Download HUMAN PHYSIOLOGY MODULE: 3 CIRCULATION

III SEMESTER BOTANY
HUMAN PHYSIOLOGY
MODULE: 3 CIRCULATION
The Blood
Blood is classified as a connective tissue, since nearly half of it is made up of cells.
However, it differ from other connective tissues in that its cells are not fixed in
position, instead they move freely in the liquid portion of the blood, the plasma.
Blood is a viscous (thick) fluid that varies in colour from bright to dark red, depending
on how much oxygen it is carrying. Its quantity differs with the size of the person; the
average adult male, weighing 70 kg has about 5-6 litres of blood. This volume
accounts for about 8% of the total body weight. It is carried through a closed system of
vessels pumped by the heart. The circulating blood is of fundamental importance in
maintaining the internal environment in a constant state (homeaostasis). Blood is
about 22% solids and 78% water. Blood is slightly alkaline, with a pH between 7.35
and 7.45.
Functions of the Blood
1. Maintenance of osmotic balance.Water being a major component of body
mass, great solvent, tissues must maintain optimum level of water to carry out
metabolic processes. Blood absorbs water from the gut and distributes it to all
organs. Loss of water from blood as happens in the case of vomiting and
diarrhoea, results in serious consequences, sometimes leading to death.
2. Transport of respiratory gases.Micro-organisms have more surface area as
compared to the bulk and hence gases simply diffuse in and out of the body,
requiring no specific respiratory organs. However, in larger animals oxygen
must be absorbed in specialized respiratory organs and then transported via an
oxygen-carrying pigment in blood, such as haemoglobin or hemocyanin and
delivered to the tissues. Carbon dioxide takes a reverse route to the outside.
3. Distribution of nutrients.Food is digested and absorbed in the intestine and
then transported via the blood and lymphatic circulation to the liver, where it is
assimilated and then supplied to all parts of body.
4. Temperature regulation.If excess metabolic heat is generated in the body,
blood circulation carries it to the body surface where it is dissipated via the
skin. In endotherms metabolic heat is evenly distributed throughout the body
by blood, while in ectothermic animals heat is absorbed from atmosphere by
skin and then transported to all parts of body evenly so that metabolic activities
can take place.
5. Transport of hormones and other chemicals.Hormones are secreted in
endocrine glands but the target organs of these hormones are located in
different parts of body. Blood carries these hormones from endocrine glands to
target organs. Pituitary located on hypothalamus of brain secretes hormones
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such as TSH, GH, Gonadotropin, prolactin, ADH etc. which are transported by
blood to other endocrine glands, which are stimulated to produce their own
hormones.
6. Defence against
gainst invaders.Blood
invaders.Blood contains granular and agranular leucocytes
which attack and kill pathogens that manage to enter the body. T
T-cells kill the
invaders chemically while B-lymphocytes
B lymphocytes produce antibodies to inactivate
pathogens. Monocytes or macrophages ingest
ingest foreign materials and tissue
debris by endophagy and digest it.
7. Disposal of wastes.Carbon
Carbon dioxide and nitrogenous wastes are constantly
produces all over the body, and being toxic must be removed from body quickly.
Blood carries them to the excretory organs such as kidneys, nephridia,
malpighian tubules, lungs etc. from where they are released outside into the
atmosphere. Toxins and excess salts are also carried via blood to the skin,
where they are excreted via the sweat glands.
8. Diagnostic material. Many kinds of chemical transformations and production
of antibodies take place in blood, which is also a carrier of a variety of
chemicals and hence can be uses as an ideal material to analyse and know the
physiological condition of the body. Therefore,
Therefore, blood test for leucocyte count,
haemoglobin, liver, kidney and thyroid function tests and a variety of other
tests can be carried out with ease using patient’s blood.
Composition of Blood
Blood is a highly specialized tissue composed of many different
different kinds of components
produced in bone marrow. Four of the most important ones are red cells
cells, white cells,
platelets, and plasma.. All humans produce these blood components - there are no
racial or regional differences.
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Red blood cells, or erythrocytes, RBCs, are relatively large microscopic cells without
nuclei. These cells normally make up 40-50% of the total blood volume. They
transport oxygen from the lungs to all of the living tissues of the body and carry away
carbon dioxide. Hemoglobin, Hb is the gas transporting protein molecule that makes
up 95% of a red cell. The number of RBCs is about 5 million cells per cubic centimeter
(cm3).
White blood cells, or leukocytes, WBCs exist in variable numbers and types but
make up a very small part of blood's volume - normally only about 1%. Some white
cells (lymphocytes) provide a physiological defense against infection by seeking out
microscopic parasites and destroying them. Their numbers increase when the body is
under attack by bacteria, viruses, fungi, or other parasites. Some white cells
(macrophages) are the blood's disposal units. They have the function of getting rid of
old, unneeded blood cells as well as foreign matter (dust and bacteria). A total WBC
count above 11,000 cells/cm3 is referred to as leukocytosis, and generally indicates a
bacterial or viral infection. Individual white cells remain viable for only 18 to 36 hours.
The several types of white blood cells are classified into two major groups, depending
on whether or not they contain visible granules in their cytoplasm.
Granulocytes are granule-containing WBCs:
Neutrophils have a multilobed nucleus and very fine granules. They are avid
phagocytes at sites of acute infection.
Eosinophils have a blue-red nucleus and large brick-red granules. Their numbers
increase rapidly during allergies.
Basophils, the rarest of all WBCs, contain large histamine-containing granules.
Histamine is an inflammatory chemical that makes blood vessels leaky and attracts
other WBCs to the inflammatory site.
Agranulocytes do not have visible cytoplasmic granules:
Lymphocytes have a large dark purple nucleus that occupies most of the cell volume.
Lymphocytes reside in lymphatic tissues and are the first immune response of the
body.
Monocytes are the largest of WBCs. When they migrate into the tissues, they change
into macrophages with an important role in fighting chronic infections.
Platelets, or thrombocytes, are cells that clot blood at the site of wounds. Platelets
are not cells in the strict sense. The are fragments of multinucleated cells called
megakaryocytes, which rupture, releasing thousands of "pieces" that quickly seal the
leak in the blood vessel. There are more than a dozen types of platelets that need to
interact in the blood clotting process. Individual platelets are about 1/3 the size of red
cells. The normal platelet count in blood is about 300,000/cm3. Platelets have a
lifespan of 7 to 10 days.
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Blood Plasma
Over half of the total volume of blood is plasma. The plasma itself is 90% water. Many
different substances dissolved or suspended in the water, make up the other 10%. The
plasma content varies somewhat, since the substances carried by the blood to and
from the organs get used and added to. However, the body tends to maintain a fairly
constant level of these substances.
After water, the next largest percentage of material in the plasma is protein. Proteins
are the principal constituents of cytoplasm and are essential to the growth and the
rebuilding of body tissues. The plasma proteins include the following:
1. Albumin, the most abundant protein in plasma, is important for maintaining the
osmotic pressure of the blood. This protein is manufactured in the liver.
2. The antibodies combat infection.
3. The blood clotting factors are also manufactured in the liver.
4. A system of enzymes made of several proteins, collectively known as complement,
helps antibodies in their fight against pathogens.
Nutrients are also found in the plasma. One group of nutrients is the carbohydrates.
The principal form of carbohydrate found in the plasma is glucose, which is absorbed
by the capillaries of the intestine following digestion. Amino acids, the products of
protein digestion, are also found in the plasma. These are also absorbed into the blood
through the intestinal capillaries. Lipids constitute a small percentage of blood
plasma. Lipids include fats. The mineral salts in the plasma appear primarily as
chloride, carbonate, or phosphate salts of sodium, potassium, and magnesium. Small
amounts of other elements also help maintain homeostasis. Many other materials,
such as waste products and hormones, are also transported in the plasma.
The Conduction System of the Heart
The cardiac cycle is regulated by specialized areas in the heart wall that forms the
conduction system of the heart. Two of these areas are tissue mass called nodes; the
third is a group of fibers called the atrioventricular bundle. The sinoatrial node, which
is located in the upper wall of the right atrium an initiates the heart beat, is called the
pacemaker. The second node, located in the ineratrial septum at the bottom of the
right atrium, is called the atrioventricular node. The atrioventricular bundle, also
known as the bundle of His, is located at the top of the interventricular septum; it has
branches that extend to all parts of the ventricle walls. Fibers travel first down both
sides of the interventricular septum in groups called the right and left bundle
branches. Smaller Purkinje fibers then travel in a branching network throughout the
myocardium of the ventricles. The order in which the impulses travel is as follows:
1. The sinoatrial node generates the electric impulse that begins the heart beat.
2. The excitation wave travels throughout the muscle of each atrium, causing it to
contract.
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Heart Sounds and Murmurs
The normal heart sounds are usually described by the syllables “lubb” and “dupp.”
The first is a longer, lower pitched sound that occurs at the start of ventricular systole.
It is probably caused by a combination of things, including closure of the
atrioventricular valves. The second, or “dupp,” sound is shorter and sharper. It occurs
at the beginning of ventricular relaxation and is due in large part to sudden closure of
the semilunar valves. Some abnormal sounds called murmurs are usually due to
faulty action of the valves. For example, if the valves fail to close tightly and blood
leaks back, a murmur is heard. Another condition giving rise to an abnormal sound is
the narrowing (stenosis) of a valve opening. The many conditions that can cause
abnormal heart sounds include congenital defects, disease, and physiological
variations.
Pulse
The ventricles pump blood into the arteries regularly about 70 to 80 times a minute.
The force of the ventricular contraction starts a wave of increased pressure that begins
at the heart and travels along the arteries. This wave, called the pulse, can be felt in
any artery that is relatively close to the surface, particularly if the vessel can be
pressed down against a bone. At the wrist the radial artery passes over the bone on
the thumb side of the forearm, and the pulse is most commonly obtained here. Other
vessels sometimes used for obtaining the pulse are the carotid artery in the neck and
the dorsalis pedis on the top of the foot.
Blood Pressure
As blood passes through the vessels in the body, it exerts pressure against the vessel
walls. This is called blood pressure. Changes in blood pressure correspond to the
phases of the heartbeat. When the ventricles contract and force blood into the
pulmonary arteries and the aorta, the pressure increases in these vessels. The
maximum pressure during the ventricular contraction is called systolic pressure. The
phase during which this occurs is called systole. The ventricles then relax and the
pressure in the pulmonary arteries and the aorta drops. The lowest pressure before
the ventricles contract is called the diastolic pressure. The phase during which this
occurs is called diastole.
Measuring Blood Pressure
Doctors commonly measure blood pressure to diagnose the health of the circulatory
system. A blood pressure reading shows how much pressure the blood exerts against
the vessel walls and indicates the condition of the heart and arteries. Blood pressure
is usually measured at an artery in the arm, using a device called a
sphygmomanometer. A sphygmomanometer is commonly known as a blood pressure
cuff, because it has a cuff that is wrapped around the upper arm and inflated to exert
pressure on a large artery in the arm. This temporarily stops the flow of blood. As air
is slowly let out of the cuff, the blood begins to flow again, and the pressure of the
blood against the walls of the artery is measured.
When a blood pressure reading is taken, it is recorded in millimetres of mercury, or
mmHg (1 mmHg = 0.133 kPa). The systolic pressure is presented over the diastolic
pressure in the form of a fraction. The blood pressure of an average healthy young
person is below 120 mmHg over 80 mmHg, or 120/80 (systolic/diastolic). As the heart
rate increases, such as during exercise, the ventricles must push a greater volume of
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blood per unit of time, so the pressure within the arterial system also increases.
Although the diastolic blood pressure in a relaxed ventricle drops to almost 0 mmHg
during each heartbeat, the blood pressure in the arteries never drops this low, so
blood keeps flowing to the tissues.
Blood pressure is affected by genetics, activity, stress, body temperature, diet, and
medications. It is normal for your blood pressure to increase when you are exercising
and to decrease when you are sleeping. However, continuous high blood pressure, also
called hypertension, causes the heart to work harder for extended periods of time. This
can cause damage to arteries and increases the risk of heart attack, stroke, and
kidney failure.
Cardiac Output and Stroke Volume
The amount of blood pumped by the heart is often referred to as cardiac output and is
measured in mL/min. Cardiac output is an indicator of the level of oxygen delivered to
the body. Therefore, cardiac output is also an indicator of the total level of work the
body’s muscles can perform. Two factors contribute to cardiac output: heart rate and
stroke volume. Heart rate is the number of heartbeats per minute. Stroke volume is
the amount of blood forced out of the heart with each heartbeat. Cardiac output =
heart rate × stroke volume.
Stroke volume is determined by two factors. The first factor is how easily the heart fills
with blood. This is related to the volume of blood returning to the heart from the veins
and the distensibility, or stretchiness, of the ventricles. The second factor is how
readily the blood is emptied from the heart. This is related to the strength of the
ventricular contraction and the pressure exerted by the artery walls.
The average person has a stroke volume of about 70 mL and a resting heart rate of
about 70 beats per minute. This means that the cardiac output for a typical adult at
rest is 70 × 70, or 4900 mL/minute. Recall that the average adult human has about 5
L of blood in their circulatory system. With a cardiac output of 4900 mL/min, the
entire volume of blood in the body passes through the heart about once every minute.
With increased physical activity, the cardiac output and rate of circulation increase.
The Electrocardiogram (ECG)
ECG is short for electrocardiogram. Electro- refers to electricity, -cardio- refers to the
heart, and -gram refers to a recording. Therefore, the electrocardiogram is a recording
of the heart's electrical activity.
The electrical pulses that cause the heart to beat create small voltage changes (only a
few milliVolts) that can be measured by electrodes placed on the skin of the chest.
These voltage measurements produce an electrocardiogram (ECG) that physicians use
to diagnose the health of the heart.
The first voltage increase, or P wave, labelled on the ECG above as P, begins when the
SA node fires and the atria contract. The next spike on the ECG is a cluster of three
waves called the QRS complex. It begins when the AV node stimulates the ventricles to
contract and the atrioventricular valves close, producing the first heart sound (“lub”).
The final wave in the cycle is the T wave. It occurs when the ventricles relax and the
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semilunar valves close to produce the second heart sound (“DUB”). The relaxation of
the ventricles is followed by the next firing of the SA node for the next heartbeat.
Blood Clotting
Blood clotting, or coagulation, is a protective device that prevents blood loss when a
blood vessel is ruptured by an injury. The many substances necessary for clotting are
normally inactive in the blood stream. Basically, the clotting process consists of the
following essential steps:
1. The injured tissues release thromboplastin, a substance that triggers the clotting
mechanism.
2. Thromboplastin reacts with certain protein factors and calcium ions to form
prothrombin activator, which in turn reacts with calcium ions to convert the
prothrombin to thrombin.
3. Thrombin, in turn, converts soluble fibrinogen into insoluble fibrin. Fibrin forms a
network of threads that entraps red blood cells and platelets to form clot.
When blood is shed, it looses its fluidity within few minutes and sets into a
semisolid jelly called clot. This phenomenon of formation of clot is called as
coagulation or clotting of blood. The clot gradually retracts and a fluid separates out,
called serum.
Mechanism:
Coagulation of blood is a complicated process in which about 13 coagulation
factors are involved. All these factors are blood proteins or their derivatives. Even if
one of the factor is defective, the whole clotting process is impaired leading to
haemorrhage. These factors are from F-I to F-XIII.
The ultimate result of the coagulation cascade is the conversion of fibrinogen into
fibrin. This conversion is catalyzed by thrombin, the active form of prothrombin. The
fibrin that forms consists of a meshwork of strands that is further stabilized by the
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formation of covalent bonds between strands. The formation of bonds is catalyzed by
factor XIIIa (the subscript a indicates the activated form of factor XIII)
Two pathways lead to the activation of thrombin:
Intrinsic pathway that involves coagulation factors already present in the plasma.
Extrinsic pathway involving coagulation factors present in damaged tissue.
Intrinsic Pathway
It is dependent on certain factors or procoagulants, all of which are present in the
blood itself. They are denoted by Roman numerals (I-XIII),
XIII), which indicates the order of
discovery. Following rupture of the blood
bl od vessel, the platelets adhere to the endothelial
wall and form clumps. Consequently the platelets disintegrate and release platelet
coagulation factors into the plasma. The platelet coagulation factors are called Pf1,
Pf2, Pf3 and Pf4. During clotting, the
he plasma coagulation factors are activated in
sequence. At first, the factor XII is activated on contact with the altered endothelial
surface. Factor XII is released from platelets. Liver is another source of this factor. In
fact, any surface other than the
the natural smooth endothelial surface activates this
factor. The active factor, XII, in turn, activates factor XI. This is followed by the
activation of Factor IX. Factor IX in the presence of calcium ions and a platelet
phospholipid
pid (Pf3) activates factor VIII. It converts inactive factor X into active factor
Xa. further reactions occur through the common path way.
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Extrinsic Pathway
It is called so because the initial factors are derived from damaged tissues and are not
present in the blood. This pathway
path
begins when tissue factor called thromboplastin
(factor III) comes in contact with factor VII in the plasma and activates it to VIIa . The
complex then activates factor X which in turn activates the conversion of prothrombin
into thrombin.
Common Pathway
The common pathway begins with the activation of the enzyme called prothrombin
activator (prothrombinase) by factor X. Prothrombin
rothrombin activator then converts
prothrombin to thrombin, in the presence of calcium ions and platelet factor 3 (Pf3).
Thrombin itself can activate prothrombin activator
activator in the presence of factor V. IIt also
activates factor XIII required in the final stage for the formation of clot. Vitamin K is
required for the formation of thrombin and certain other factors such as facto
factors IX and
X. Thrombin
hrombin is a proteolytic enzyme that cleaves fibrinogen to fibrin molecules. The
fibrin molecules join end to end to form long strands of fibrin polymers which
aggregate to form a three dimensional network. This gives the so-called
called ‘soft clot
clot’. A
more stable ‘hard clot’ is formed by covalent cross-linking
c
linking between the side chains of
adjacent fibrin molecules. Formation of hard clot requires an enzyme called fibrin
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stabilizing factor. Thrombin also stimulates intrinsic pathway by facilitating clumping
of blood platelets and their disintegration for releasing more coagulation factors.
High Blood Pressure (Hypertension): Hypertension is the term for blood pressure
that is higher than normal (120/80). In this measurement 120 mm Hg (millimetres of
mercury pressure) is the systolic, or pumping, pressure and 80 mm Hg is the diastolic,
or resting, pressure. If repeated checks of blood pressure of an individual is 140/90
(140 over 90) or higher, it shows hypertension. High blood pressure leads to heart
diseases and also affects vital organs like brain and kidney.
Myocardial infarction: Myocardial infarction or acute myocardial infarction (AMI) is
the medical term for an event commonly known as a heart attack. An MI occurs when
blood stops flowing properly to a part of the heart, and the heart muscle is injured
because it is not receiving enough oxygen. Usually this is because one of the coronary
arteries that supplies blood to the heart develops a blockage due to an unstable
buildup of white blood cells, cholesterol and fat. The event is called "acute" if it is
sudden and serious.
A person having an acute MI usually has sudden chest pain that is felt behind the
breast bone and sometimes travels to the left arm or the left side of the neck.
Additionally, the person may have shortness of breath, sweating, nausea, vomiting,
abnormal heartbeats, and anxiety. Women experience fewer of these symptoms than
men, but usually have shortness of breath, weakness, a feeling of indigestion, and
fatigue. In many cases, in some estimates as high as 64%, the person does not have
chest pain or other symptoms. These are called "silent" myocardial infarctions.
Important risk factors are previous cardiovascular disease, old age, tobacco smoking,
high blood levels of certain lipids (low-density lipoprotein cholesterol, triglycerides) and
low levels of high density lipoprotein (HDL) cholesterol, diabetes, high blood pressure,
lack of physical activity, obesity, chronic kidney disease, excessive alcohol
consumption, and the use of cocaine and amphetamines.[
Arteriosclerosis: Arteriosclerosis is a general term that is used to describe several
conditions in which the walls of the arteries thicken and lose some of their elastic
properties, thus becoming harder. The most common type of arteriosclerosis is called
atherosclerosis. This is a condition in which plaque (fatty deposits, calcium, and
fibrous tissues) builds up on the inside of artery walls. As the artery narrows due to
this build-up, blood flow is decreased and blood pressure is increased. Plaque is
especially dangerous if it occurs in arteries that supply the heart, brain, legs, and
kidneys. Depending on where the build-up of the plaque occurs, atherosclerosis may
lead to angina (chest pain), blood clots, shortness of breath, heart attack, or heart
failure. More than 90 percent of heart attacks are caused by atherosclerosis. Healthy
lifestyle choices (such as exercise, not smoking, and eating a diet low in saturated fat
and high in fruits and vegetables) help to reduce the risk of developing this condition.
Angina: It is also called ‘angina pectoris’. A symptom of acute chest pain appears
when no enough oxygen is reaching the heart muscle. Angina can occur in men and
women of any age but it is more common among the middle-aged and elderly. It
occurs due to conditions that affect the blood flow.
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Heart Failure: Heart failure means the state of heart when it is not pumping blood
effectively enough to meet the needs of the body. It is sometimes called congestive
heart failure because congestion of the lungs is one of the main symptoms of this
disease. Heart failure is not the same as cardiac arrest (when the heart stops beating)
or a heart attack (when the heart muscle is suddenly damaged by an inadequate blood
supply).
Bradycardia is a relatively slow heartrate of less than 60 beats/minute. During rest
and sleep, the heart may beat less than 60 beats/minute but usually does not fall
below 50 beats/minute.
Tachycardia refers to a heart rate over 100 beats/minute.
Hemophilia: Hemophilia is a group of inherited blood disorders in which the blood
does not clot properly. Bleeding disorders are due to defects in the blood vessels, the
coagulation mechanism, or the blood platelets. An affected individual may bleed
spontaneously or for longer than a healthy person after injury or surgery. When
coagulation factors are missing or deficient the blood does not clot properly and
bleeding continues.
There are two main types of hemophilia - Hemophilia A (due to factor VIII deficiency)
and Hemophilia B (due to factor IX deficiency). They are clinically almost identical and
are associated with spontaneous bleeding into joints and muscles and internal or
external bleeding after injury or surgery. The conditions are both X-linked and
virtually all sufferers of hemophilia are males. Female carriers may also bleed
abnormally, because some have low levels of the relevant clotting factor.
People with hemophilia have a genetic mutation in the affected gene on the X
chromosome, which results in reduced production of Factor VIII or IX and creates a
bleeding tendency, because coagulation takes much longer than normal, thus making
the clot weak and unstable.
Queen Victoria was a carrier and passed the mutation to her son Leopold, and
through several of her daughters to members of the royal families of Spain, Russia,
and Germany.
Angiogram : An angiogram is an X-ray test that uses a special dye and camera to take
pictures of the blood flow in an artery or a vein. An angiogram can be used to look at
the arteries or veins in the head, arms, legs, chest, back, or belly.
During an angiogram, a thin tube called a catheter is placed into a blood vessel in the
groin (femoral artery or vein) or just above the elbow (brachial artery or vein). The
catheter is guided to the area to be studied. Then an iodine dye is injected into the
vessel to make the area show clearly on the X-ray pictures. This method is known as
conventional or catheter angiogram. The angiogram pictures can be made into regular
X-ray films or stored as digital pictures in a computer.
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An angiogram can find a bulge in a blood vessel It can also show narrowing or a
blockage in a blood vessel that affects blood flow. An angiogram can show if coronary
artery disease is present and how bad it is.
Angioplasty: Angioplasty is the technique of mechanically widening narrowed or
obstructed arteries. An empty and collapsed balloon on a guide wire, known as a
balloon catheter, is passed into the narrowed locations and then inflated to a fixed size
using water pressures some 75 to 500 times normal blood pressure (6 to 20
atmospheres). The balloon forces expansion of the inner white blood cell/clot plaque
deposits and the surrounding muscular wall, opening up the blood vessel for improved
flow, and the balloon is then deflated and withdrawn. Sometimes, a small permanent
wire-mesh tube, called a vascular stent, is inserted into the blocked area during the
procedure. This stent holds the vessel open and reduces the chance of the blockage
redeveloping.
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow
of blood through the circulatory system. A clot that breaks free and begins to travel
around the body is known as an embolus.
Pulmonary Thrombosis
A pulmonary Thrombosis (pulmonary embolism -PE) is a blood clot in the lung. The
clot usually forms in smaller vessels in the leg, pelvis, arms, or heart, but occasionally
the clot can be large. When a clot forms in the large veins of the legs or arms, it is
referred to as a deep venous thrombosis (DVT). The pulmonary embolism occurs when
part or all of the DVT breaks away and travels through the blood in the veins and
lodges in the lungs. The clot travels through the vessels of the lung continuing to
reach smaller vessels until it becomes wedged in a vessel that is too small to allow it to
continue further. The clot blocks all or some of the blood from traveling to that section
of the lung.
Cerebral Thrombosis
When arteries supplying blood to the brain are damaged, cutting off the flow of
oxygen and nutrients to brain tissue, the result is a stroke. An ischemic stroke can
occur when a clot in a blood vessel blocks the flow of blood to the brain. A
hemorrhagic stroke occurs when a blood vessel in the brain bursts and blood flows
into the surrounding brain tissue. Both types of stroke kill the brain cells in the
affected area. The longer the brain goes without oxygen, the greater the risk of
permanent brain damage. Damage from a stroke varies from partial paralysis to death.
Death occurs when nerve control to vital organs is affected.
Pericarditis is an inflammation of the pericardium. This can lead to a decrease in the
amount of serous fluid surrounding the heart, which in turn causes the pericardial
layers to bind and stick together, forming painful adhesions that interfere with heart
movements.
Lymph
Lymph is the fluid within the lymphatic capillaries and vessels; which is derived from
tissue fluid. Tissue fluid is derived from the blood plasma. A certain amount of this
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fluid and waste products from the cells is returned to the venous capillaries, but with
in the tissue spaces fine capillary vessels known as lymphatic capillaries begin, which
help to drain the waste products and water from the interstitial spaces. Also larger
sized materials or substances of the result of phagocytosis of pathogenic microorganisms are drained away in the lymphatic capillaries and vessels.
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