Cardiovascular System

Chapter

15

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Chapter 15Cardiovascular System

• heart• blood vessels

Average Size of Heart• 14 cm long• 9 cm wide

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Location of Heart

• posterior to sternum• medial to lungs• anterior to vertebral column• base lies beneath 2nd rib• apex at 5th intercostal space• lies upon diaphragm

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Coverings of Heart

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Wall of Heart

Three layers• endocardium

• forms protective inner lining• membrane of epithelial and connective tissues

• myocardium• cardiac muscle• contracts to pump blood

• epicardium• serous membrane• protective covering• contains capillaries and nerve fibers

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Heart Chambers

Right Atrium• receives blood from

• inferior vena cava• superior vena cava• coronary sinus

•sends blood to right ventricle

Left Atrium• receives blood from pulmonary veins•sends blood to left ventricle

Right Ventricle• receives blood from right atrium•sends blood to lungs

Left Ventricle• receives blood from left atrium•sends blood to body

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Heart Valves

Tricuspid Valve• right A-V valve• between right atrium and right ventricle

Bicuspid Valve (Mitral)• left A-V valve• between left atrium and left ventricle

Pulmonary Valve• semilunar valve• between right ventricle and pulmonary trunk

Aortic Valve• semilunar valve• between left ventricle and aorta

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Coronal Sections of Heart

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Heart Valves

Tricuspid Valve Pulmonary and Aortic Valve

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Skeleton of Heart

• fibrous rings to which the heart valves are attached

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Path of Blood Through the Heart

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Path of BloodThrough the Heart

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Blood Supply to Heart

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Blood Supply to Heart

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Angiogram of Coronary Arteries

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Heart Actions

Atrial Systole/Ventricular Diastole Atrial Diastole/Ventricular Systole

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Cardiac Cycle

Atrial Systole/Ventricular Diastole• blood flows passively into ventricles• remaining 30% of blood pushed into ventricles• A-V valves open/semilunar valves close• ventricles relaxed• ventricular pressure increases

Ventricular Systole/Atrial diastole• A-V valves close• chordae tendinae prevent cusps of valves from bulging too far into atria• atria relaxed• blood flows into atria• ventricular pressure increases and opens semilunar valves• blood flows into pulmonary trunk and aorta

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Heart Sounds

Lubb• first heart sound • occurs during ventricular contraction• A-V valves closing

Dupp• second heart sound• occurs at completion of ventricular contraction• semilunar valves closing

Murmur – abnormal heart sound15-18

Heart Sounds

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Cardiac Muscle Fibers

Cardiac muscle fibers form functional syncytia• group of cells that function as a unit• atrial syncytium• ventricular syncytium

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Cardiac Conduction System

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Cardiac Conduction System

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Muscle Fibers in Ventricular Walls

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Electrocardiogram

• recording of electrical changes that occur in the myocardium• used to assess heart’s ability to conduct impulses

P wave – atrial depolarizatoinQRS wave – ventricular depolarizationT wave – ventricular repolarization

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Electrocardiogram

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Electrocardiogram

A prolonged QRS complex may result from damage to the A-V bundle fibers

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Summary of Changes During Cardiac Cycle

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Regulation of Cardiac Cycle

• physical exercise• body temperature• concentration of various ions

• potassium• calcium

• parasympathetic impulses decrease heart action• sympathetic impulses increase heart action• cardiac center regulates autonomic impulses to the heart

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Regulation of Cardiac Cycle

Autonomic nerve impulses alter the activities of the S-A and A-V nodes

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Blood Vessels

• arteries• carry blood away from ventricles of heart

• arterioles• receive blood from arteries• carry blood to capillaries

• capillaries• sites of exchange of substances between blood and body cells

• venules• receive blood from capillaries

• veins• carry blood toward ventricle of heart

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Arteries and Arterioles

Artery• thick strong wall • endothelial lining• middle layer of smooth muscle and elastic tissue• outer layer of connective tissue• carries blood under relatively high pressure

Arterioles• thinner wall than artery• endothelial lining• some smooth muscle tissue• small amount of connective tissue• helps control blood flow into a capillary

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Walls of Artery and Vein

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Arteriole

• smallest arterioles only have a few smooth muscle fibers• capillaries lack muscle fibers

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Metarteriole

connects arteriole directly to venule

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Capillaries• smallest diameter blood vessels• extensions of inner lining of arterioles• walls are endothelium only• semipermeable• sinusoids – leaky capillaries

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Capillary Network

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Regulation of Capillary Blood Flow

Precapillary sphincters

• may close a capillary• respond to needs of the cells• low oxygen and nutrients cause sphincter to relax

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Exchange in the Capillaries

• water and other substances leave capillaries because of net outward pressure at the capillaries’s arteriolar ends• water enters capillaries’s venular ends because of a net inward pressure• substances move in and out along the length of the capillaries according to their respective concentration gradients

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Venules and Veins

Venule• thinner wall than arteriole• less smooth muscle and elastic tissue than arteriole

Vein• thinner wall than artery• three layers to wall but middle layer is poorly developed• some have flaplike valves• carries blood under relatively low pressure• serves as blood reservoir

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Venous Valves

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Blood Volumes in Vessels

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Arterial Blood Pressure

Blood Pressure – force the blood exerts against the inner walls of the blood vessels

Arterial Blood Pressure• rises when ventricles contract• falls when ventricles relax• systolic pressure – maximum pressure• diastolic pressure – minimum pressure

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Pulse

• alternate expanding and recoiling of the arterial wall that can be felt

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Factors That InfluenceArterial Blood Pressure

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Control of Blood Pressure

Controlling cardiac output and peripheral resistance regulates blood pressure

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Control of Blood Pressure

If blood pressure rises, baroreceptors initiate the cardioinhibitory reflex, which lowers the blood pressure

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Control of Blood Pressure

Dilating arterioles helps regulate blood pressure

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Venous Blood Flow

• not a direct result of heart action• depends on skeletal muscle contraction• depends on breathing• depends on venoconstriction

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Central Venous Pressure

• pressure in the right atrium• factors that influence it alter flow of blood into the right atrium• affects pressure within the peripheral veins• weakly beating heart increases central venous pressure• increase in central venous pressure causes blood to back up into peripheral vein

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Pulmonary Circuit

• consists of vessels that carry blood from the heart to the lungs and back to the heart

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Blood Flow Through Alveoli

• cells of alveolar wall are tightly joined together• the high osmotic pressure of the interstitial fluid draws water out of them

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Systemic Circuit

• composed of vessels that lead from the heart to all body parts (except the lungs) and back to the heart• includes the aorta and its branches• includes the system of veins that return blood to the right atrium

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Major Vessels of Arterial System

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Major Blood VesselsAssociated With Heart

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Aorta and Its Principal Branches

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Abdominal Aorta and Its Major Branches

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Arteries to Neck, Head, and Brain

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Cerebral Arterial Circle• Circle of Willis• formed by anterior and posterior cerebral arteries, which join the internal carotid arteries

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Arteries to Shoulder and Upper Limb

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Arteries to Thoracic Wall

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Arteries to Pelvic Region

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Main Branches of External Iliac Artery

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Major Vessels of the Venous System

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Major Veins of the Brain, Head, and Neck

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Major Veins of the Upper Limb and Shoulder

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Veins That Drain the Thoracic Wall

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Veins That Drain the Abdominal Viscera

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Hepatic Portal Vein

Hepatic portal vein drains one set of capillaries and leads to another set

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Main Veins of the Lower Limb and Pelvis

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Life-Span Changes

• deposition of cholesterol in blood vessels• heart enlarges• cardiac muscle cells die• fibrous connective tissue of heart increases• adipose tissue of heart increases• blood pressure increases• resting heart rate decreases

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Clinical Application

Arrhythmias

Ventricular fibrillation• rapid, uncoordinated depolarization of ventricles

Tachycardia• rapid heartbeat

Atrial flutter• rapid rate of atrial depolarization

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