Circulation - anatomy

• Blood vessels - carry blood from the heart to tissues (arteries and arterioles do this).
• Arteries and Arterioles - carry blood AWAY from the heart.
• Arteries have thick walls composed of elastic and muscular fiber.
• Arterioles are smaller branches of arteries.
• Capillaries - narrow microscopic arterioles. They are one cell layer thick.
• Veins and venules - Take blood from capillaries to the heart.
• Venules drain blood from capillaries and join to form a vein.
• Veins have valves which allow for easy flow.
• Skeletal muscle contraction also makes for easy flow.
• Veins contain about 75% of the bodys blood.
• Vena Cava is the body's biggest vein.
• Myocardium - a major portion of the heart that is composed of CARDIAC MUSCLE.
• Epithelial & fibrous tissue called pericardium covers the heart. It forms a tissue called PERICARDAL SAC.
• The pericardial sac contains lubricating liquid.
• THERE ARE 4 CHAMBERS IN THE HEART: two chambers on each side.
• The smaller chambers on top are called ATRIUM.
• The larger chamber below it is called VENTRICLE
• The left ventricle is larger than the right because the right only pumps blood to the lungs, but the left pumps blood to the entire body.
• There are valves i n between the atrias and ventricles called "ATRIOVENTRICULAR VALVES".
• Atrioventricular valves control the flow of blood between the chambers, and prevent backflow.
• The atrioventricular valve separating the right atrium from the right ventricle is called the Tricuspid valve.
• The atrioventricular valve between the left atrium and left ventricle is called the "Bicuspid valve"
• Strong fibrous strings - Chordae Tendinae support valves.
• Each ventricle has semilunar valves that are attached to blood vessels. Blood flows through these on its way out of the heart.
• The right ventricle has a pulmonary semilunar valve
• The left ventricle has an Aortic Semilunar Valve.
• PATH OF BLOOD THROUGH HEART IN STEPS: 1.) DEOXYGNATED BLOOD enters through the RIGHT ATRIUM.
• In the "lubdub " heartbeat sound, LUB comes from atria contracting while ventricles are relaxed.
• DUB is when ventricles contract while atria relax.
• The heartbeat sound is caused by vibrations in the heart when valves close.
• Systole - CONTRACTION OF HEART
• Diastole - RELAXTION of heart
• The cardiac cycle occurs 70 times per minute.
• The heart has a special tissue called Nodal Tissue. It has characteristics of both nerve and muscle tissue.
• Two nodal regions: SA Node (called pacemaker) located in the upper wall of the right atrium.
• SA nodes initiate the heartbeat. It also keeps the heartbeat regular.
• AV nodes: found in the base of the right atrium near the septum.
• How fast the heart goes is under nervous control
• Heart rate center in the brain is called MEDULLA OBLANGATA
• The Medulla Oblangata can speed up the heart rate and decrease the heart rate according to stimuli received by the AUTONOMIC NERVOUS SYSTEM