3.2 Biol2220: Cardiovascular System - Blood Anatomy & Physiology

The Cardiovascular System: Overview & Functions

• The cardiovascular system distributes nutrients, oxygen, and hormones to all cells in the body
• It carries away metabolic waste products, including CO2
• The system consists of blood, heart, capillaries, arteries, and veins

Blood: Composition & Functions

• Blood is composed of 5-6 liters in males and 4-5 liters in females
• Blood has two fractions: plasma (55% of total blood volume) and formed elements
• Plasma contains 92% water, electrolytes, proteins, and nutrients
• Formed elements include blood cells (99.9%), platelets, and white blood cells (0.1%)
• Red blood cells (RBCs) have no nucleus, are bi-concaval, and contain 95% hemoglobin (Hb)
• Hb can reversibly bind 4O2 and 4CO2, and each RBC contains 280 million molecules of Hb
• White blood cells include five types and are involved in fighting pathogens, inducing inflammation, and producing antibodies
• Platelets are involved in blood clotting, engulf and destroy pathogens, and induce inflammation

Hematocrit

• Hematocrit is the proportion of RBCs in blood
• Normal hematocrits are different for males and females

Hemoglobin & The Bohr Effect

• Hemoglobin (Hb) molecule consists of four polypeptide chains: two alpha chains and two beta chains
• Each polypeptide chain is attached to a prosthetic group called heme, which has one atom of iron at its center
• One molecule of oxygen can bind to each heme
• The Bohr effect describes how changes in pH, temperature, and CO2 affect oxygen transport

White Blood Cells (WBCs)

• WBCs include neutrophils, eosinophils, basophils, and others
• Neutrophils are the most abundant WBCs and are involved in phagocytosis
• Eosinophils increase in number in response to parasitic infections and release granules that are cytotoxic to invaders
• Basophils increase in number during infection and release histamine, serotonin, and other mediators that contribute to inflammation

Platelets

• Platelets are cell fragments produced from megakaryocytes
• Platelets are involved in blood clotting and are maintained at a homeostatic level of 150,000-350,000 per microliter
• Platelet count can be affected by various factors, including biologic triggers, drugs, and autoimmunity

Blood Clotting (Hemostasis)

• Blood clotting is a complex process that involves coagulation and the formation of a blood clot
• Coagulation is initiated by collagen, which activates platelets and forms a platelet plug
• Primary hemostasis involves the formation of a platelet plug, which is then stabilized by fibrin molecules
• Coagulation factors include vitamin K, calcium, and phospholipids

Control & Diagnostic Testing

• Coagulation testing includes activated partial thromboplastin time (aPTT), international normalized ratio (INR), and D-dimer tests
• Bleeding time test measures platelet function, and platelet count measures platelet number
• von Willebrand's disease, liver disease, and vitamin K deficiency can affect coagulation tests
• D-dimer test detects overactivation of the fibrinolytic system and is used to diagnose disseminated intravascular coagulation (DIC) and deep vein thrombosis (DVT)

Immunity and Body Defenses

• Types of immune cells:
  • Neutrophils: 50-70% of total immune cells, numerous short-lived phagocytes
  • Eosinophils: 1-5%, stain red, attack parasites
  • Basophils: 0.1%, stain blue, release histamine
  • Natural Killer (NK) cells: cytotoxic or killer cells
  • Mast cells: associated with allergies and anaphylaxis
  • T-lymphocytes (T cells): play a central role in cell-mediated immunity
  • B-lymphocytes (B cells): produce antibodies

Innate Immunity - Phagocytosis

• Associated with Neutrophils, Monocytes, and Macrophages
• Phagocytosis: process by which cells engulf and digest foreign particles and microorganisms
• Enzymes in lysosome digest bacterium, triggering an inflammatory response

Innate Immunity - Cell-Mediated Immunity

• Cytotoxic or killer cells (CD8 T cells): recognize and kill infected cells
• CD8 T cells recognize antigens on the surface of infected cells, attach to these cells, and secrete perforins
• Perforins punch holes into the infected cells, killing them

Innate Immunity - TLRs (Toll-Like Receptors)

• TLRs are innate immune sensors that trigger a cascade of events to kill or protect against pathogens
• They are transmembrane proteins present on macrophages and a few other cells
• They are conserved across vertebrates and are a very important part of the innate immune system
• They recognize and bind to microbial components, such as bacterial lipopeptides, lipoteichoic acid, LPS, flagellin, and bacterial and viral DNA and RNA

Innate Immunity - Cytokines

• Cytokines are small proteins secreted by cells of the immune system
• Examples: Interferons, Interleukins, and Tumor Necrosis Factor (TNF)
• They affect the behavior of other cells and are key players in both innate and acquired immunity
• Cytokines are released by many cells of the immune system, including Neutrophils, Macrophages, Cytotoxic/Killer cells, and Lymphocytes

Innate Immunity - Interferons (IFN)

• Signaling proteins produced by virus-infected monocytes and lymphocytes
• They inhibit protein synthesis and "interfere" with virus replication
• Warn neighboring cells that a virus is present, and if we didn't have IFNs, most of us would probably die of influenza virus infection

Innate Immunity - Interleukins

• Interleukins are numbered (1-37) and are not stored inside cells
• They are quickly synthesized and secreted in response to infection
• They are key modulators of the behavior of immune cells
• Mostly secreted by T-lymphocytes and Macrophages

Innate Immunity - Tumor Necrosis Factor (TNF)

• Main role is in the regulation of immune cells
• It is an endogenous pyrogen (able to induce fever) and can induce apoptotic cell death, cachexia, inflammation, and inhibit tumorigenesis and viral replication

Adaptive (Acquired) Immunity

• Immunity: not being susceptible to disease
• Types of immunity: Innate and Adaptive
• Adaptive immunity: after exposure, the body remembers specific invader and relies on the production of antibodies
• 2 x 2 Matrix: Immunity is either active or passive, and either natural or artificial

Antigens

• Antigens are also known as Immunogens
• An antigen is a substance that confers identity
• The immune system recognizes, responds to, and remembers molecules that are antigens
• The specific part of an antigen recognized by an antibody or receptor is called an epitope
• Immunogenicity: the ability to induce a humoral (antibody) and/or cell-mediated immune response

Antibodies

• Antibodies are also known as Immunoglobulins
• Protein molecules produced by activated B cells (Plasma Cells)
• Y-shaped molecule with hinges
• Ends include variable regions where antigen binding occurs
• Antibodies made by a single B cell are all the same, differ from those made by another in the "variable region" of the antibody
• Antibodies occur in 2 forms: Soluble and Membrane-bound
• Examples of antibodies: IgG, IgM, IgA, IgD, and IgE

Learn about the basic functions and components of the cardiovascular system, including blood, heart, capillaries, and arteries. Understand the roles of distributing nutrients and oxygen and carrying away metabolic waste products.