Chapter 17 HAPS

Components of Blood

Blood consists of plasma (~55%) and formed elements (~45%)

Plasma

The liquid portion of blood that makes up about 55% of blood volume and transports nutrients, hormones, wastes, and proteins

Formed Elements

The cellular components of blood including RBCs, WBCs, and platelets

Red Blood Cells (RBCs)

Make up about 99% of formed elements and transport oxygen and carbon dioxide

White Blood Cells (WBCs)

Less than 1% of blood volume

function in immune defense

Platelets

Cell fragments involved in blood clotting and hemostasis

ABO Blood Type A

Has A antigens on RBCs and anti-B antibodies in plasma

ABO Blood Type B

Has B antigens on RBCs and anti-A antibodies in plasma

ABO Blood Type AB

Has both A and B antigens on RBCs and no anti-A or anti-B antibodies

universal recipient

ABO Blood Type O

Has no A or B antigens on RBCs and both anti-A and anti-B antibodies

universal donor

Rh Positive

Has Rh antigen (D antigen) on RBCs

Rh Negative

Lacks Rh antigen on RBCs

Type A Compatibility

Can receive A and O blood

can donate to A and AB

Type B Compatibility

Can receive B and O blood

can donate to B and AB

Type AB Compatibility

Can receive A, B, AB, and O blood

can donate only to AB

Type O Compatibility

Can receive only O blood

can donate to all ABO blood types

Blood Typing Test

Blood is mixed with anti-A and anti-B antibodies

agglutination indicates the presence of the corresponding antigen

Distributive Function of Blood

Transports oxygen, nutrients, hormones, and wastes throughout the body

Regulatory Function of Blood

Helps regulate body temperature, pH, and fluid balance

Protective Function of Blood

Prevents blood loss through clotting and protects against pathogens through immune cells

Erythropoiesis

The production of red blood cells in red bone marrow

Stimulus for Erythropoiesis

Low blood oxygen levels (hypoxia)

Erythropoietin (EPO)

Hormone released primarily by the kidneys that stimulates RBC production

Inhibition of Erythropoiesis

Restoration of normal oxygen levels reduces EPO secretion

Leukopoiesis

The production of white blood cells in red bone marrow

Stimulus for Leukopoiesis

Infection, inflammation, or immune system demand

Colony-Stimulating Factors (CSFs)

Hormones that stimulate white blood cell production

Interleukins

Chemical messengers that promote leukopoiesis

Inhibition of Leukopoiesis

Resolution of infection or reduced immune demand

Location of Erythropoiesis and Leukopoiesis

Red bone marrow

Red Blood Cell Structure

Biconcave, anucleate cell packed with hemoglobin

Red Blood Cell Function

Transports oxygen and some carbon dioxide

Red Blood Cell Lifespan

Approximately 120 days

Hemoglobin

Iron-containing protein in RBCs that binds oxygen

Hemoglobin Structure

Consists of four globin protein chains and four heme groups containing iron

Fate of Globin After RBC Death

Broken down into amino acids and recycled

Fate of Iron After RBC Death

Recycled and stored for future hemoglobin synthesis

Fate of Heme After RBC Death

Converted to bilirubin and excreted in bile

White Blood Cell Structure

Nucleated cells with various shapes depending on type

White Blood Cell Function

Protects the body against infection and foreign substances

White Blood Cell Lifespan

Varies from hours to years depending on cell type

Granulocytes

WBCs with visible cytoplasmic granules

Neutrophils

Most abundant WBC

phagocytize bacteria

Eosinophils

Defend against parasites and participate in allergic reactions

Basophils

Release histamine and heparin during inflammation

Agranulocytes

WBCs lacking visible granules

Lymphocytes

Include B cells, T cells, and NK cells

involved in adaptive immunity

Monocytes

Largest WBCs

become macrophages in tissues

Platelet Structure

Small cell fragments derived from megakaryocytes

Platelet Function

Initiate blood clotting and vessel repair

Platelet Lifespan

Approximately 7–10 days

Neutrophil Appearance

Multi-lobed nucleus with pale granules

Eosinophil Appearance

Bilobed nucleus with red-orange granules

Basophil Appearance

Dark blue-purple granules that often obscure the nucleus

Lymphocyte Appearance

Large round nucleus with thin rim of cytoplasm

Monocyte Appearance

Kidney-shaped nucleus with abundant cytoplasm

Hemostasis

The process that stops bleeding following vascular injury

Vascular Spasm

Immediate constriction of damaged blood vessels to reduce blood loss

Platelet Plug Formation

Platelets adhere to exposed collagen and aggregate at the injury site

Platelet-Derived Growth Factor (PDGF)

Chemical released by platelets that promotes vessel repair

Coagulation

Formation of a fibrin mesh that stabilizes the platelet plug

Fibrinogen

Soluble plasma protein converted into fibrin during clotting

Fibrin

Insoluble protein strands that form the clot framework

Clot Retraction

Platelets contract and pull wound edges closer together

Fibrinolysis

Breakdown and removal of a blood clot after healing

Heparin

Natural anticoagulant that inhibits clot formation

Hematocrit

Percentage of blood volume occupied by red blood cells

Normal Hematocrit

Approximately 37–54%, depending on sex and age

Hemoglobin Test

Measures concentration of hemoglobin in blood

WBC Count

Measures number of white blood cells in a blood sample

Platelet Count

Measures number of platelets in a blood sample

Differential WBC Count

Determines percentages of different WBC types

Blood Typing Lab

Determines ABO and Rh blood groups through agglutination reactions

Diapedesis

Movement of white blood cells through capillary walls into tissues

Positive Chemotaxis

Attraction of white blood cells toward chemical signals released from damaged or infected tissues

Leukopenia

Abnormally low white blood cell count

Fibrinogen

Plasma protein that is converted into fibrin during clotting

Heparin

Anticoagulant released by basophils and mast cells that prevents excessive clotting

Hemocytoblast

Hematopoietic stem cell that gives rise to all blood cells

PDGF

Platelet-derived growth factor that stimulates tissue repair and healing

Thrombocytopenia

Abnormally low platelet count that increases bleeding risk

Anemia

Condition characterized by reduced oxygen-carrying capacity of blood

Polycythemia

Excessive number of red blood cells causing increased blood viscosity

Leukemia

Cancer involving abnormal production of white blood cells

Hemophilia

Genetic disorder resulting in impaired blood clotting

Thrombus

Stationary blood clot that forms within a blood vessel

Embolus

Detached clot or other material traveling through the bloodstream

Clinic Question Focus

Relate symptoms to disorders involving RBCs, WBCs, platelets, clotting, oxygen transport, and immune function

Homeostatic Imbalance

Any condition in which blood composition or function deviates from normal and disrupts body homeostasis