstitial fluid, 3/4 (11 liters) of the extracellular fluid, – the plasma, which makes up almost 1/4 of the extracellular fluid, or about 3 liters. Body fluid compartments PAGE 16 Extracellular Fluid Compartment The plasma is the noncellular part of the blood. It exchanges substances continuously with the interstitial fluid through the pores of the capillary membranes, highly permeable to almost all solutes in the extracellular fluid The extracellular fluids are constantly mixing → the plasma and interstitial fluids have about the same composition except for proteins. Body fluid compartments PAGE 17 Extracellular Fluid Compartment Most common (skeletal muscle) Intestine/kidney Liver Boron and Boulapaep Concise Medical Physiology, Chapter 20,.Copyright © 2021 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 18 ECF ICF The intracellular fluid contains: The extracellular fluid, including the plasma and the interstitial fluid, contains: only small quantities of Na and Cl ions large amounts of Na and Cl almost no Ca ions ions, large amounts of K and phosphate ions reasonably large amounts of moderate quantities of Mg and sulfate bicarbonate ions, ions small quantities of K, Ca, Mg , large amounts of protein—almost four phosphate, and organic acid times as much as in the plasma. ions Body fluid compartments PAGE 19 Comparisons of the composition of the extracellular fluid, including the plasma and interstitial fluid, and the intracellular fluid Guyton and Hall Textbook of Medical Physiology, Chapter 25, Copyright © 2016 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 20 Basic Principles of Osmosis and Osmotic Pressure Because cell membranes are relatively impermeable to most solutes but are highly permeable to water (i.e., they are selectively permeable), whenever there is a higher concentration of solute on one side of the cell membrane, water diffuses across the membrane toward the region of higher solute concentration. – If a solute such as NaCl is added to the extracellular fluid, water rapidly diffuses from the cells through the cell membranes into the extracellular fluid until the water concentration on both sides of the membrane becomes equal. – Conversely, if a solute such as NaCl is removed from the extracellular fluid, water diffuses from the extracellular fluid through the cell membranes and into the cells. The rate of diffusion of water is called the rate of osmosis. Body fluid compartments PAGE 21 Basic Principles of Osmosis and Osmotic Pressure The osmolal concentration of a solution is called – osmolality when the concentration is expressed as osmoles per kilogram of water; – osmolarity when it is expressed as osmoles per liter of solution. In dilute solutions such as the body fluids, these two terms can be used almost synonymously because the differences are small. Body fluid compartments PAGE 22 Osmotic Equilibrium Large osmotic pressures can develop across the cell membrane. for each milliosmole concentration gradient of an impermeant solute (one that will not permeate the cell membrane), about 19.3 mm Hg of osmotic pressure is exerted across the cell membrane. – If the cell membrane is exposed to pure water and the osmolarity of intracellular fluid is 282 mOsm/L, the potential osmotic pressure that can develop across the cell membrane is more than 5400 mm Hg. osmotic imbalance → large forces that can move water across the cell membrane → relatively small changes in the concentration of impermeant solutes in the extracellular fluid can cause large changes in cell volume. Body fluid compartments PAGE 23 Isotonic, Hypotonic, and Hypertonic Fluids. Osmolality deals with how many osmoles (effective or not) in a fluid. Tonicity is the capability of a solution to modify the volume of cells by altering their water content. only deals with effective osmoles. Is highly dependent on the solute permeability of cell membranes Guyton and Hall Textbook of Medical Physiology, Chapter 25, Copyright © 2016 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 24 Isotonic, Hypotonic, and Hypertonic Fluids. Clinical Surgery. © 2023. Body fluid compartments PAGE 25 Effect of Adding Saline Solution to the Extracellular Fluid Effect of adding isotonic, hypertonic, and hypotonic solutions to the extracellular fluid after osmotic equilibrium. The normal state is indicated by the solid lines, and the shifts from normal are shown by the shaded areas. The volumes of intracellular and extracellular fluid compartments are shown in the abscissa of each diagram, and the osmolarities of these compartments are shown on the ordinates. Guyton and Hall Textbook of Medical Physiology, Chapter 25, Copyright © 2016 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 26 Effect of Adding Saline Solution to the Extracellular Fluid If isotonic saline is added to ECF, – the osmolarity does not change in ECF, ; therefore, no osmosis occurs – an increase in ECF, – NaCl largely remain in the ECF because the cell membrane is virtually impermeable to NaCl Body fluid compartments PAGE 27 Effect of Adding Saline Solution to the Extracellular Fluid If a hypertonic solution is added to the ECF , – the ECF osmolarity increases → causes osmosis of water out of the cells into the extracellular compartment, – almost all the added NaCl remains in the extracellular compartment, – fluid diffuses from the cells into the ECF space to achieve osmotic equilibrium. – The net effect is an increase in extracellular volume (greater than the volume of fluid added), a decrease in intracellular volume, and a rise in osmolarity in both compartments. Body fluid compartments PAGE 28 Effect of Adding Saline Solution to the Extracellular Fluid If a hypotonic solution is added to theECF, – the osmolarity of the ECF decreases, – some of the extracellular water diffuses into the ICF until the intracellular and extracellular compartments have the same osmolarity, – both the IC and the EC volumes are increased by the addition of hypotonic fluid, although the intracellular volume increases to a greater extent. Body fluid compartments PAGE 29 Plasma Interstitial Intracellular (mOsm/L H 2 O) (mOsm/L H 2 O) (mOsm/L H 2 O) Na + 142 139 14 K+ 4.2 4.0 140 Ca ++ 1.3 1.2 0 Mg ++ 0.8 0.7 20 Cl − 106 108 4 Others 4.8 3.9 10 Total mOsm/L 299.8 300.8 301.2 Corrected osmolar 282.0 281.0 281.0 activity (mOsm/L) Most Important Osmolar Substances in Extracellular and Intracellular Fluids  Body fluid compartments PAGE 30 Plasma osmolarity is not routinely measured. Corrected osmolar activity refers to the adjustment made to osmolarity measurements to account for the impact of certain substances in the blood that can falsely elevate or lower osmolarity readings. In clinical practice, corrected osmolar activity is often calculated using formulas that take into consideration the concentrations of glucose, sodium, blood urea nitrogen (BUN) in the blood. The traditional formula: o Corrected Osmolarity = 2(Na) + (Glucose/18) + (BUN/2.8) o Na - mmol/L, Glucose - mg/dL, and BUN - in mg/dL Body fluid compartments PAGE 31 Clinical Abnormalities of Fluid Volume Regulation: Hyponatremia and Hypernatremia Because Na and its associated anions (mainly Cl) account for more than 90 % of the the solute in the ECF , plasma Na concentration is a reasonable indicator of plasma osmolarity under many conditions. When plasma Na concentration is reduced more than a few milliequivalents below normal (about 140 mEq/L) - hyponatremia. When plasma Na concentration is elevated above normal - hypernatremia. Body fluid compartments PAGE 32 Clinical Abnormalities of Fluid Volume Regulation: Hyponatremia Decreased plasma Na concentration can result from: – loss of NaCl from the extracellular fluid – addition of excess water to the extracellular fluid Conditions that can cause hyponatremia: – diarrhea and vomiting. – over use of diuretics- that inhibit the ability of the kidneys to conserve Na – certain types of Na + -wasting kidney diseases – ADH exccesive secretion Body fluid compartments PAGE 33 Consequences of Hyponatremia: Cell Swelling Rapid changes in cell volume as a result of hyponatremia can have profound effects on tissue and organ function, especially the brain. An abrupt reduction in plasma Na concentration, can cause brain cell edema and neurological symptoms, including headache, nausea, lethargy, and disorientation. If plasma Na concentration rapidly falls below 115 to 120 mmol/L, brain swelling →to seizures, coma, permanent brain damage, and death. – Because the skull is rigid (the brain cannot increase its volume by more than about 10 %) → is forced down the neck (herniation) → to permanent brain injury and death. Body fluid compartments PAGE 34 Consequences of Hyponatremia: Cell Swelling Brain cell volume regulation during hyponatremia. During acute hyponatremia, there is diffusion of H 2 O into the cells ( 1 ) and swelling of the brain tissue (indicated by the dashed lines). With chronic hyponatremia, the brain swelling is attenuated by the transport of solutes from the cells. Guyton and Hall Textbook of Medical Physiology, Copyright © 2016 by Elsevier, Inc. All rights reserved. Body fluid compartments PAGE 35 Clinical Abnormalities of Fluid Volume Regulation: Hypernatremia Increased plasma Na concentration, which also causes increased osmolarity, can be due to: – either loss of water from the extracellular fluid, which concentrates the Na + ions, – excess Na + in the extracellular fluid. Causes: – dehydration caused by water intake that is less than water loss, as can occur with sweating during prolonged, heavy exercise. – inability to secrete ADH “central” diabetes insipidus →the kidneys excrete large amounts of dilute urine → dehydration and increased concentration of Na + chloride in the extracellular fluid. Body fluid compartments PAGE 36 Consequences of Hypernatremia: Cell Shrinkage Hypernatremia is much less common than hyponatremia, Severe symptoms usually occur only with rapid and large increases in the plasma Na concentration above 158 to 160 mmol/L. – adaptative mechanism - hypernatremia promotes intense thirst and stimulates secretion of ADH, which both protect against a large increase in plasma and extracellular fluid Na. Severe hypernatremia can occur: in patients with impaired sense of thirst, in persons with diabetes insipidus. Correction of hypernatremia can be achieved by administering hypo-osmotic NaCl or dextrose solutions. Blood composition PAGE 37 Blood is a complex fluid consisting of: – plasma —extracellular fluid rich in proteins – formed elements RBCs (or erythrocytes), WBCs (leukocytes, which include granulocytes, lymphocytes, and monocytes), platelets (thrombocytes). Total blood volume is ∼70 mL/kg body weight in the adult woman and ∼80 mL/kg body weight in the adult man Whole blood is a suspension of cellular elements in plasma. Blood composition PAGE 38 Spinning down a sample of blood containing an anticoagulant for ~5 minutes at 10,000 g: the bottom fraction contains formed elements — RBCs (or erythrocytes), WBCs and platelets (thrombocytes); the top fraction is blood plasma The RBCs having the highest density are at the bottom of the tube, whereas most of the WBCs and platelets form a whitish gray layer—the buffy coat —between the RBCs and plasma. Medical Physiology, Chapter 18, Copyright © 2017 by Elsevier, Inc. All rights reserved Blood composition PAGE 39 Plasma is a pale-white watery solution of electrolytes, plasma proteins, carbohydrates, and lipids. – Pink-colored plasma suggests the presence of hemoglobin caused by hemolysis (lysis of RBCs) and release of hemoglobin into the plasma. – A brown-green color may reflect elevated bilirubin levels. – Plasma can also be cloudy in cryoglobulinemias. The electrolyte composition of plasma differs only slightly from that of interstitial fluid on account of the volume occupied by proteins and their electrical charge  Blood composition PAGE 40 Plasma proteis Proteins are present in all body fluids, but it is the plasma proteins of the blood are examined most frequently for diagnostic purposes. Changes in the concentrations of individual proteins occur in many conditions, and their measurement can provide useful diagnostic information. Principal plasma proteins are albumin, fibrinogen, globulins, and other coagulation factors. The molecular weights of plasma proteins range up to 970 kDa More than 100 individual proteins have a physiological function in the plasma Blood composition PAGE 41 Plasma proteins Plasma proteins at a normal concentration of ~7.0 g/dL (6.4–8.3 g/dL) Albumin: 3.5–5.0 g/dL Protein, total α 1 -globulin: 0.1–0.3 g/dL Electrophoresis α 2 -globulin: 0.6–1.0 g/dL β-globulin: 0.7–1.1 g/dL γ-globulin: 0.8–1.6 g/dL Blood composition PAGE 42 Plasma proteis Function Example thyroxine-binding globulin (thyroid hormones) Transport apolipoproteins (cholesterol, triglyceride) transferrin (iron) Humoral immunity immunoglobulins Maintenance of oncotic pressure all proteins, particularly albumin Enzymes renin coagulation factors Protease inhibitors α 1 -antitrypsin Buffering all proteins Blood composition PAGE 43 Plasma proteins In very general terms, variations in plasma protein concentrations can be caused by: – the rate of protein synthesis , – the rate of removal, – the volume of distribution. Only changes in the more abundant plasma proteins (i.e. albumin or immunoglobulins) will have a significant effect on the total protein concentration.  PAGE 44 Blood composition Plasma proteins Oncotic pressure = colloid osmotic pressure= the osmotic pressure generated by large molecules (especially proteins) in solution all molecules (60 kD) cannot pass the capillary wall ex. proteins medium sized molecules ~their charge, shape, etc. → the capillary wall is a semipermeable membrane for proteins Blood composition PAGE 45 Plasma proteins Albumin generates about 70% of the oncotic pressure. This pressure is typically 25-30 mmHg. The oncotic pressure increases along the length of the capillary, particularly in capillaries having high net filtration (e.g., in renal glomerular capillaries), because the filtering fluid leaves behind proteins leading to an increase in protein concentration.  PAGE 46 Blood composition Starling forces. In arterioles, the hydrostatic pressure is about 30 - 37 mmHg, with an interstitial (tissue) pressure of 1 mmHg opposing it. the osmotic pressure (oncotic pressure) exerted by the plasma proteins is approximately 25 - 28 mmHg → a net outward force of about 10 - 11 mmHg drives fluid out into the interstitial spaces.  PAGE 47 Blood composition Starling forces. In venules, the hydrostatic pressure is about 17 mmHg, the oncotic and interstitial pressures remain the same ; → a net force of about 9 mmHg attracts water back into the circulation. If the concentration of plasma proteins is markedly diminished (eg, due to severe protein malnutrition), fluid is not attracted back into the intravascular compartment and accumulates in the extravascular tissue spaces, a condition known as edema.  PAGE 48 Blood composition The normal balance of hydrostatic and oncotic pressures is such that there is net movement of fluid out of the capillaries at their arteriolar ends and net movement in at their venular ends (indicated here by arrows). P c [HP c , capillary hydrostatic pressure]). π c , Capillary oncotic pressure; π i , interstitial oncotic pressure; P i , interstitial hydrostatic pressure. Netter's Essential Physiology, Chapter 1, 2016 by Elsevier, Inc. All rights reserved. Blood composition PAGE 49 Albumin Edema - can be caused by: an increase in capillary hydrostatic pressure, a decrease in plasma oncotic pressure an increase in capillary permeability. Clinical Biochemistry © 2024. Blood composition PAGE 50 Albumin The plasma concentration of albumin ranges from 3.5 to 5.5 g/dL, which provides the body with a total plasma albumin pool of ~135 g. Albumin – is synthesized by the liver – has a half-life in the circulation of ~20 days. Urinary losses of albumin are normally negligible (