All About Blood and Its Components

• Blood is a specialized bodily fluid in animals, delivering nutrients and oxygen. Blood delivers nutrients and waste. Blood consists of blood cells suspended in blood plasma.
• Plasma, 55% of blood fluid, is mainly water (92% by volume) and contains dissolved proteins, glucose, mineral ions, hormones, carbon dioxide, and blood cells.
• Blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
• Red blood cells are the most abundant, delivering oxygen to tissues.
• White blood cells, part of the immune system, defend against infection.
• Platelets are responsible for blood clotting.
• Blood circulates via blood vessels, propelled by the heart's pumping.
• Vertebrate blood is red due to hemoglobin, an iron-containing protein in red blood cells.

Blood Functions

• Transports oxygen from the lungs throughout the body.
• Transports carbon dioxide from the body to the lungs for exhalation.
• Transports nutrients from the digestive tract throughout the body.
• Transports waste from cells to the kidneys for excretion.
• Transports hormones from glands to target tissues.
• Regulates body temperature via heat distribution.
• Maintains fluid balance by regulating water content in cells and tissues.
• Maintains pH balance as a buffer.
• Protects against infection by transporting white blood cells and antibodies.
• Forms clots to prevent excessive blood loss.

Blood Components

Plasma

• Plasma is the clear, straw-colored liquid remaining after removing blood cells, platelets, and other elements.
• It makes up about 55% of total blood volume.
• Plasma is about 92% water, acting as a solvent.
• It contains proteins like albumin, globulins, and fibrinogen.
• Albumin maintains osmotic pressure, preventing fluid leakage from vessels.
• Globulins include antibodies (immunoglobulins) for infection and transport proteins for lipids and hormones.
• Fibrinogen is essential for clotting, converting to fibrin.
• Plasma contains electrolytes like sodium, potassium, calcium, magnesium, chloride, bicarbonate, and phosphate, vital for fluid, nerve, muscle, and pH balance.
• Plasma carries nutrients like glucose, amino acids, fatty acids, and vitamins to cells.
• Plasma carries waste like urea, creatinine, and bilirubin to the kidneys and liver for excretion.
• Plasma transports hormones to target tissues, regulating functions.
• Plasma contains dissolved gases, though red blood cells carry most oxygen.

Red Blood Cells (Erythrocytes)

• Red blood cells (erythrocytes) transport oxygen from the lungs to tissues and carbon dioxide back to the lungs.
• They are produced in bone marrow.
• Mature red blood cells are biconcave discs, increasing surface area for gas exchange and allowing passage through capillaries.
• Red blood cells are flexible, deforming in capillaries and returning to shape.
• Red blood cells are filled with hemoglobin, a protein that binds oxygen and gives blood its red color.
• Hemoglobin contains iron, essential for oxygen binding.
• Red blood cells lack a nucleus and organelles, maximizing space for hemoglobin.
• Red blood cell count for males is 4.7 to 6.1 million cells per microliter (µL).
• Red blood cell count for females is 4.2 to 5.4 million cells per µL.
• Red blood cells have a lifespan of about 120 days, and old or damaged cells are removed by the spleen and liver.

White Blood Cells (Leukocytes)

• White blood cells (leukocytes) defend the body against infection, invaders, and abnormal cells.
• They are produced in bone marrow and lymphatic tissues.
• White blood cells are nucleated.
• They are classified as granulocytes (neutrophils, eosinophils, basophils) or agranulocytes (lymphocytes, monocytes).
• Neutrophils are the most abundant and first responders, engulfing pathogens through phagocytosis.
• Eosinophils are involved in allergic reactions and parasitic infections, releasing toxic substances.
• Basophils are the least common, involved in allergic reactions and inflammation, releasing histamine.
• Lymphocytes include T cells, B cells, and NK cells.
• T cells are involved in cell-mediated immunity, directly attacking infected cells.
• B cells produce antibodies, marking antigens for destruction.
• NK cells are involved in innate immunity, killing cells without prior sensitization.
• Monocytes differentiate into macrophages and dendritic cells, which are phagocytic and present antigens to T cells, initiating an immune response.
• Normal white blood cell count is 4,500 to 11,000 cells per microliter (µL).
• White blood cells can move into tissues to fight infection and inflammation.

Platelets (Thrombocytes)

• Platelets (thrombocytes) are small cell fragments critical in blood clotting and hemostasis.
• They are produced in bone marrow from megakaryocytes.
• Platelets lack a nucleus.
• In vessel damage, platelets adhere and aggregate, forming a plug to stop bleeding.
• Platelets release substances that activate the coagulation cascade, forming a fibrin clot.
• Fibrin stabilizes the platelet plug, creating a durable clot.
• Normal platelet count is 150,000 to 450,000 platelets per microliter (µL).
• Platelets have a short lifespan of about 7 to 10 days.
• Platelets are removed from circulation by the spleen and liver.

Blood is a vital fluid that transports nutrients and oxygen to cells while removing waste. It consists of plasma, red blood cells (oxygen transport), white blood cells (immune defense), and platelets (clotting). The heart pumps blood through vessels, ensuring the body's functions.