Composition and Functions of Blood

Study Notes

Composition of Blood

Blood is a complex tissue consisting of a fluid matrix, plasma, and formed elements.
Plasma accounts for about 55% of blood volume and is composed primarily of water, proteins (albumin, globulins, fibrinogen), electrolytes, nutrients, hormones, and waste products.
Formed elements include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
Erythrocytes are the most numerous formed element and are responsible for oxygen transport.
Leukocytes are involved in the immune response and defense against pathogens.
Platelets play a crucial role in blood clotting.

Functions of Blood

Oxygen transport: Erythrocytes carry oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.
Nutrient transport: Blood transports nutrients absorbed from the digestive system to the body's cells.
Waste removal: Blood carries metabolic waste products, such as urea and creatinine, from the tissues to the kidneys for elimination.
Hormone transport: Blood transports hormones from endocrine glands to target tissues.
Regulation of body temperature: Blood helps to regulate body temperature by distributing heat throughout the body.
Maintenance of acid-base balance: Blood buffers help maintain a stable pH in the body.
Protection against disease: Leukocytes and antibodies in blood provide protection against pathogens and foreign substances.
Blood clotting: Platelets and clotting factors in blood prevent excessive bleeding after injury.

Red Blood Cells (Erythrocytes)

Erythrocytes are biconcave discs that lack nuclei and other organelles in mature form.
They contain hemoglobin, a protein that binds to oxygen and gives blood its red color.
Erythrocytes are produced in bone marrow in a process called erythropoiesis.
Their lifespan is about 120 days.
They are removed by macrophages in the spleen and liver.
Hemoglobin's oxygen-carrying capacity is critically dependent on iron.

White Blood Cells (Leukocytes)

Leukocytes are part of the immune system and are responsible for defending the body against infection and disease.
They are classified into different types, each with specific roles, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
These cells are crucial in fighting off pathogens and foreign bodies.
Lymphocytes, including B and T cells, are vital for adaptive immunity.
Leukocytosis refers to an elevated white blood cell count, often indicative of an infection.

Platelets (Thrombocytes)

Platelets are cell fragments that play a vital role in blood clotting.
They are formed in bone marrow from megakaryocytes.
When a blood vessel is damaged, platelets adhere to the damaged site and aggregate to form a plug.
They release clotting factors, triggering a cascade of reactions that lead to blood clot formation.
This process prevents excessive blood loss.

Blood Types

Blood types are determined by the presence or absence of specific antigens on the surface of red blood cells.
The most common blood typing system is the ABO system (A, B, AB, and O).
The Rh factor (positive or negative) is another important blood group system.
Blood transfusions require careful matching of blood types to avoid adverse reactions.

Blood Disorders

Anemia is a condition characterized by a deficiency in red blood cells or hemoglobin.
Leukemia involves uncontrolled proliferation of white blood cells.
Hemophilia is a disorder characterized by a defect in blood clotting factors.
Sickle cell disease is an inherited disorder that affects the shape of red blood cells.
These and other blood disorders can result in a variety of symptoms and require specific medical management.

Blood Vessel Structure

Blood vessels (arteries, veins, capillaries) are the conduits for blood flow throughout the body.
Arteries carry oxygenated blood away from the heart, while veins carry deoxygenated blood back to the heart.
Capillaries are the smallest blood vessels, facilitating the exchange of substances between blood and tissues.
Blood vessel walls have structural features adapted to the specific function of each vessel type.

Description

Explore the intricate components of blood, including plasma and formed elements such as red and white blood cells, as well as platelets. Learn about the vital functions blood performs, like oxygen transport, nutrient delivery, and waste removal from the body.