3.2.Topic content
Introduction
Body is formed by solids and fluids. The fluid part is more than 2/3 of the whole body.
Water forms most of the fluid part of the body.
In human beings, the total body water varies from 45 to 75% of body weight. In a normal young adult male, body contains 60-65% of water and 35-40% of solids. In a normal young adult female, the water is 50 to 55% and solids are 45-50%. In females, water is less because of more amount of subcutaneous adipose tissue. In thin persons, water content is more than in obese persons. In old age, water content is decreased due to increase in adipose tissue. The total quantity of body water in an average human being weighing about 70 kg is about 40 l iters.
1.. Isotonic Solutions
The solutions having the same effective osmolality (tonicity) as body fluids are called isotonic solution. The examples are 0.9% sodium chloride solution (normal saline) and 5% glucose solution.
The red blood cells placed in isotonic solution (normal saline) neither gain nor lose water by osmosis (Fig. 1). This is because of the osmotic equilibrium between inside and outside the cell across the cell membrane.
2.. Hypertonic Solutions
Solutions like 2% sodium chloride solution, having greater effective osmolality than the body fluids are called hypertonic solutions. When red blood cells are placed in hypertonic solution, water moves out of the cells (exosmosis) resulting in shrinkage of the cells (crenation).
FIGURE 1: Effect of hypertonic and hypotonic solutions on red blood cells
3. Hypotonic Solutions
The solutions, which have less effective osmolality than the body fluids are called hypotonic solutions. The example is 0.3% sodium chloride solution. When the red blood cells are taken in hypotonic solution, water moves into the cells (endosmosis) resulting in swelling and rupture (hemolysis) of the cells.
APPLIED PHYSIOLOGY—DEHYDRATION
DEFINITION
Significant decrease in water content of the body is known as dehydration. This is observed more commonly in children than adults.
CONDITIONS WHEN DEHYDRATION OCCURS
Dehydration is common in the following conditions:
1. Severe diarrhea and vomiting leading to decrease in body water, sodium and other electrolytes.
2. Increased urinary output because of renal diseases or adrenal insufficiency leading to lack of aldosterone. In the absence of aldosterone, the reabsorption of sodium and chloride by the renal tubules reduces and urine output increases.
3. Insufficient intake of water.
4. Excessive sweating leading to heat frostration, i.e. extreme loss of water, heat and energy.
COMPLICATIONS OF DEHYDRATION
Dehydration reduces blood volume and cardiac output resulting hypovolemic cardiac shock. In severe conditions of dehydration, renal failure and coma occur.
Blood is a connective tissue in fluid form. It is considered as the fluid of life because it carries oxygen from lungs to all parts of the body and carbon dioxide from all parts of the body to the lungs. It is known as fluid of growth because it carries nutritive substances from the digestive system and hormones from endocrine gland to all the tissues. The blood can also be called the fluid of health. Because it protects the body against the diseases and gets rid of the waste products and unwanted substances by transporting them to the excretory organs like kidneys.
PROPERTIES OF BLOOD
Following are the properties of the blood.
1. Color:
2. Volume: The volume of blood in a normal adult is 5 liters.
3. Reaction and pH: Blood is slightly alkaline and its pH in normal conditions is 7.4.
4. Specific gravity:
The specific gravity of total blood: 1.052 to 1.061
The specific gravity blood cells: 1.092 to 1.101
The specific gravity of plasma: 1.022 to 1.026
5. Viscosity: Blood is five times more viscous than water.
It is mainly due to red blood cells and plasma proteins.
6. Blood temperature
7. Blood densit: 1,056-1,060.
Blood color - depends on hemoglobin. Blood is red in color. Arterial blood is brightly red because of oxyhemoglobin (hemoglobin connected with oxygen) big amount. Venous blood is dark red with blue shade or purple red. Such blood color is linked with presence not only of oxydated hemoglobin but also reducted hemoglobin.
Blood temperature depends greatly on organ metabolism level from which it outflows. The more intensive metabolism level is, the higher is the temperature of blood that outflows from it. Thus, venous blood temperature is bigger always in one and the same organ than the one of the arterial blood. Though, this rule does not correspond to skin superficial veins because they are in touch with atmospheric air and participate indirectly in heat-exchange. Blood temperature is fluctuated from 37 to 40°C under resting conditions in different vessels in homoiothermal animals and human being. So, blood outflowing from lover through veins can have the temperature equal to 39,7°C. Blood temperature is increased significantly at intensive muscular activity.
Blood density is increased at blood condensation; is decreased – at its liquerfaction. Density level depends on formed elements (mainly erythrocytes) amount and proteins concentration.
Acid-alkaline equilibrium – correlation between acid and alkaline equivalent in blood. This is reaction caused by H+-ions concentration. Ph or hydrogen index is used for its evaluation. If pH is equal to 7,0 the environment is called neutral; less than 7,0 – acid; more than 7,0 – alkaline. Norma: in venous blood – 7,34, arterial blood – 7,4; blood in a whole – 7,35-7,47. At muscular tension increasing acid products come into blood (lactic acid, carbonic acid) and movement to acid side (acidosis) is observed. At increased carbonic acid releasing (with lungs at hyperventillation) movement to alkaline side (alkalosis) occurs.
COMPOSITION OF BLOOD
Blood contains the blood cells which are called formed elements and the liquid portion known as plasma.
BLOOD CELLS
Three types of cells are present in the blood.
1. Red blood cells or Erythrocytes
2. White blood cells or Leukocytes
3.Platelets or Thrombocytes
Hematocrit Value
If blood is collected in a hematocrit tube along with suitable anticoagulant and centrifuged for 30 minutes with a speed of 3000 RPM (revolutions per minute), there are blood cells settle down at the bottom having a clear plasma at the top. The plasma forms 55% and the red blood cells form 45% of the total blood. The volume of red blood cells expressed in percentage is called the hematocit value or packed cell volume (PCV).
In between the plasma and the red blood cells there is a thin layer of white buffy coat. This white buffy coat is formed by the aggregation of white blood cells and platelets.
PLASMA
Plasma is a straw coloured clear liquid. It contains 91 to 92% of water and 8 to 9% of solids. The solids are the organic and the inorganic substances.
Organic Substances of the Plasma
The following are the organic substances of the plasma.
1. Proteins: The proteins present in the plasma are albumins, globulins and fibrinogen. These are specifically known as plasma proteins.
2. Carbohydrates: The carbohydrate is present in plasma mainly in the form of glucose.
3. Fats: The lipid substances present in plasma are the neutral fats, phospholipids and cholesterol.
4. Amino acids: Plasma contains both essential and nonessential amino acids.
5. Nonprotein nitrogenous substances: The plasma also contains some nonprotein nitrogenous substances like ammonia, creatine, creatinine, xanthine, hypoxanthine, urea and uric acid.
6. Internal secrets: The plasma contains many hormones.
7. Enzymes: The enzymes like amylase, carbonic anhydrase, alkaline phosphatase, acid phosphatase, lipase, esterase, protease and transaminase are present in plasma.
8. Antibodies: The plasma contains many antibodies, which are called immunoglobulins.
Inorganic Substances of the Plasma
Following are the inorganic substances present in plasma.
1. Sodium
2. Calcium
3. Potassium
4. Magnesium
5. Chloride
6. Iodide
7. Iron
8. Phosphates
9. Copper.
Gases Present in Plasma
Oxygen and carbon dioxide are also present in plasma.
The Table 1 gives the normal values of some important substances in blood.
TABLE 1: Blood level of some important substances
Glucose |
3,5-5,5 mmol/l |
Cholesterol |
3,9-6,5 mmol/l |
Plasma proteins (globulins, albumins, fibrinogen)
|
23-35 g/l, 35-50 g/l, 2-4 g/l
|
Iron |
11-31 mcmol/l |
Calcium |
2,25-2,74 mmol/l |
Bilirubin (total, unconjugated, conjugated) |
8,55-20,52, 1,7-17,1, 2,2-5,1 mcmol/l |
FUNCTIONS OF BLOOD
1. NUTRIENT FUNCTION
Nutritive substances like glucose, amino acids, lipids and vitamins derived from digested food are absorbed from gastrointestinal tract and carried by blood to different parts of the body for growth and for production of energy.
2. RESPIRATORY FUNCTION
Transport of respiratory gases is done by the blood. It carries oxygen from alveoli of lungs to different tissues and carbon dioxide from tissues to alveoli.
3. EXCRETORY FUNCTION
Waste products formed during various metabolic activities the tissues are removed by blood and carried to the excretory organs like kidney, skin, liver, etc.
4. TRANSPORT OF HORMONES AND ENZYMES
The hormones and some of the enzymes are carried by blood to different parts of the body from the source of secretion.
5. EGULATION OF WATER BALANCE
Water content of the blood is freely interchangeable with interstitial fluid. This helps in the regulation of water content of the body.
6. REGULATION OF ACID-BASE BALANCE
The plasma proteins and hemoglobin act as buffers and help in regulation of acid base balance.
7. REGULATION OF BODY TEMPERATURE
Because of the high specific heat of blood, it is responsible for maintaining the ther-moregulatory mechanism in the body, i.e. the balance between heat loss and heat gain in the body. Not only temperature making equal but also creating conditions for heat-production or heat-releasing in organism occurs at blood movement. Bigger blood amount passage through skin vessels in hot weather encourages to heat-emission. Cutaneous vessels are constricted in cold weather, blood is pushed in abdominal cavity that leads to heat-saving.
8. STORAGE FUNCTION
Water and some important substances like proteins, glucose, sodium and potassium are оnstantly required by the tissues. Blood serves as a readymade source for these substances. And, these substances are taken from blood during the conditions like starvation, fluid loss, electrolyte loss, etc.
9. DEFENSIVE FUNCTION
Blood plays important role in the defense of the body. The white blood cells are responsible for this function. Neutrophils and monocytes engulf the bacteria by phagocytosis. Lymphocytes are involved in immunity (both humoral and cell-mediated). Eosinophils are responsible for detoxification, disintegration am removal of foreign proteins. In general, blood coagulation and fibrinolysis (clot destruction), antioxidants belong to this wide function.
The proteins in the plasma are:
1. Serum albumins
2. Serum globulins and
3. Fibrinogen.
When the blood is shed out of the blood vessel or collected in a container, the coagulation occurs. In this process, the fibrinogen is converted into fibrin and the blood cells are attached to this fibrin forming the blood clot. After about 45 minutes, a straw colored fluid leaves blood clot. This fluid is called serum. The serum is different from plasma in its protein content. The serum contains only the albumins and globulins. The fibrinogen is absent in serum because, it is converted into fibrin during the coagulation of the blood. Serum contains all the other constituents of plasma except fibrinogen.
Thus, the Serum = Plasma - Fibrinogen. Because of this, the albumins and globulins are usually called serum albumins and serum globulins.
NORMAL VALUES
The normal values of the plasma proteins are:
Total proteins : 60-80 g/l
Serum albumins : 35-50 g/l,
Serum globulins : 23-35 g/l
Alpha1 - : 1-4 g/l
Alpha2 - : 4-12 g/l
Beta- : 5-11 g/l
Gamma- : 5-16 g/l
Fibrinogen : 2-4 g/l
PROPERTIES OF PLASMA PROTEINS
The following are the properties of plasma proteins.
1. MOLECULAR WEIGHT
The molecular weight of albumin : 69,000
The molecular weight of globulin: 156,000
The molecular weight of fibrinogen: 4,00,000
Thus, the molecular weight of fibrinogen is greater than that of other two proteins.
2. ONCOTIC PRESSURE
The plasma proteins are responsible for the oncotic or osmotic pressure in the blood. The osmotic pressure exerted by proteins in the plasma is called colloidal osmotic pressure. Oncotic pressure represents osmotic pressure part and depends on proteins content in solution. Although proteins concentration is rather big in a solution, molecules general amount is relatively low due to their big molecular weight. That is why oncotic pressure is not more than 25-30 mm Hg. Albumins play a major role in exerting oncotic pressure. The share of their contribution to oncotic pressure determining is 80%. It is so because of their low molecular weight and molecules big amount in plasma.
Oncotic pressure plays important role in watery exchange regulation. The bigger is oncotic pressure, the more water is maintained in vascular bed and the less is transported into the tissues and on the contrary. Oncotic pressure not only influences on tissular liquid and lymph formation but also regulates uroformation and water absorbtion in intestine.
Hypoproteinemy observed at proteinic fasting as well as kidneys hard pathological conditions leads to edemas because water can not be maintained in vascular bed and comes to the tissues.
3. SPECIFIC GRAVITY
The specific gravity of the plasma proteins is 1,026.
4. BUFFER ACTION
The acceptance of hydrogen ions is called buffer action. At birth acidosis is physiologic. Ph is supported by: buffer systems, excretory organs and lungs.
Buffer systems:
bicarbonate,
phosphate,
protein,
hemoglobin (75 per cent of all system).
The plasma proteins have 1/6 of total buffering action of the blood.
ORIGIN OF PLASMA PROTEINS
IN EMBRYO
In embryonic stage, the plasma proteins are synthesized by the mesenchyme cells. In embryo, the albumins are synthesized first and other proteins are synthesized later.
IN ADULTS
In adults, the plasma proteins are synthesized mostly from reticuloendothelial cells of liver. The plasma proteins are also synthesized from spleen, bone marrow and disintegrating blood cells and general tissue cells. Gamma globulin is synthesized from B-lymphocytes.
FUNCTIONS OF PLASMA PROTEINS
The plasma proteins are very essential for the body. The following are the various functions of the plasma proteins
1. ROLE IN COAGULATION OF BLOOD
Fibrinogen is essential for the coagulation of blood. During coagulation of blood, the fibrinogen is converted into fibrin.
2. ROLE IN DEFENSE MECHANISM OF BODY
The gamma globulins play an important role in the defense mechanism of the body by acting as antibodies (immune substances). These protein are also called immunoglobulins. The antibodies react with antigens of various microorganisms, which cause diseases like diphtheria, typhoid, streptococcal infections, mumps, influenza, measles, hepatitis, rubella, poliomyelitis, etc.
3. ROLE IN TRANSPORT MECHANISM
Plasma proteins are essential for the transport of various substances in the blood. Albumin, alpha globulin and beta globulin are responsible for the transport of the hormones, enzymes and respiratory gases, particularly carbon dioxide. The alpha and beta globulins play an important role in the transport of metals in the blood.
4. ROLE IN MAINTENANCE OF ONCOTIC PRESSURE IN BLOOD
Because of their large size, the plasma proteins cannot pass through the capillary membrane easily and remain in the blood. In the blood these proteins exert the colloidal oncotic pressure. The oncotic pressure exerted by the plasma proteins is about 25 mm Hg. In this way, the plasma proteins play an important role in the maintenance of oncotic pressure of blood.
Since the concentration of albumins is more than the other plasma proteins, it exerts maximum pressure, globulins are the next and fibrinogen exerts least pressure.
Importance of Oncotic Pressure - Starling's Hypothesis
Oncotic pressure exerted by the plasma proteins is involved in the exchange of various substances between blood and the cells through capillary membrane. According to Starling's hypothesis, the net filtration through capillary membrane is proportional to the hydrostatic pressure difference across the membrane minus the oncotic pressure difference.
5. ROLE IN REGULATION OF ACID-BASE BALANCE
Plasma proteins, particularly the albumins, play an important role in regulating the acid- base balance in the blood. This is because of the virtue of their buffering action
6. ROLE IN VISCOSITY OR INTERNAL FRICTION OF BLOOD
It is often determined comparatively to water viscosity: if the latest one is equal to 1, blood viscosity is equal to 4,0-5,0. In new-borned - 10,0-14,0; in 1 month – like in the adult. In girls this index is less than in boys. Main reasons for viscosity increasing:
in mountains;
hypercapnia (carbonic acid content increasing in blood);
inflammations;
hypertony;
atherosclerosis;
at feeding of mainly animal food (proteins-rich) – meat, eggs.
Main reasons for viscosity decreasing:
at vegeteranian feeding.
Viscosity depends on formed elements (mainly erythrocytes) amount and proteins concentration. The plasma proteins provide viscosity to the blood, which is important to maintain the blood pressure. Albumin provides maximum viscosity than the other plasma proteins.
7. ROLE IN ERYTHROCYTE SEDIMENTATION RATE (ESR) EITHER BLOOD SUSPENSIONAL STABILITY OR VELOCITY SEDIMENTATION RATE (VSR).
Blood represents suspension from physical-chemical point of view because formed elements are in plasma in a suspended state. Suspension is a liquid containing other substance particles that are distributed equally. Erythrocytes suspension in plasma is sustained by their surface hydrophilic nature as well as their negative membrane surface charge that they possess like other formed elements. Thus, erythrocytes are pushed away one from another. If formed elements negative charge is reduced that can be connected with positive proteins of cathions adsorbtion than favorable conditions are created for erythrocytes mutual gluing. Such a gluing is especially powerful at fibrinogen and gamma-globulins adsorbtion on their membrane. Mentioned proteins form so-called bridges between separate erythrocytes due to which their aggregation occurs and so-called coin columns are formed. Real power of aggregation represents difference between force in formed bridges, force of negatively charged red blood cells electrostatic pushing away and shift power causing aggregates decomposition. It is not excluded that proteins molecules connection at the erythrocytes surface takes place due to weak hydrogenic bonds as well as dispersal forces of Van-der-Waals.
If erythrocytes aggregation is observed in organism than blood viscosity is increased that can create favorable conditions for blood intravascular coagulation as well as blood pressure increasing. Moreover, “coin columns” prevent cells, tissues and organs normal blood supply at their sludging in capillaries.
If one puts blood in the test-tube after preliminary adding substances preventing coagulation than one can see after some time that plasma was divided into two layers: the superior one consists mainly of plasma and the inferior one – of formed elements. Taking into account mentioned features Ferreus proposed to study erythrocytes suspension stability while their sedimentation determining in blood the coagulation of which is liquidated by preliminary adding of citric sodium. Nowadays this reaction is known as erythrocytes sedimentation velocity or rate (ESR). Other name is velocity sedimentation rate (VSR). This method is rather simple in usage, non-specific (gives information at many physiological and pathological conditions) and that is why is still judiciously used in theoretical and practical medicine all over the world.
Normal VSR is determined by plasma normal proteinogram. This index depends on age and sex. It is equal to 6-12 mm/h in adult men, 8-15 mm/h in adult women, 15-20 mm/h in the old of both sexes, 1-2 mm/h in babies (it reaches adult values up to sexual maturation period). The biggest contribution to VSR has highly-molecular protein fibrinogen. Women have bigger fibrinogen level than men (it is physiological facility to prevent regular menstrual bleedings and bleedings during labors). That is why VSR can reach even 15-20 mm/h at menstruations and 20-30 mm/h during pregnancy.
Erythrocytes concentration and proteins (especially highly-molecular ones) content are two distinguishing factors that determine VSR level. So, if erythrocytes number is little (anemia) than the resting number of them are easily to be sedimentated than to their normal or increased number in one and the same volume. Thus, anemia is accompanied by increased VSR, erythrocytosis (red blood cells increased number) – decreased VSR.
Inflammatory, infection diseases are accompanied by proteins content increasing in blood (immunoglobulins at infection, acute-phased proteins at inflammation) especially of highly-molecular ones. It leads to VSR rising. Tumors (especially cancerogenous) are connected with very-highly molecular proteins production which are absorbed on cells (erythrocytes in part). As the scientists concluded, VSR rising from 40 and upper can testify to tumors or temporal arteriitis (this disease should be excluded). VSR equal to 100 mm/h is a cancer distinguishing feature. Burnings and combustions are accompanied by tissular proteins enforced decomposition (catabolism) and, thus, hyperproteinemy, that leads to VSR rising. Other pathological conditions the VSR increasing at which is a diagnostic criterium are as follows as: myocardial infarction, post-operative period, hemoblastoses (myelomic disease at which Bens-Jons' protein causes occlusion in vessels in kidney capillaries in part that can lead to kidney insufficiency and death; Waldenstrem's disease, disease of immunoglobulins hard chains at which lymphocyte anomalous precursor produce only hard chains of lg that lead to their level rising in blood and thus enforced absorbtion onto erythrocytes external membrane), chronic active hepatitis (as a result of hyperglobulinemy), liver cirrhosis, tuberculosis, amyloidosis, collagenoses (tissues proteins catabolism).
VSR reducing is observed at erythremy and symptomatic erythrocytoses (erythrocyte number increasing), viral hepatitis (hypoglobulinemy result), mechanic jaundice, different hypoproteinemies, salicylates and calcium chloride taking. VSR decreasing lower than 3 mm/l is unfavorable diagnostic sign because it testifies to blood viscosity increasing.
VSR level depends more on plasma features in bigger extent than on erythrocytes ones. So, if to put male erythrocytes with normal VSR in a pregnant woman plasma than they will begin their sedimentation with the same velocity like female erythrocytes during pregnancy.
8. ROLE AS RESERVE PROTEINS
During the conditions like fasting, inadequate food intake or inadequate protein intake, the plasma proteins are utilized by the body tissues. Because of this, the plasma proteins are called the reserve proteins.
Shortly,
Albumins – (60 % or 35-50 g/l) produced in liver; are agile, low-weighted, they are important for:
oncotic pressure support;
bilirubin transport;
hard metals salts transport;
fat acids transport;
medicines transport (proteins increase action periods for them).
Globulins (40% or 30-35 g/l) are formed in liver, bone marrow, spleen. Role:
form antibodies;
antitoxins;
agglutinines;
blood coagulation (some of them are clotting factors);
phospholipid transport;
cholesterol transport;
steroid hormones transport;
oncotic pressure support (less than albumins);
blood density support;
buffers;
blood viscosity determination;
nutritive function.