Blood consists of Plasma which is a fluid medium in which erythrocytes (RBC),Leukocytes (WBC) and thrombocytes (Platelets) are suspended.Plasma is a complex solution of proteins,salts and numerous metabolic substances.
Composition of blood
Blood is compose of the following elements in their correct proportions
1. Plasma proteins (Constituents of blood)
These include Albumin that serves as transport medium,Globulins for defense and Fibrinogen for Coagulation.Other substances present in plasma include :
- Cellular products like antibodies,enzymes,hormones
- Cellular waste products such as Urea,Uric acid
- Gases such Carbon dioxide,Oxygen,Nitrogen dioxide
- Electrolytes such as cations such as Potassium,Calcium,Iron ions and Anions such as Bicarbonates,sulphates,chloride.
- Other substances includes fatty acid,amino acids,iodine
2. Whole Blood
It is made up of water which constitute about 90% dissolved substances.Of the remaining 10% or dissolved substances approximately 7ù are plasma proteins while 3% constitute electrolytes.
3. Formed Elements or components
This constitute about 45% of blood volume.It consists of the following
- White Blood cells which acts as scavengers and immunizing agents
- Platelets which function in blood coagulation
- Red Blood Cells which carries Oxygen and Carbon Dioxide
Properties and Characteristics of Blood
- Blood constitute about 8% of total body weight
- Blood is composed of cells dispersed through the liquid portion that is the plasma
- An average of 5.0 to 5.6 liters is blood is in a 70kg man
- Specific gravity of blood is 1.055 to 1.065
- Specific gravity of plasma is about 1.026 and that of Red Blood Cells is 1.9093
- Cells in uncoagulated and undisturbed blood settles down slowly because of small size and large surface area of Red Blood Cells, and also because Red blood cells contains iron.The rate of sedimentation is known as Erythrocyte sedimentation rate (ESR)
- Separation of plasma from cells can be done by centrifugation in about 5 minutes at 5.000g.The longer the time of centrifugation,the more the removal of entrapped plasma from the cells
- Blood has a high viscosity than water.Viscosity of plasma ranges from between 1.3 to 2.0 while that of blood ranges from 1.5 to 3.0 and that of water is 1.0
- The osmotic pressure of human blood is about 5.100mmHg approximately the pressure of 0.9% saline solution.The osmotic pressure is chiefly due to varying concentration of salts,waste products,sugar,protein etc
- Blood has a slightly higher blood temperature than that of the body
- Blood has a metallic taste and scent
- Blood has an Erythrocin red color
Functions of Blood
- Transport of Oxygen from the lungs to the tissues and Carbon dioxide from the tissues to the lungs. The oxygen carrying pigment is called Hemoglobin and is responsible for the Red color of the blood.
- Blood conveys food nutrients such as amino acids,glucose,vitamins,electrolytes,fatty acids from the intestine tp the liver via the hepatic portal vein,while fats are convey from the alimentary canal to the tissues via the lymphatics.
- Blood convey waste products of metabolism (Urea, uric acid,carbon dioxide,creatinine from tissues where they are produced for elimination via the skin,kidneys etc
4. Regulation of body temperature
- Blood transport heat formed in the more active tissy to other parts of the ody thereby helping to regulate body temperature.
5. Transport of Hormones
- Hormones are transported by blood from endocrine glands where they are produced to other parts of the body where they have regulatory role.
6. Buffered Action
- The buffering power of haemoglobin helps to maintain the constancy of pH of blood
7. Maintenance of Osmotic Pressure
- Plasma protein exert osmotic pressure which influence the exchange of fluid between blood tissues
- Blood contain plasma and platelets which contain all the products required for blood clotting
- Blood contain lysine,antitoxins and antibodies which are essential for body protection.