Physiology of Circulatory System

Physiology of Circulatory SystemBaldomero, Dela Rosa, Navarro, Yumol

PHYSIOLOGY OF CIRCULATORY SYSTEM

John Rex N Baldomero, Camille Bianca L Dela Rosa, Julianne Eris T Navarro, Regene C Yumol

ABSTRACT

The circulatory system is the organ system that transports nutrients, gases, hormones, heat, and nitrogenous wastes to all the cells in the body in order to perform the metabolic processes necessary to sustain life. Its proper function is affected by many factors such as temperature, pH, activity of the organism, certain chemicals, the size and health status of the organism, and the organism’s own genetic make-up. The effects of these factors are determined by changing the normal body conditions of the frog and a human. It was found out that an increase in the heart rate is brought about by an increase in temperature, acidic conditions, intensity of the activity, and excess in calcium ions while decrease in the heart rate is caused by sodium and potassium ions. Blood clotting is also observed by placing blood in a capillary tube and breaking the tip to observe the formation of threads. It took approximately three minutes for the blood clot to form. Lastly, the blood type of different individuals were determined by mixing a sample of their blood with anti-serum A and B and observing for the presence of agglutination. It was found out that blood type A agglutinated with anti-serum A, blood type B with anti-serum B, blood type O no agglutination, and blood type AB agglutinated with both serums.

Introduction

The respiratory gases and nutrients taken inside the organism’s body have to be able to reach all parts of the body in order for the organism to perform all the metabolic process necessary to sustain life. However, diffusion alone is not adequate for transporting substances, especially in the animal body where long networks of blood vessels are the ones responsible for transporting the nutrients and gases needed by the body (Campbell and Reece, 2007). Diffusion is inefficient over distances of more than a few millimeters, because the time it takes for a substance to diffuse from one place to another is proportional to the square of the distance (Campbell and Reece, 2007). This means that it would take a very long time for the substances to reach all parts of the body if relying on diffusion alone. The circulatory system solves this problem by ensuring that no substance must diffuse very far to enter or leave a cell (Campbell and Reece, 2007). By rapidly transporting fluid in bulk throughout the body, the circulatory system functionally links the aqueous environment of the body cells to

organs specialized for gas exchange, nutrient absorption, and waste disposal (Campbell and Reece, 2007).

Not all animals possess a circulatory system. The microscopic protozoans and simpler animals such as sponge, cnidarians, and ctenophores, and flatworms require no circulatory system because of the simplicity of their body plan (Biology 22 General Zoology Laboratory Manual, n.d.). In these animals, a body wall only two cells thick encloses a central gastrovascular cavity, which serves both in digestion and in the distribution of substances throughout the body (Campbell and Reece, 2007). The fluid inside the cavity is continuous with the water outside through a single opening; thus, both the inner and outer tissue layers are bathed by fluid (Campbell and Reece, 2007). Since digestion begins in the cavity, only the cells of the inner layer have direct access to nutrients, but the nutrients have to diffuse only a short distance to reach the cells of the outer layer (Campbell and Reece, 2007).

However, for animals with many cell layers, gastrovascular cavities are insufficient for internal transport because diffusion


distances are too great for adequate exchange of nutrients and gases. In such animals, two types of circulatory systems have evolved: open and close. Both have the basic components: a circulatory fluid (blood), a set of tubes (blood vessels) through which the blood moves throughout the body, and a muscular pump (the heart) (Campbell and Reece, 2007). The heart powers the circulation by using metabolic energy to elevate the hydrostatic pressure of the blood, which flows down a pressure gradient through its circuit and back to the heart. This blood pressure is the motive force for fluid movement in the circulatory system.

In insects, other arthropods, and most mollusks, blood bathes the organs directly in an open circulatory system. There is no distinction between blood and interstitial fluid, and this general body fluid is called the hemolymph (Campbell and Reece, 2007). One or more hearts pump the hemolymph into an interconnected system of spaces surrounding the organs, called sinuses (Campbell and Reece, 2007). The chemical exchange in this type of circulatory system occurs between the hemolymph and the body cells (Campbell and Reece, 2007). When the heart contracts, it pumps hemolymph through vessels out into sinuses. When the heart relaxes, it draws hemolymph into the circulatory system through pores called ostia. Body movements that squeeze the sinuses help circulate the hemolymph.

In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid. One or more hearts pump blood into large vessels that branch into smaller ones coursing through the organs. Here materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells (Campbell and Reece, 2007). Earthworms, squids, octopuses, and all vertebrates have closed circulatory systems.

The proper functioning of the various components of the circulatory system is affected by several factors such as temperature, pH, activity of the organism, certain chemicals, the size and health status of the organism, and

the organism’s own genetic make-up (Biology 22 General Zoology Laboratory Manual, n.d.). Changes in the normal conditions of these factors in the body have significant effects in the activity of the circulatory system.

This experiment focuses primarily on the factors that affect the proper functioning of the circulatory system, blood clotting and blood groupings. It aims to identify the different factors that affect circulation and their effects, how blood clotting occurs and the different substances involved in the process, and how agglutination in the different blood types occur. Specifically, this experiment has the following objectives: 1) to identify various factors that affect the heart rate and explain why they do; 2) to explain the process of blood clotting and give some factors that affects its rate; and 3) to determine the blood type of a person through a simple procedure and explain the basic reactions of the various blood groups to the simple chemical test.

Results

A. Rate of Heartbeat

Table 1.0 Measurement of frog and man’s rate of heartbeat.

Subject Average Rate of Heartbeat (bpm)

Frog 79Man 96

The man’s rate of heartbeat is faster than the frog’s.

a. Effect of Temperature on the Rate of Heartbeat

Table 1.1 Measurement of the frog’s heartbeat in varying temperatures.

Temperature

Average Rate of Heartbeat (bpm)

Cold 67Warm 58.7


The frog’s rate of heartbeat is faster in a lower temperature than in a higher temperature.

b. Effect of Activity on the Rate of Heartbeat

Table 1.2 Measurement of a man’s heartbeat in varying activities.

Activity Average Rate of Heartbeat (bpm)

Sitting 75.3Standing 81.7Jumping 100

The rate of heartbeat was fastest after doing jumping jacks for two minutes.

c. Effect of pH on the Rate of Heartbeat

Table 1.3 Measurement of the frog’s heartbeat in varying pH.

pH Average Rate of Heartbeat (bpm)

Acidic 39Normal 47

The frog’s rate of heartbeat is faster in a normal pH condition.

d. Effect of Selected Ions on the Rate of Heartbeat

Table 1.4 Measurement of the frog’s rate of heartbeat in varying ions.

Ion Average Rate of Heartbeat (bpm)Sodium 32

Potassium 58Calcium 58

An excess of the three ions decreased the frog’s rate of heartbeat.

B. Blood Clotting

It took three minutes for the blood at the broken tip of the capillary tube to form fine threads.

C. Blood Groupings

Figure 1.0a Agglutination of blood type A in the presence of anti-serum A (a) and anti-serum B (b).

Figure 1.0b Agglutination of blood type B in the presence of anti-serum A (a) and anti-serum B (b).


Figure 1.0c Agglutination of blood type O in the presence of anti-serum A (a) and anti-serum B (b).

Figure 1.0a Agglutination of blood type AB in the presence of anti-serum A (a) and anti-serum B (b).

Table 2.0 Agglutination of the different blood types in the presence of different anti-serums.

Blood Type/Agglutination

Anti-serum A

Anti-serum B

A + -B - +O - -

AB + +

In blood type A, there is agglutination is the slide where anti-serum A was added. In blood type B, the same happened in the slide where anti-serum B was added. No agglutination occurred in blood type O. On the other hand, both slides agglutinated in blood type AB.

Discussion


The cycle of the heart filling up with blood and pumping in out again is called the cardiac cycle, and it is felt as the heartbeat (Campbell and Reece, 2007). The cardiac cycle also refers to events related to the flow of blood that occurs from the beginning of one heartbeat to the beginning of the next. The cardiac cycle is made up of two phases: contraction and relaxation of the heart. Systole, or the contraction of the heart, forces blood out into the pulmonary artery and arch of aorta under high pressure towards the different parts of the body (Hallare n.d.). This stage produces the loud and longer sound “lub” that is heard when the blood from the atria strike the stationary blood in the ventricles and also due to the closure of the atrioventricular valve – the valve between the atrium and the ventricle that functions to prevent the backflow of blood (Hallare, n.d.). The relaxation phase, or diastole, is the period when blood enters the ventricle from the atrium (Hallare, n.d.). This phase produces the soft and short sound “dub” that occurs when the blood from the ventricles strikes the stationary blood in the arteries and also due to the closure of the semilunar valve – the valve between the left atrium and the left ventricle (Hallare, n.d.). Hence, one heartbeat is made up of one systole and one diastole.

The heart controls its own beat using a group of cells at the top of the right atrium called the sinoatrial node (Cavendish, 2000). This node is the heart’s pacemaker – it sends out the nerve signals needed for each


heartbeat, at a rate of about 60 to 100 signals a minute in humans.

The frequency of the cardiac cycle is described by the heart rate. It is the number of beats per unit time, usually in minutes and is measured in beats per minute or bpm.

The rate at which the heart beats varies with the size of the organism. The smaller the animal, the higher the heart rate (Cavendish, 2000). This is because the smaller the animal is, the higher its metabolic rate (the total amount of energy an animal uses in a unit of time) due to the animal’s large surface area to volume ratio. Because of the animals’ large surface area to volume ratio, heat leaves the body faster. To maintain the amount of heat necessary to survive which is produced by the body’s metabolism, the animal must compensate by having higher metabolic rates to keep their body temperature regulated (Cavendish, 2000). This metabolic rate, in turn, depends on the cells’ oxygen supply. Therefore, there is a greater need for a faster heart rate in order to supply nutrients and oxygen to the different cells of the body to serve as energy for the chemical processes that maintains life.

Theoretically, the frog should have higher heart rate than the man. The results may have turned out as such due to various reasons. The human subject may have been tired, emotional, or has a heart disease during the experiment resulting in a higher rate of heartbeat. It may also be due to the frog having a heart diseases resulting in a slower heartbeat. It may be also due to the carelessness of the person counting the heartbeat of both subjects.


In order to function normally, the heart is kept in an environment with a constant temperature. This is because temperature is a chonotropic agent, an agent that either increases or decreases the heart rate. However, temperature is not an inotropic agent, which is a chemical that alter contractility of cardiac muscle. These inotropic agents alter the force

muscle contraction. Thus, temperature only increases the rate of heartbeat but does not change the force of the heart contraction.

An increased body temperature increases the permeability, or membrane potential, of the cardiac muscle membrane to various ions which results in an acceleration of the self-excitation of the cardiac muscles (Gupta, n.d.). In higher temperatures, calcium channels open faster, the actin binds to the myosin quickly resulting in a faster heart rate. On the other hand, the calcium channels open slower in lower temperatures and the actin binds to the myosin slowly, resulting in a slower heart rate. Thus, increased body temperature greatly increases the heart rate.

Theoretically, the rate of the heartbeat should be faster in a higher temperature. Like the previous result, it may have been due to the frog having a heart diseases or the carelessness of the person counting the heartbeats.


During respiration, the cells take in oxygen and expel carbon dioxide as a waste product. When performing a light activity, the relationship between the heart rate and oxygen consumption is linear. This means that as heart rate increases, oxygen consumption increases at the same rate and magnitude. When the intensity of the activity goes beyond the moderate range, the relationship of the rate of heartbeat and oxygen consumption is no longer linear. This is because as muscles go beyond sixty percent of their force-generating capacity, the muscles spend a longer time compressing the arteries and veins, and blood flow is reduced (Valentin, O’Rourke & Alexander, n.d.). The body tries to compensate for this by having the heart beat more frequently. However, blood flow is still restricted, so heart rate increases at a much faster rate than oxygen delivery. Increased activity will mean increase heart rate in order to supply the working tissue with sufficient oxygen. Also, the heart beats faster in order to expel carbon dioxide faster.



The blood has a pH of 7.35-7.45 maintained by the carbonate-bicarbonate system. Theoretically, an acidic environment causes an increase in the heart rate because there is an increase in the concentration of carbon dioxide due to the reaction of the hydrogen ions of the acid with the bicarbonate found in the blood to form water and carbon dioxide illustrated in the following reactions:

1 H+ + HCO3- -> H2CO3

2 H2CO3 -> H2O + CO2

To compensate for the increase in the level of carbon dioxide, the heart beats faster in order to expel carbon dioxide faster.

Theoretically, the rate of the heartbeat should be faster in lower pH or acidic conditions. Like the previous result, it may have been due to the frog having a heart diseases or being tired after being subjected to various experiments, or the carelessness of the person counting the heartbeats.

d. Effect of Varying Ions on the Rate of Heartbeat

The fluid in the heart must contain a proper balance of the three essential ions i.e. sodium ions, potassium ions, and calcium ions. If these three ions are present in proper proportions, the heart is able to maintain its normal contractility for hours in an oxygenated environment. On the other hand, if the concentrations of these ions are altered, then the heart rate will also be changed.

These ions present in the blood all play an important role in the generation of an action potential. Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane (Action Potential, n.d.). In animal cells, there are two primary types of action potentials, one type generated by voltage-gated sodium channels, the other by voltage-gated calcium channels (Action Potential, n.d.). Sodium-based action potentials usually last for less than one millisecond, whereas calcium-

based action potentials may last for 100 milliseconds or longer. Sodium ions are involved in the depolarization, or change in the polarity of the membrane within milliseconds. When depolarization happens, sodium channels open and sodium ions rush inside the cell. An influx of sodium ions quickly depolarizes the skeletal myocyte and triggers calcium release from the sarcoplasmic reticulum.

Calcium ions are also involved in the depolarization of the cardiac action potential. In the cardiac action potential, instead of sodium calcium is used in the depolarization. In cardiac myocytes, the release of calcium ions from the sarcoplasmic reticulum is induced by the influx of calcium ions into the cell through voltage-gated calcium channels on the sarcolemma (Cardiac Action Potential, n.d.). This phenomenon is called calcium-induced calcium release and increases the myoplasmic free calcium ions concentration causing muscle contraction.

On the other hand, potassium ions are involved in repolarization wherein sodium channels close but the potassium channels open so that the potassium ions move out of the cell bringing the gradient to normal. This applies to both types of action potential.

Excess sodium ions cause depression of the cardiac function and interfere with the effectiveness of calcium in bringing about normal muscular contraction. On the other hand, reduced sodium ions can cause fibrillation (the heart contracts at an extremely high rate and in an uncoordinated fashion such that little or no blood is actually pumped by the heart).

Excess potassium ions reduce the heart rate as well as the strength of contraction. This weakening of the strength of contraction is caused by a decreased resting membrane potential with resulting decrease in the intensity of the action potential. Meanwhile, an excess of this ion can also cause the heart to dilate and become flaccid.

Excess calcium ions cause spastic contraction of the heart. When a large amount of calcium ions are present, the heart relaxes during diastole and eventually stops in systole


(calcium rigor). Reduced calcium ions reduce the heart rate similar to high potassium levels.

In the results, increased concentrations of all ions decreased the heart rate of the frog. This may be due to the heart being tired after being subjected to different experiments.

B. Blood Clotting

Bloor clotting is an important mechanism that prevents the excessive loss of blood. Injury (or cut) to the blood vessel is normally followed by a series of reactions that results in a blot clot, that seals the opening and prevents the loss of blood or hemostasis.

There are three steps involved in blood clotting: vasoconstriction, temporary platelet plug formation, and clotting of blood itself (Hallare, n.d.). The clotting process begins when the endothelium of a blood vessel is damaged, exposing connective tissue in the vessel wall to blood. Platelets then adhere to the collagen fibers in the connective tissue. This causes the release of serotonin from the platelets, which promotes the constriction of the blood vessels, or vasoconstriction. This step limits the flow of blood to the area of injury.

The contact of the platelets to collagen in the inured wall releases ADP and PAF (Potent Aggregating Factor), which attracts more platelets and stimulated the formation of pseudopods in the platelets. The pseudopods enable the platelets to bind together, forming a temporary plug to stop the blood loss.

The temporary plug is reinforced by a clot of fibrin to permanently stop the blood loss. Fibrin is formed via a multistep process: clotting factors released from the clumped platelets or damaged cells mix with clotting factors in the plasma, forming an activation cascade until factor X is activated. This clotting factor converts a plasma protein called prothrombin to its active form, thrombin. Thrombin itself is an enzyme that catalyzes the final step of the clotting process, the conversion of fibrinogen to fibrin. The threads of fibrin become interwoven into a net over the platelets through factor XIII and calcium ions.

Red cells then adhere to this net. The combination of the red cells and platelets entangled within a tight fibrin net forms a blood clot, a stronger and more permanent plug to stop the blood loss, through factor XIII and calcium ions(Campbell and Reece, 2007).

In the experiment, it took three minutes for the blood clot to form. The rate of the formation of blood clot depends upon the number of platelets in the blood. The higher the number of platelets, the faster the formation.

C. Blood Groupings

The membranes of the red blood cells, like those of all body cells, bear highly specific glycoproteins, or antigens, which identify each cells from all others or one person as unique from all others. The presence or absence of specific antigens, called agglutinogens, in the surface of the red blood cells is the basis for the ABO blood group system, the most important blood group system concerning blood transfusions. This system breaks the blood types down into four categories: type A which has antigen A on the membrane of the red blood cell, type B which has antigen B, type O which has no antigens, and type AB which has both antigens(Campbell and Reece, 2007).

An antigen is any molecule that could become a target of the immune response. If the body recognizes an antigen as foreign, it will launch an immune response that will cause the destruction of the antigen. This immune response involved the presence of antibodies. An antibody is a molecule produced by the immune system that binds to an antigen and triggers its destruction. Unique to the ABO blood group system is the presence of preformed antibodies called agglutinins. These agglutinins act against red blood cells that are not present on a person’s own red blood cell. The plasma of type A blood contains agglutinin B, the plasma of type B blood has agglutinin A. The plasma of type AB has neither agglutinins A nor B. The plasma of type O has both agglutinins. Table 3.0 summarizes the


agglutinogens and agglutinins present in each blood group.

Table 3.0 Summary of the agglutinogens and agglutinins present in each blood group.

Blood Group Blood Agglutinogen

Plasma Agglutinin

O None Anti-A/Anti-BA A Anti-BB B Anti-A

AB AB none

Agglutination results when the agglutinogen on the surface of the red blood cells reacted with the agglutinins present in the blood plasma. Clumping results when agglutinogen A reacted with agglutinin A, and agglutinogen B with agglutinin B. This happens when the antibodies binds to the antigen and brings them together, forming a large complex resulting in agglutination(Campbell and Reece, 2007).

Blood grouping is a method to determine the specific blood type of a person. Determining the blood type of a person is made possible by mixing sample of the individual’s blood with a drop of a known serum containing anti-A or anti-B agglutinin to see which combination causes agglutination, like what is done in the experiment. A person’s blood type is A if there is agglutination in the slide where anti-serum A is mixed. This is because the agglutinogen A in the red blood cells reacted with the agglutinin A present in the serum, forming clumps of blood. The same applies to blood type B. The sample mixed with anti-serum B will agglutinate because the agglutinogen present in the red blood cells of type B reacted to the agglutinin B present in the serum. No agglutination will occur in blood type O because of the absence of both agglutinogens, preventing agglutination. This is the reason why type O is considered the universal donor. On the other hand, agglutination will occur on both samples if the person’s blood type is AB. This is because of the presence of both agglutinogens in the red blood

cells of the individual. For this reason, type AB is considered the universal recipient.

Knowing one’s blood type is necessary during blood transfusion because mixing the blood of a person containing a specific agglutinogen can trigger a reaction with the agglutinins present in the blood of another individual(Campbell and Reece, 2007).

Conclusion

The circulatory system is one of the most important organ systems in the animal body. Without it, an animal would not be able to survive because the organism does not have a mechanism that transports gases, nutrients, hormones, heat, and waste to the different cells of the body.

The proper functioning of the various components of the circulatory system is affected by several factors such as temperature, pH, activity of the organism, certain chemicals, the size and health status of the organism, and the organism’s own genetic make-up.

Maintaining a constant body temperature is important for an organism because it influences the permeability of the membrane of the cardiac muscles to the different ions present in the blood, thereby affecting the intensity of the action potential. An increase in the body’s temperature therefore increases the rate of the heartbeat because an increase in temperature increases the permeability of the membrane.

The intensity of the activity also affects the heart rate. A more strenuous activity means that the muscles must exert themselves in order to perform the activity, resulting is the fast production of carbon dioxide and rapid oxygen consumption. The heart beats faster in order to supply the cells with oxygen faster.

The body’s pH also influences the rate of heartbeat because an acidic environment increases the amount of carbon dioxide present due to the reaction of the hydrogen ions of the acid with the bicarbonate which results to water and carbon dioxide, while a basic environment maintains the normal amount of


the said gas. Therefore, a low pH increases the heart rate of the organism in order to expel carbon dioxide faster.

Ions such as sodium, potassium, and calcium also influence the rate of the heartbeat because these ions are involved in the generation of the action potential. Excess sodium and potassium decreases the heart rate of the organism while excess calcium causes spastic contraction of the heart.

Blood clotting involves three processes: vasoconstriction, temporary platelet plug formation, and blood clotting. When the endothelium of the blood vessels is damaged, the collagen fibers of the connective tissue are exposed, making the platelets adhere to them and releasing serotonin makes the blood vessels constrict. The platelets then release ADP and Potent Aggregating Factor (PAF) which enables the platelets to form a plug to provide emergency protection against blood loss. Finally, fibrin in the blood will be activated by a series of activation via the clotting factors present in the blood. The fibrin will then be interwoven into a net over the platelets and, through factor XIII and calcium ions, will form a blood clot which permanently stops the loss of blood.

The ABO blood group is based on the presence or absence of certain antigens, called agglutinogen on the surface of the red blood cells. Type A has agglutinogen A, type B agglutinogan B, type O no agglutinogen, and type AB both agglutinogens. There are also antibodies in the plasma of the blood called agglutinin. Type A has anti-B, type B has anti A, type O has both agglutinin, and type AB has no agglutinin. The reaction between the same antigen and agglutinin, for example agglutinogen A and anti-A, is called agglutination in which the antibodies bond to the antigen and converge them, forming clumps. This process can determine the blood type of a person by mixing a sample of the blood with serums containing anti-A and anti-B. If agglutination with anti-A occurs, the blood type of the individual is A, if with anti-B blood

type B, if no agglutination type O, if there is agglutination with both serums blood type AB.

Materials and Methods


In the exercise, three separate experiments were conducted. These experiments were focused on the rate of heartbeat, blood clotting and blood groupings. All materials for these experiments were obtained from the laboratory stockroom. Likewise, equipments were also taken from the stockroom.

For the rate of heartbeat, the heart of a pithed frog was exposed through an incision through the midline of the thorax and abdomen. With a pair of forceps, the heart was exposed by destroying the fascia and the pericardium surrounding the heart. The heart was kept moist by placing a drop of Ringer’s solution every 15 seconds. The heart was not exposed to air or such currents. Three trials of the measurement of the heart’s beat per minute were taken. The average of these trials was then taken. Using a stethoscope, three trials of the measurement of the heartbeat of a volunteer from the class was also taken. The average of the three trials was also computed for.

The experiment on the rate of heartbeat was divided into four sub experiments, each concerning a factor affecting the heart rate.


The first sub experiment focused on the effect of temperature on the rate of heartbeat. The heart of the frog was subjected to cold Ringer’s solution, about 10 degrees Celsius in temperature. Three measurements of the heart beat were taken and the average was computed. The heart was then allowed to go back to normal by adding Ringer’s solution of normal temperature. Afterwards, the similar


procedure was done, only with cold Ringer’s solution of about 40 degrees Celsius.


The second sub experiment focuses on the effect of activity on the rate of heart beat. The average pulse rate of a volunteer was taken under the following conditions: (a) sitting quietly, (b), after standing at attention or two minutes and (c) after doing jumping jacks for two minutes.


The third sub experiment focused on the effect of pH on the rate of the heart beat. A drop of 1.0% acetic acid was placed on the heart of the frog and the number of beats per minute was counted. The acid was washed off with Ringer’s solution and the procedure was repeated until three heartbeat measurements were acquired. Data was recorded.

d. Effect of Varying Ions on the Rate of Heartbeat

The fourth sub experiment concentrated on the effect of selected ions on the rate of heart beat. The heart of the frog was carefully removed from the frog and then placed in thirty milliliters of Ringer’s solution in a 100 milliliter beaker. The heart was cleansed and then transferred to another thirty milliliters of Ringer’s solution. The heart was then transferred to a thirty milliliter solution of each of the following and then afterwards returning them to the Ringers solution to normalize:

0.06% sodium chloride, 0.15% potassium chloride and 0.012% calcium chloride. Three trials were done on each solution and the average of these three measurements was recorded, along with the observations.

B. Blood Clotting

For blood clotting, the tip of the left ring finger was cleansed with alcohol and pricked with a sterile lancet. A capillary tube was then used to carefully draw blood from the finger. The tube was filled with blood and it was kept warm. After two minutes, the tip of the capillary tube was broken. The clotting time was recorded.

C. Blood Groupings

For blood groupings, one end of a clean side was marked “A” and another “B”. A finger of a volunteer was pricked and a drop of blood was placed on each side of a side. A drop of Anti-B and Anti-A serum were immediately placed on the blood. The blood and the serum were mixed with a toothpick. Clumping was observed and further reactions were recorded.

Author Contributions

The author(s) have made the following declarations about their contributions: Performed the experiments: BLD ETN RCY. Analyzed the data: JRB BLD ETN RCY. Contributed reagents/materials/analysis tools: JRB BLD ETN RCY. Wrote the paper: JRB BLD ETN RCY.

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Physiology of Circulatory System