Cardiovascular System
Characteristics of Blood
• Connective tissue• Plasma and cells• Transports substances
between body cells and the external environment
Blood Volumes
• Varies with body size, fluid and electrolyte concentrations, and amount of adipose
• Average adult volume – 5 liters (4-5 L for women, 5-6 L for men)
• Hematocrit – usually 45%
Blood Cell Types
• Erythrocytes – RBCs• Leukocytes – WBCs• Thrombocytes -
platelets
Red Blood Cells (RBCs)
• Biconcave disks that thin near the centers increased surface area for transporting gases
• Have nuclei early in development, but extrude them
• No nucleus – more room for hemoglobin, but cannot reproduce or make proteins
Hemoglobin
• Oxygen-carrying protein
• 1/3 of each RBC• Gives blood its color• Oxyhemoglobin• Deoxyhemoglobin• Hypoxia• Cyanosis
Red Blood Cell Counts
• RBCC – the number of RBCs in 1 mm3 of blood
• Adult male average – 4.6 – 6.2 million
• Adult female average – 4.2 – 5.4 million
• Determines blood’s oxygen carrying capacity
• Important diagnostic tool
Blood Cell Production • RBCs are normally
flexible, elastic, and able to pass through small blood vessels
• More fragile as they age
• Macrophages phagocytize and destroy damaged RBCs in the liver and spleen
Breakdown of Hemoglobin
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or s to red in live r
Iron
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B ilive rd in(g reen p ig m en t)
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White Blood Cells (WBCs)• Function to protect against
disease– Phagocytize bacterial cells
– Produce antibodies
• Move by diapedesis• 2 main types:
– Granulocytes – neutrophils, eosinophils, and basophils
– Agranulocytes – monocytes and lymphocytes
Granulocytes
• Lobed nucleus with 2-5 sections
• Dark staining nucleus and pale granules
• 54-62% of WBCs• Contain many
lysosomes – actively phagocytizes bacteria
Granulocytes
• Contains coarse, uniformly sized granules
• 2 lobes on nucleus• Stains red• 1-3% of WBCs• Kills parasites• Helps control inflammation
and allergic reactions
Granulocyte
• Fewer, more irregular granules than eosinophils
• Granules stain deep blue• Less than 1% of WBCs• Contain heparin (inhibits
blood clotting) and histamine (increases blood flow to injured tissues)
Agranulocytes
• Largest blood cells• May live weeks
months• 3-9% of WBCs• Discussed later
Agranulocyte
• Form in red bone marrow and lymphatic system
• Slightly larger than RBCs• Large, round nucleus with
rim of cytoplasm• May live for years• 25-33% of WBCs• Discussed more later
White Blood Cell Count (WBCC)
• Number of WBCs in 1 mm3 of blood
• Adult average – 5000 – 10,000 cells
• Leukocytosis• Leukopenia• Differential WBCC (DIFF)
– More neutrophils – bacterial infection
– More eosinophils – parasitic infection, allergic reaction
• Leukemia
Platelets• Not complete cells• Form from megakaryocytes
that fragment• Lack nuclei• Half size of RBCs• Live 10 days• Average count – 130,000 –
360,000 cells• Help close breaks in
damaged blood vessels• Initiate formation of blood
clots
Plasma• 92% water• Functions include:
– Transporting nutrients, gases, and vitamins
– Regulating fluid and electrolyte balance
– Maintaining pH
Plasma Proteins
Hemostasis
• Vasospasm• Platelet plug formation• Coagulation• Fibroblasts invade clot
Hemostasis
Blood Groups
• ABO blood group is based on the presence or absence of 2 major antigens (RBC surface molecules)
• 4 possible combinations:– A
– B
– AB
– O
Rh Blood Group
Cardiovascular System – Pulmonary and Systemic Circuits
System Overview
• System consists of the heart and the blood vessels
• Function: to bring oxygen and nutrients to all body cells and to remove waste
Heart Location
Coverings of the Heart
• Pericardium– Fibrous pericardium
– Parietal pericardium
– Visceral pericardium
• Pericardial cavity• Pericardial fluid
reduces friction
Walls of the Heart
• Epicardium• Myocardium• Endocardium
– Purkinje fibers
Heart Chambers
• 4 chambers of the heart– Atria
• Thin walls• Receive blood returning to the
heart• Auricles
– Ventricles• Thicker walls• Receive blood from atria• Force blood out of heart
• Septum
Heart Valves
• Atrioventricular valves– Tricuspid – right– Bicuspid – left
• Semilunar valves– Pulmonary – right– Aortic – left
• Chordae tendinae• Papillary muscles
Blood Supply to the Heart
• Coronary arteries• Cardiac veins• Coronary sinus
Cardiac Cycle
• Cardiac cycle – series of events that constitute a complete heartbeat
• Systole – contraction• Diastole – relaxation
Cardiac Cycle
• Heart Sounds – “lub-dup”
• Lub – ventricular systole– AV valves close
• Dup – ventricular diastole– SL valves close
• Murmur
Cardiac Conduction System
• Coordinates the events of the cardiac cycle
• Consists of clumps and strands of specialized cardiac muscle that initiate and distribute impulses throughout the myocardium
Nodes of Cardiac Conduction System
• Sinoatrial node – AKA “pacemaker”– Just beneath
epicardium
– Located in right atrium near opening of superior vena cava
– Initiates impulses without nervous stimulation
Nodes of Cardiac Conduction System
• Atrioventricular node– Located in inferior portion
of septum
• AV bundle (bundle of His)– Large fibers run through the
interventricular septum
• Purkinje fibers– Spread from septum into
papillary muscles
– Stimulate ventricular contraction
Regulation of Cardiac Cycle
• Parasympathetic and sympathetic fibers from medulla oblongata run to the nodes – Secrete acetylcholine
to decrease heart rate– Secrete norepinephrine
to increase heart rate
• Cardiac center
Electrocardiogram (ECG)
• Recording of the electrical changes in the myocardium during the cardiac cycle
• P – atrial systole• QRS – ventricular
systole; covers atrial diastole
• T – ventricular diastole
Blood Vessels
Arteries
• Strong, elastic vessels that carry blood away from the heart
• Lead to finer branches called arterioles
Artery Layers
• Tunica interna – simple squamous epithelium for smooth surface
• Tunica media – largest layer; smooth muscle and elastic CT
• Tunica externa – CT that attaches artery to surrounding tissues
Capillaries• Smallest diameter blood
vessels• Extensions of inner lining of
arterioles• Connect arterioles and venules• Allow exchange between
blood and tissue fluid• More abundant around
muscles and nerves• Blood flow controlled by
precapillary sphincters• Exchanges occur by diffusion,
osmosis, and filtration
Veins• Carry blood back to the right
atrium of the heart• Form from microscopic
venules that are continuous with capillaries
• Structure similar to arteries, but less developed tunica media
• Many have valves to prevent blood backflow
• Act as blood reservoirs when hemorrhage causes decrease in arterial blood pressure
Blood Pressure• The force blood exerts against
the inner walls of blood vessels• Refers primarily to arterial
blood pressure• Increases during ventricular
systole – systolic pressure (100-140)
• Decreases during ventricular diastole – diastolic pressure (70-90)
• Pulse
Factors that Affect Blood Pressure
• Heart action – how much blood enters arteries
• Blood volume
• Peripheral resistance – friction between blood and vessels
• Blood viscosity
• Hypertension and stroke