Transcript Physiology - Govt.Home Science College ,Chandigarh

Contents :
Blood- composition and function.
Blood group and related diseases.
Heart : functions and functioning of heart.
Bhavneet Kaur
Physiology Lecturer
Govt Home Science college
Sector 10
Chandigarh
BLOOD
 Blood is a highly specialized circulating tissue
consisting of several types of cells suspended in a fluid
medium known as plasma.
 Blood contain both extracellular fluid (the fluid in
plasma) and intracellular fluid (the fluid in the red blood
cells). However, blood is considered to be a separate
fluid compartment because it is contained in a chamber
of its own, the circulatory system.
 The average blood volume of adults is about 7 % of
body weight or about 5 litres. About 60% of blood is
plasma and 40 % is red blood cells, but these
percentages vary considerably depending on gender,
weight and other factors.
FUNCTIONS OF BLOOD
Since blood is a circulating fluid and almost every organ receives a blood
supply, it performs a number of vital functions in the body which are as
follows:

RESPIRATION: Transport of oxygen from the lungs to different tissues, and
the transport of carbon dioxide from the tissues to lungs is mainly effected by
blood.

TRANPORT OF FOOD MATERIALS: Blood is the only medium by means of
which the absorbed food materials are transported.

EXCRETION: Metabolic wastes like urea, uric acid, creatinine, water, carbon
dioxide, etc., are transported by blood, to kidney, lungs, skin and intestine for
removal.

REGULATION OF BODY TEMPERATURE: Blood distributes heat
generated in the muscles by the oxidation of carbohydrates and fats,
throughout the body.

MAINTENANCE OF ACID-BASE BALANCE: The blood has buffering
capacity and maintains normal acid-base balance in the body.
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REGULATION OF WATER BALANCE: Water balance between blood
and tissues fluid.
DEFENSE: Blood affords protection to the body against infections and
forgine antigen and antibodies .
TRANSPORT OF HORMONES AND METABOLITES: Blood serves as
a medium to distribute hormones, chemicals and essential metabolites to
different parts of the body.
COAGULATION: It is part of body’s self-repair mechanism.
COMPONENTS OF BLOOD
PLASMA: It is a pale yellow or gray yellow, slightly alkaline , somewhat
viscous fluid has a constant chemical composition. The various
components of plasma are:
Water
: 90 %
Inorganic Salts : 1 %
Proteins
: 7 - 8%
Food materials, waste products, dissolved gasses , regulatory
substances( vitamins, hormones, enzymes, anticoagulants,
choleterol and antibodies ).
: 1%
FUNCTIONS/PROPERTIES OF PLASMA PROTEINS
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RAW MATERIAL : plasma proteins act as a source of proteins for the
tissue cells which may synthesize their own proteins from them.
BUFFERS : The plasma proteins act as buffers by virtue of their power
of H ion acceptance , but they account for less than 1/6 th of the total
buffering power of the blood. These plasma proteins as aminoacids
serve as acid- base buffers. They maintain pH of the blood by combining
with acids and bases.
OSMOTIC PRESSURE : The plasma protein normally have an osmotic
pressure of 25mm.Hg and thus influence the exchange of fluid between
blood and tissue.
TRANSPORT : Plasma proteins transport certain materials in
combination with them. For Example:
Thyroxine and Vitamin B12 are bound to α- globulin. Lipids are bound to
β- globulin.
VISCOSITY : The viscosity of the blood is a factor in maintaining the
peripheral resistance and thereby , the arterial blood pressure. This
viscosity of a protein solution depends far more on the shape of the
protein than on its size.
RED BLOOD CELLS OR ERYTHROCYTES.
A unique feature of the RBCs is the presence of a red, iron
containing , oxygen carrying pigment, the hemglobin They are
confined to the blood. They are lacking in the lymph and tissue
fluid. The size of RBC are 7-8 ųm in diameter and 2 ųm thick near
the rim. There are 600 RBC to every one WBC. A normal healthy
adult man and women have 5 and 4.5 million RBC s /mm³ of blood
respectively. The new born has higher no of RBC. The increase in
count of RBC is called Polycythemia which is seen during exercise
to meet the increased demand of oxygen and at high altitudes.
Human RBC has a life span of 120 days. About 2 to 10 million
RBC s are destroyed every second in human being. The portion of
aminoacid breaks down into its constitutional amino acids whereas
iron of the haem portion is extracted and stored I the liver as
ferritin. Excess RBC’s are stored in spleen.
ERYTHROPOIESIS : Formation of red blood corpuscles is called
erythropoiesis. It occurs in liver and mesenchyme in early fetus, in
spleen and bone marrow in late fetus, in red bone marrow of long
bones in the children, and red bone marrow of skull, ribs, sternum
an vertebrae in the adults. It is controlled by feed back mechanism.
LEUCOCYTES or WHITE BLOOD CELLS
Granulocytes
(3 types)
1 Eosinophils
2 Basophils
3 Neutrophils
Agranulocytes
(2 types)
1 Lymphocytes
2 Monocytes
GRANULOCYTES : are characterized by the presence of granules in their
cytoplasm. They are also called polymorphonuclear leukocytes (PMN or
PML) because of the varying shapes of the nucleus which is usually lobed
into three segments. Granulocytes are released from the bone marrow by
the regulatory complement proteins
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EOSINOPHILS : (2-6%) They have bilobed nucleus, play role in allergic
reactions and parasitic infections , their number increase sharply in certain
diseases. Eosinophils are cytotoxic ( chemicals that inhibit or prevent
normal physiology of a cell). They take acidic strains.
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BASOPHILS : (0-2%) They take basic strain, lowest in number, their
number increases during infections, have S shaped nucleus. Basophiles
get converted into mast cells which secrete histamine ,involved in allergic
reactions. Histamine causes dilation and increased permeability of
capillaries close to the basophil. Injured basophils and other leukocytes
will release another substance called prostaglandins that contributes to
an increased blood flow to the site of infection. Both of these
mechanisms allow blood clotting elements to be delivered to the
infected.
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NEUTROPHILS : ( 60-70% ) They have multilobed nucleus, takes
neutral strains, play role in specific immunity. Neutrophils are phagocytes
they are ferocious eaters and rapidly engulf invaders coated with
antibodies and complement and damaged cells or cellular debris.
Neutrophils do not return to the blood, they turn into pus cells and die.
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AGRANULOCYTES : They have relatively clear cytoplasm.
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LYMPHOCYTES: (20-30%) They have rounded nucleus, provide
specific immunity.
B Lymphocytes: These are responsible for making antibodies.
T Lymphocytes: There are 3 subsets of these:
1.Inflammatory T cells: that recruit macrophages and neutrophils to the
site of infection or other tissue damage.
2.Cytotoxic T Lymphocytes: kills virus-infected and tumor cells.
3.Helper T cells: enhances the production of antibodies by B cells.
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MONOCYTES: (2-8%) They are maximum in size. They leave blood and
become macrophages. They provide non specific immunity.
PLATELETS
Platelets, also called thrombocytes, They are not true cells. They are
fragments of big cells called magakaryocytes. They are present in bone
marrow and split into small fragments called platelets. Their production is
regulated by the hormone called Thrombopoietin. The sticky surface of
the platelets allow them to accumulate at the site of broken blood vessels
to form a clot. This aids in the process of hemostasis ("blood stopping").
Platelets secrete factors that increase local platelet aggregation. Tissue
Thromboplastin- clotting factor released by injured tissue . This tissue
thromboplastin innitiates the process of clotting. This will convert
Prothrombin
Thrombin .Prothrombin is an inactivate form of thrombin.
Thrombin converts Fibrinogen
Fibrin. Fibrin threads will forms a
mesh/network with it platelets are attached and form a clot.
ABO BLOOD GROUP SYSTEM
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The ABO blood group system is the most important blood type
system (or blood group system) in human blood transfusion. The
associated anti-A antibodies and anti-B antibodies are usually
IgM antibodies, which are produced in the first years of life by
sensitization to environmental substances such as food, bacteria
and viruses. The ABO blood group system discovered by the
Austrian scientist Karl Landsteiner in 1900. The ABO locus is
located on chromosome 9.
The H antigen is an essential precursor to the ABO blood
group antigens. The H locus is located on chromosome 19. The
ABO locus has three main alleleic forms: A, B, and O. The A allele
encodes a glycosyltransferase that bonds α-NAcetylgalactosamine to D-galactose end of H antigen, producing
the A antigen. The B allele encodes a glycosyltransferase that joins
α-D-galactose bonded to D-galactose end of H antigen, creating
the B antigen. The O allele differs slightly from the A allele
by deletion of a single nucleotide – Guanine at position 261. This
results in H antigen remaining unchanged in case of O groups.
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Due to the presence of isoantibodies against non self blood group
antigens, individuals of type A blood group immediately raises anti-B
antibodies against B-blood group RBCs if transfused with blood from B
group. The anti-B antibodies bind to B antigens on RBC and
causes complement-mediated lysis of the RBCs. The same happens for B
and O groups (which raises both anti-A and anti-B antibodies). However
only blood group AB does not have anti-A and anti-B isoantibodies. Hence
they can receive blood from all groups and are universal recipient.
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Individuals with type A blood can receive blood from donors of type A and
type O blood.
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Individuals with type B blood can receive blood from donors of type B and
type O blood.
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Individuals with type AB blood can receive blood from donors of type A,
type B, type AB, or type O blood.
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Individuals with type O blood can receive blood from donors of only type O.
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Individuals of type A, B, AB and O blood can receive blood from donors of
type O blood. Type O- blood is called the universal donor.
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Type O carries anti-A and anti-B antibodies in the serum. To transfuse a
type A, B, or AB recipient with type O whole blood would produce a
hemolytic transfusion reaction due to the antibodies found in the serum of
whole blood.
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No antibodies are formed against the H antigen, except in those
individuals with the Bombay phenotype.
Blood groups are inherited from both parents. The ABO blood type is
controlled by a single gene (the ABO gene) with three alleles: i, IA,
and IB.
The IA allele gives type A, IB gives type B, and i gives type O. As
both IA and IB are dominant over i, only ii people have type O blood.
Individuals with IAIA or IAi have type A blood, and individuals
with IBIB or IBi have type B. IAIB people have both phenotypes, because A
and B express a special dominance relationship: codominance, which
means that type A and B parents can have an AB child. A type A and a
type B couple can also have a type O child if they are both heterozygous
(IBi,IAi)
Subgroups of type A
A1 and A2
The A blood type contains about twenty subgroups, of which A1 and
A2 are the most common (over 99%). A1 makes up about 80% of all
A-type blood, with A2 making up the rest. These two subgroups are
interchangeable as far as transfusion is concerned, however
complications can sometimes arise in rare cases when typing the
blood.
RH BLOOD GROUP SYSTEM
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It is the clinically most important blood group system
besides ABO. The Rh blood group system currently consists of 50
defined blood group antigens among which the 5 antigens D, C, c,
E, and e are the most important ones. The commonly used
terms Rh factor, Rh positive and Rh negative refer to the D
antigen only. Besides its role in blood transfusion, the Rh blood
group system, in particular the strongest D antigen, is a relevant
cause of the hemolytic. Individuals either have, or do not have,
the "Rh factor" on the surface of their red blood cells. This term
strictly refers only to the most immunogenic D antigen of the Rh
blood group system. This is usually indicated by Rh positive (does
have the D antigen) or Rh negative (does not have the D antigen).
The main antigens are D, C, E, c and e, which are encoded by
two adjacent gene loci, the RHD gene which encodes the RhD
protein with the D antigen (and variants) and the RHCE gene
which encodes the RhCE protein with the C, E, c and e antigens
(and variants). There is no d antigen. Lowercase "d" indicates the
absence of the D antigen (the gene is usually deleted or
otherwise nonfunctional).
DISEASES ASSOCIATED WITH BLOOD GROUPS
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HEMOLYTIC DISEASE OF THE NEWBORN OR RH
INCOMPATIBILITY :This condition occurs when there is an
incompatibility between the blood types of the mother and the
fetus. These terms do not indicate which specific antigen-antibody
incompatibility is implicated. The disorder in the fetus due to Rh D
incompatibility is known as erythroblastosis fetalis.
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When the condition is caused by the Rh D antigen-antibody
incompatibility, it is called Rh D Hemolytic disease of the newborn.
Here, sensitization to Rh D antigens (usually by feto-maternal
transfusion during pregnancy) may lead to the production of
maternal IgG anti-D antibodies which can pass through
the placenta. This is of particular importance to D negative females
of or below childbearing age, because any subsequent pregnancy
may be affected by the Rhesus D hemolytic disease of the
newborn if the baby is D positive. The vast majority of Rh disease
is preventable in modern antenatal care by injections of IgG anti-D
antibodies (Rho(D) Immune Globulin).
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ABO HEMOLYTIC DISEASE OF THE NEWBORN :ABO blood
group incompatibilities between the mother and child does not
usually cause hemolytic disease of the newborn (HDN) because
antibodies to the ABO blood groups are usually of the IgM type,
which do not cross the placenta; however, in an O-type
mother, IgG ABO antibodies are produced and the baby can
develop ABO hemolytic disease of the newborn.
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THALASSAEMIA :is an inherited autosomal recessive blood
disease. In thalassemia, the genetic defect results in reduced rate
of synthesis of one of the globin chains that make up hemoglobin.
Reduced synthesis of one of the globin chains can cause the
formation of abnormal hemoglobin molecules, thus
causing anemia, the characteristic presenting symptom of the
thalassemias. Hemoglobinopathies imply structural abnormalities
in the globin proteins themselves. The two conditions may overlap,
however, since some conditions which cause abnormalities in
globin proteins (hemoglobinopathy) also affect their production
(thalassemia). Thus, some thalassemias are hemoglobinopathies,
but most are not. Either or both of these conditions may cause
anemia.
 SICKLE-CELL DISEASE :or sickle-cell anaemia is a genetic life-long
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blood disorder characterized by red blood cells that assume an abnormal,
rigid, sickle shape. Sickling decreases the cells' flexibility and results in a
risk of various complications. The sickling occurs because of a mutation in
the haemoglobin gene. Life expectancy is shortened, with studies
reporting an average life expectancy of 42 and 48 years for males and
females, respectively.
Sickle-cell anaemia is the name of a specific form of sickle-cell disease in
which there is homozygosity for the mutation that causes HbS. Sickle-cell
anaemia is also referred to as "HbSS", "SS disease", "haemoglobin S" or
permutations thereof. In heterozygous people, who have only one sickle
gene and one normal adult haemoglobin gene, it is referred to as "HbAS"
or "sickle cell trait". Other, rarer forms of sickle-cell disease include sicklehaemoglobin C disease (HbSC), sickle beta-plus-thalassaemia (HbS/β+)
and sickle beta-zero-thalassaemia (HbS/β0).
HAEMOPHILIA : is a group of hereditary genetic disorders that impair the
body's ability to control bloodclotting or coagulation, which is used to stop
bleeding when a blood vessel is broken. Haemophili A (clotting factor
VIII deficiency) is the most common form of the disorder, occurring at
about 1 in 5,000–10,000 male births.
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The heart is a specialised muscle that contracts regularly and
continuously, pumping blood to the body and the lungs. The
pumping action is caused by a flow of electricity through the heart
that repeats itself in a cycle. If this electrical activity is disrupted for example by a disturbance in the heart's rhythm known as
an 'arrhythmia' - it can affect the heart's ability to pump properly.
The heart's natural pacemaker - the SA node - sends out regular
electrical impulses from the top chamber (the atrium) causing it to
contract and pump blood into the bottom chamber (the ventricle).
The electrical impulse is then conducted to the ventricles through a
form of 'junction box' called the AV node. The impulse spreads into
the ventricles, causing the muscle to contract and to pump out the
blood. The blood from the right ventricle goes to the lungs, and the
blood from the left ventricle goes to the body.
The heart has four chambers - two at the top (the atria) and two at
the bottom (the ventricles). The normal trigger for the heart to
contract arises from the heart's natural pacemaker, the SA node,
which is in the top chamber (see the diagram, right). The SA node
sends out regular electrical impulses causing the atrium to contract
and to pump blood into the bottom chamber (the ventricle). The
electrical impulse then passes to the ventricles through a form of
'junction box' called the AV node (atrio-ventricular node). This
electrical impulse spreads into the ventricles, causing the muscle
to contract and to pump blood to the lungs and the body.
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The electrical activity of the heart can be detected by doing an
'electrocardiogram' (also called an ECG). An ECG recording looks
something like the one shown below.
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There are four heart valves. They are all one-way valves to keep
blood moving through the various chambers of the heart.
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The mitral valve guards the opening between the atrium and the
ventricle in the left side of the heart. It allows blood to flow forward
from the atrium to the ventricle, and prevents blood from flowing
backwards. The mitral valve has tiny cords attached to the walls of
the ventricles. This helps support the valve’s small flaps or leaflets.
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The aortic valve, also called a semi-lunar valve, has three
segments that prevent the return of the blood from the aorta to the
left ventricle. It looks like three half Ping-Pong balls. Valves on the
heart’s left side need to withstand much pressure. Sometimes they
wear out and leak or become thick and stiff.
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The pulmonary valve is located at the junction of the pulmonary
artery and the right ventricle. When the right ventricle contracts,
the pulmonary valve opens, forcing the blood into the artery which
leads to the lungs. It is also a semi-lunar valve. When the chamber
relaxes, this valve closes and prevents a backflow of the blood.
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The tricuspid valve is located between the upper and lower
chamber in the right side of the heart. Its position corresponds to
the mitral valve in the left side of the heart.
CARDIAC CYCLE
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The heart has an increasing rhythmic activity. It pumps blood by its
contraction and relaxation. The contraction of the heart is
called systole and the relaxation is called diastole. The contraction
and relaxation together constitute the heart beat. The heart beats
at the rate of 72 beats per minute. The changes that occur in the
heart during the beat one is repeated in the same order in the next
beat. This cyclical repetition is called cardiac cycle. During the
cardiac cycle, blood flows through the cardiac chambers in a
specific manner and direction, the backward flow being prevented
by the valves. There are 3 main events in the cardiac cycle,
namely
a) Auricular systole
b) Ventricular systole
c) Joint diastole
COMPLETE
CARDIAC
DIASTOLE
(0.4 SEC)
AURICULAR
SYSTOLE
(0.1 SEC)
VENTRICULA
SYSTOLE
(0.3 SEC)
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AURICULAR SYSTOLE : This phase involves the contraction of
the 2 auricles, pushing the blood into the respective ventricles.
There is no back flow of blood due to the presence of the bicuspid
and the tricuspid valves. The atrial systole takes 0.1 second. This
is followed by the atrial diastole when both the auricles relax
simultaneously. This is about 0.7 seconds.
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VENTRICULAR SYSTOLE: This takes place alongside auricular
diastole. The pressure on the blood in the ventricles increases.
The auriculo ventricular valves close rapidly to prevent the
backward flow of blood into the auricles. This closing of the
auriculo ventricular valves at the start of ventricular systole
produces first heart sound called lubb.
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As the pressure in the ventricle increases, than that in the great
arteries, namely pulmonary artery and the aorta, the semilunar
valves guarding the openings of these arteries open and blood
enters them. From the right ventricle, the deoxygenated blood
enters the pulmonary artery. From the left ventricle, the
oxygenated blood enters the dorsal aorta, to be taken to all body
parts. Ventricular systole takes about 0.3 seconds.
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JOINT DIASTOLE :Ventricular systole is followed by ventricular
diastole. The auricles are already in diastole, so all the chambers
of the heart are in diastole. When the ventricles are in diastole, the
pressure in the ventricles decreases more than that in the great
arteries. So to prevent the backward flow of blood, the semilunar
valves close rapidly. This produces the second heart sound called
dup.
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During a complete cardiac diastole, blood from the superior and
inferior vena cava flows into the auricles slowly. The pressure in
the ventricles decreases and finally becomes lower than atrial
pressure. Then the AV values open and blood (auriculo ventricular
valves) from the atria starts entering into the relaxing ventricles. A
complete cardiac diastole takes only 0.4 seconds. An entire
cardiac cycle is completed in 0.8 seconds.
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MYOCARDIAL INFARCTION (MI) or acute myocardial
infarction (AMI), commonly known as a heart attack, is the
interruption of blood supply to part of the heart, causing some
heart cells to die. This is most commonly due to occlusion
(blockage) of a coronary artery following the rupture of
a vulnerable atherosclerotic plaque, which is an unstable collection
of lipids (fatty acids) and white blood
cells (especially macrophages) in the wall of an artery. The
resulting ischemia (restriction in blood supply) and oxygen
shortage, if left untreated for a sufficient period of time, can cause
damage or death (infarction) of heart muscle tissue (myocardium).
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Symptoms of acute myocardial infarction include sudden chest
pain (typically radiating to the left arm or left side of the
neck), shortness of
breath, nausea, vomiting, palpitations, sweating and anxiety (often
described as a sense of impending doom).