Blood

BLOOD

Blood is the body fluid, which is a type of connective tissue. It is flowing inside our body. Blood has several important roles to play. 

• It carries oxygen and nutrients to the tissue and carries waste products away.
• Blood helps in maintain body temperature and normal pH levels in tissues.
• The protective functions of blood includes clot formation and the prevention of infection.

                                            BLOOD COMPOSITION

Blood is a fluids that is flows in body. It is composed by two parts :

• Inter-cellular fluid is called plasma.
• Blood cells or corpuscles which is float in plasma.

Thus, blood consists of fluid (plasma) containing cells (erythrocytes, leukocytes and more). The plasma forms 55%  of the blood volume whereas the cells occupy remaining 45%.

The composition of blood are as follows:

                Water    -   91.0% 

                Protein  -   08.0%

                  Salts    -   0.9 % 

            The balance (0.1%) is made up of traces of number of organic material: glucose, creatinine, fats, uric acid, urea, antigens, enzymes. 

Now, we discuss about plasma and blood corpuscles.

PLASMA 

Plasma is a fluid in which cells are suspended. Plasma is faint yellow in colour and has a slightly alkaline pH. Plasma is 90% water and 10% solutes. The normal plasma volume is 3 liters in an adults. Plasma is differ from other body fluids by the presence of a significant concentration of proteins. It contains different types of proteins which perform a wide range of functions. Normal plasma has proteins in concentration of 6-8 gm per 100 ml of plasma. There are basically three types of plasma proteins, namely:

• Albumin   (4-5 g/ml) : It maintains plasma volume by holding water at the capillary level.
• Globulin    (2-3 g/ml) : It is the body defense against invading pathogens.
• Fibrinogen (0.3 g/ml) :It helps in form a mesh-work of solid fibrin that clots blood.

Functions of plasma proteins

• Osmotic pressure: Plasma proteins exert an osmotic pressure of 25 mm Hg, which helps in maintaining plasma volume.
• Viscosity: Plasma proteins account for about half of the viscosity of blood.
• Antibodies: Plasma proteins act as antibodies, which protect us from infections.
• Clotting: Plasma proteins associated with the coagulation of blood.

BLOOD CELLS

The cells found in the blood is called corpuscles. There also three types :

• Red Blood Cells (RBC) or Erythrocytes
• White Blood Cells (WBC) or Leukocytes
• Platelets or Thrombocytes :

Erythrocytes or RBCs : 

They are red in colour and biconcave in shape ,which has at least three major advantages, as,

1. RBCs can swell quite bit before bursting in a hypotonic solution, 
2. The biconcave shape can squeeze through narrow spaces by even bending along the middle, 
3. Its shape implies large surface to volume ratio which increase the efficiency of oxygen transfer

Dimensions of RBCs : The mean diameter is 7.5 microns, maximum thickness at edges is about 2.5 microns and minimum thickness in the center is about 0.8 microns.

The number of RBCs in the blood is about 5 million per cubic mm blood in normal healthy adults. It is about 0.5 million per cubic in men than women.

It is occupy about 45% of blood volume.

Function of RBCs : 

1. These cells help in transportation of oxygen , which is made possible by the high affinity , which is haemoglobin (Hb) has for oxygen, RBCs , contain haemoglobin, a protein that binds oxygen. 
2. It also play a role in carbon dioxide transport.
3. It also maintains the pH of blood.

Leukocytes or WBCs :

 

They are colourless. They are the army of the human body. Whenever a germ or an infection enter in a human body then WBCs snap to attention and destroy the culprit.

WBCs are divided into two types on the basis of presence and absence of granules in the cytoplasm

1. Granulocytes: They are further classified in basophils, eosinophils, neutrophils 
2. Agranulocytes: They are divide in monocytes and lymphocytes.

these further classifications is based on size, granules, nucleus.

Each type of leukocyteis present in the blood in different proportions
                   NEUTROPHILLS    :  50 - 70%
                   EOSINOPHILS        :   2  -  4%
                   BASOPHILS            : 0.5 -  1%
                  LYMPHOCYTES      : 20  - 40%
                   MONOCYTES         :  3   -   8%

Neutrophils:  These cells are most abundant in WBCs. These cells has pink fine powdery granules. The nucleus of these cells are multi-lobes. Neutrophils squeeze through the capillary walls and into infected tissue where they kill the invaders(e.g., bacteria) and engulf the remnants by phagocytosis.

Eosinophils : The eosinophils is brick red coarse granules. It has bi-lobed spectacle shaped nucleus. Their numbers increase sharply in certain disease, especially infestation by parasitic worms and allergies.

Basophils : These cells have purple coarse granules. This is very small portion of WBCs  but very important part of body's immune response. They release histamine and other chemicals that act on blood vessels when the immune response is triggered.

Monocytes : It is the largest WBC. The nucleus of monocytes is kidney shaped that surrounded by an equal amount of cytoplasm. Monocytes leaves the cells and become macrophages. Macrophages are large, phagocytic cells that engulf foreign matter that enter the body and daed and dying cells of the body.

Lymphocytes : These cells have diverse functions. The most abundant lymphocytes are

1. B Lymphocytes or B cells : They plays a large role in Humoral Immune Response. B cells are essential component of the adaptive immune system. B cells spend their entire early life in the bone marrow.                                                                                                                                                                          
2. T Lymphocytes or T cells : They plays a central role in Cell mediated Immunity. T cells leave the bone marrow in early age and travel to thymus, where they mature

These cells produce antibodies and kill the invading foreign material.

PLATELETS :

Blood platelets are the smallest formed by the pinching of a very large bone marrow cell called megakaryocyte. Platelets literally mean a small plate. The platelets form a plug to stop bleeding when an injury disrupt the lining of blood vessel.

Their diameter is about 2-3 micrometer and the density in the blood is 2,00,000 - 3,00,000 per millimeter cube.

  

Functions of platelets : 

1. These cells prevent the excessive loss of blood from wounds.
2. Platelets re;lease a chemical substance called serotonin that cause vasoconstriction
3. These cells aggregate to plug the vascular plug to site of injury.

These all about the blood, their portions and functions.