Blood: Characteristics, Cells, Plasma, and Transfusions

Blood

A type of connective tissue whose cells are suspended in a liquid extracellular matrix, called plasma.

Blood Function

Transports substances between body cells and the external environment and helps maintain a stable internal environment.

Blood Volume

Varies with body size, fluid and electrolyte balance, and adipose content. Average (70 kg male) is 5 liters.

Formed Elements

Blood cells (45% by weight), which is composed mainly of red blood cells but includes red, white, and platelets

Hematocrit (HCT)

Quantitative analysis of the formed elements (red,white,platelets) portion of blood, also known as packed cell volume (PCV).

Plasma

Liquid portion of blood (55% by weight) that contains water, proteins, amino acids, carbohydrates, lipids, vitamins, hormones, electrolytes, and cellular wastes.

Erythrocytes

Red blood cells that compose 99% of blood cells.

Leukocytes

White blood cells that are part of the immune system.

Thrombocytes

Platelets that are involved in blood clotting.

Hematopoietic Stem Cells

Cells in red bone marrow of adults that give rise to all blood cells.

Myeloid Stem Cells

Stem cells that differentiate into various types of blood cells.

Lymphoid Stem Cells

Stem cells that differentiate into lymphocytes.

Hemoglobin

A protein in red blood cells that binds oxygen; composed of globin and heme (iron).

Oxyhemoglobin

Hemoglobin bound to oxygen, appearing bright red.

Deoxyhemoglobin

Hemoglobin not bound to oxygen, appearing darker red or purple.

Red Blood Cell Count (RCC)

The number of red blood cells per mm3 of blood.

Erythropoiesis

The production of red blood cells.

Anucleate

Mature red blood cells that lack nuclei, allowing more room for hemoglobin and oxygen.

Hemostasis

The process that prevents and stops bleeding, involving mechanisms that help achieve it.

Blood Typing

A method used to determine blood type to avoid adverse reactions following blood transfusions.

Blood Reactions

Reactions that may occur between fetal and maternal tissues.

Red Bone Marrow

Site of red blood cell production in adults.

Erythropoietin

Hormone produced by kidney and liver that stimulates erythropoiesis.

Negative Feedback Mechanism

Process involving erythropoietin that maintains stable RBC numbers.

Chemoreceptors

Cells in kidney and liver that detect low blood oxygen.

Dietary Factors Affecting Red Blood Cell Production

B12, folic acid, and iron are needed for RBC production.

Intrinsic Factor

Substance secreted by the stomach that allows B12 absorption.

Anemia

Condition resulting from a lack of proper nutrients affecting RBC production.

Average Life-span of RBCs

120 days.

Macrophages

Cells in the liver and spleen that destroy worn RBCs.

Hemoglobin Breakdown

Hemoglobin is broken into globin and heme.

Iron Recycling

Iron in hemoglobin is recycled after RBC destruction.

Heme Breakdown

Heme is broken into biliverdin, bilirubin, and bile.

Granulocytes

Type of leukocyte approximately 12-14µ in diameter.

Neutrophils

Most abundant WBC (54%-62%) that performs phagocytosis.

Eosinophils

1-3% of total WBC, responsible for killing parasites and allergic reactions.

Basophils

<1% of total WBC, release heparin and histamine.

Monocytes

3-9% of total WBC, largest WBC (12-20 µ) that performs phagocytosis.

Lymphocytes

25-33% of total WBC, involved in immunity and can live for months to years.

Diapedesis

Process by which leukocytes move through blood vessel walls to enter tissues- towards an infection site

Leukocytosis

Condition where WCC > 10500.

Leukopenia

Condition where WCC < 3500.

Differential White Blood Cell Count

DIFF indicates the percentage of each particular leukocyte.

Leukemia

Abnormal (uncontrolled) production of specific types of immature leukocytes.

Platelets (Thrombocytes)

Fragments of giant cells called megakaryocytes.

Function of platelets

Blood clotting.

Blood plasma

Clear, yellow liquid composed of water, proteins, nutrients, gases, electrolytes, and many more substances.

Water in plasma

92% of plasma volume; functions as solvent, in transport, temperature regulation, and serves as site of metabolic reactions.

Plasma Proteins

7% of plasma volume; all produced in the liver.

Albumin

Maintains osmotic pressure of cells (0.9%); transports fatty acids.

Globulins

Includes antibodies.

Fibrinogen

Involved in blood clotting.

Gases in plasma

Includes oxygen (needed for cellular respiration), carbon dioxide (produced by cell respiration), and nitrogen (use unknown).

Nutrients in plasma

Includes amino acids and monosaccharides (i.e., glucose).

Nonprotein Nitrogenous Substances

Plasma wastes including urea (amino acid metabolism), uric acid (nucleotide metabolism), creatinine (creatine metabolism), creatine (CP to recycle ADP to ATP in muscle & brain), and bilirubin (hemoglobin metabolism).

Plasma Electrolytes

Includes sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate; maintain osmotic pressure, resting membrane potential, and pH.

Regulatory Substances in plasma

Includes enzymes and hormones.

Steps of Hemostasis

1. Vascular spasm (vessel walls constrict); 2. Platelet plug formation; 3. Blood coagulation (formation of a blood clot).

Vascular Spasm

Vessel walls constrict to reduce blood flow.

Platelet Plug Formation

Platelets become sticky and adhere to one another, releasing serotonin for further vasoconstriction.

Blood Coagulation

Formation of a blood clot through a complex cascade of events requiring calcium ions.

Extrinsic Clotting Mechanism

Starts when platelet contacts damaged tissue or tissue outside of blood vessel, leading to prothrombin activator (PA) release.

Prothrombin to Thrombin

PA and Ca2+ cause prothrombin to convert to thrombin.

Fibrin

Thrombin catalyzes the conversion of fibrinogen to fibrin, which makes up the meshwork of the clot.

Intrinsic Clotting Mechanism

Starts when blood contacts a foreign substance and leads to the final step of fibrinogen converting to fibrin.

Thrombus

An abnormal blood clot in a vessel.

Embolus

A clot or fragment of a clot that moves in a vessel.

Fibrinolytic System

Provides checks and balances so that blood clotting does not go awry.

Embolism

When an embolus gets lodged in a small vessel obstructing blood flow.

Tissue Plasminogen Activator (TPA)

Naturally produced substance injected quickly (within 1 hour) post-Myocardial Infarction to dissolve coronary thrombus and within 3 hours post-stroke to dissolve a cerebral blockage.

Heparin

An anticoagulant naturally produced by basophils and mast cells, also used as a pharmacologic agent during open-heart surgery and hemodialysis.

Warfarin (Coumadin)

An anticoagulant given to patients prone to thrombosis, slower acting than heparin.

Antigens

Substances present on the cell membrane surface of erythrocytes (red blood cells).

Antibodies

Substances produced in plasma against non-self antigens.

Hemolysis

The serious condition of bursting of RBC that occurs if the RBC antigen and plasma antibody are the same.

ABO Blood Group

An inherited trait determined by the antigens on a person's RBC, with 4 types: A, B, AB, O.

Type A Blood

Blood type with antigen A on RBC.

Type B Blood

Blood type with antigen B on RBC.

Type AB Blood

Blood type with both antigen A & B on RBC.

Type O Blood

Blood type with neither A nor B antigen on RBC.

Anti-A Antibodies

Antibodies developed by persons with Type B blood against antigen A.

Anti-B Antibodies

Antibodies developed by persons with Type A blood against antigen B.

Anti-A and Anti-B Antibodies

Antibodies developed by persons with Type O blood against both antigen A and B.

Agglutination

Clumping of red blood cells seen in the laboratory when RBC antigen and plasma antibody are the same.

Fibroblasts

Cells that invade a clot, forming connective tissue throughout.

Protein-splitting enzymes

Enzymes that may eventually destroy a clot.

Deep Vein Thrombosis (DVT)

A condition related to thrombus detection in veins.

Universal donor

A person with type O blood.

Universal recipient

A person with type AB blood.

Rh positive

Group of antigens present on RBC.

Rh negative

Lack of antigens on RBC.

Erythroblastosis fetalis

Hemolytic disease of the newborn (HDN).

RhoGAM

A drug that destroys the mother's anti-Rh antibodies before they can cross the placenta to harm the baby.

Erythrocyte

Scientific name for red blood cell.

Leukocyte

Scientific name for white blood cell.

Thrombocyte

Scientific name for platelet.

Function of erythrocytes

Transportation of oxygen.

Function of leukocytes

Fight infection/control disease.

Function of thrombocytes

Blood clotting.

Neutrophil

General phagocytosis; acute bacterial infections.