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Blood Notes- HA 2nd Years Anatomy Notes Blood

Blood Notes- HA 2nd Years Anatomy Notes Blood

Blood is a liquid connective tissue which is pumped out by heart through different blood vessels.

Functions of blood: *CTEVT

1. It carries O2 from lungs to tissues and CO2 from tissues to lungs.
2. It carries nutrients from the alimentary tract to tissues and cells, wastes to excretory organs.
3. It carries hormones secreted by endocrine glands to their target glands and organs.
4. It carries heat produced in tissues.
5. It contains clotting factors that coagulate blood.
6. It carries protective substances e.g. antibodies to the area of infection.
7. It maintains pH.
8. It maintains water and electrolyte balance.

Properties of Blood:
Blood Cell
Blood Cells

  •  The total blood volume in an adult is 5 ltr.
  •  8% of total body weight.
  • Arterial blood is bright red.
  • Venous blood is dark red.
  • Warmer than body temperature.
  • pH: 7.35- 7.45
  • Osmotic pressure is 25 mmHg.
  • Specific gravity is 1.045- 1.065
  • Viscosity is 4.5- 5.5

Composition of blood: * CTEVT

Blood is composed of plasma (55%) and blood cells(45%).
The constituents of plasma are:
a. Water (90 - 92%)
b. Plasma Proteins: Albumins, Globulins (Including Antibodies), Fibrinogen, Clotting Factors
c. Inorganic Salts (Mineral Salts): Sodium Chloride, Sodium Bicarbonate, Potassium,
Magnesium, Phosphate, Iron, Calcium, Copper, Iodine, Cobalt
d. Nutrients, Principally From Digested Foods, e.g. monosaccharides (mainly glucose), amino
acids, fatty acids, glycerol and vitamins
e. Organic waste materials, e.g. Urea, uric acid, creatinine
f. Hormones secreted by endocrine glands
g. Enzymes, e.g. Certain clotting factors
h. Gases, e.g. Oxygen, Carbon Dioxide, Nitrogen.

Plasma proteins: *CTEVT
Plasma proteins are components of plasma which make up 7% of plasma.
There are main three plasma proteins: Albumin, Globulin and fibrinogen.
a. Albumin: it is the most abundant plasma protein.
  • - It is synthesized in the liver.
  • - Normal value = 3.5- 5 g/dl
  • - It maintains normal plasma osmotic pressure.
  • - It acts as a carrier molecule for lipid and steroid hormones.
b. Globulin: it is also synthesized in the liver and remained in lymphoid tissue.
  • - Normal value = 2.0 – 2.5 g/dl
  • - It acts as antibodies and play a role in immunity.
  • - It inhibits some proteolytic enzyme activity.
c. Fibrinogen: it is synthesized in the liver.
  • - It is essential for coagulation.
  • - Normal value = 0.2 – 0.45 g/dl
Functions of plasma proteins:
  • 1. Maintains osmotic pressure
  • 2. Provides viscosity of blood
  • 3. Essential for coagulation
  • 4. Defence mechanism/ provides immunity
  • 5. Transport various substances
  • 6. Regulate acid-base balance
There are 3 types of blood cells:
a. Erythrocytes( Red Blood Cells)
b. Leukocytes(White Blood Cells)
c. Thrombocytes(Platelets)
a. Erythrocytes( Red Blood Cells
  • - It makes up about half of the human blood.
  • - It is a biconcave disc with flattened and depressed centre
  • - It has no nucleus
  • - Its average diameter is 7 micrometre and 2 micrometres thick.
  • - It is produced in the red bone marrow of long, flat & irregular bones.
  • - They are destroyed in the liver and spleen.
  • - Average life span is 120 days.
  • - Normal count = 4-6 million/mm3
  • - Functions: It transports CO2 & O2.
                    Hemoglobin in RBC acts as a buffer.
                    It carries antigen which determines blood group

b. Leukocytes( White Blood Cells)
  • - These are largest blood cells and accounts for 1% of blood volume.
  • - They contain nuclei in their cytoplasm.
  • - Normal count= 4000-12000/ mm
  • - Leukocytes are classified as:
1. Granulocytes : neutrophil, eosinophil & basophil 
blood cells
blood cells
Functions of WBC:
1. It protects against infection, inflammation.
2. It helps in the repair of injured tissue.
3. It defences against diseases by the synthesis of gamma globulin.
4. It shows Phagocytosis.
c. Platelets( Thrombocytes):
- They are the smallest non-nucleated cells.
- They are plate-like or rod-shaped cells.
- Their life span is 8-11 days.
- Normal count= 2, 00,000- 3, 50,000/ mm3.
- The main function of platelets is clotting.
Haemopoiesis/hematopoiesis: *CTEVT
The process of formation and maturation of blood cells is called hemopoiesis.
Formation of RBC is called erythropoiesis, the formation of WBC is called leucopoiesis and formation of platelets are called thrombopoiesis.

Sites of a hemopoiesis: before birth- yolk sac, liver, spleen and after birth- red bone marrow of long,
flat and irregular bones.
Hemopoiesis occurs after the differentiation of mesenchymal cells called hematopoietic stem cells
(hemocytoblasts). They further develop into two types of cells: myeloid stem cells and lymphoid stem cells.

Myeloid cell is the red bone marrow of the humerus, femur, ribs, sternum, pelvis, and portions of the
skull that produces erythrocytes, granular leukocytes, monocytes and platelets. Lymphoid cell including the lymph nodes, tonsils, spleen, and thymus produces the lymphocytes.
The process is described as following:
Factors affecting erythropoiesis: *CTEVT
a. Hypoxia
b. Iron
c. Folic acid
d. Vitamin B12
e. Erythropoietin 
Blood Group:
Individuals have different types of antigen on the surfaces of their red blood cells, these antigens,
which are inherited, is called the individual's blood group.

Basis of transfusion reaction: *CTEVT
Individuals make antibodies to these antigens, but not to their own type of antigen, since if they did the antigens and antibodies would react causing a transfusion reaction. These antibodies circulate in the bloodstream and the ability to make them, like the antigens, is genetically determined and not
associated with acquired immunity.

If individuals are transfused with the blood of the same group, i.e. possessing the same antigens on the surface of the cells, their immune system will not recognise them as foreign and will not reject them. However, if they are given blood from an individual of a different blood type, i.e. with a different type of antigen on the red cells, their immune system will mount an attack upon them and destroy the transfused cells. This is the basis of the transfusion reaction; the two blood types, the donor and the recipient, are incompatible.

ABO system: *CTEVT
There is a wide distribution of antigens in population, on the basis of which blood group is determined. If
a person has antigen A called group A, if antigen B then called group B, if both then called group AB
and if neither of them called group O.
Blood group A individuals cannot make anti-A (and therefore do not have these antibodies in their
plasma) since otherwise, a reaction to their own cells would occur; they do, however, make anti-B.
Blood group B individuals, for the same reasons, make only anti-A. Blood group AB make neither, and blood group O make both anti-A and anti-B
ABO system
ABO System

Because blood group AB people make neither anti-A nor anti-B antibodies, they are known as
universal recipients: transfusion of either type A or type B blood into these individuals is safe, since
there are no antibodies to react with them. Group O people have neither A nor B antigens on their
red cell membranes and their blood may be safely transfused into A, B, AB or O types; group O is
known as the universal donor.
The Rhesus system
The red blood cell membrane antigen is the Rhesus (Rh) antigen or Rhesus factor. About 85% of
people have this antigen; they are Rhesus positive (Rh+) and do not, therefore, make anti-Rhesus
The remaining 15% have no Rhesus antigen (they are Rhesus negative or Rh-). Rh- individuals are capable of making anti-Rhesus antibodies, but are stimulated to do so only in certain circumstances, e.g. in pregnancy, or as the result of an incompatible blood transfusion.
Blood clotting factors: *CTEVT
Blood clotting factors 1
Blood clotting factors 1

Blood clotting factors 2
Blood clotting factors 2
Hemostasis: *CTEVT
Hemostasis is defined as the arrest of bleeding. It is the process of forming clots in the walls of damaged blood vessels and preventing blood loss while maintaining blood in the fluid state within the vascular system. Events of hemostasis are as following:
a. Vasoconstriction
b. Platelet plug formation
c. Coagulation
d. Fibrinolysis
a. Vasoconstriction:
When blood vessels are damaged the platelets come into contact with damaged blood vessels,
their surface becomes sticky and adhere to the damaged wall. They release a chemical which causes
vasoconstriction and minimizes the blood loss.

b. Platelet plug formation:
Platelets move to an area of damage and stick together to form seal called platelet plug. This
process is called platelet aggregation.

c. Blood coagulation(clotting):
Blood clotting results in the formation of an insoluble thread-like mesh of fibrin which traps blood
cells and is much stronger than the rapidly formed platelet plug. In the final stages of this
process prothrombin activator acts on the plasma protein prothrombin converting it to
thrombin. Thrombin then acts on another plasma protein fibrinogen and converts it to fibrin.
Prothrombin activator can be formed by two processes: the extrinsic and intrinsic pathway.
The extrinsic pathway occurs rapidly (within seconds) when there is tissue damage outside the
circulation. Damaged tissue releases a complex of chemicals called thromboplastin or tissue
factor, which initiates coagulation.
The intrinsic pathway is slower (3-6 minutes) and is confined to the circulation. It is triggered
by damage to a blood vessel lining (endothelium) and the effects of platelets adhering to it.
Extrinsic Pathway
Extrinsic Pathway
Intrinsic Pathway
Intrinsic Pathway

    d. Fibrinolysis:
    The breakdown of the clot is called fibrinolysis. An inactive substance called plasminogen is
    present in the clot and is converted to the enzyme plasmin by activators released from the
    damaged endothelial cells. Plasmin initiates the breakdown of fibrin to soluble products that are
    treated as waste material and removed by phagocytosis.
    Hemoglobin: (Hb/Hgb)
    Hemoglobin is a red pigment present in erythrocytes.
    Oxygen molecules attached to hemoglobin molecules within erythrocytes give blood its red
    colour. A hemoglobin molecule consists of four protein chains called globins, each of which is
    bound to one heme, a red-pigmented molecule. Each heme contains an atom of iron that can
    combine with one molecule of oxygen. Thus, the hemoglobin molecule as a whole can transport
    up to four molecules of oxygen. The combination of oxygen with hemoglobin is described by
    the oxygen hemoglobin dissociation curve.
    1 gm of hemoglobin carries 1.34 ml of oxygen; this is called oxygen-carrying capacity.
    Normal values: male= 14-18g/dl, female= 12-16g/dl
    Types of hemoglobin:
    1. Hemoglobin A (about 95% - 98%): Hgb A contains two alpha (α) chains and two betas (β)
    2. chains, present in adult
    3. Hgb A2 (2% - 3%): has two alpha and two deltas chains Hgb F (up to 2%): the primary hemoglobin produced by the fetus during gestation; Hgb F has two alpha (α) and two gammas (γ) chains

    Erythroblastosis Fetalis (“Hemolytic Disease of the Newborn”)
    Erythroblastosis fetalis is a disease of the fetus and newborn child characterized by agglutination and
    phagocytosis of the fetus’s red blood cells. In most instances of erythroblastosis fetalis, the mother is
    Rh-negative and the father Rh-positive. The baby has inherited the Rh-positive antigen from the father, and the mother develops anti-Rh antibodies from exposure to the fetus’s Rh antigen. In turn, the mother’s antibodies diffuse through the placenta into the fetus and cause red blood cell agglutination. An Rh-negative mother having her first Rh-positive child usually does not develop sufficient anti-Rh antibodies to cause any harm. However, about 3 per cent of second Rh-positive babies exhibit some signs of erythroblastosis fetalis; about 10 per cent of third babies exhibit the disease, and the incidence rises progressively with subsequent pregnancies.

    Thrombus: An abnormal clot that develops in a blood vessel is called a thrombus. 
    Embolus: Once a clot has developed, the continued flow of blood past the clot is likely to break it away from its attachment and cause the clot to flow with the blood; such freely flowing clots are known as

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