Blood - General, Blood - Functions, & Plasma

Introduction to Blood

• Blood is classified as a connective tissue.

• The four types of body tissues are:

  • Epithelial

  • Connective

  • Muscular

  • Nervous

• Blood does not contract (not muscular), send action potentials (not nervous), or cover/create glands (not epithelial).

Composition of Blood

• Blood is divided into two main components:

  • Plasma: The liquid part.

  • Formed Elements: Living cells (includes erythrocytes and leukocytes) and fragments of cells (platelets).

Components of Formed Elements

• Erythrocytes (Red Blood Cells):

  • Known as red blood cells or RBCs.

  • The term "erythro" means red.

• Leukocytes (White Blood Cells):

  • Known as white blood cells.

  • The term "leuko" means white.

• Platelets (Thrombocytes):

  • Fragments of cells involved in clotting.

Hematocrit Test

• Definition: A test used to determine the ratio of red blood cells to plasma.

• Procedure:

  1. Blood sample is mixed in a test tube.

  2. A centrifuge spins the sample to separate components:

     • Red blood cells settle at the bottom.

     • Plasma floats on top.

     • A thin layer (buffy coat) forms between plasma and red blood cells, containing leukocytes and platelets.

Normal Ratios by Hematocrit Test

• Red Blood Cells: ~45%

• Plasma: ~55%

• Buffy Coat: ~1%

• Variances:

  • Male hematocrit: 47% ± 5%

  • Female hematocrit: 42% ± 5%

Clinical Implications of Hematocrit Values

• Anemia:

  • Condition characterized by lower than normal red blood cell levels.

• Polycythemia Vera:

  • Condition with an excess of red blood cells, leading to increased blood viscosity.

• Leukemia:

  • Characterized by high leukocyte levels in the buffy coat.

Characteristics of Blood

• Stickiness: Caused by glucose content.

• Color:

  • Oxygenated blood: Scarred red (high oxygen).

  • Deoxygenated blood: Dark red (high carbon dioxide).

• pH Level:

  • Normal pH range: 7.35 to 7.45 (slightly alkalotic).

  • Below 7.35: Acidic (acidosis).

  • Above 7.45: Basic (alkalosis).

Volume and Composition of Blood

• Blood makes up ~8% of body weight:

  • Male: ~5.6 liters.

  • Female: ~4-5 liters (less due to menstrual cycle).

Functions of Blood

• Distribution:

  • Transports oxygen and nutrients to body cells.

  • Removes waste like carbon dioxide.

  • Distributes hormones.

• Regulation:

  • Maintains body temperature by distributing heat.

  • Regulates pH through buffers.

  • Maintains fluid levels in the circulatory system.

• Protection:

  • Prevents blood loss through clotting.

  • Defends against infections with white blood cells and antibodies.

Plasma: The Fluid Matrix of Blood

• Composed of ~90% water.

• Contains over 100 different solutes (nutrients, gases, hormones, waste, proteins, inorganic ions).

Plasma Proteins

• Albumin (60%):

  • Acts as a substance carrier (e.g., medication, nutrients).

  • Functions as a blood buffer for pH regulation.

  • Major contributor to osmotic pressure, preventing plasma leakage from vessels.

• Globulins (36%):

  • Used to form antibodies as part of the immune response,

  • Assist in marking invaders for destruction.

• Fibrinogen (4%):

  • Necessary for blood clotting via interaction with platelets.

  • Essential in sealing breaches in blood vessel walls.

Clinical Significance of Plasma Proteins

• Albumin:

  • Lower production (e.g., due to liver damage) leads to edema due to plasma leakage.

• Globulins:

  • Important in immune responses; deficiencies affect disease resistance.

• Fibrinogen:

  • Vital for clotting; impairments lead to increased bleeding risk (e.g., in alcoholics).