Biology Chapter: Blood Functions and Properties

Blood

• Blood is a specialized body fluid that circulates throughout the body.
• It carries oxygen, carbon dioxide, nutrients, hormones, and other substances.

Properties of Blood

• Arterial blood is scarlet red due to its high oxygen content.
• Venous blood is purple red due to its higher carbon dioxide content.
• The average blood volume in an adult is 5 liters.
• Blood is alkaline with a pH of 7.4.
• The specific gravity of blood is 1.052 to 1.061.
• Blood is five times more viscous than water due to red blood cells and plasma proteins.

Functions of Blood

• Distribution and transport: Delivers oxygen and nutrients to the body.
• Maintenance of body temperature: Absorbs and distributes metabolic heat.
• Regulation and maintenance of normal pH: Buffers maintain pH and water content of cells.
• Protection: Carries immune system components to prevent infection.

Composition of Blood

• Blood is composed of cells and plasma.
• Cells: Erythrocytes (RBC), Leukocytes (WBC), Platelets, Plasma proteins
• Plasma: Liquid part of blood containing water, organic and inorganic substances.

Plasma

• Composed of 92% water, 7% plasma proteins, and less than 1% other materials.
• Functions: Transports nutrients and gases, regulates fluid and electrolyte balance, helps maintain stable pH.

Serum

• Serum is plasma without plasma proteins.

Plasma Proteins

• Albumins: Maintain osmotic pressure and transport hormones and fatty acids.
• Globulins: Transport iron, fats, and fat-soluble vitamins. Gamma globulins function as antibodies.
• Fibrinogen: Involved in clotting.

Formed Elements

• All blood cells are formed elements, including erythrocytes, leukocytes, and platelets.
• Synthesized in bone marrow.
• Erythrocytes are synthesized in the marrow of flat bones (skull, vertebrae, ribs, breastbone, and pelvis) in adults.

Erythrocytes (RBC)

• Carry hemoglobin (Hb), which comprises about 1/3 of the RBC's total weight.
• An adult male has 5-6 million RBCs/mm3, while women and children have 4.5-5 million RBCs/mm3.
• RBCs are tiny, flexible, and biconcave disks.
• They lack a nucleus and other organelles.
• RBCs have a lifespan of 120 days.
• Function: Transport oxygen and carbon dioxide.

Hemoglobin (Hb)

• Hb is the oxygen-carrying component of RBCs.
• Hb binds reversibly to oxygen.
• Two forms:
  • Oxyhemoglobin: Hb bound to oxygen, gives blood bright red color.
  • Deoxyhemoglobin: Hb without oxygen, has a dark red color.
• Hb is composed of 4 globin molecules, each containing a heme group.

Leukocytes (WBC)

• Represent only ~1% of total blood volume.
• Synthesized in bone marrow.
• Differences from RBCs:
  • Contain a nucleus and organelles
  • Do not contain hemoglobin
  • Move in and out of blood vessels with amoeboid motion (Diapedesis)
• Function: Defense mechanism and immunity.

Leukocytes (WBC) - Groups

• Granulocytes: Contain lobed nuclei and cytoplasmic granules, short lifespan (~12 hours).
• Agranulocytes: Contain spherical or oval nuclei, lack cytoplasmic granules, long lifespan (greater than 12 hours).

White Blood Cell Count

• Total leukocyte count is 4,000 - 10,000/cu mm.
• Leukocytosis: Increased WBC count.
• Leukopenia: Decreased WBC count.
• Life span: 12–20 days.

Platelets (Thrombocytes)

• Anucleate cell fragments formed from megakaryocytes.
• Megakaryocytes are derived from stem cells in bone marrow.
• Platelets have a lifespan of about 10 days.
• Contain cytoplasmic granules filled with enzymes.
• Function: Stop bleeding through the formation of platelet plugs and blood clotting.

Blood Groups (Types)

• There are four main blood groups: A, B, AB, and O.

This quiz explores the properties, functions, and composition of blood in the human body. Learn about arterial and venous blood characteristics, the role of blood in temperature regulation, and its crucial functions in maintaining health. Test your knowledge of this essential biological fluid.