BLOOD

The blood is a liquid connective tissue ,consisting  of a liquid part called plasma  and a cellular or solid  part called formed elements ,consisting  of blood cells or blood corpuscles .It is a dynamic  connective tissue  which adjusts  its composition  continuosly according to  need of the body    .                                                                        PLASMA ;It is a whole  blood minus formed element  [blood corpuscles and blood platelets] ,  and can  be separated from  the whole body by centrifugation .If it is  left to stand , it coagulates , forming  a gel-like matter and  a clear  fluid called serum .The serum  is similar to the  plasma excepts that is lack  coagulation  factors  .The  plasma, atransparent ,alkaline  and yellow fluid is composed of about 90% water and about 10%   solid and it contributes  to about 55%  of the blood volume .The solid part of the plasma  consists of proteins , inorganic salts  and other substances  such as  glucose  , amino acids  , urea , enzymes ,hormones, anti bodies , oxygen  ,carbon -dioxide , etc. The inorganic constituents of the plasma are  Na,K,CL,HCO3, CA,etc.                     The main plasma proteins include albumin , globulin  and fibrinogen  which are large molecules  and cannot pass through  the thin wall of the blood  capillaries.These proteins  contribute   mostly to the osmotic pressure  of the plasma .Besides ,these   also help to buffer changes  in the blood acidity [ph] .The albumin is most  abundants and the plasma proteins  and accounts  for the most osmotic pressure of the plasma .It checks  excess loss of fliud from  the blood .It also  help many substance  dissolved in the plasma by binding to them .Thus it plays  important role in plasma transport .The globulin exists as alpha , beta  and  gamma globulins . the gamma globulins  are antibodies which are involved in the  immunological  defence of the body.The alpha and beta globulins  contribute to the osmotic pressure  of the blood and also  seve as carrier for substances.The fibrinogen, produced  in the liver , serves as  foundation of the  coagulation of the blood during  which it gets converted into  insoluble fibrins as a networks of fibres .                            Blood  corpuscles or blood cells ; The  formed element of the blood are represent by blood corpuscles  which are of three basic types ,the erythrocytes[=red blood corpusles , or red blood cells  written as RBCin the abbreviated form] ,Leucocytes [=whitwe blood corpuscles or cells  written as  WBC in the abbreviate form]  .                                                                                                                                                Red blood cells [RBC]  These blood cells are called erythrocytes  are very small ,circular , bicon cave and dislike , about 8 u  in diameter and 2u in thicknesss .Their bicon cave  area provides more surface area  , favouring  more diffusion  in and out .These4  are pliable elastic cells  that bend , flex and twist  while passing through tiny vehicles  the cappilaries  In mammals ,including man except camel and limma , the mature red blood cells  lacks nucleus ,i.e., it is not nucleated .The red blood cells contain  haemoglobin  which gets more spaces for its accomodation  in them  due to absence  of the nucleus .The individual red blood cells are pale yellow but when aggregated ,these appear reddish.The  outer surface of the RBC has plasma  membrane compose of  lecithin   nad cholesterol  .This membrane enclose a homogenos  matrix called stroma .containing loosely  arranged network of fibrous   and globular proteins  which form the cyto skeleton .This is attached to the inner surface of the plasma membrane  and  gives disc-like shape to the RBC .However  , other  other cell organelles  are absent due to  absence of the nucleus .The stroma contain haemoglobin  which gives pale red colour  to the cell .Each erythrocyte  has 200 to 300 molecules of the  haemoglobin accounting fo the one- third of  its volume .