Blood and Cardiovascular System

Chapter 19 Blood

An Introduction to Blood and the Cardiovascular System

The Cardiovascular System consists of:

1. A pump (the heart)

2. A conducting system (blood vessels)

3. A fluid medium (blood)



Blood is a specialized fluid of connective tissue that contains cells suspended in a fluid matrix

Physical Characteristics of Blood

Three General Characteristics of Blood

38°C (100.4°F) is normal temperature

High viscosity

Slightly alkaline pH (7.35–7.45)


How much blood do we have?

Blood volume (liters) = 7 percent of body weight (kilograms)

Adult male: 5–6 liters

Adult female: 4–5 liters


Important Functions of Blood

Transportation of dissolved substances

Oxygen and carbon dioxide

Nutrients

Hormones

Immune system components

Waste products


Protection

Restriction of fluid losses at injury sites

Defense against toxins and pathogens


Regulation

Stabilization of body temperature

Regulation of pH and ions

Whole Blood

Plasma

Fluid consisting of:

Water

Dissolved plasma proteins

Other solutes


Formed elements

RBC = red blood cell or erythrocytes transport oxygen

WBC = white blood cells or leukocytes part of the immune system

Platelets= cell fragments involved in clotting

Plasma

Makes up 50–60% of blood volume

More than 90% of plasma is water


Two fluid compartments:

Extracellular fluids (EF) = all fluid outside of cells

  • Interstitial fluid (IF)
  • Plasma


Intracellular fluids (ICF) = all fluid inside of cells


Materials that plasma and Interstitial fluid (IF) exchange across capillary walls

Water

Ions

Small solutes

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Serum

Liquid part of a blood sample in which dissolved fibrinogen converts to solid fibrin

(protein-rich liquid that separates out when blood coagulates)

Plasma Proteins


More than 90% made in liver

  • Antibodies made by plasma cells
  • Peptide hormones made by endocrine organs


Albumins (60%)

Transport substances such as fatty acids, thyroid hormones, and steroid hormones


Globulins (35%)

  • Antibodies, also called immunoglobulins
  • Transport globulins (small molecules): hormone-binding proteins, metalloproteins, apolipoproteins (lipoproteins), and steroid-binding proteins
Help to transport ions, hormones and lipids


Fibrinogen (4 percent)

Molecules that form clots and produce long, insoluble strands of fibrin

clotting


Other Plasma Proteins

1 percent of plasma

Changing quantities of specialized plasma proteins


Peptide hormones normally present in circulating blood

Insulin

prolactin (PRL)

glycoproteins thyroid-stimulating hormone (TSH)

follicle-stimulating hormone (FSH)

luteinizing hormone (LH)

Hemopoiesis - blood formation

Process of producing formed elements

By myeloid and lymphoid stem cells form from pluripotent stem cell - cells with capacity to develop into several types of cells


Fractionation

Process of separating whole blood Into plasma and formed elements for clinical analysis

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Red blood cells (RBCs)

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Red blood cells (RBCs)

Abundance of RBCs

Make up 99.9 percent of blood’s formed elements


Red blood cell count – the number of RBCs in 1 microliter of whole blood

Male: 4.5–6.3 million

Female: 4.2–5.5 million

Three Important Effects of RBC Shape on Function

1.High surface-to-volume ratio - quickly absorbs and releases oxygen

2.Discs form stacks called rouleaux - smooth the flow through narrow blood vessels

3.Discs bend and flex entering small capillaries - a 7.8-µm RBC passes through 4-µm capillary

Life of a RBC

Life Span of RBCs - live about 120 days

  • Lack nuclei, mitochondria, and ribosomes
  • No cell repair
  • Anaerobic metabolism


RBC Formation and Turnover

1 percent of circulating RBCs wear out per day

About 3 million new RBCs per second


Hemoglobin Conversion and Recycling

Macrophages of liver, spleen, and bone marrow monitor RBCs

Engulf RBCs before membranes rupture (hemolyze)

Hemoglobin

Hemoglobin (Hb)- protein molecule that binds and transports oxygen and carbon dioxide

  • The red pigment that gives whole blood its color

Normal hemoglobin (adult male) = 14–18 g/dL whole blood

Normal hemoglobin (adult female) = 12–16 g/dL whole blood


Hemoglobin Structure

Complex quaternary structure with four globular protein subunits

Each with one molecule of heme, each heme contains one iron ion


Hemoglobin Function

  • Carries oxygen to peripheral capillaries with low oxygen and hemoglobin releases oxygen
  • Binds carbon dioxide to form carbaminohemoglobin and carries it to lungs


Fetal Hemoglobin

Strong form of hemoglobin found in embryos

Takes oxygen from mother’s hemoglobin

Red blood cell formation and recycling

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Hemoglobin Conversion and Recycling


Hemoglobin Conversion and Recycling

Hemoglobinuria

Hemoglobin breakdown products in urine due to excess hemolysis in bloodstream

Hematuria

Whole red blood cells in urine due to kidney or tissue damage

Hemoglobin Conversion and Recycling

Phagocytes break hemoglobin into components

Globular proteins to amino acids

Heme to biliverdin

Iron

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Breakdown of Biliverdin

Biliverdin (green) is converted to bilirubin (yellow)

Bilirubin is excreted by liver (bile)

Jaundice is caused by bilirubin buildup

Converted by intestinal bacteria to urobilins and stercobilins

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Iron Recycling

Iron removed from heme leaving biliverdin

To transport proteins (transferrin)

To storage proteins (ferritin and hemosiderin)

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Regulation of Erythropoiesis

Building red blood cells requires:

Amino acids

Iron

Vitamins B12, B6, and folic acid

Pernicious anemia = Low RBC production due to unavailability of vitamin B12


Stimulating Hormones

Erythropoietin (EPO) also called erythropoiesis-stimulating hormone

Secreted when oxygen in peripheral tissues is low (hypoxia)

Due to disease or high altitude

Blood typing

Surface Antigens: cell surface proteins that identify cells to immune system

Normal cells are ignored and foreign cells attacked


Blood Types

Are genetically determined by presence or absence of RBC surface antigens A, B, Rh (or D)

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Rh Factor

Also called D antigen

Either Rh positive (Rh+) or Rh negative (Rh-)

Only sensitized Rh- blood has anti-Rh antibodies

Agglutinogens

Antigens on surface of RBCs

Screened by immune system

Plasma antibodies attack and agglutinate (clump) foreign antigens

Cross-Reactions in Transfusions

transfusion reaction

Plasma antibody meets its specific surface antigen

Blood will agglutinate and hemolyze

Occurs if donor and recipient blood types not compatible

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Testing for Transfusion Compatibility

Performed on donor and recipient blood for compatibility

Without cross-match, type O- is universal donor

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White blood cells (WBCs)

Also called leukocytes

Do not have hemoglobin so appear white

Have nuclei and other organelles


WBC functions

Defend against pathogens

Remove toxins and wastes

Attack abnormal cells


Types of WBCs

Neutrophils

Eosinophils

Basophils

Monocytes

Lymphocytes

WBC Circulation and Movement

Where are WBCs found?

Connective tissue proper

Lymphatic system organs

Small numbers in blood

5000 to 10,000 per microliter

WBC Circulation and Movement

Four Characteristics of Circulating WBCs

Can migrate out of bloodstream

Have amoeboid movement

Attracted to chemical stimuli (positive chemotaxis)

Some are phagocytic

Neutrophils, eosinophils, and monocytes

Neutrophils

Also called polymorphonuclear leukocytes

50–70 percent of circulating WBCs

Pale cytoplasm granules with:

Lysosomal enzymes

Bactericides (hydrogen peroxide and superoxide)

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Basophils

Are less than 1 percent of circulating WBCs

Accumulate in damaged tissue

Release histamine

Dilates blood vessels

Release heparin

Prevents blood clotting

Neutrophil Action

Very active, first to attack bacteria

Engulf and digest pathogens

Degranulation

Removing granules from cytoplasm

Defensins (peptides from lysosomes) attack pathogen membranes

Release prostaglandins and leukotrienes

Form pus

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Eosinophils (Acidophils)

2–4 percent of circulating WBCs

Attack large parasites

Excrete toxic compounds

Nitric oxide

Cytotoxic enzymes

Are sensitive to allergens

Control inflammation with enzymes that counteract inflammatory effects of neutrophils and mast cells

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Lymphocytes

20–40 percent of circulating WBCs

Are larger than RBCs

Migrate in and out of blood

Mostly in connective tissues and lymphoid organs

Are part of the body’s specific defense system

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Monocytes

2–8 percent of circulating WBCs are large and spherical

  • Enter peripheral tissues and become macrophages
  • Engulf large particles and pathogens
  • Secrete substances that attract immune system cells and fibroblasts to injured area

Three Classes of Lymphocytes

1.T cells

  • Cell-mediated immunity
  • Attack foreign cells directly


2.B cells

  • Humoral immunity
  • Differentiate into plasma cells
  • Synthesize antibodies


3.Natural killer (NK) cells

  • Detect and destroy abnormal tissue cells (cancers)
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WBC Production

All blood cells originate from hemocytoblasts

Which produce progenitor cells called myeloid stem cells and lymphoid stem cells


WBC Development

WBCs, except monocytes

Develop in bone marrow

Monocytes

Develop into macrophages in peripheral tissues

WBC Production

Myeloid stem cells

Produce all WBCs except lymphocytes

Lymphoid stem cells

Lymphopoiesis – the production of lymphocytes

Regulation of WBC Production

Colony-stimulating factors (CSFs)

Hormones that regulate blood cell populations

M-CSF stimulates monocyte production

G-CSF stimulates production of granulocytes
(neutrophils, eosinophils, and basophils)

GM-CSF stimulates granulocyte and monocyte
production

Multi-CSF accelerates production of
granulocytes, monocytes, platelets, and RBCs

Differential Count and Changes in WBC Profiles

Detects changes in WBC populations

Infections, inflammation, and allergic reactions


WBC Disorders

Leukopenia

Abnormally low WBC count

Leukocytosis

Abnormally high WBC count

Leukemia

Extremely high WBC count

Platelets

Cell fragments involved in human clotting system

Nonmammalian vertebrates have thrombocytes (nucleated cells)

Circulate for 9–12 days

Are removed by spleen

2/3 are reserved for emergencies


Platelet Production

Also called thrombocytopoiesis

Occurs in bone marrow

Megakaryocytes

Giant cells in bone marrow

Manufacture platelets from cytoplasm

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Platelet Counts


150,000 to 500,000 per microliter

Thrombocytopenia

Abnormally low platelet count

Thrombocytosis

Abnormally high platelet count

Hemostasis - cessation of bleeding

Three phases of hemostasis
1. Vascular phase

2. Platelet phase

3. Coagulation phase

Three Functions of Platelets

1.Release important clotting chemicals

2.Temporarily patch damaged vessel walls

3.Reduce size of a break in vessel wall

Hormonal controls of Platelet Production

Thrombopoietin (TPO)

Interleukin-6 (IL-6)

Multi-CSF

Vascular phase

A cut triggers vascular spasm that lasts 30 minutes

Endothelial cells contract and expose basement membrane to bloodstream

Endothelial cells release:

chemical factors ADP, tissue factor, and prostacyclin

local hormones, endothelins


These stimulate smooth muscle contraction and cell division

Endothelial plasma membranes become “sticky” and seal off blood flow

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Platelet Phase

Begins within 15 seconds after injury

Platelet adhesion (attachment) to:

  • Sticky endothelial surfaces
  • Basement membranes
  • Exposed collagen fibers

Platelet aggregation forms platelet plug that closes small breaks

During platelet phase

Activated platelets release clotting compounds

1. Adenosine diphosphate (ADP)

2. Thromboxane A2 and serotonin

3. Clotting factors

4. Platelet-derived growth factor (PDGF)

5. Calcium ions

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Factors That Limit the Growth of the Platelet Plug

1.Prostacyclin, released by endothelial cells,
inhibits platelet aggregation

2. Inhibitory compounds released by other WBCs

3. Circulating enzymes break down ADP

4. Negative (inhibitory) feedback from serotonin

5. Development of blood clot isolates area

The Coagulation Phase

Begins 30 seconds or more after the injury

Blood clotting (coagulation)

Cascade reactions

Chain reactions of enzymes and proenzymes

Form three pathways

Convert circulating fibrinogen into insoluble fibrin

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Clotting Factors

Also called procoagulants

Proteins or ions in plasma

Required for normal clotting

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Three Coagulation Pathways

1.Extrinsic pathway

2. Intrinsic pathway

3. Common pathway

Extrinsic Pathway

Begins in the vessel wall

Outside bloodstream

Damaged cells release tissue factor (TF)

TF + other compounds = enzyme complex

Activates Factor X

Intrinsic Pathway

Begins with circulating proenzymes

Within bloodstream

Activation of enzymes by collagen

Platelets release factors (e.g., PF-3)

Series of reactions activates Factor X

The Common Pathway

Where intrinsic and extrinsic pathways converge

Forms complex prothrombin activator

Converts prothrombin to thrombin

Thrombin converts fibrinogen to fibrin

Feedback Control of Blood Clotting

Stimulates formation of tissue factor

Stimulates release of PF-3

Forms positive feedback loop (intrinsic and extrinsic)

Accelerates clotting

Feedback Control of Blood Clotting

Anticoagulants (plasma proteins)

Antithrombin-III

Alpha-2-macroglobulin

Heparin

Aspirin

Protein C (activated by thrombomodulin)

Prostacyclin

Calcium Ions, Vitamin K, and Blood Clotting

Calcium ions (Ca2+) and vitamin K are both essential to the clotting process

Clot Retraction

Pulls torn edges of vessel closer together reducing residual bleeding and stabilizing injury site

Reduces size of damaged area making it easier for fibroblasts, smooth muscle cells, and endothelial cells to complete repairs