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The Cardiovascular System

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Objectives:• Describe the functions of the cardiovascular system• List and describe the structure of the types of blood vessels• Compare and contrast pulmonary and systemic circulation• Identify the external and internal structures of the heart and

their functions• Describe how the heart beat is generated• Describe the events of a cardiac cycle• Describe blood pressure and how it is measured• Describe the composition of whole blood• Describe the composition of plasma• Describe the various formed elements and their functions• Describe the process of hemostasis• Identify and describe various disorders of the cardiovascular

system• Identify risk factors associated with coronary disease

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Functions:

• A closed system of the heart and blood vessels– The heart pumps blood– Blood vessels allow blood to circulate to

all parts of the body

• to deliver oxygen and nutrients to and remove carbon dioxide and other waste products from the bodies tissues

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Blood Vessels: Types• Taking blood to the tissues and back

– Arteries - large, thickest walled, carry blood away from heart, blood is moved by the pumping of the heart

– Arterioles - smaller, thinner walled, carry blood away from heart, blood is moved by pumping of the heart

– Capillaries - smallest, thinnest vessels, one cell layer thick, site of exchange of materials between the blood and body tissues

– Venules - thinner walled vessels, carry blood back towards heart

– Veins - thin walled vessels, large lumen, have valves present which keep blood moving in one direction, blood is moved by “milking” action due to the contraction of skeletal muscles

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Structure of Vessels• Three layers (tunics)

– Tunic interna• Endothelium• Lines interior of vessels• Decreases friction from blood flow

– Tunic media• Smooth muscle• Middle layer• Changes diameter of vessels • Controlled by sympathetic nervous system

– Tunic externa• Mostly fibrous connective tissue• External layer• Supports and protects vessels

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Structure of Vessels

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Blood Movement Through Veins

• Blood is squeezed forward through vein when skeletal muscles contract

• A valve opens allowing blood to fill chambers

• Valves close when backflow of blood occurs, preventing blood from going backwards

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Capillaries

• Only one cell layer thick, just tunica interna

• Due to thinness exchanges can be made across the membrane between the blood and tissues

• Microcirculation – blood flow moves from arteries into capillaries where materials are exchanged, then into veins

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Capillary Transport Mechanisms

• 4 routes for materials to cross the capillary walls– Diffusion across the plasma membrane– Endocytosis/Exocytosis– Intercellular clefts – gaps in plasma membrane– Fenestrated capillaries – mainly areas of filtration

and absorption (like intestines or kidneys)

• Intercellular clefts and fenestrated capillaries depend on osmotic pressure in interstitial fluid surrounding capillaries

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External Coverings of the Heart

• Pericardium – a double serous membrane– Visceral pericardium

• Next to heart

– Parietal pericardium• Outside layer

• Serous fluid fills the space between the layers of pericardium

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External Coverings of the Heart

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Muscular Tissue• Cardiac muscle: branched at the end with

striations present, usually only one nucleus is present per cell

• branches of each fiber come into contact at specialized junctions called intercalated discs

• involuntarily controlled

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External Structure of the Heart

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Great Vessels of Heart• Aorta (largest blood vessel in the body)

– Leaves left ventricle, carries oxygenated blood to all parts of the body

• Pulmonary arteries– Leave right ventricle, carries deoxygenated blood to the

lungs• Vena cava (Superior and Inferior)

– Enters right atrium– superior vena cava brings deoxygenated blood from the

upper part of the body– inferior vena cava brings deoxygenated blood from the

lower part of the body• Pulmonary veins (four)

– Enter left atrium, brings oxygenated blood from the lungs • Ligamentum Arteriosum

– ligament between aorta and pulmonary trunk that holds the vessels in place

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External Anatomy of the Heart

• Heart is divided into four chambers– Atria

• Receiving chambers– Right atrium– Left atrium

– Ventricles• Discharging chambers

– Right ventricle– Left ventricle

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Blood Circulation

• Pulmonary circulation – process of blood flow from right side of heart lungs back to left side of heart– Pulmonary trunk – heart pumps oxygen poor blood out of heart

to lungs to get oxygen and release carbon dioxide; breaks into the pulmonary arteries

• Systemic circulation – process of blood flow from the left side of heart pump to body tissues back to right side of heart

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Blood Circulation: Pulmonary and

Systemic PathwaysCOCO22 is given off by is given off bythe blood into the lungsthe blood into the lungsand Oand O22 is picked up is picked up by the blood from theby the blood from thelungs.lungs.

OO22 is given off by is given off bythe blood and the blood and and COand CO22 is picked up is picked up by the blood from theby the blood from thebody’s tissue.body’s tissue.

Animation video

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Coronary Blood Supply

• Blood in the heart chambers does not nourish the myocardium

• The heart has its own nourishing circulatory system– Coronary arteries– Cardiac veins– Blood empties into the right atrium via the

coronary sinus

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Internal Structures of the Heart: Heart Wall

• Three layers– Epicardium

• Outside layer• This layer is the parietal pericardium• Connective tissue layer

– Myocardium• Middle layer• Mostly cardiac muscle

– Endocardium• Inner layer• Endothelium

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Internal Structures of Heart• Right and left side act as separate pumps• Four chambers

– Atria• Receiving chambers

– Right atrium– Left atrium

– Ventricles• Discharging chambers

– Right ventricle– Left ventricle

• The valves allow blood to flow in only one direction• Four valves

– Atrioventricular valves – between atria and ventricles• Bicuspid valve (left)• Tricuspid valve (right)

– Semilunar valves between ventricle and artery• Pulmonary semilunar valve• Aortic semilunar valve

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Internal Structures of the Heart

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The Heart’s Pace Maker: Regulation of Heartbeat

Special tissue sets the pace

• Sinoatrial node– Pacemaker

• Atrioventricular node• Atrioventricular bundle• Bundle branches• Purkinje fibers

• Contraction is initiated by the sinoatrial node

• Sequential stimulation occurs at other autorhythmic cells Fibrillation results when SA node

is not working properly.

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ECG: Electrocardiagram• This graph shows the electrical changes which occur when the

muscles of the heart wall depolarize and repolarize.

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ECG: Electrocardiogram

• The first little upward notch of the ECG tracing is called the "P wave." The P wave indicates that the atria (the two upper chambers of the heart) are contracting to pump out blood.

• The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part indicates that the ventricles (the two lower chambers of the heart) are contracting to pump out blood to the body.

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ECG: Electrocardiogram

• The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.

• The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.

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Cardiac Cycle

• Atria contract simultaneously• Atria relax, then ventricles contract• Systole = contraction• Diastole = relaxation• Cardiac cycle – events of one complete heart

beat– Mid-to-late diastole – blood flows into ventricles– Ventricular systole – blood pressure builds before

ventricle contracts, pushing out blood– Early diastole – atria finish re-filling, ventricular

pressure is low

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Cardiac Cycle

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Cardiac Cycle: Valves

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The Heart’s Pace Maker: Regulation of Heartbeat

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Cardiac Output

• The amount of blood pumped out by each side of the heart in 1 minute.

• Stroke volume – the volume of blood pumped out by a ventricle with each heartbeat.

• Heart rate – the number of heart beats per minute

• CO = HR x SV

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Cardiac Output

• Example: – Resting values

• HR = 75 beats/min• SV = 70 ml/min

–CO = HR (75 beats/min) x SV (70 ml/beat)

–CO = 5250 ml/min

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Pulse Pulse – Pulse –

pressure wave pressure wave of blood as it of blood as it passes passes through an through an arteryartery

Monitored at Monitored at “pressure “pressure points” where points” where pulse is easily pulse is easily palpatedpalpated

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Blood Pressure• Measurements by health professionals are

made on the pressure in large arteries– Systolic – pressure at the peak of ventricular

contraction– Diastolic – pressure when ventricles relax

• Pressure in blood vessels decreases as the distance away from the heart increases

• Human normal range is variable– Normal

• 140–110 mm Hg systolic• 80–75 mm Hg diastolic

– Hypotension• Low systolic (below 110 mm HG)• Often associated with illness

– Hypertension• High systolic (above 140 mm HG)• Can be dangerous if it is chronic

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Blood Pressure

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Diseases and Disorders of the Cardiovascular System

Myocardial infarction: heart attack• blockage of coronary artery which

supplies the myocardium• cardiac muscle dies causing the heart

not to function properly• can be due to formation of deposits

of cholesterol and lipids called plaques, blood clots called thrombus, or an embolism which is a blood clot that forms somewhere else in the body, breaks free and lodges in a coronary artery stopping the flow of blood

Angina pectoralis: sharp pain radiating into the left arm and /or neck accompanied by a feeling of pressure within the chest - a classic symptom of problems with blood flow to the heart muscle itself

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Diseases and Disorders of the Cardiovascular System

• Congestive Heart Failure: Cardiac decompensation causes blood circulation to become inadequate tissues don’t get the support needed to supply oxygen and carry out wastes

• Ectopic Focus – the sinoatrial node doesn’t work properly causing abnormal pacing

• Fibrillation – condition in which the heart becomes uncoordinated and can no longer function as a pump

• Heart Block – the atrioventricular nodes are damaged • Incompetent valve – one or more valves in the heart

become damaged causing blood to leak back through (no longer one way flow)

• Pulmonary congestion – initial condition when the left side of the heart fails (blood still pumping through right side, but gets backed up when left side stops pumping.)

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Diseases and Disorders of the Cardiovascular System

• Atherosclerosis: commonly called “hardening of the arteries”

• arteries began to loose elasticity due to aging and formation of plaques in their walls

• They narrow and reduce blood supply to regions of the body particularly the brain and heart

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Diseases and Disorders of the Cardiovascular System

• Aneurysm: a weakened area within the wall of an artery or arteriole

• Because of the high pressure, the vessel wall balloons out and can rupture when the wall becomes stretched too thin leads to a serious internal hemorrhage (internal bleeding)

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Diseases and Disorders of the Cardiovascular System

• Arrhythmia: due to the irregular beat of the heart

• may be due to damage to the SA or AV node, or the myocardium

• commonly treated with medications or by the implantation of an artificial pace-maker Bradycardia: the heart is beating too slow

• Tachycardia: the heart is beating too fast

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Blood• The only fluid tissue in the human body• Classified as a connective tissue

– Living cells = formed elements– Non-living matrix = plasma

• Color range– Oxygen-rich blood is scarlet red– Oxygen-poor blood is dull red

• pH must remain between 7.35–7.45• Blood temperature is slightly higher than

body temperature

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Blood: Plasma• Composed of approximately 90 percent water• Includes many dissolved substances

– Nutrients– Salts (metal ions)– Respiratory gases– Hormones– Proteins : Albumin – regulates osmotic pressure,

Clotting proteins – help to stem blood loss when a blood vessel is injured, Antibodies (globulins) – help protect the body from antigens

– Waste products

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Blood: Formed Elements

• Erythrocytes = red blood cells

• Leukocytes = white blood cells

• Thrombocytes or Platelets = cell fragments

• Formed in red bone marrow (hematopoiesis)

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Whole Blood Composition

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Blood: Formed Elements p. 313

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Blood: Formed Elements

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Red Blood Cells• Anucleate – no nucleus (unable to grow and

divide)• Live about 100-120 days – remains eliminated

by spleen and liver• Developing RBCs divide many times and begin

hemoglobin synthesis– After enough hemoglobin produced, the cell ejects the

nucleus and organelles causing the cell to collapes inward (concave shape) (takes 3-5 days)

• RBC production controlled by hormone erythropoietin– Production not based on number of RBCs, based on

amount of oxygen in blood

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Blood: Formed elements

Basophil Eosinophil Lymphocyte

Monocyte Neutrophil

Red Blood Cells Platelets

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Blood Mini-Lab

• Obtain prepared slide of blood

• Identify and sketch at least 5 different formed elements (use color pencils)– You’ll sketch 1 picture – please see me to get

approval for your drawing BEFORE you draw!

• Analysis: – Explain the differences between the various

white blood cells you saw in your slide.

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Hematopoiesis

• Blood cell formation

• Occurs in red bone marrow– Skull, pelvis, ribs, sternum, humerus and

femur

• All formed elements from hemocytoblast (stem cell)– Lymphoid stem cell: produces lymphocytes– Myeloid stem cell: produces all other formed

elements

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Blood: Formed Elements

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Hemostasis

• Stoppage of blood flow

• Result of a break in a blood vessel

• Hemostasis involves three phases– Platelet plug formation– Vascular spasms– Coagulation

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Hemostasis: Platelet Plug Formation

• Collagen fibers are exposed by a break in a blood vessel

• Platelets become “sticky” and cling to fibers

• Anchored platelets release chemicals to attract more platelets

• Platelets pile up to form a platelet plug

• Positive Feed-back Mechanism

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Hemostasis: Vascular Spasms

• Anchored platelets release serotonin

• Serotonin causes blood vessel muscles to spasm

• Spasms narrow the blood vessel, decreasing blood loss

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Hemostasis: Coagulation

• Injured tissues release thromboplastin• PF3 (a phospholipid) interacts with

thromboplastin, blood protein clotting factors, and calcium ions to trigger a clotting cascade

• Prothrombin activator converts prothrombin to thrombin (an enzyme)

• Thrombin joins fibrinogen proteins (water soluble) into hair-like fibrin (insoluble in water)

• Fibrin forms a meshwork (the basis for a clot)

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Forming Blood Clot

erythrocytes

thrombocytes

fibrin

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Blood Groups• What happens if blood loss occurs?

– 15-30% = weakness– >30% = shock & possible death

• Classifications: – Based on proteins (antigens) of plasma

membrane– Antibodies act to agglutinate (clump) and lyse

foreign RBCs because of the antigens– 2 groups: ABO types & Rh types

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Blood Groups

• Transfusions of wrong blood type can cause death. If wrong blood type is given: – Antibodies recognize foreign antigens causing

clumping– Clogs small vessels throughout body– A few hours later, RBCs are lysed and

hemoglobin is released into blood (hemolysis)– Released hemoglobin blocks kidneys causing

kidney failure

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Diseases and Disorders of the Blood

• Hemophilia: a genetic disorder due to the fact that there is a clotting factor missing necessary for clot formation to stop bleeding.

• can bleed to death from simple injuries or bruising of the body

• more common in males than females (sex-linked)

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Diseases and Disorders of the Blood

• Leukemia: cancer of the bone marrow which produces blood cells

• many different forms of this disease depending upon which type of blood stem cells are involved

• the cells typically do not mature and inhibit the production of other types of blood cells necessary for survival

Noamal Bone Marrow AML Bone Marrow

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Diseases and Disorders of the Blood

• Anemia: due to the lack of Erythrocytes or low levels of hemoglobin in erythrocytes, or abnormal erythrocytes (sickle cell)

• inhibits the proper transport of oxygen in the body

• several forms of anemia