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Circulatory System -- Fill in the blanks style lecture notes with occasional extras about what was especailly important to remember and some further explanations.

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Biomedical Physio & Kines
BPK 142
Paul Lee

1 THE CIRCULATORY SYSTEM Anatomy of the Circulatory System The circulatory system is composed of the __heart_, blood vessels, and blood. Function of the circulatory system - transport essential materials (__oxygen__, fuel molecules, __hormones__, etc.) throughout the body to cells where they are needed and to collect waste materials (_carbon diaoxide___, _lactic acid__, urea, etc.) generated by the body's metabolic activity. Circulatory system is divided into two sections: (a) Pulmonary circuit - blood vessels going to and from the __lungs__ (b) __Systemic__ circuit - blood vessels going to and from the rest of the tissues of the body A. Heart The heart is a four chamber, __muscular___ __pump__ which propels blood through the blood vessels. Atria - the two _upper__ chambers of the heart Ventricles - the two lower chambers A __septum__ divides the left and right sides of the heart  two pumps. The right ventricle pumps blood through the ___pulmonary__ circuit while left ventricle pumps blood through the __systemic__ circuit. The wall of the left ventricle is _thicker__ than the wall of the right ventricle because the systemic circulation is a much higher pressure system than the pulmonary circulation. The direction of blood flow through the heart is controlled by unidirectional __valves__. Heart murmur - valve is damaged or does not close properly ---> blood regurgitates, causing a noise. The heart muscle (myocardium) is a specialized type of muscle - __cardiac_ muscle. Unlike skeletal muscle, all of the fibers or cells in cardiac muscle are anatomically __interconnected___ - functional syncytium. When one fiber contracts, all fibers contract. 2 The fibers of the atria are separate from the fibers of the ventricles. B. Conduction System of the Heart The heart's inherent contractile rhythm originates in an area of specialized tissue located in the posterior wall of the right atrium - the ___S-A node__, the normal pacemaker of the heart. Pathway of conduction of the wave of depolarization (cardiac impulse) across the heart: Atrial muscle fibers  contraction S-A node A-V node  A-V bundle  left and right bundle branches  _Purkinhie fibers__ which travel throughout the ventricular myocardium  simultaneous contraction of the left and right __ventricles__. The wave of depolarization is delayed in the A-V node for approximately 0.10 seconds in order to give the atria time to contract and empty their contents into the ventricles. Electrocardiography (ECG) - record the wave of depolarization as it passes across the heart using _electrodes__ on the surface of the body. Components of a normal ECG waveform: P wave - represents __atrial__ depolarization QRS wave - represents _ventricular___ depolarization T wave - represents ventricular __repolarization____ Arrhythmia - an irregularity in the ___rhythm____ of the heartbeat Diagnosing arrhythmias - look at heart rate, amplitude and shapes of the components of the ECG waveform, and time intervals. [Don’t need to know.] Examples of arrhythmias: a) atrial - tachycardia b) nodal - second and third degree heart blocks c) ventricular - premature ventricular contraction (PVC), ventricular tachycardia, ventricular fibrillation C. Blood Supply to the Heart The heart muscle is supplied by two major arteries which originate from the aorta just above the aortic valve - left _coronary__ artery and right __coronary_ artery. The large veins of the heart converge and empty into the right atrium. Since cardiac muscle is highly dependent on aerobic metabolism, it has a rich _blood__ supply. At rest, normal blood flow to the myocardium is about _5%_ of the total 3 cardiac output. Approximately ___70-80%__ of the oxygen is extracted from blood flowing in the coronary vessels compared to an average of _30%__ in other tissues. D. Blood Vessels Arteries - blood vessels that carry blood __away__ from the heart. They range in size from the aorta which is about 25 mm in diameter in man to those about 0.5 mm. Going from large arteries  medium-sized arteries  small arteries  _arterioles__, there is less elastic tissue in the wall of the artery and more __smooth__ muscle. Arterioles - arteries under 0.5 mm in diameter By constricting or relaxing the thick layer of _smooth_ muscle in the walls of arterioles, blood flow can be increased or decreased to various capillaries. Arteries and arterioles constitute the __high__ pressure part of the circulatory system. Capillaries - very tiny (10 microns diameter), thin-walled vessels. This is the site of exchange of __nutrients/wastes_____ and _gasesH__ between the blood and tissues. All other organs of the circulatory system exist only to serve the capillary beds. Capillaries in the human body: - surface area = 6000 sq. meters - 60,000 miles long - mass - twice the size of the liver Venules - small vessels which conduct venous blood from capillaries to __veins_ Veins - vessels that convey blood __toward__ the heart. In general, veins are of greater ___diameter__, but thinner-walled than the arteries with which they travel. There are both superficial and deep veins Veins also have _smooth__ muscle in their walls which allow them to change their diameter [List of arteries and veins that we need to memorize are in the lab manual, unit 16] The venules and the veins constitute the _low_ pressure part of the circulatory system. Valves - found in those _veins__ which carry blood against the force of __gravity__, especially in the veins of the legs Mechanisms involved in return of blood to the heart: a) __Pressure___ difference between left ventricle and right atrium - 120 mm Hg - 3 mm Hg = 117 mm Hg driving pressure b) Skeletal muscle pump - active muscles squeeze the _veins_ and push the blood towards the heart 4 c) Respiratory pump - decreased pressure in thoracic cavity during _inspiration__  easier for blood to return from lower portions of body via inferior vena cava  thoracic cavity  right atrium of heart E. Blood Blood is composed of specialized cells (red blood cells, white blood cells, and platelets) suspended in a liquid, _plasma__ which makes up 50 to 60% of blood by volume. The blood volum
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