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Definition of Blood

• Blood is a specialized connective tissue that circulates throughout the body via a complex network of blood vessels.
• It comprises a liquid component, called plasma, and cellular components, including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

General Characteristics of Blood

• Composition: Blood is approximately 55% plasma and 45% formed elements (cellular components).
• Plasma: The liquid portion of blood, mainly composed of water, proteins (albumin, globulins, fibrinogen), electrolytes, hormones, and nutrients.
• Red Blood Cells (Erythrocytes): Contain hemoglobin, a protein that transports oxygen throughout the body. They are biconcave discs, which maximizes their surface area for efficient oxygen uptake.
• White Blood Cells (Leukocytes): Crucial for the immune response, part of the body's defense against infection and disease. Leukocytes include various types, each with specific roles in fighting infection (e.g., neutrophils, lymphocytes, monocytes).
• Platelets (Thrombocytes): Essential for blood clotting, which prevents excessive bleeding. They are small, irregular cell fragments that initiate the formation of blood clots.
• pH: Blood maintains a slightly alkaline pH (7.35-7.45), which is crucial for normal bodily functions. A deviation from this range can have severe consequences.
• Temperature: Blood temperature closely matches core body temperature.
• Viscosity: Blood is more viscous than water due to the presence of cells and proteins.
• Volume: The average adult human has approximately 5 liters of blood.
• Color: The color of blood varies with oxygenation. Oxygenated blood appears bright red, while deoxygenated blood is darker red.
• Functions: Blood plays a vital role in transporting nutrients, hormones, gases (oxygen, carbon dioxide), and waste products throughout the body. It also helps regulate body temperature, pH, and fluid balance.

Specific Roles and Functions of Blood Components

• Oxygen Transport (Red Blood Cells): Hemoglobin in red blood cells binds to oxygen in the lungs and releases it in tissues where it's needed.
• Immune Response (White Blood Cells): Different types of white blood cells protect the body from pathogens by identifying, engulfing, and destroying invading organisms.
• Blood Clotting (Platelets): Platelets are essential for forming blood clots at sites of injury, preventing blood loss.
• Nutrient Transport: Plasma carries various nutrients, including glucose, amino acids, and vitamins, to the body's cells.
• Waste Removal: Blood transports metabolic waste products, like carbon dioxide and urea, to the excretory organs for elimination.
• Hormone Transport: Plasma carries hormones, which act as chemical messengers regulating various bodily functions, from glands to target organs.
• Temperature Regulation: Blood helps to distribute heat throughout the body, maintaining a stable internal temperature.
• pH Regulation: Blood buffers maintain a constant pH, crucial for enzyme activity and overall cellular function.