Circulatory System Provides O 2 and nutrients to all body cells and removes wastes.

1. Circulatory SystemProvides O2 and nutrients to all body cells and removes wastes.

2. Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm • Coverings of the heart • Enclosed in a layered pericardium • Pericardial space between layers is fluid filled • Wall of heart • Endocardium – inner layer • Myocardium – middle; mostly cardiac muscles • Epicardium (visceral pericardium) – outer layer

3. Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm • Heart Chambers, Valves & Blood Flow • Heart is divided into 4 chambers – 2 atria, 2 ventricles • R. chambers and valves – O2 poor blood • R. atrium receives blood from superior & inferior vena cava & coronary sinus • Blood passes through tricuspid valve to R. ventricle • Blood passes through pulmonary semilunar valve to L. & R. pulmonary arteries ***only arteries to carry O2 poor blood***

4. Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm • Heart Chambers, Valves & Blood Flow • L. chambers and valves – O 2 rich • Blood returns from lungs via L. & R. pulmonary veins ***only veins to carry O2 rich blood*** • O2 rich blood dumps into L. atrium • Blood passes through bicuspid valve into L. ventricle • Blood passes through aortic semilunar valve to aorta • Distributed to the rest of body (systemic circulation)

5. Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

6. Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

7. Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm • http://www.youtube.com/watch?v=mH0QTWzU-xI (blood flow through the heart) • http://vimeo.com/8321006 (animation - blood flow)

8. Actions of the Heart • Cardiac Cycle • Pressure within chambers rises & falls in repeated cycles • Contraction of heart – systole Relaxation of heart – diastole • When atria are relaxes (atrial diastole) blood flows into them from veins (about 70% of blood flows directly into ventricles) • When atria contract (atrial systole) the remaining 30% of blood flows into ventricles • As ventricles contract (ventricular systole) bicuspid/tricuspid valves are pressed closed; blood flows either to lungs or body • Stroke volume = volume of blood ejected from ventricles • http://www.youtube.com/watch?v=jLTdgrhpDCg

9. Actions of the Heart • Heart Sounds • Described as lub-dub • Due to the vibrations produced by the blood & valve movements • Lub – occurs as A-V valves are closing/ventricles contract • Dub – occurs as semilunar valves are closing/ventricles relax

10. Actions of the Heart • http://www.youtube.com/watch?v=te_SY3MeWys

11. Actions of the Heart • Cardiac Conduction System – Fig. 12-7 • Composed of specialized cardiac muscle tissue and functions to initiate and conduct depolarization waves through the myocardium • Signal is initiated by S-A node located in upper part of R. atrium (known as the pace maker of the heart). • Ability to excite themselves • Impulses spread into surrounding myocardium • Atria contract

12. Actions of the Heart • Cardiac Conduction System – Fig. 12-7 • Impulses travel slowly from S-A node (so atria have time to contract) to A-V node located in lower part of R. atrium • Impulses now travel quickly to A-V bundle (bundle of His) and then to Purkinje fibers • Ventricles contract – muscle fibers in ventricular walls are arranged in whorls that “wring” blood out of ventricles

13. Actions of the Heart • Regulation of the Cardiac Cycle • Heartbeat is affected by physical exercise, body temp. and concentration of various ions • Parasympathetic impulses cause a decrease in heart rate • Sympathetic impulses cause an increase in heart rate

14. Blood Vessels – Closed circuit of tubes; - Fig.

15. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Arteries & Arterioles • Adapted to carry relatively high pressure blood AWAY from the heart • Arterioles are branches of arteries • Walls of arteries consist of layers of endothelium, elastic membrane, smooth muscle, and connective tissue ***walls of arteries are thicker than walls of veins or capillaries***

16. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Capillaries – form connections between arterioles & venules • Consist of a single layer of cells that forms a semipermeable membrane • Capillary density varies directly with tissue metabolic rates • Muscle & nerve – rich supply • Cartilaginous, epidermis, cornea (low metabolic rates) lack capillaries

17. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Capillaries – form connections between arterioles & venules • Capillary flow is regulated by opening & closing of precapillary sphincters • Open when cells are low in O2 • Close when cellular needs are met

18. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Capillaries – form connections between arterioles & venules • Gasses, nutrients, and metabolic by-products are exchanged between capillary blood & tissue fluid • Diffusion provides the most important means of transport • Filtration due to the hydrostatic pressure of blood causes outward movement of fluid at the arterial end of capillary • Osmosis causes a net inward movement of fluid at the venule end of a capillary

19. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Capillaries – form connections between arterioles & venules

20. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Capillaries – form connections between arterioles & venules

21. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 • Veins & venules • Venules continue from capillaries and merge to form veins • Veins carry blood TOWARD the heart • Contain valves to keep blood moving toward the heart • Venous walls are similar to arterial walls, but are thinner and contain less muscle and elastic tissue.

22. Blood Vessels – Closed circuit of tubes; - Fig. 12-9 http://www.youtube.com/watch?v=HNuPWdfjDoc

23. Blood Pressure • Blood pressure is the force exerted by blood against the insides of the blood vessels – Fig. 12-16 (also see – Clinical Application pg. 327) • http://www.youtube.com/watch?v=0L3hV-PLlC4 (how to take blood pressure) • Arterial blood pressure • Produced primarily be heart action; rises & falls with phases of the cardiac cycle • Systolic pressure occurs when the ventricles contract; diastolic pressure occurs when the ventricles relax

24. Blood Pressure

25. Blood Pressure • Factors that influence arterial blood pressure • Blood Volume • An increase in volume causes an increase in pressure • A decrease in volume causes a decrease in pressure

26. Blood Pressure • Factors that influence arterial blood pressure • Heart Action • Volume of blood discharged from L. ventricle with each contraction is called stroke volume (70ml – 75ml) • Cardiac output = volume discharged in 1 minute • Cardiac output = stroke volume x heart rate (ex. 75ml x 70 beats/min. = 5250 ml/min) • If stroke volume increases & heart rate stays the same the cardiac output increases causing an increase in blood pressure

27. Blood Pressure • Factors that influence arterial blood pressure • Peripheral Resistance – friction between the blood and the walls of the blood vessels • An increase in PR causes an increase in bp • A decrease in PR causes a decrease in bp • Viscosity – physical property – thickness • An increase in viscosity causes an increase in bp • A decrease in viscosity causes a decrease in bp

28. Blood Pressure • Control of Blood Pressure – heart rate is regulated by different portions of medulla oblongata • Venous Blood Flow • Not a direct result of heart action; it depends on skeletal muscle contraction, breathing movements, and venoconstriction • Many veins contain flaplike valves that prevent blood from backing up

29. Blood Pressure • Central Venous Pressure – pressure in the R. atrium • Influenced by factors that alter flow of blood into R. atrium • Ex. – A weak heart causes an increase in pressure in R. atrium which causes the flow of blood to slow which causes pressure to increase in peripheral veins

30. Paths of Circulation

31. Paths of Circulation • Pulmonary Circulation • Composed of vessels that carry blood from R. ventricle to lungs and back to l. atrium • Pulmonary capillaries contain lower pressure than systemic capillaries (R. ventricle contracts with less force than L. ventricle • Exchange of oxygen and carbon dioxide; tightly joined epithelial cells of alveoli prevent most substance from entering alveoli

32. Paths of Circulation • Pulmonary Circulation

33. Paths of Circulation • Systemic Circulation • http://www.youtube.com/watch?v=0jznS5psypI • Vessels that carry blood from L. ventricle to body cells and back to R. atrium • Includes aorta & branches & system of veins • Hepatic portal – the route of blood flow through the liver (fig. 12-14); blood passes through 2 capillary beds before returning to the heart • Renal circulation – the route of blood through kidneys (fig. 17-3 pg. 443); blood passes through 2 capillary beds before returning to the heart • Coronary Circulation – The delivery of oxygen & nutrients andthe removal of carbon dioxide & wastes from cardiac muscletissue

34. Paths of Circulation • Hepatic Portal Circulation

35. Paths of Circulation • Renal Circulation

36. Paths of Circulation • Coronary Circulation

37. Fetal Blood & Circulation • Blood is carried between the placenta and the fetus by umbilical vessels • Fetal blood carries more O2 than maternal blood • Blood enters fetus through umbilical vein (O2 rich) and partially bypasses the liver by means of the ductusvenosus • Blood enters R. atrium & partially bypasses the lungs by means of the foramen ovale • Blood entering the pulmonary trunk partially bypasses the lungs by means of the ductusarteriosus • Blood enters umbilical arteries from the internal iliac arteries (O2 poor)

38. Fetal Blood & Circulation http://www.youtube.com/watch?v=OV8wtPYGE-I