Blood flows in the whole body to transport components from one cell to another. It carries in it various cells known as blood cells, water, several ions, hormones, and other soluble and insoluble proteins. The white blood cells also are known by the name of leukocytes contribute to immune body defenses. They fight with foreign particles to eliminate them from the body. In the case of blood flow from the injured site, blood thrombocytes accumulate along with the clotting factors to prevent blood leakage and the entry of any microbe inside the body. The role of blood in inflammation is to increase the redness of the infected site. The antibodies, a synthesis of the immune system travel via the blood to the site of action and fight the foreign antigens that reached the blood. The transport of immune cells to areas infected by pathogen entry also occurs via blood flow.
A mixture of several cells, ions, water makes up the blood that flows in our body. These components can be categorized under two headings:
Blood cells: All the cellular components present in the blood come in this category. It includes the oxygen-binding red blood cells, the leukocyte or white blood cells, and the thrombocytes. The white blood cell component of this fluid performs the immune functions of the body. Neutrophils, macrophages, eosinophils, basophils, acidophils, are the various structurally and functionally different component cells of the leucocytes.
Blood plasma: The solvent in which all these formed components are present is known as blood plasma. Ions dissolved in the water make up the blood plasma. The concentration of blood plasma is the indicator of the osmolarity of body fluids.
Other components: This category is made of other protein and non-protein components like hormones, carrier proteins, etc.
Blood and body defenses:
Components of the blood apart from the transport functions serve a role in the body defense. They function as a barrier to the pathogens and other foreign particles that have entered the body. The activities that contribute to the defensive nature of blood are:
The cells that fight with the antigen to resist its entry are present in the blood. The leukocytes form the immune dense. Monocytes, neutrophils engulf the pathogen inside their body and lyse it with chemical mechanisms. The active pathogen is killed by this action and then, they eliminate its presence from the blood and prevent them to reside in deeper tissues of the body, making it difficult for the immune system to recognize and attack them. The transport of these phagocytic cells to the area which has been attacked by the pathogen is facilitated by the flowing nature of the blood.
On injury, it is the action of blood cells thrombocytes, to seal the injury point by accumulating at the region of injury. This prevents any pathogen to make its entry into the body via that injured site. Several blood clotting factors also mark their presence in the blood. They also function in resisting the pathogen entry via injured sites directly into the blood.
The cells which are no longer active in the body to function are removed via blood transport. Blood carries these cells to the site of their destruction.
The membrane of blood cells harbors several antigens that can differentiate between the body cells and the foreign cells. This activity is responsible for the rejection of grafts and organs that are derived from a non-homologous organism. When they interact with the receptors of those organs, they characterize them as foreign cells for the body and carry out their destruction.
Inflammation is a type of defense mechanism which is a component of the body’s natural immunity that requires the activity of eosinophil cells of the blood. The increased blood flow towards the site of inflammation provides a characteristic sign i.e. redness to the injured area.
Antibodies: A component of one of the two types of immunity known as acquired immunity is released in the blood. Antibodies show binding specificity to foreign molecules. Specific antibodies are produced as a response for a specific antigen. Blood has a high concentration of antibodies to fight the antigen that has invaded and has been recognized by the body for its presence.
