Anatomy and Physiology The Cardiovascular System
The cardiovascular systemcontains the heart, blood vessels (BVs), and blood. • Its functionis to transport oxygen and nutrients throughout the body. It does this by circulating blood. • An average body contains~5 liters of blood but the heart pumps~7,000 liters of blood daily while the heart contracts~2.5 billion times in an average lifetime.
The Heart: • This is a powerful pump • It is foundin the thoracic (chest) cavity behind the sternum and mediastinum • Average heart sizeis 14 X 9 cm • It is separated into chambers:2 right and 2 left (or 2 upper and 2 lower)
It is covered by thepericardium (a membrane) which has 2 layers: • Visceral pericardium(covers the heart; inner layer); a.k.a. epicardium • Parietal pericardium(covers the visceral pericardium; outer layer) • The pericardial cavityis the space between these layers which contains serous fluid • Pericarditisis inflammation of the pericardium usually caused by viral or bacterial infection.
This is composed of 3 layers: • Epicardiumprotects the heart (reduces friction); this contains connective tissue & adipose • Myocardiumis the middle layer; contains mostly cardiac tissue • Endocardiumis the innermost layer; contains epithelium & connective tissue and elastic & collagenous fibers The Heart Walls
There are 4 chambers: • The atria (sing. atrium) receive blood • The ventriclessend blood (from the atria) • The right & left chambers are separated by a wall called the septum. • There are several valves in the heart that provide the main function of regulating blood flow in ONE direction only (prevents backflow). Heart Chambers and Valves:
The Heart Walls and Chambers: http://www.texasheartinstitute.org/HIC/Topics/images/myocard.jpg
Atrioventricular valves(a.k.a.A-V valvesb/c they are between the atria and ventricles): there is 1 on the right & 1 on the left. • Tricuspid valveis between the right atrium and ventricle; blood flows from the right atrium to the right ventricle. • Bicuspid valveis between the left atrium and ventricle; blood flows from the left atrium to the left ventricle. • Pulmonary valve: at the base of the pulmonary trunk; this enables blood to leave the heart (and flow to the lungs thru thepulmonaryarteries); blood flows out of the right ventricle • Aorta valve: at the base of theaorta (a large artery); blood flows out of the left ventricle Heart Valves:
Heart Valves: http://www.google.com/imgres
Pulmonary Circulation: (heart to lungs) • Pulmonary arteries: carry blood to lungs • Pulmonary veins: return blood from lungs to heart (left side) Systemic Circulation: (heart to rest of body) • Aorta: main artery (largest) that pumps blood from heart to all body tissues (except lungs) • Superior & Inferior Vena Cava: bring blood back into heart from body tissues.
Blood Flow Path: begins with O2 poor blood: Right Atrium Right Ventricle Pulmonary Trunk Pulmonary Arteries Alveoli of lungs for O2 Pulmonary Veins Left Atrium Left Ventricle Aortic Valve Aorta Body
This coordinates the cardiac cycle • Contains the sinoatrial node(a.k.a.S-A node) located beneath the epicardium: • This acts as the pacemaker of the heart b/c it is rhythmic (meaning it starts impulses, thereby generating the heart’s rhythm). • Contains the atrioventricular node(a.k.a.A-V node) located beneath the endocardium • This acts as the impulse conduction pathway between the atria and ventricles The Cardiac Conduction System:
Cardiac Cycle & Sounds: http://www.google.com/imgres • The cardiac cycleis 1 heart contraction AND 1 heart relaxation, or a complete heartbeat. • Atrial systoleis atrial contraction while atrial diastoleis atrial relaxation. • When listening to the heartbeat with a stethoscope, it sounds like lubb-dupp. The lubbis ventricular contraction while the duppis ventricular relaxation.
A murmuris a sound that is heard when there is slight damage to a valve of the heart. • The damage is the leaking of blood through a valve b/c the valve does not completely close. http://www.google.com/imgres
An electrocardiogram (a.k.a.ECG) is a recording of electrical charges in the myocardium during a cardiac cycle. • Heart problems can be detected with the use of an ECG. http://www.google.com/imgres http://www.google.com/imgres
Heart Regulation: The heart rate can change(temporarily) by certain factors: • Neural (ANS) controls: stress • Hormones & ions: changes or imbalances in electrolytes (Ca++, Na+, K+), thyroxine, or epinephrine • Physical factors: temperature, age, gender http://www.google.com/imgres
These include the arteries, arterioles, capillaries, venules and veins. • The arteriestake blood away from the heart; vasoconstriction & vasodilation(opening & closing of an artery) controls blood flow and blood pressure. Blood Vessels (BVs): Oxygenated Blood (red) http://cache.eb.com/eb/image?id=92806&rendTypeId=34
Arteries (& Veins) have 3 layers: • Tunica intimais the innermost layer containingendothelium (internal epithelium) which helps prevent blood clotting • Tunica mediais the middle layer • Tunica externais the outermost layer • The arteriolescome from the arteries (they are smaller arteries) http://www.medicalook.com/systems_images/Veins.jpg
Capillariesare the smallest BVs • Found between arteries and venules • Gases & nutrients are exchanged thru their membranes (semipermeable) • This occurs by diffusion, filtration & osmosis • The amount of capillaries found within a tissue varies according to the tissue’s O2 requirement (more O2 required=more capillaries)
Venulesare small veins • Veinscarry blood to the heart from the body; these run parallel to arteries. • Veins have 3 layers (like arteries) but not as distinct • Thinner walls than arteries • Less elastic but greater diameter than arteries • Manycontain valves which act as flaps preventing backflow of blood
Varicose Veins: http://www.brvsa.com/images/varicose2.jpg http://www.brvsa.com/venous.htm http://www.wakeradiology.com/Portals/0/Varicose1.jpg
Vital Signs: Arterial pulse, blood pressure, rate of respiration, and body temperature. • Pulse: each beat of the left ventricle as it travels through the arterial system. Physiology of Circulation:
A pulse is felt at certain points on the body. This is due to an artery close to the surface of the skin. • This is the contraction and relaxation of an arterial wall. http://www.google.com/imgres
Blood pressurecan be defined as the force of blood against BVs. • When the ventricles contractwith the maximum pressure is thesystolic pressure. • When the ventricles relax with the lowest pressure isthediastolic pressure. http://www.google.com/imgres Blood Pressure:
Heart action: this determines the total volume of blood entering the arterial system. • Blood volume: this is ~5 liters or 8% of body weight. This equals the sum of the elements and plasma. • Blood volume is proportional to bp (normally). When blood volume decreases, bp drops; dehydrationwill also influence bp b/c it affects blood volume. Factors that Influence Blood Pressure: http://www.google.com/imgres
Factors that Influence Blood Pressure: • Peripheral Resistance: this is the force of the friction between blood and blood vessels. This can hinder blood flow. • Blood viscosity: this is the ease with which blood particles move past each other. Greater viscosity=greater resistance. • Thicker blood (meaning it has more parts) creates higher bp. http://www.google.com/imgres
Additional Factors that may influence blood pressure: • ANS • Renal Factors (kidneys) • Temperature • Hormones • Diet Factors that Influence Blood Pressure:
Look up in text or online! • Know the following: endocarditis, angina, infarct, ischemia, fibrillation, tachycardia, bradycardia, congestive heart failure, pulmonary edema, varicose veins, thrombophlebitis, hypotension, hypertension, atherosclerosis, and coronary artery disease