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
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
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
Red blood cells (RBCs)
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
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
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
Iron Recycling
Iron removed from heme leaving biliverdin
To transport proteins (transferrin)
To storage proteins (ferritin and hemosiderin)
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)
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
Testing for Transfusion Compatibility
Performed on donor and recipient blood for compatibility
Without cross-match, type O- is universal donor
White blood cells (WBCs)
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)
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
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
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
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)
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
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
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
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
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
Clotting Factors
Also called procoagulants
Proteins or ions in plasma
Required for normal clotting
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
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
Reduces size of damaged area making it easier for fibroblasts, smooth muscle cells, and endothelial cells to complete repairs