The Cardiovascular System(The Circulatory System)· 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· The function of the cardiovascular

system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

The Heart· Location

· Thorax between the lungs· Pointed apex directed toward left hip

· About the size of your fist

The Heart

Figure 11.1

The Heart: Coverings· Pericardium – a double serous

membrane· Visceral pericardium

· Next to heart· Parietal pericardium

· Outside layer· Serous fluid fills the space

between the layers of pericardium

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

External Heart Anatomy

Internal Heart Anatomy

The Heart: Chambers· 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 Heart: 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

Valves open as blood is pumped throughHeld in place by chordae tendineae (“heart strings”)Close to prevent backflow

The Heart: Associated Great Vessels

· Aorta· Leaves left ventricle

· Pulmonary arteries· Leave right ventricle

· Vena cava· Enters right atrium

· Pulmonary veins (four)· Enter left atrium

The Heart: Cardiac Cycle

                                                         

Blood Circulation

Coronary Circulation· 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

Heart Attack: A Block of one of these arteries that cause the muscle cells to die.

One treatment is a bypass surgery

The Heart: Conduction System· Intrinsic

conduction system (nodal system)· Heart muscle

cells contract, without nerve impulses, in a regular, continuous way

The Heart: Conduction SystemSpecial tissue sets

the pace

Sinoatrial node

Pacemaker

Atrioventricular node

Atrioventricular bundle

Bundle branches

Purkinje fibers

Heart Contractions

Figure 11.5

The Heart: Cardiac Cycle· Atria contract simultaneously

· Atria relax, then ventricles contract

· Systole = contraction

· Diastole = relaxation

· 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

·Cardiac cycle – events of one complete heart beat

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

Measuring Arterial Blood Pressure

Variations in Blood Pressure· 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

Blood Vessels: The Vascular System

· Taking blood to the tissues and back· Arteries· Arterioles· Capillaries· Venules· Veins

Blood Vessels: Anatomy· Three layers (tunics)

· Tunic intima· Tunic media

Smooth muscle

Controlled by sympathetic nervous system

· Tunic externaMostly fibrous connective tissue

Also called Tunica adventitia

Differences Between Blood Vessel Types

· Walls of arteries are the thickest

· Lumens of veins are larger

· Skeletal muscle “milks” blood in veins toward the heart

· Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

The Vascular System

Movement of Blood Through Vessels

· Most arterial blood is pumped by the heart

· Veins use the milking action of muscles to help move blood

Major Arteries of Systemic Circulation

Major Veins of Systemic Circulation

Capillary Beds

· True capillaries – exchange vessels

· Oxygen and nutrients cross to cells

· Carbon dioxide and metabolic waste products cross into blood

·Capillary beds consist of two types of vessels

· Vascular shunt – directly connects an arteriole to a venule

Diffusion at Capillary Beds

Hepatic Portal Circulation

Blood flow to the liverLiver receives blood from 2 sources

◦Hepatic Artery◦Hepatic Portal Vein

Leaves via Hepatic VeinSinusoids

◦Chambers in liver where cells and blood have direct contact

Breakdown of RBC’sOccurs in LiverPhagocytosisProtein portion broken down firstIron (Fe3+) gets recycled

◦Transported back to bone marrowOther parts are stored till reused or

metabolized

Chapter 10Blood

·The only fluid tissue in the human body

·Classified as a connective tissue

· Living cells = formed elements

· Non-living matrix = plasma

Blood Plasma· Composed of approximately 90 percent

water· Includes many dissolved substances

· Nutrients· Salts (metal ions)· Respiratory gases· Hormones· Proteins· Waste products

Formed Elements· Erythrocytes = red blood cells

· Leukocytes = white blood cells

· Platelets = cell fragments

Erythrocytes (Red Blood Cells)· The main function is to carry oxygen· Anatomy of circulating erythrocytes

· Biconcave disks· Essentially bags of hemoglobin· Anucleate (no nucleus)· Contain very few organelles

· Outnumber white blood cells 1000:1

Hemoglobin· Iron-containing protein

· Binds strongly, but reversibly, to oxygen

· Each hemoglobin molecule has four oxygen binding sites

· Each erythrocyte has 250 million hemoglobin molecules

Erythrocytes (Red Blood Cells)

· The main function is to carry oxygen· Anatomy of circulating erythrocytes

· Biconcave disks· Essentially bags of hemoglobin· Anucleate (no nucleus)· Contain very few organelles

· Outnumber white blood cells 1000:1

Control of Erythrocyte Production

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· Rate is controlled by a hormone (erythropoietin)

· Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood

· Homeostasis is maintained by negative feedback from blood oxygen levels

Control of Erythrocyte Production

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Figure 10.5

Fate of Erythrocytes

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· Unable to divide, grow, or synthesize proteins

· Wear out in 100 to 120 days

· When worn out, are eliminated by phagocytes in the spleen or liver

· Lost cells are replaced by division of hemocytoblasts

Leukocytes (White Blood Cells)· Crucial in the body’s defense against

disease· These are complete cells, with a nucleus

and organelles· Able to move into and out of blood

vessels (diapedesis)· Can move by ameboid motion· Can respond to chemicals released by

damaged tissues

Leukocyte Levels in the Blood

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· Normal levels are between 4,000 and 11,000 cells per millimeter

· Abnormal leukocyte levels· Leukocytosis

· Above 11,000 leukocytes/ml· Generally indicates an infection

· Leukopenia· Abnormally low leukocyte level· Commonly caused by certain drugs

Types of Leukocytes

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· Granulocytes· Granules in their

cytoplasm can be stained

· Include neutrophils, eosinophils, and basophils

Figure 10.4

Types of Leukocytes

Slide 10.10bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· Agranulocytes· Lack visible

cytoplasmic granules

· Include lymphocytes and monocytes

Figure 10.4

Platelets· Derived from ruptured multinucleate cells (megakaryocytes)

· Needed for the clotting process

· Normal platelet count = 300,000/mm3

Hemostasis

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· Stoppage of blood flow

· Result of a break in a blood vessel

· Hemostasis involves three phases· Platelet plug formation

· Vascular spasms

· Coagulation

Platelet Plug Formation

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· 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

Vascular Spasms

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· Anchored platelets release serotonin

· Serotonin causes blood vessel muscles to spasm

· Spasms narrow the blood vessel, decreasing blood loss

Coagulation

Slide 10.21aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· 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)

Coagulation

Slide 10.21bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· Thrombin joins fibrinogen proteins into hair-like fibrin

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

Blood Clotting

Slide 10.22Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· Blood usually clots within 3 to 6 minutes

· The clot remains as endothelium regenerates

· The clot is broken down after tissue repair

Undesirable Clotting

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· Thrombus· A clot in an unbroken blood vessel

· Can be deadly in areas like the heart

· Embolus· A thrombus that breaks away and floats

freely in the bloodstream

· Can later clog vessels in critical areas such as the brain

Bleeding Disorders

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· Thrombocytopenia· Platelet deficiency

· Even normal movements can cause bleeding from small blood vessels that require platelets for clotting

· Hemophilia· Hereditary bleeding disorder

· Normal clotting factors are missing

Heart DiseaseAtherosclerosis

◦Formed from fatty acid deposits that build-upPlatelets collect on outer surface

◦Release clotting factor, causes blood clot Thrombus If breaks free, embolus

◦Stroke, mycardial infarction, cononary thrombus

Causes of Heart DiseaseAgeGenetic FactorsHypertensionSmokingDiet