AP12 - Circulatory System (components of blood)

Describing the components of blood

Shape of RBC

RBC’s - Erythrocytes

Shape (allows cells to fit through small, bent capillaries)

• Biconcave, flexible

• 7-8 × 10^-6 m in diameter

• 1-2 × 10^-6 m thin

Function of RBC

Function

• Highly specialized for gas transport

• 1 mL of blood has 4-6 million RBC’s

• Each RBC has about 200 million hemoglobin molecules, allowing blood to carry about 60x more oxygen than plasma without hemoglobin

  • Hemoglobin is a protein with 4 tertiary chains each containing a heme group in the center

    • Each heme has an iron ion that helps O2 bind

Origin of RBC

Origin (erythropoesis)

• Have no nucleus (makes room for hemoglobin) and thus have a short lifespan

• Millions die/second

• Therefore, are continuously synthesized in the red bone marrow (ends of long bones)

• Occurs when kidney detects low oxygen levels and releases REF

• REF combines with proteins in the liver to form erythropoetin, which stimulates the stem cells in the bone marrow to begin erythropoesis

Shape of WBC

WBC - Leukocytes

• Large, irregularly-shaped

• Has nucleus

• Capable of independent movement

Function of WBC

1) Neutrophils - Phagocytize and destroy bacteria in tissues, after 20, cell dies and becomes pus

2) Eosinophils - Phagocytic, also cause tissue inflammation in presence of bateria

3) Basophils - Like eosinophils

4) Monocytes - Very large, often enlarge further to become a macrophage which scavenges bacteria, dead cells & debris

5) Lymphocytes - 2 kinds (T cells and B cells)

• B- cells mature in bone marrow and produce antibodies that bind to antigens

• T-cells mature in thymus and directly attack cells that bear antigens

Origin of WBC

• 5 types of WBC’s are all made in bone marrow from stem cells

Shape of Platelets

Platelets - Thrombocytes

• Small fragments of cells produced in bone marrow, involved in clotting

Function of Platelets

Blood clotting

1. Damaged tissues have “sticky edges” - platelets adhere to each other. Releases ADP and attract other platelets. After ~5 min, a temporary patch forms

2. Tissues and platelets release a prothrombin activator, causing prothrombin (in plasma) to become an enzyme: thrombin

3. Thrombin converts fibrinogen (in plasma) to fibrin and causes it to polymerize into long winding strands

4. Fibrin winds around platelet plug like a net, trapping more platelets and RBC’s, taking about 20 min (a more permanent patch)

Origin of Platelets

Produced in bone marrow

Major components of plasma

• Blood contains 45% formed elements and 55% plasma

• Plasma is a pale yellowish fluid

  • 92% of plasma is water

  • 7-8% is dissolved gases, salts, nutrients, wastes, hormones & plasma proteins

• Major proteins of plasma

  • Fibrinogen (clotting)

  • Albumin (regulates water balance)

  • Lipoproteins (transports cholesterol & products of lipid digestion)

  • Antibodies (bind to foreign proteins & therefore protect against pathogens)

• Plasma proteins are too big to cross the capillaries (and move into tissues) and therefore the plasma is hypertonic to the interstitial fluid

Explain the role of antigens

• Antigens are molecules found on the surface of pathogens and toxins, each with a unique shape.

• Role

  • 1. When antigens enter the body, the immune system recognizes them as foreign and reacts.

  • 2. Antigens activate B lymphocytes, causing them to produce specific antibodies that match the antigen’s shape

  • 3. Antigens allow the immune system to identify and distinguish harmful invaders from the body’s own cells

  • 4. Create immune memory, after exposure to an antigen, memory cells remain in the body, allowing a faster and stronger response if the same antigen enters again

Explain the role of antibodies

• Antibodies play a key role in the immune system, helping the body recognize and defend against harmful invaders such as bacteria, viruses, and toxins

• Are Y-shaped proteins that has an end region complimentary to a specific antigen made by special WBC’S called B lymphocytes (B cells) and releases into plasma. Each antibody is designed to recognize a specific antigen (a unique marker on a pathogen)

• Role

  • 1. Recognize and bind to pathogens

  • 2. Neutralize pathogens by binding, blocking them from entering or damaging body cells

  • 3. Clump pathogens together (agglutination), making them easier for immune cells to destroy (immobilized)

  • 4. Help immune cells destroy pathogens