Chapter 19 The Cardiovascular System: The Blood

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INTRO

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The cardiovascular system consists of the:Blood VesselsHeartBlood

a connective tissue, is composed of plasma and formed elements (cells and cell fragments, etc.).

COMPONENTS OF BLOOD

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Blood consists of 55% plasma

91.5% water and 8.5% solutes (proteins, nutrients, enzymes, hormones, respiratory gases, electrolytes, and waste products.)

45% formed elements

Components of Blood

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Blood Plasma Proteinsalbumin

maintain blood osmotic pressureglobulins (immunoglobulins)

antibodies bind to foreignsubstances called antigens

form antigen-antibody complexesfibrinogen

for clotting

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Functions of Blood

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Transportation O2, CO2, metabolic wastes, nutrients, heat &

hormonesRegulation

pHbody temperature

coolant properties of water vasodilatation of surface vessels dump

heatwater content of cells by interactions with

dissolved ions and proteinsProtection from disease & loss of blood

Physical Characteristics of Blood

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Thicker (more viscous) than waterTemperature of 100.4 degrees FpH 7.48 % of total body weightBlood volume varies

5 to 6 liters in average male4 to 5 liters in average femalehormonal negative feedback systems

maintain constant blood volume and osmotic pressure

FORMATION OF BLOOD CELLS

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Called- Hematopoiesis or hemopoiesisHow? From stem cells (pluripotent become

myeloid and lymphoidWhere? In bone marrowRegulated by- growth factors

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ObjectivesCompare and contrast erythrocytes and

leukocytes.ID various leukocytes based on structure

and function.Describe the steps hemostasis and factors

affecting whether one will occur.

Red Blood Cells or Erythrocytes (Figure 19.4a)

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Contain oxygen-carrying protein hemoglobin that gives blood its red color1/3 of cell’s weight is hemoglobin

Biconcave diskincreased surface area/volume ratio flexible shape for narrow passagesno nucleus or other organelles

no cell division or mitochondrial ATP formationNormal RBC count

male 5.4 million/drop ---- female 4.8 million/dropnew RBCs enter circulation at 2 million/second

Hormones

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increase the number of cell and platelet precursors.

Hemoglobin

RBC’s contain hemoglobinglobin proteinOne heme(iron) pigment that carries oxygen

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Hemoglobin Transport

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can carry 4 oxygen molecules from lungs to tissue cells

transports CO2 waste from tissue cells to lungs for release

transports nitric oxide & super nitric oxide helping to regulate BP through vasoconstriction and vasodilation, respectively.

Erythropoiesis:

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What is it? The creation of erythrocytes (RBC’s)Where does it happen? in adult red bone marrow

of certain bonesWhat causes it? stimulus for erythropoiesis is

hypoxia (Figure 19.6).Major steps include:

1. Proerythroblast starts to produce hemoglobin2. Nucleus is ejected & a reticulocyte is formed 3. Reticulocytes escape from bone marrow into the

blood4. Remaining organelles get ejected to become a

mature RBC

WHITE BLOOD CELLS

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Leukocytes (white blood cells or WBCs) are nucleated cells and do not contain hemoglobin.

Two principal types are granular (neutrophils, eosinophils, basophils)

and agranular (lymphocytes and monocytes) do not

have cytoplasmic granules. They differentiate into macrophages (fixed and wandering).

Leukocytes have surface proteins, as do erythrocytes.

WBC Physiology

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Less numerous than RBCs5000 to 10,000 cells per drop of blood

Only 2% of total WBC population is in circulating blood at any given timerest is in lymphatic fluid, skin, lungs, lymph nodes &

spleen

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WBC Type FunctionNeutrophils and wandering or fixed macrophages

phagocytosis

Eosinophils combat the effects of histamine in allergic reactions, phagocytize antigen-antibody complexes, and combat parasitic worms

Basophils develop into mast cells that liberate heparin, histamine, and serotonin in allergic reactions that intensify the inflammatory response

B lymphocytes differentiate into tissue plasma cells that produce antibodiesin response to the presence of foreign substances called antigens

T lymphocytes destroy foreign invaders directly

WBC examination

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A differential white blood cell count is a diagnostic test in which specific white blood cells are enumerated. Because each type of WBC plays a different role, determining the percentage of each type in the blood assists in diagnosing the condition.

Neutrophil (Granulocyte)

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Eosinophil (Granulocyte)

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Basophil (Granulocyte)

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Lymphocyte (Agranulocyte)

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Monocyte (Agranulocyte)

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Platelet (Thrombocyte) Anatomy

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HEMOSTASIS

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A clot is a gel consisting of a network of insoluble protein fibers (fibrin) in which formed elements of blood are trapped (Figure 19.10).

The chemicals involved in clotting are known as coagulation (clotting) factors; most are in blood plasma, some are released by platelets, and one is released from damaged tissue cells (Table 19.4).

Blood clotting involves a cascade of reactions that may be divided into three stages: formation of prothrombinase (prothrombin activator), conversion of prothrombin into thrombin, and conversion of soluble fibrinogen into insoluble fibrin (Figure 19.11).

The Blood Clotting ProcessMajor Steps:

1. Platelets become sticky when at the edge of a broken blood vessel and clump at the site.

2. Platelets then release protein clotting factor, thromboplastin.

3. Thromboplastin converts prothrombin (which is already in the blood) to the enzyme thrombin.

4. Thrombin then converts a plasma protein called fibrinogen into a sticky mesh of fibrin filaments (clot).

Both vitamin K and Ca are important in the clotting process

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Role of Vitamin K in Clotting

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Normal clotting requires adequate vitamin Kfat soluble vitamin absorbed if lipids are

presentabsorption slowed if bile release is insufficient

Required for synthesis of 4 clotting factors by hepatocytesfactors II (prothrombin), VII, IX and X

Produced by bacteria in large intestine

Intravascular Clotting

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Thrombosisclot (thrombus) forming in an unbroken blood vessel

forms on rough inner lining of BVif blood flows too slowly (stasis) allowing clotting factors to

build up locally & cause coagulationmay dissolve spontaneously or dislodge & travel

Embolus clot, air bubble or fat from broken bone in the blood

pulmonary embolus is found in lungsLow dose aspirin blocks synthesis of thromboxane

A2 & reduces inappropriate clot formationstrokes, TIAs and myocardial infarctions

Anticoagulants and Thrombolytic Agents

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Anticoagulants suppress or prevent blood clottingheparin

administered during hemodialysis and surgerywarfarin (Coumadin)

antagonist to vitamin K so blocks synthesis of clotting factorsslower than heparin

stored blood in blood banks treated with citrate phosphate dextrose (CPD) that removes Ca+2

Thrombolytic agents are injected to dissolve clotsdirectly or indirectly activate plasminogenstreptokinase or tissue plasminogen activator (t-PA)

Blood Groups and Blood Types

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RBC surfaces are marked by genetically determined glycoproteins & glycolipids agglutinogens or isoantigensdistinguishes at least 24 different blood groups

ABO, Rh, Lewis, Kell, Kidd and Duffy systems

RH blood groups

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AntigenPeople with Rh on RBC surface are Rh+. Normal

plasma contains no anti-Rh antibodiesAntibodies develop only in Rh- blood type & only

with exposure to the antigentransfusion of positive bloodduring a pregnancy with a positive blood type fetus

Transfusion reaction upon 2nd exposure to the antigen results in hemolysis of the RBCs in the donated blood

DISORDERS: HOMEOSTATIC IMBALANCES

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Anemia Sickle-cell Hemophilia Disseminated intravascular clotting Acute leukemiachronic leukemia