INTRODUCTIONBlood has been described as the ‘elixir’ of life.

Its’ red color comes from the several million red cells, present in it.

FLUID – PLASMA55% .

- transport

- defense

- normal oncotic pressure

SOLID CELLS

45%

- 3 types

+

RBC – O2 transport

WBC - defense PLATELETS - clotting

These red cells contain a coloring substance, or hemoglobin.

This substance allows red cells to carry oxygen to the organs and tissues.

Carbon dioxide is also carried

by the red cells.

Production of Erythrocytes: Erythropoiesis

There are also ‘white’ cells which protect the body from infections by destroying the bacteria.

PHAGOCYTE LYMPHOCYTE

Tiny bodies called platelets help in clotting of blood.

This prevents excessive bleedingThese cells are all suspended in a clear liquid

called plasma.Plasma conveys important enzymes, protein,

and hormones to different parts of the body, and helps to remove waste material.

The blood also keeps

the temperature equal

throughout the body.

Blood is made of red blood cells, platelets, and various white blood cells.

BONE MARROWThe bone marrow is present in the bone

cavities. It can be considered as one of the largest organs

in the body, and also one of the most active. In children, blood cells are produced in the

marrow cavities of all the bones.Gradually, it gets replaced by fat (yellow

marrow). In the adult blood cells are produced in the bone

marrow of selected bones (e.g. backbone – vertebral column, ribs, bones of the skull, etc.)

Bones require their own blood supply which travels through the periosteum to the inner bone marrow.

RED BLOOD CELLSRBCs are also called erythrocytes.They are tiny (7.5u in diameter, 2u thick)

biconcave discs.

A few facts about RBCsThey survive for about 120 days.The average normal RBC count is

- for men 5.4 million/uL

- for women 4.8 million/uL

Hemoglobin is the most important component of red blood cells. It is composed of a protein called heme, which binds

oxygen. In the lungs, oxygen is exchanged for carbon dioxide. Abnormalities of an individual's hemoglobin value can indicate defects in red blood cell balance. Both low and

high values can indicate disease states.

Formation of RBCsTakes place in the bone marrow.A feedback exists – if the RBC count rises,

further increases are inhibited.Low levels of oxygen in the atmosphere

stimulate the formation of RBCs. This is an important part of the body’s adjustment to high altitudes. People living in the mountains actually do have higher RBC counts than usual.

RBC formation is regulated by a substance secreted by the kidneys.

Destruction of RBCsAbout 5 X 1011 RBCs are destroyed everyday,

in the liver and spleen.

Functions of RBCsCarriage of oxygen.Hemoglobin (Hb) – the red pigment – acts as

the vehicle for the transport of oxygen from the lungs, via the heart to the rest of the body.

Also carries CO2, though greater amounts of CO2 are transported dissolved in plasma.

Average Hb level in normal men 16gdL and 14gdL in normal women.

Iron is essential for the synthesis of Hb.Hence after excessive bleeding iron

supplements (tonics) plus a diet rich in iron are necessary for more Hb to be formed.

Carriage of CO2 (less significant) – as described above, most of the CO2 is dissolved in plasma.

Presence of specific substances on their surface, which are responsible for ‘typing’ blood into

different groups.

Antigen is a substance that can provoke an immune response. Typically, antigens are substances not usually found in the body.

WHITE BLOOD CELLSWBCs or leukocytes consists of 5 categories of

cells.Each category has a distinct shape and

appearance.Some cells are smaller than RBCs (5u in

diameter) whereas others are definitely bigger (15 u in diameter).

Formation and destruction of WBCsThe WBCs are formed in the bone marrow.The different categories of cells have different

stimuli for production.For e.g. one category (called neutrophils) are

produced in large number whenever there is short or severe (acute) infection.

There life span also differs.Some categories (e.g. neutrophils) may survive

upto 7 hours. In contrast other cells (lymphocytes) are called

‘memory cells.’

They are able to ‘remember’ an invader for several months, even years.

If the invader enters the body again, these memory cells are alerted, and the body’s response to the second invasion is much more extensive and rapid.

LEUKOCYTES (WHITE BLOOD CELLS)Leukopoiesis

Myeloblasts become all of the granular leukocytes Monoblasts become monocytes Lymphoblasts become lymphocytes.

Granulocytes

Neutrophils

Eosinophils

Basophils

Agranulocytes

Lymphocytes

Monocytes

Functions of WBCs WBCs are concerned with defense. Some of them are concerned with fighting acute

(short, severe) infections, whereas others fight chronic infections.

Some WBCs are capable of moving in the tissues, acting like vigilant guards.

If they encounter a bacterium, they may consume it or make it inactive.

The pus which may be seen oozing out of an infected wound, is made up of dead WBCs.

A particular category of WBCs – the eosinophils – are increased in allergic reactions and also in cases of worm infestation.

PLATELETSThe platelets are tiny bodies, 2-4um in

diameter.There are about 0.25 to 0.4 million/uL of

circulating blood.They have a half life of about 7 days.The platelets are called thrombocytes, because

they release thrombin, which aids in blood clotting.

Functions Platelets are concerned with repairing blood

vessels. For e.g., if an artery or vein becomes slightly torn

or perforated, the platelets help to fill the gap by forming a blood clot until it is repaired by new tissue growth.

Stickiness of platelets may be an important contributing factor in patients with heart disease, in whom the blood vessels to the heart muscle get blocked.

Research studies were investigated that the aspirin reduces the stickiness.

Platelets (Thrombocytes)

Formation

• Large multinucleated cells that pushes against the wall of the capillary.

• Cytoplasmic extensions stick through and separate.

PLASMA Plasma is the fluid portion of the blood. It constitutes about 5% of the body weight. If blood is allowed to clot, then a clear, straw

colored fluid oozes out. This is the serum. It is similar to plasma, except that serum does not

have clotting factors. It contain all the vital substances, except oxygen,

which must be transported through the body. These vital substances include digested food, salts,

hormones, enzymes, substances essential for clotting of blood, and antibodies, which are important for defense.

BLOOD GROUPS & TRANSFUSION

GROUPS ON RED CELLS

IN PLASMA

CAN RECEIVE

FROM

A A anti B A O

B B anti A B O

AB AB none All

O none anti A

anti B

O

Human body can be ‘typed or grouped’ on the basis of the presence (or absence) of specific substances present on the surface of the RBCs.

These substances ‘meet’ other substances in the plasma.

If the substances ‘compatible,’ then there is no difficulty.

When the 2 substances are not compatible, the RBCs clump together, and these clumps block the blood vessels.

It is easy to understand why this would be disastrous. Hence, it is essential to check the blood groups,

before giving a blood transfusion.

There is also the ‘Rh factor,’ which must be taken into account before giving blood transfusion.

This factor is named after the experimental Rhesus monkey.

If Rh present on the red cells, then the person is said to be Rh positive.

Rh negative, people are those who do not have the factor.

This is determined genetically, as an inherited characteristic.

If a Rh negative person Rh positive blood, antibodies against the Rh factor are formed.

If the same person receives a subsequent transfusion of Rh positive blood, then the antibody – factor reaction can have serious consequences.

Percentage of the Population With Each Blood Type

Rh+ Rh-

O 38.5% 6.5%

A 34.3% 5.7%

B 8.6% 1.4%

AB 4.3% 0.7%

TISSUE FLUID & LYMPH Tissue fluid consists of water, dissolved

substances, and occasional large molecules (including some amount of protein) which leave the blood vessels through the walls.

Most of this fluid returns to the blood via veins. The reminder (10-20%) enters the lymphatic

circulation, and is called lymph. Lymph is transported in lymph vessels. Circulating lymph passes through lymph glands

or nodes before finally returning to the blood via veins in the neck.

Unlike the circulation of blood, circulation of lymph does not depend on the pumping of the heart.

Among different factors which influence lymphatic circulation, movement (contraction of the muscles) plays a significant part.

LYMPH NODES The lymph nodes are present in different parts of

the body. They are specially numerous in the neck, armpit,

groin, and close to the different organs.

They have three main functions: They manufacture lymphocytes, part of the defense

system. They act as filters, removing bacteria and other

particles before the lymph joins the blood once more.

They manufacture antibodies against specific infections.

Lymph nodes of the neck

Lymph nodes of the armpit

Lymph nodes of the groin

SPLEEN The spleen is located in the peritoneal cavity, just

below the diaphragm, on the left side. It can be considered as the headquarters of the

WBCs. Impurities are picked up by these cells and

carried in the blood stream to the spleen. Old, worn out RBCs are destroyed by the spleen. The spleen also acts as a storehouse of blood. When the spleen contracts and forces more blood

into the general circulation. Old WBCs are destroyed in lymph glands.

SPLEEN

Body's Transport SystemBlood travels around the body in over 75,000

miles of arteries, veins and capillaries. Stretched end-to-end, that's three times around

the world! They transport oxygen from the lungs, remove

carbon dioxide from the cells and carry nutrients, hormones and water to all parts of the body.

Humans are endothermic and keep a constant body temperature of 37 °C.

The circulatory system plays a big part in regulating body temperature and it is self-repairing.

A blood clot quickly forms to seal up a cut before new tissue grows to replace the damaged area.

Arteries Capillaries Veins

Carry blood:

away from the heart

from arteries to veins

towards the heart

Pressure: high low very low

Walls are: thick and muscular with elastic fibres

very thin and leaky - one cell thick

thin

Blood is: Oxygenated (except pulmonary artery)

exchanging nutrients and gases with cells

de-oxygenated (except pulmonary vein)

Pulse: Strong none none