Blood is a vital fluid that circulates throughout the body and is responsible for carrying oxygen and nutrients to the cells. It is considered as the ‘fluid of life’ because it carries oxygen from lungs to all parts of the body and carbon dioxide from all parts of the body to the lungs. It is known as ‘fluid of growth’ because it carries nutritive substances from the digestive system and hormones from endocrine gland to all the tissues. The blood is also called the ‘fluid of health’ because it protects the body against the diseases and gets rid of the waste products and unwanted substances by transporting them to the excretory organs like kidneys.
Properties of Blood:
Colour:
Artery Blood: Red
Venous Blood: Purple
Volume: Avg. volume in Normal Adult:4-6L
* Male: 5 L *Female: 4.5 L
Newborn Baby: 450 mL
It is about 8% of body weight in a normal young adult ; weighing about 70Kg
Viscosity: Blood is about 5 times more viscous than water, mainly due to RBC and Plasma Protein
Composition:
Blood is composed of plasma, red blood cells, white blood cells, and platelets. Plasma is the liquid portion of blood that makes up about 55% of blood volume. Red blood cells, also called erythrocytes, are responsible for carrying oxygen to the cells. White blood cells, also called leukocytes, play a role in the immune system. Platelets are important for blood clotting. The blood is also called the ‘fluid of health’ because it protects the body against the diseases and gets rid of the waste products and unwanted substances by transporting them to the excretory organs like kidneys.
Plasma:
Plasma is a yellowish liquid component of blood that makes up about 55% of total blood volume. It is composed of mostly water, electrolytes, and proteins, including albumin, globulins, and fibrinogen. Plasma serves several important functions in the body, including maintaining blood volume and pressure, transporting nutrients and waste products, and playing a critical role in the immune response. Plasma can be separated from other blood components and used for transfusions, such as in cases of severe bleeding or blood loss. Plasma also contains clotting factors, which can be used to treat certain bleeding disorders. Certain medical conditions, such as liver disease or kidney disease, can affect the composition of plasma and lead to health problems.
Erythrocytes: RBC
Red blood cells (RBCs) are the non-nucleated formed elements in the blood. RBC’s are also known as erythrocytes (erythros = red). Red color of the red blood cell is due to the presence of the coloring pigment called hemoglobin. RBCs play a vital role in transport of respiratory gases. RBCs are larger in number compared to the other two blood cells, namely white blood cells and platelets. RBC’s are non-nucleated, except the only mammal that has Nucleated RBC is Camel 🐪 In Adult Male, RBC count is 5 million/cu mm and in Female RBC count is 4.5 million/cu mm RBC’s are generally disc and biconcave (dumbell ) shaped. RBC’s are larger in number compared toWBC and Platelets. Old RBC’s are destroyed in Reticuloendothelial system.
Function of RBC:
Transport of Oxygen from Lungs to tissue and CO2 from tissue to Lungs Buffering action in Blood (Maintains acid-base balance) Helps in determination of blood group (RBC carries the blood group antigen) RBCs contain enzymes that help protect the body from oxidative damage and maintain the integrity of cell membranes. RBCs play a role in the immune system by interacting with white blood cells to help fight infections. RBCs are produced in the bone marrow and have a lifespan of about 120 days. After this time, they are removed from circulation and broken down by the liver and spleen.
Destruction of RBC:
Leukocytes: WBC
White blood cells (WBCs) are also known as leukocytes and are a type of blood cell that helps the body fight infection and disease. There are several types of WBCs, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with a specific role in the immune system. WBCs are produced in the bone marrow and circulate in the blood and lymphatic system. Abnormal WBC counts can be indicative of certain medical conditions, such as infections, autoimmune disorders, and some types of cancer. WBC counts can be measured through a simple blood test called a complete blood count (CBC). Certain medications and medical treatments, such as chemotherapy, can affect WBC counts and increase the risk of infections. Maintaining a healthy immune system through proper diet, exercise, and hygiene can help prevent some WBC-related health problems.
Thrombocytes: Platelets
Platelets, also known as thrombocytes, are small, disc-shaped cell fragments found in the blood of vertebrates. They are formed by fragmentation of megakaryocytes, which are found in the bone marrow. Platelets lack a nucleus and have a lifespan of about 7-10 days. They are essential for blood clotting and wound healing. Platelets play a crucial role in hemostasis, the process by which bleeding is stopped. They are responsible for forming blood clots at the site of injury, which helps to prevent excessive bleeding. Platelets also release growth factors that stimulate the repair and regeneration of damaged tissues. Additionally, platelets are involved in the immune response and play a role in the formation of new blood vessels.
References:
- K Sembulingam PhD and Prema Sembulingam PhD Essentials of Medical Physiology, JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD
- National Cancer Institute. (2021). White Blood Cell (WBC) Count.
- National Heart, Lung, and Blood Institute. (2020). Blood Tests.
- Mayo Clinic. (2021). White Blood Cell Count (WBC).
- Rocco, M. (2021). Plasma Composition. StatPearls Publishing.
- Blood Basics. American Society of Hematology. (2021). Plasma.
- Hemostasis and Platelets - https://www.ncbi.nlm.nih.gov/books/NBK26404/
- Platelets: Their Role in Hemostasis, Thrombosis, and Inflammation - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701489/
- Platelets and Their Role in Wound Healing - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599445/
