Cardiovascular System: Blood

18.1 Functions & General Composition of Blood

  • Characteristics of Blood

    • Blood is continuously regenerated connective tissue.

    • It is the only liquid tissue.

    • Blood is transported through the cardiovascular system.

  • General Functions of Blood

    • Transportation:

    • Moves gases (O₂, CO₂), nutrients, wastes, hormones.

    • Regulation:

    • Helps in temperature regulation, and pH balance.

    • Protection:

    • Defends against pathogens and forms clots to stop blood loss.

  • Constituents of Blood

    • Composed of formed elements (living blood cells) and plasma.

    • Formed Elements:

    • Erythrocytes (Red Blood Cells - RBCs)

    • Leukocytes (White Blood Cells - WBCs)

    • Platelets (cell fragments).

    • Plasma:

    • Fluid portion that contains plasma proteins, nutrients, hormones, ions, and waste products.

Cardiovascular System Overview

  • The cardiovascular system is made of the heart and blood vessels.

  • Functions:

    • The heart pumps blood throughout the body.

    • Blood vessels:

    • Veins: Move blood toward the heart (deoxygenated blood).

    • Arteries: Move blood away from the heart (oxygenated blood).

    • Capillaries: Site of exchange between blood and tissues; oxygen and nutrients exit blood while CO₂ and wastes enter.

Components of Blood in Detail

  • Hemocytes:

    • Erythrocytes:

    • Transport respiratory gases (O₂ and CO₂).

    • Leukocytes:

    • Defend against pathogens.

    • Platelets:

    • Form clots to stop blood loss.

  • Plasma:

    • The liquid component of blood containing dissolved molecules and proteins.

    • Transports formed elements, dissolved molecules, and ions.

  • Blood Characteristics:

    • Oxygenated blood is bright red.

    • Deoxygenated blood is dark red.

    • Average blood volume: 4-6 L (about 5 L).

    • Blood viscosity: thicker than water, influenced by the relative amounts of dissolved substances.

    • Normal blood pH: between 7.35-7.45 (slightly alkaline), critical for protein stability and functioning.

Blood Composition and Concentration

  • Hematocrit:

    • Percentage of volume occupied by formed elements.

    • Normal values: 30-60% in children, 35-50% in adults.

    • Men: 42-56%, Women: 38-46%.

    • Elevated hematocrit can indicate dehydration, high altitude.

    • Lowered hematocrit indicates anemia.

  • Blood Smear Analysis:

    • Thin layer of blood on a slide that is stained.

    • Erythrocytes: most abundant, pink anucleate, biconcave disks.

    • Leukocytes: larger than erythrocytes, nucleated, varied in shape.

    • Platelets: small fragments circulating in blood.