Blood is the fluid present in the humans as well as other animals responsible for transportation of all the necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. It is a dense connective tissue.
Blood is one of the most important and most frequently encountered evidence in criminal investigations. It can be found in almost every type of criminal activity including physical violence,murders,assaults,etc.
Blood basically consists of water ,cells, enzymes,proteins and other Inorganic substances.
FUNCTIONS OF BLOOD
Blood carries out three important functions: Transportation , Defense and Regulation
- Supply oxygen to the tissues by binding to hemoglobin,which is present in red blood cells.
- Supply nutrients such as glucose, amino acids etc.
- Removal of waste such as carbon dioxide by forming carbamino-haemoglobin, urea and lactic acid.
- Immunological functions,including circulation of white blood cells,and detection of foreign material by antibodies
- Coagulation due to presence of fibrin which is a clotting factor.
- Functions as messenger by Transporting hormones to the receptor sites.
- Regulation of body temperature.
COMPOSITION OF BLOOD
- The blood constitutes 1/13th of the body weight. The average adult has a blood volume of roughly 5 litres.
- The blood is composed of two parts:
The characteristic colour is imparted by hemoglobin,a unique iron-containing protein. Hemoglobin brightens in colour when saturated with oxygen(oxyhemoglobin)and darkens when oxygen is removed(deoxyhemoglobin).
- RBCs or Erthrocytes
Red blood cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest of the body and then returns carbondioxide from the body to the lungs so it can be exhaled. Blood appears red because of the large number of red blood cells, which get their color from the hemoglobin. The percentage of whole blood volume that is made up of red blood cells is called the hematocrit and is a common measure of red blood cell levels.
2. WBCs ( Leucocytes )
- There are two types of Leucocytes: Granulocytes and Agranulocytes
- Granulocytes contain granules or sacs in their cytoplasm and they originate from the bone marrow . They have four lobes and are also known as polymorphonuclear leukocytes.
- Agranulocytes do not have granules or sacs in their cytoplasm and they originate from the lymphoid. They have only one lobe and are known as mononuclear leukocytes due to the presence of just one nucleus.
Granulocytes are of three different types:
Agranulocytes are of two different types
3. Platelets – The blood platelets are the smallest cells of the blood. They lack nucleus. They range in 200,000–500,000.
Platelets are formed in the bone marrow by the cells known as megakaryocytes. The function of the platelets is related to hemostasis.
Platelets have adhesive and cohesive properties which enables them to coagulate and form a hemostatic or platelet plug; in this way they play an important role in blood clotting. Consequently they play a major role in wound healing.
Let us now talk about the fluid part of the blood.
The total blood plasma volume is 2.7–3.0 liters in an average human. It comprises of:
- water(upto 95%by volume)
- dissolved proteins(6–8%)(e.g.,serum albumins, globulins, and fibrinogen)
- carbondioxide(plasma being the main medium for excretory product transportation),
FUNCTION: It plays a vital role in an intravascular osmotic effect that keeps electrolyte concentration balanced and protects the body from infection and other blood disorders.
- Albumins are the most common plasma proteins and they are responsible for maintaining the osmotic pressure of blood
- Globulins include immunoglobins which are important for the immune system and transport hormones
- Fibrinogen proteins make up most of the remaining proteins in the blood. Fibrinogens are responsible for clotting blood to help prevent blood loss.
The term serum refers to plasma minus the clotting factors and blood cells.