Circulation — The Heart and Blood Vessels

1. Circulation — The Heart and Blood Vessels Chapter 9

2. Circulatory System • Accepts oxygen, nutrients, and other substances from the respiratory and digestive systems and delivers them to cells • Accepts carbon dioxide and wastes from cells and delivers them to respiratory and urinary systems for disposal

3. Functional Connections food, water intake oxygen intake DIGESTIVE SYSTEM RESPIRATORY SYSTEM elimination of carbon dioxide nutrients, water, salts carbon dioxide oxygen CIRCULATORY SYSTEM URINARY SYSTEM water, solutes elimination of food residues rapid transport to and from all living cells elimination of excess water, salts, wastes

4. Cardiovascular System • Heart • Blood vessels • Arteries • Arterioles • Capillaries • Venules • Veins

5. Location of the Heart • Heart is about size of a fist • Lies in thoracic cavity between the lungs • Enclosed in the pericardium

6. Layers of Heart Wall • Inner layer of the pericardium is the outer layer of the heart wall • Beneath that is the myocardium, the thick cardiac muscle tissue • Thin endocardium lines the chambers of the heart and blood vessels

7. Heart Structure • Each side has two chambers • Upper atrium • Lower ventricle • Valves between atria and ventricles

8. Heart Valves three cusps two cusps left AV valve (bicuspid or mitral valve) right AV valve (tricuspid) left semilunar valve right semilunar valve Heart from above with atria removed

9. Cardiac Cycle • Contraction phase is systole • Relaxation phase is diastole Mid to late diastole . Early diastole Ventricular systole

10. Direction of Blood Flow • Superior and inferior vena cava • Right atrium • Right ventricle • Pulmonary artery • Pulmonary veins • Left atrium • Left ventricle • Aorta

11. Pulmonary Circuit right pulmonary artery left pulmonary artery Short loop that oxygenates blood capillary bed of left lung capillary bed of right lung pulmonary trunk (to systemic circuit) (from systemic circuit) pulmonary veins heart lungs

12. Systemic Circuit capillary beds of head and upper extremities aorta (to pulmonary circuit) (from pulmonary circuit) Longer loop that carries blood to and from body tissues heart capillary beds of other organs in thoracic cavity capillary bed of liver capillary beds of intestines

13. Hepatic Portal System • Carries blood from capillaries in digestive organs to capillaries in the liver • Enables liver to detoxify substances from digestive tract before they are carried to the body

14. Statins: Heart-Saving Drugs • Interrupt the metabolic pathway in the liver that creates cholesterol • Increase receptor proteins that bind with and remove LDL cholesterol • Raise blood level of “good” cholesterol (HDLs) • Lower blood levels of triglycerides

15. Conduction and Contraction SA node • SA node in right atrium is pacemaker • Electrical signals cause contraction of atria • Signal flows to AV node and down septum to ventricles

16. Nervous System • Triggers the contraction of skeletal muscle • Can only adjust the rate and strength of cardiac muscle contraction • Centers for neural control of heart functions are in the spinal cord and parts of the brain

17. Blood Pressure • Highest in arteries, lowest in veins • Systolic pressure is peak pressure (ventricular contraction) • Diastolic pressure is the lowest • Greatest pressure drop is in arterioles

18. Arteries, Arterioles, Capillaries • Arteries: main transporters of oxygenated blood • Arterioles: diameter is adjusted to regulate blood flow • Capillaries: diffusion occurs across thin walls

19. Venous System • Blood flows from capillaries into venules, then on to veins • Veins are large-diameter vessels with some smooth muscle in wall • Valves in some veins prevent blood from flowing backward

20. Controlling Blood Pressure • Cardiac output adjusted by controls over rate and strength of heartbeat • Total resistance is controlled by vasoconstriction of arterioles • Baroreceptor response is main short-term control of blood pressure

21. Velocity of Flow Varies • Volume of blood flowing through vessels always has to equal heart’s output • Flow velocity is highest in large-diameter transport vessels • Flow velocity is slowest in capillary beds; blood spreads out into many vessels with greater total cross-sectional area

22. Diffusion Zone • Capillary beds are the site of exchange between blood and interstitial fluid • Capillary is a single sheet of epithelial cells • Flow is slow; enables gases to diffuse across membranes of blood cells and across endothelium

23. Bulk Flow • Movement of water and solutes in response to fluid pressure to venule inward-directed osmotic movement from arteriole outward-directed bulk flow cells of tissue

24. Net Bulk Flow • Normally, ultrafiltration only slightly exceeds reabsorption • Fluid enters interstitial fluid and eventually returns to blood by way of lymphatic system • High blood pressure causes excessive ultrafiltration and results in edema

25. Risk Factors for Cardiovascular Disease • Smoking • Gender (maleness) • Genetic factors • Old age • High cholesterol • Obesity • Lack of exercise • Diabetes mellitus

26. Hypertension • Blood pressure above 140/90 • Tends to be genetic • May also be influenced by diet • Contributes to atherosclerosis • “Silent killer” - few outward signs

27. Atherosclerosis • Arteries thicken, lose elasticity, and fill up with cholesterol and lipids • High LDL level increases risk

28. Arrhythmias • Bradycardia - slow heart rate • Tachycardia - 100+ beats/minute • Atrial fibrillation - irregular heartbeat • Ventricular fibrillation - uncontrolled contraction of ventricles; quickly fatal

29. Lymphatic System • The circulatory system is leaky • Some fluid is forced out of the smallest vessels and into the interstitial fluid • Vessels of the lymphatic system pick up this fluid, filter it, and return it to the circulatory system

30. Lymph Vascular System • Fluid enters lymph capillaries • Capillaries merge into lymph vessels • Lymph vessels converge into ducts that funnel fluid into veins in the lower neck

31. Lymph Nodes • Located at intervals along lymph vessels • Act as a filter for lymph • Contain lymphocytes that can recognize a foreign invader

32. Lymphoid Organs • Central to the body’s defense • Tonsils • Spleen • Thymus gland