Heart and Blood Vessels

1. Heart and Blood Vessels

2. Jugular vein Carotid artery Subclavian vein Superior vena cava Subclavian artery Inferior vena cava Aorta Renal vein Renal artery Common iliac vein Femoral vein Femoral artery Common iliac artery Great saphenous vein Figure 8.9

3. Three Types of Blood Vessels Transport Blood • Arteries • Carry blood away from heart • Blood under high pressure • Capillaries • Metabolic exchange with tissues • Veins • Return blood to heart • Very low pressure

4. Arteries Structure Thick-walled, three layers Innermost: endothelium Middle smooth muscle Outer: connective tissue Branch into arterioles Small arteries

5. Arterioles and Precapillary Sphincters • Blood flow • Heart → Arteries → Arterioles → Capillaries • Precapillary sphincters: control flow into capillaries • Vasodilation: increases blood flow to capillaries • Vasoconstriction: decreases blood flow to capillaries

6. Capillaries • Structure • Smallest blood vessels • Thin-walled: one cell-layer thick • Porous • Function: exchange of substances with interstitial fluid

7. Veins Structure Three layers, thin-walled Larger lumen than arteries Functions Serve as blood reservoirs Blood flow Capillaries → Venules → Veins → Heart

8. Venous Return to the Heart • Mechanisms in blood return • Contraction of skeletal muscles • One-way valves • Pressure changes associated with breathing

9. The Heart - Layers Surrounded by fibrous sac –pericardium Layers of the heart Epicardium: thin covering Myocardium: cardiac muscle Endocardium: thin lining

10. Heart Chambers • Four chambers • Right atrium • Left atrium • Right ventricle • Left ventricle

11. Heart Vessels • Superior and inferior vena cava • Carry low-oxygen blood into RA from body • Pulmonary trunk and arteries • Carry low-oxygen blood from RV to lungs • Pulmonary veins • Carry high-oxygen blood from lungs to LA • Aorta • Carries high-oxygen blood from LV to body

12. Aorta L. Pulmonary Artery Superior vena cava Pulmonary trunk R. Pulmonary Artery Inferior vena cava

13. Heart Valves • Prevent backflow • Two atrioventricular valves • Tricuspid valve • Between RA and RV • Mitral (bicuspid) valve • Between LA and LV • Two semilunar valves • Pulmonary valve • Between RV and pulmonary trunk • Aortic valve • Between LV and aorta

15. Two Circuits of Circulation • Pulmonary circuit • RV  Pulmonary trunk/arteries lungs (oxygen)  pulmonary veins  LA • Systemic circuit • LV  aorta  arteries of body  capillaries  veins  SVC and IVC  RA

16. Cardiac Cycle • Atrial systole • Both atria contract • AV valves open, semilunar valves closed • Ventricles fill • Ventricular systole • Both ventricles contract • AV valves close, semilunar valves open • Blood flows into arteries • Diastole • Both atria and ventricles relax • Semilunar valves close

18. Heart Sounds and Heart Valves Lub-dub heart sound Lub: closing of AV valves during ventricular systole Dub: closing of semilunar valves during ventricular diastole Heart murmurs Caused when blood flow is disturbed May be a sign of a defective valve

19. Cardiac Conduction System SA node Cardiac pacemaker Initiates heartbeat Pace can be modified by nervous system AV node Relays impulse AV bundle and Purkinje fibers Carry impulse to ventricles

20. Electrocardiogram (EKG/ECG) Tracks electrical activity of heart Characteristic pattern P wave: impulse across atria QRS complex: spread of impulse thru septum and ventricles T wave: end of electrical activity in ventricles EKGs can detect Arrhythmias Ventricular fibrillation

21. Blood Pressure Force blood exerts on walls of blood vessels Systolic pressure – highest pressure, during ventricular systole Diastolic pressure – lowest pressure, during ventricular diastole Measurement Use sphygmomanometer “Normal” readings Systolic pressure <120 mmHg Diastolic pressure <80 mmHg

22. Blood Pressure Hypertension: high blood pressure The silent killer At risk for stroke, heart attack, bleeding, kidney disease Hypotension: blood pressure too low Inadequate blood supply to organs Clinical signs – dizziness, fainting Causes – orthostatic, severe burns, blood loss

23. Regulation of Blood Pressure Baroreceptors: pressure receptors in arteries Steps in mechanism: Blood pressure rises, vessels stretched Signals sent to cardiovascular center in medulla oblongata Heart signaled to lower rate and force of contraction Arterioles vasodilate, reducing resistance to blood flow Combined effect lowers blood pressure

24. Regulation by Nervous and Endocrine Systems Medulla oblongata signals Sympathetic nerves – constrict blood vessels, raise blood pressure Parasympathetic nerves – dilate blood vessels, lower blood pressure Hormones: epinephrine (adrenaline) triggers sympathetic response Local requirements dictate local blood flow Exercise – increased blood flow and cardiac output

25. Cardiovascular Disorders Angina pectoris: chest pain narrowed coronary arteries impair blood flow Myocardial infarction/heart attack: permanent cardiac damage due to blockage in a coronary artery Congestive heart failure: decrease in pumping efficiency Embolism: blockage of blood vessels Aneurysm: ballooning of artery due to hypertension, hardening of arteries (atherosclerosis) Stroke: impaired blood flow to the brain

26. Heart Attack • Also known as myocardial infarction • Permanent damage to myocardium • Symptoms • Intense chest pain, nausea, heaviness in the chest, difficulty breathing, pain radiating to left arm, jaw, back, upper abdomen • Diagnosis • EKG • Blood test for cardiac enzymes • Prevention/Treatment • Clot-busting medications • CABG (bypass)

27. Aorta Vein grafts Plaque blocking blood flow Figure 8.19

28. Reducing Risk of Cardiovascular Disease Smoking – don’t Blood lipids – monitor cholesterol levels Exercise – regular and moderate Blood pressure – treat hypertension Weight – being overweight increases risk of heart attack and stroke Control of diabetes mellitus – early diagnosis and treatment delays onset of related problems Stress – avoid chronic stress