Blood is the River of life
Last Updated on Thursday, 13 March 2008 00:00 Thursday, 13 March 2008 00:00
What is Blood?
Blood is a fluid tissue containing many suspended cells and can be found flowing through the circulatory system transporting substances. These substances may include the digested food substances like amino acids and glucose, excretory products of the body, heat from the respiring body organs and tissues and oxygen and carbon dioxide for respiration. Apart from the transportation of substances, blood also serves to protect the body against pathogens. Pathogens are disease-causing organisms able to inflict disease against the body.
In this section you will learn the composition of our blood, its disorders and how it can transport essentials as well as waste products through our body's vessels. Take an insight into the complete blood count, blood pressure and blood donation and much more for additional information.
- Blood Composition
- White Blood Cells
- Blood Platelets
- Blood Disorders
- RBC Disorders
- Sickle cell anemia
- Polycythemia vera
- White Blood Cells Disorders
- Blood Clotting Disorders
- Christmas disease
- Blood platelets disorders
- Other disorders
- Blood poisoning
- Multiple Myeloma
- RBC Disorders
- Blood clotting
- Blood groups
- Complete Blood Count
- Blood pressure
- Blood donation
The average human being has 5 liters of blood in his body. 55% of the blood is made up of plasma constituting the fluid part of the blood. The cells and platelets that are present in our blood make up the other 45%.
- White Blood Cells
- Blood Platelets
Plasma is a pale yellowish fluid with a total volume of 2-3 liters in a normal adult.
Its contents are :
Plasma proteins are made up of 3 main types.
- Serum Albumin
- Serum Globulin
Most of the proteins are produced by the liver apart from the Serum Globulin which is produced by the body's immune system. Serum Albumin composed of 60% of the total plasma protein. It is the smallest of the 4 plasma proteins and can pass through capillary walls. Hence this will usually lead to a small leakage into the intestinal fluid. Nonetheless, this has been exploited by medical science to be an effective medium of testing for abnormalities in the body and damaged organs or diseases. Serum Globulins make up 36% of the total plasma protein. This can be further split into 3 fragments, the alpha, beta and gamma. Globulins aid in the inflammatory response of the body. Fibrinogen and prothrombin are important in the clotting process of blood.
Protein Functions Include:
- Transportation of insoluble substances around the body by allowing them to bind to protein molecules.
- Protein reserve for the body
- Blood clotting
- Responses in accordance to disease (inflammatory response)
- Protection from infection the gamma globulins function
- Striking balance for the pH of the blood
Inorganic ions play a very important role in the blood.
Without sodium, the body will lack extracellular fluid and might affect the blood pressure, leading to insufficient circulation of oxygen causing drowsiness, nausea etc. Lack of potassium will result in muscle abnormalities and weakness, leading to vomiting and diarrhoea. Hence all the inorganic ions facilitate in a very important role as do other cells within the blood.
Blood plasma carry organic substances such as nutrients. They may include digested food substances like glucose, sucrose and amino acids. Other nutrients in transit in the plasma include glycerol, triglycerides, cholesterol and vitamins. Waste products of the body are also transmitted in the blood plasma. They include urea and cellular waste that will be excreted out of the body. Hormones, such as cortisol and thyroxine are also transported around the body in plasma attached to plasma proteins. Medicine and drugs also circulate within the plasma.
Red Blood Cells (Erythrocytes)
Red blood cells are the most common cells found in blood. There are about 5 million red blood cells in each cubic millimeter of blood or approximately 250 million red blood cells in every drop of blood. This number varies with individuals in accordance to heredity, gender and state of health. These cells are produced by the bone marrow and have a lifespan of 3-4 months. When they die, they are destroyed by macrophages in the liver and spleen. This process releases iron to be stored in the liver and bile pigments to be excreted.
Structure of A Red Blood Cell
Red blood cells have a bi-concave shape with a flattened center. It has a diameter less than 0.01 millimeters and do not have a nucleus. Red blood cells contain a protein chemical known as haemoglobin, which gives it the red color. Haemoglobin contains iron, which can easily transport gases such as oxygen and carbon dioxide. Red blood cells are highly elastic, rendering it able to squeeze through capillary walls bigger than itself.
Functions of Red Blood Cells
Red blood cells are important in the process of respiration. Gases involved in respiration are carried around the body through these cells. Oxygen readily combines with haemoglobin to form oxy-haemoglobin in the lungs where there is high concentration of oxygen. However, oxy-haemoglobin is an unstable compound and will break down to release oxygen when there is low concentration of oxygen in the surroundings. Hence there will be an even distribution of oxygen to all parts of the body. Red blood cells also carry part of the carbon dioxide waste from the cells through most is transmitted through plasma as soluble carbonates.
White Blood Cells (Leucocytes)
White blood cells are responsible for the defense system in the body. There are approximately 6,000 white blood cells per millimeter of blood or ½ a million white blood cells in every drop of human blood. White blood cells fight infections and protect our body from foreign particles, which includes harmful germs and bacteria. White blood cells, the red blood cells are formed from the stem cell of the bone marrow. It has a life-span of a couple of days. When they die, they are destroyed by surrounding white blood cells and replaced with new ones.
Structure of White Blood Cells
|White blood cells are colorless without haemoglobin. It contains a nucleus and has an irregular shape. Though there are fewer white blood cells than red blood cells, they are much bigger in size. They can change their shape easily and this allows them to squeeze through walls of the blood vessels into the inter-cellular spaces.|
Types of White Blood Cells
Unlike the Red blood cells or platelets, there are 5 different types of white blood cells, each serving a different purpose in our body’s immune system.
Neutrophils make up 55%-70% of the total white blood count in the bloodstream. They have a segmented nuclei and it is said to be ‘C’ shaped. Neutrophils can be most commonly found near sites of infection or injury where they will stick to the walls of the blood vessels and engulf any foreign particles that try to enter the bloodstream. They can also be found in the pus of wounds.
|Eosinophils make up 2%-5% of the total blood count and mainly attacks parasites and any antigen complexes. These cells are also responsible for allergic response within the blood.|
|Basophils make up less than 1% of the total white blood count. They secrete anti-coagulant and antibodies, which mediate hypersensitivity reactions within the blood. They are known to have phagocytory features though they are more often related to immediate immune reaction against external germs and diseases.|
|Monocytes, though having only 5%-8% in the total white blood count, are the largest of the 5 types of white blood cells. They act as tissue macrophages and remove foreign particles and prevent the invasion of germs which cannot be effectively dealt with by the neutrophils. They have been known to have phagocytic functions.|
|Lymphocytes produce anti-bodies against toxins secreted by bacteria and infecting germs. These antibodies will be excreted into the plasma to kill bacteria in the blood as well as act as anti-toxins. These anti-bodies will cause the foreign particles to cluster together, rendering them easily engulfed by the phagocytes. However, the nature of lymphocytes is highly specific and they can only recognize certain antigens.|
Structure of Blood Platelets
Blood Platelets are granular non-nucleated fragments of cytoplasm in the form of oval discs. A platelet consists of two parts, a clear outer ground susbstance occupying the greater part of the platelet and a central part that contains granules.
Functions of Blood Platelets
They secrete a hormone called serotonin which constricts torn blood vessels. They also have a major role in accumulating at sites of injury sticking together to plug gaps in broken blood vessels. They are rich in a certain activator that activates some proteins found in plasma. These proteins are thrown out in the form of fibers as a network. This network traps the escaping RBCs and forms a clot that will seal the cut blood vessels and so bleeding is stopped.