CIRCULATION AND BLOOD Anatomy Review -- Blood Vessel Structure and Function the blood vessels of the body form a closed delivery system that begins and ends with the heart Should know: Pathway of systemic circuit and pulmonary circuit Systemic circuit consists of blood vessels that carry blood to and from body tissues, where oxygen and nutrients are released from blood and CO2 and other wastes are picked up; left side of heart pumps blood through systemic circuit Pulmonary circuit consists of blood vessels that carry blood to and from lungs, where CO2 is unloaded from blood and oxygen is picked up; right side of heart pumps blood through pulmonary circuit Relative roles of lining epithelium, smooth muscle, and connective tissue Lining epithelium is tissue that lines blood vessels, the heart, and cavities of the digestive and respiratory systems Smooth muscle is type with no externally visible striations. Occurs in walls of hollow organs, such as blood vessels and the stomach Connective tissue provides binding and support Blood Vessel Walls Made up of 3 tunics and a lumen, a cavity through which blood passes Tunica intima [endothelium] Innermost layer of blood vessel; consists of endothelium underlain by thin connective tissue; forms smooth, friction-reducing lining of blood vessel Tunica Media Middle layer of blood vessel composed largely of circularly-arranged smooth muscle cells and elastic fibers in sheets; muscle cells contract and relax, changing diameter of vessel; elastin allows vessels to stretch and recoil Tunica adventitia Outermost layer of blood vessel; mostly loosely woven collagen fibers; protects and binds blood vessel to surrounding structures Comparison of arteries, capillaries, and veins Artery Transports blood from heart Exposed to highest pressures of any vessels Has thicket tunica media of any vessels Elastic arteries Type with most elastin in tunica media Closest to heart Expands for systole and recoils for diastole Forms a kinda peristaltic movement Muscular arteries Most smooth muscle in tunica media of 3 types Delivers blood to specific organs Activity regulated by vasomotor fibers [sympathetic nerves] Pressure [that was high in aorta] begins to decline here Arterioles Smallest type of artery Usually where capillaries branch off Capillary Smallest type of blood vessel Capillary walls consist only of thin tunica intima [endothelial cells] Allows for exchanges of materials between blood and tissue cells Capillary bed [where most are located] Made up of precapillary sphincter, shunt, and true capillary Interweaving networks of capillaries that consists of a shunt that connects the arteriole and venule and true capillaries, where exchanges take place b/t blood and tissue cells Blood flow no longer pulses and pressure continues to drop Veins Venous valve One-way valve found in veins where blood flow opposes gravity, as in limbs Prevents backflow as blood travels towards heart Formed from folds of tunica intima Muscular pump Contracting skeletal muscles press against veins, forcing blood through one-way venous valves Respiratory pump The pressure changes occurring during breathing that enhance venous return During inhalation, pressure decreases in the thoracic cavity and increases in the abdominal cavity creating an upward ?sucking? effect that pulls blood towards the heart Type of blood vessel that carries blood towards the heart Walls are thinner and lumens are larger than in arteries Tunica adventitia is heaviest cell layer Venule Usually where capillaries branch off Smallest type of vein Anatomy Review: The Heart The heart is the transport system pump; the delivery routes are the blood vessels. Using blood as the transport medium, the heart propels oxygen, nutrients, wastes, and other substances to and past the body cells. Heart anatomy Superior vena cava Vein that returns blood to the right atrium from body regions superior to diaphragm Right coronary artery Branches from base of aorta and supplies oxygenated blood to right side of heart Right atrium Heart chamber that receives oxygen-poor blood from the body Chordae tendineae Cords [?heart strings?] that anchor AV valve flaps to the papillary muscles Papillary muscle Muscle bundles that project from ventricular walls Connected to AV valve flaps via chordae tendineae Contract to hold AV valve flaps in closed position Right ventricle Heart chamber that pumps oxygen-poor blood to the lungs Inferior vena cava Vein that returns blood to right atrium from body regions inferior to diaphragm Aorta Largest artery in the body Receives oxygen-rich blood from left ventricle Tricuspid valve Prevents backflow into the right atrium when right ventricle contracts Has 3 flaps Also known as right atrioventricular [AV] valve Coronary sinus Vessel that collects oxygen-poor blood from cardiac veins Empties blood into right atrium Fossa ovalis Shallow depression in the interatrial septum marking the spot where an opening, the foramen ovale, existed in fetal heart Pulmonary semilunar valve Valve at entrance to pulmonary trunk Prevents backflow into right ventricle Pulmonary trunk Vessel that receives oxygen-poor blood from the right ventricle Splits into the right and left pulmonary arteries, which carry blood to the lungs Left atrium Chamber that receives oxygen-rich blood from the lungs Left pulmonary valve Artery that branches off the pulmonary trunk to carry oxygen-poor blood to the left lung Left ventricle Heart chamber that pumps oxygen-rich blood to the body Anterior interventricular artery Branch of left coronary artery Supplies oxygenated blood to interventricular septum [which partitions the ventricles] and anterior walls of both ventricles Great cardiac vein Cardiac vein in anterior interventricular sulcus Collects oxygen-poor blood from capillary beds of myocardium Left ventricle Chamber that pumps oxygen-rich blood to the body Pulmonary circuit carries blood to and from lungs to pick up oxygen Involves right side of the heart Systemic circuit carries blood to and from body tissues to release nutrients and oxygen and to pickup CO2 and wastes Involves left side of the heart Cardiac muscle is made up of cardiac myofibrils, intercalated discs [interlocking], and nuclei Intrinsic Conduction System The intrinsic conduction system sets the basic rhythm of the beating heart. It consists of autorhythmic cardiac cells that initiate and distribute impulses [action potentials] throughout the heart. Intrinsic conduction system Coordinates heart activity by determining direction and speed of heart depolarization Anatomy SA node Mass of autorhythmic cells located in the right atrial wall near the entrance of the superior vena cava (SA = sinoatrial) Generates impulses about 75 times per minute Sets pace for entire heart [i.e. pacemaker] Internodal pathway Carries impulses from SA node to AV node AV node [AV=atrioventricular] Mass of autorhythmic cells located in the inferior portion of the interatrial septum above the tricuspid valve Each impulse is delayed briefly, allowing atria to contract before ventricles AV bundle Autorhythmic cells located in the inferior part of the interatrial septum Only electrical connection between atria and ventricles Also known as bundle of His Bundle branches Two branches resulting from splitting of the AV bundle Conveys impulses down the interventricular septum Purkinje fibers Fibers that run through the interventricular septum, penetrate the heart apex, then turn superiorly and ramify in the ventricular walls, conveying impulses throughout the ventricles That list is the pathway of depolarization Action potentials, which spread from the autorhythmic cells of the intrinsic conduction system to the contractile cells, are electrical events. Subsequent contraction of the contractile cells is a mechanical event that causes a heartbeat ECG wave P Wave = atrial depolarization QRS complex = ventricular depolarization T wave = ventricular repolarization
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