Anatomy & Physiology: Blood

Blood Introduction

• Specialized connective tissue with a fluid extracellular matrix known as plasma
• Blood volume is about 5L in adults and circulates through the cardiovascular system, with body size affecting actual amount.

Blood Composition

• Reddish circulating fluid containing plasma and various cells
• Plasma makes up the extracellular matrix
• Red blood cells, white blood cells, and platelets are all present

Functions of Blood

• Supplies nutrients like glucose, fatty acids, and amino acids to cells
• Transports oxygen (O2), carbon dioxide (CO2), and hormones throughout the body
• Facilitates protection from blood loss and disease.
• Regulates body temperature.

Characteristics of Blood

• Blood is viscous, meaning it is thicker than water
• Blood temperature ranges from 36°C to 37°C
• Blood accounts for 8% of the body's total weight
• Males have a typical blood volume of 5-6 liters
• Females have a typical blood volume of 4-5 liters

Components of Blood

• Blood consists of two main components including cells (45%) and plasma (55%)

Plasma Composition

• Plasma consists of 92% water, 7% plasma proteins, and 1% other solutes.
• Water in plasma transports organic and inorganic molecules, formed elements, and heat.
• Plasma proteins include albumins (60%), globulins (35%), fibrinogen (4%), and regulatory proteins (<1%).
  • Albumins contribute to osmotic pressure and transport lipids and steroid hormones
  • Globulins transport ions, hormones, and lipids, also providing immune functions
  • Fibrinogen is essential for blood clotting
  • Regulatory proteins act as enzymes, proenzymes, and hormones
• Other solutes include electrolytes (essential for cellular activities), organic nutrients (for ATP, growth, and cell maintenance), and organic wastes (carried to breakdown or excretion sites).

Cellular Composition of Blood

• Formed elements constitutes 45% of blood
• Red blood cells constitute 99.9% of formed elements
• Platelets constitute 0.1% of formed elements
• White blood cells constitute 0.1% of formed elements
  • Neutrophils make up 50-70%White blood cells
  • Lymphocytes make up 20-30% of white blood cells
  • Monocytes make up 2-8% of white blood cells
  • Eosinophils make up 2-4% of white blood cells
  • Basophils make up less than 1% of white blood cells

Blood Cells

• Three types including Red blood cells (erythrocytes), white blood cells (leukocytes) and platelets

Red Blood Cells

• Erythrocytes are biconcave shaped cells with elastic membranes and no nucleus
• Hemoglobin constitutes about 95% of an RBC's components and is the red pigment
• Enzymes, salts, and other proteins make up the remaining 5%
• RBCs are formed in red bone marrow and have an average lifespan of four months
• Approximately 2-10 million red blood cells are formed and destroyed every second
• RBC’s main function is to transport oxygen and carbon dioxide
• Males typically contain 5-5.5 million RBCs per cubic millimeter of blood.
• Females typically contain 4-4.5 million RBCs per cubic millimeter of blood.

Red Blood Cell Composition

• Hemoglobin makes up 95% of a red blood cell’s protein
• Hemoglobin is a globular protein with four subunits, each containing a globin protein chain, a heme molecule, an iron atom, and an oxygen-binding site
• Phagocytes help in recycling hemoglobin from damaged or dead RBCs

Erythropoiesis

• Process by which red blood cells are formed
• Occurs primarily in the bone marrow and is stimulated by erythropoietin (EPO)
  • EPO increases when oxygen levels are low
• Development stages include erythroblasts and reticulocytes

Blood Type

• Determined by the presence or absence of specific antigens (agglutinogens) on the outer surface of red blood cells.
• Antigens present are A, B, and Rh.
• Antibodies (agglutinins) in plasma react with foreign antigens on red blood cells which leads to the clumping and rupture of RBCs
• Anti-Rh antibodies are produced after exposure to Rh-positive blood cells

White Blood Cells

• Leukocytes are colorless and much larger than red blood cells
• There are between 7,000 to 8,000 WBCs per cubic millimeter of blood
• The are formed in the bone marrow
• White blood cells account for approximately 1% of blood volume in healthy Humans
• Only 2% of the total WBC population circulates in the blood at any given time, with the rest located in the skin, lungs, and spleen

Function of White Blood Cells

• White blood cells are involved in the immune system
• They protect the body against infectious disease and foreign invaders
• Leukocytes defend the body against pathogens, toxins, abnormal cells, and damaged cells

Properties of WBCs

• Diapedesis is the process by which WBCs push through blood vessel walls to enter tissues
• Chemotaxis helps them navigate towards specific chemicals released by bacteria or injured cells
• White Blood cells can be categorized as granulocytes or agranulocytes

Granulocytes

• Neutrophils are 50-70% of circulating WBCs, and are phagocytic.
• Eosinophils are less common, phagocytic, and attracted to foreign proteins
• Basophils release histamine to promote inflammation

Agranulocytes

• Lymphocytes are found mostly in the lymphatic system
  • Provide specific defenses, attack foreign cells, produce antibodies, and destroy abnormal cancer cells
• Monocytes migrate into tissues and become macrophages
  • Live as phagocytic amoeba

Production of WBCs

• Myeloid Stem cells produce granulocytes and monocytes
• Lymphoid cells produce lymphocytes through a process known as lymphopoiesis • The Lymphocytes then enter the blood and migrate to lymphoid tissues

WBC vs RBC Ratio

• WBCs outnumber RBCs by 1000 to 1
• White blood cells protect the body against infection and assist in the repair of damaged tissues
• Neutrophils engulf bacteria, and lymphocytes handle specific immune defenses

Platelets

• Platelets are also known as thrombocytes
• These are cell fragments released from megakaryocytes
• Platelets do not have a nucleus and are random shaped
• Size is between 2-4 microns
• Platelets are normally found between 150,000 to 400,000 per drop blood

Platelet Function

• Platelets helps in stopping bleeding quickly when there's blood vessel damages
  • This process is also known as Hemostasis
• Their life span is only about 5-9 days, forming in bone marrow
• Platelets helps to prevent hemorrhage by stopping excessive blood loss

Hemostasis

• The process which stops the loss of blood from damaged vessels
• Is largely dependent on platelets and soluble proteins or clotting factors

Plasma composition

• Plasma constitutes 55% of blood.
• Plasma is about 90% water itself

Plasma composition continued

• Plasma is primarily composed of water, which dissolves proteins, salts, nutrients, and waste
  • Inorganic ions or mineral ions
  • Plasma proteins
  • Organic nutrients in the blood
  • Nitrogenous waste products
  • Hormones
  • Gases
• There is more protein and oxygen in plasma than there is in interstitial fluid
• Plasma proteins fall into three classes including Albumins, Globulins and Fibrinogen

Plasma Composition Function

• Maintains blood pressure, regulates body temperature
• Contains minerals, salts, and hormones

Disorders of Blood

• Anemia is a condition characterized by a deficiency of red blood cells, which leads to reduced oxygen-carrying capacity of the blood, fatigue, cold intolerance, and paleness, and a lack of oxygen for ATP and heat production
• Leukemia involves the uncontrolled production of white blood cells (leukocytes)., and is also known as blood cancer
  • Symptoms include pale skin, tiredness, fever and weight loss
    • Treatment for Leukemia requires blood change with bone marrow transplants, though expensive it is effective
• Thalassemia is a genetically transmitted disease where an abnormal type of hemoglobin is produced
  • More common in children.
    • Treatments requires the replacement of blood with normal blood, or a bone marrow transplant

Immune System as a functional system:

• Functional system instead of an organ system
• Includes a skin, lining of mucous membranes, secrete, blood cells, vasculature, bone marrow, liver tissue, lymphatic system, and lymphoid organs

The Immune System function

• Immunity includes defending against pathogens, removing worn-out cells and tissue debris, identifying and destroying abnormal or mutant cells, and rejecting foreign cells
• Can cause inappropriate responses such as allergies and autoimmune diseases

Anatomical Classification of the Immune System

• System consists of following elements including
  • Cells include lymphocytes, antigen-presenting cells
  • Lymphatic tissue is diffuse and nodular.
  • Lymphatic organs lymph nodes, spleen, and thymus
  • Lymphatic vessels carry cells's and fluid

Lymphoid Organs

• Classified in to primary and secondary organs
• Primary organs include Thymus and Bone marrow
• Secondary include Spleen, Lymph nodes and MALT.

Primary Lymphoid Organs

• The bone marrow, thymus, and gut-associated lymphoid tissue are the initial "education centers" of the immune system
  • Lymphocytes differentiate into immunocompetent cells in these organs
  • Differentiation here is antigen-independent
• Lymphocytes then enter the blood and lymph, populate the epidermis, mucosae, connective tissue, and secondary lymphoid organs

Secondary Lymphoid Organs.

• Lymph nodes, lymphatic nodules, tonsils, and the spleen act as secondary "education centers"
  • Immunocompetent lymphocytes differentiate into immune effector and memory cells, undergoing antigen-dependent activation and proliferation
• Lymphocytes carry out functions in the connective tissue, secondary lymphoid organs and mucosal surfaces lining epithelia
• Participate in cell-mediated immunity and humoral responses like antibody production

Immunity

• Immunity is body's ability to resist or eliminate foreign materials, or abnormal cells

Immune Response

• A broad response can be seen in both systems regarding their innate and adaptive functions

Immunity Differences

• As an innate responses, It can involve epithelium, in G I system/cellular response
  • Respond immediately
  • Need a previous exposure to substance
• Adaptive responses can involve lymphocytes B, T, NK as the major players
  • Can identify an attack to reinforce immunity to a specific origin

Innate vs Adaptive Immunity

• Innate immunity has no time lag and is not antigen-specific
  • Has no memory
• Adaptive immunity has lag with antigen
  • Generates memory

Innate Immune System

• Consists of both External defenses and Internal Defenses

Innate Immunity; External Defenses

• Physical, mechanical and biological barriers

Anatomical Barriers: Mechanical

• Consists of skin with epidermis, dermis, sweat and oil glands
• Mucociliary elevator, which involves the removal of mucus, saliva, tears and urine

Anatomical Barriers: Chemical

• antimicrobial peptides and the acid PH levels of the stomach
• Enzymes like lysozyme found in tears/saliva

Anatomical Barriers: Biological

• Normal flora act as microbes found in many parts of our body

The Immune System Cont: Components of Blood

• Complement and coagulation proteins, cytokines, and leukocytes constitute the components of blood central to the innate immune system.

White Blood Cells: The Line of Defense

• Macrophages, Eosinil, lymphocyte, nutrophil & bassophil

Neutrophils in the Innate Immune Response

• Neutrophils are the most abundant white blood cells (50-60%) and are efficient phagocytes
• Key cells for the innate immune response

Phagocytosis

• WBCs/ neutrophils eat and digest microbes
  • The neutrophil extends its plasma membrane around the materials in the process of ingestion.
  • The membrane fuses together and forms a phagosome

What in the granules of Neutophil

• Lysozyme which helps digest bacterial
• Antimicrobial proteins in order to aid in digestion

Monocytes

• These are about 50%
• They migrated to the tissues and become macrophages

Macrophages

• Are "Big eaters”
• Involved in neutrophils present in only blood
• Support antigen presentation

Natural Killer Cells

• Natural killer cells are neither B-lymphocytes nor T-lymphocytes
• They are an important part of the innate immune system that kill cells infected with viruses or bacteria and cancer cells

Characteristics NK Cells

• NK cells differentiate to kill: - uninfected/ abnormal cells - microbe infected and cancer cells

Toll-Like Receptors

• Toll-like receptors (TLRs) are transmembrane proteins that are present on macrophages/ few other cells and trigger a cascade of events to kill or protect against pathogens
  • Serve as Inante Sensors
• TLRs conserve across vertebrates and are part of the innate immune system

Summary

• When external are breach, then internal defenses play which involve Neutrophils, Monocytes(macrophages),NK cells and TLRs