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Chapter 18. Cardiovascular System. Cardiovascular = circulatory. Heart & closed system (arteries, veins, capillaries) Appears early in development – heartbeat at 4 wks. Heart.

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Chapter 18


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    1. Chapter 18 Cardiovascular System

    2. Cardiovascular = circulatory • Heart & closed system (arteries, veins, capillaries) • Appears early in development – heartbeat at 4 wks.

    3. Heart • In mediastinum – behind sternum, between 2nd & 6th ribs 2/3 to the left of midline, lies between 5th & 8th thoracic vertebrae • 4-chambered – size & shape of closed fist • CPR – cardiopulmonary resuscitation – heart compressions & artificial respiration • Apex – lower border of the heart, blunt point, lies on the diaphragm, points to the left • Base – upper border, below 2nd rib

    4. Size of heart influenced by age, body type, & state of contraction • Between puberty and 25 yrs., reaches adult shape & weight • 310g avg. male • 225g avg. female • Shape resembles individual (tall = elongated, stocky = transverse) – avg. length 12cm, width 9cm, depth 6cm

    5. Heart coverings • Pericardium – loose-fitting inextensible sac – 2 parts: a. fibrous portion – tough white fibrous sac b. serous portion – produces pericardial fluid – 2 layers: i. parietal layer = lining inside fibrous pericardium ii. visceral layer = adheres to heart 2. Epicardium = visceral layer

    6. Heart structure • Epicardium = outer layer – part of serous pericardium’s visceral layer • Myocardium = thick, contractile middle layer - intercalated discs join cardiac cells to make a continuous mass = syncytium – muscles can pass action potential along large area of heart = compresses with great force – cells are autorhythmic

    7. 3. Endocardium = delicate layer lining interior of myocardial wall - endothelial tissue - covers trabeculae – muscular beam-like projections - forms valves

    8. Chambers of the Heart • 4 chambers (2 atria & 2 ventricles) • Right & left sides are separated by the septum • Atria – upper chambers - “receiving chambers” – receive blood from veins - myocardial wall not very thick

    9. 2. Ventricles – lower chambers - “pumping chambers” – thicker myocardial wall than atria – left is thicker than right because pumps to most of the body http://www.phschool.com/science/biology_place/biocoach/cardio1/interior.html

    10. Valves – permit blood flow • 2 atrioventricular (AV) valves – guard opening between atria & ventricles (also called cuspid valves) - right has 3 flaps = tricuspid valve - left has 2 flaps = bicuspid/mitral valve - allows blood to flow from the atria to the ventricles without backflow

    11. 2 semilunar valves – opening between pulmonary artery or aorta and the ventricles - prevents backflow into ventricles - pulmonary semilunar valve – in between pulmonary artery & right ventricle - aortic semilunar valve – in between aorta & left ventricle ://www.phschool.com/science/biology_place/biocoach/cardio1/valves.html

    12. Skeleton of Heart • Fibrous structure of connected rings – support for heart valves and attachment of myocardium – also electrical barrier between atria & ventricles

    13. Flow of Blood through Heart • Right atrium  right AV valve (tricuspid)  right ventricle  pulmonary semilunar valve  pulmonary artery  lungs  pulmonary veins  left atrium  left AV valve (mitral)  left ventricle  aortic semilunar valve  aorta  everywhere in body except lungs (vena cavas return blood to heart) http://www.phschool.com/science/biology_place/biocoach/cardio1/vessels.html

    14. Blood Supply to Heart Tissue • Coronary arteries – provide myocardial cells with blood - come off of aorta - ventricles get more blood because they get it directly from the coronary arteries, atria get blood from branches

    15. Anastomoses – one or more branches from the artery – provides a detour for the blood to travel if the main route becomes blocked • Myocardial infarction – death of heart cells due to lack of blood flow • Cardiac veins – take oxygendepleted blood to the right atrium through coronary sinus (some drain directly into right atrium) - path closely follows the path of coronary arteries

    16. Conduction System of Heart • 4 structures (impulses): 1. Sinoatrial node (SA node, pacemaker) – right atrial wall, near superior vena cava 2. Atrioventricular node (AV node) – lower right atrium, along interatrial septum

    17. 3. Atrioventricular bundle (bundle of His) – 2 bundles of cardiac muscle fibers that extend from AV node down the sides of the interventricular septum 4. Purkinje fibers – small extensions from the AV bundle onto the ventricle walls http://www.phschool.com/science/biology_place/biocoach/cardio1/intconduct.html

    18. Blood Vessels • Artery – carries blood away from the heart - all carry oxygenated blood, EXCEPT pulmonary artery - color red - small arteries = arterioles

    19. 2. Vein – carries blood to the heart - all carry deoxygenated blood , EXCEPT pulmonary vein - color blue - small veins = venules - sinuses – very large venous space

    20. 3. Capillaries – microscopic vessels, carry blood from arteries to veins - sinusoids – take the place of capillaries in irregular, microscopic places Circulation: heart  arteries  arterioles  capillaries  venules  veins  heart

    21. Structure of blood vessels – 3 layers • Tunica adventitia – outermost layer – strong, flexible fibrous connective tissue - holds vessels open, prevents tearing during movement - thickest layer in veins - 2nd thickest in arteries

    22. 2. Tunica media – middle layer – smooth muscle tissue sandwiched by an elastic connective tissue layer - permits changes in diameter - innervated by nerves and supplied with blood by vasa vasorum (tiny vessels)

    23. 3. Tunica intima – innermost layer – endothelial tissue, smooth lining, continuous with heart *** only layer in capillaries - thin, allows for efficient exchange of materials - some capillary cells have fenestrations (numerous holes) http://www.phschool.com/science/biology_place/biocoach/cardio2/structure.html

    24. Functions of Capillaries • Most important because they deliver & collect essential materials • Very tiny, but very numerous – keep cells supplied with vital materials & rid injurious waste • “primary exchange vessels” of cardiovascular system

    25. Efficient exchange because capillaries are so small that blood flows at its slowest rate (maximum contact time between blood & tissue) – this is called microcirculation http://www.phschool.com/science/biology_place/biocoach/cardio2/capillary.html

    26. Function of Arteries • Arteries distribute blood to arterioles, arterioles distribute blood to capillaries • Also maintain normal blood pressure and circulation = “resistance vessels” • Smooth muscles in arteriole walls act as precapillary sphincters – reduce flow to capillaries when the muscles contract & constrict • Increase blood flow when they relax & dilate http://www.phschool.com/science/biology_place/biocoach/cardio2/factors.html

    27. Functions of Veins • Return blood to heart • Collectors and reservoir vessels • Can accommodate varying amount of blood without a change in blood pressure because of great ability to stretch capacitance = ease of stretch • Reservoir function is to maintain normal circulation • Heart is primary pump – keeps blood moving

    28. Circulatory Routes • Blood flow = from left ventricle through blood vessels of the entire body (except lungs) and back to the right atrium = systemic circulation • right ventricle to lungs to left atrium = pulmonary circulation

    29. Systemic circulation: left ventricle  ascending aorta  arteries  tissues, organs  arterioles  capillaries  venules  veins  vena cavas  right atrium http://www.phschool.com/science/biology_place/biocoach/cardio2/pathway.html

    30. Generals about arteries • Deliver blood from the heart to organs & tissues • Main artery can branch into arterioles, which branch into capillaries – these are called end-arteries – can cause serious damage if blocked

    31. Some arteries branch into other branches of the same or other arteries = arterial anastomoses – these are more common further from the heart • Aorta = main artery that serves the trunk - ascending aorta – first few cm, sends blood up out of left ventricle - descending aorta – sends blood down thoracic cavity (thoracic aorta) to abdominal cavity (abdominal aorta)

    32. Generals about veins • Return blood from body to heart to be oxygenated in the lungs • Superior vena cava – drains head, neck, thorax, upper extremity • Inferior vena cava – drains lower trunk & extremity

    33. Fetal Circulation • Differs before birth because fetal blood secures oxygen & nutrients from maternal blood instead of from fetal lungs and digestive organs

    34. Additional blood vessels & structures in fetus • Umbilical arteries (2) – carry fetal blood to the placenta • Placenta – attached to uterine wall – exchange oxygen and other materials between maternal & fetal blood – NO MIXING of fetal & maternal blood (diffusion)

    35. 3. Umbilical vein – returns oxygenated blood from the placenta * Umbilical cord = 2 umbilical arteries & umbilical vein 4. Ductus venosus – continuation of u. vein which drains into inferior vena cava

    36. 5. Foramen ovale – opening in the septum between the right & left atria so that the blood bypasses the fetal lungs because already oxygenated (and lungs not functioning yet) 6. Ductus arteriosus – connects the pulmonary artery with the descending thoracic aorta (another detour to avoid the lungs)

    37. Almost all fetal blood is a mixture of oxygenated & deoxygenated • Special structures non longer needed shortly after birth – umbilical vessels, ductus venosus, and ductus arteriosus become fibrous ligaments over time • Foramen ovale becomes functionally closed when newborn takes first breath – complete closure takes about 9 mos. • Separation of oxygenated & deoxygenated blood occurs after birth