Anaphy Cardiovascular
Cards (42)
- The Cardiovascular SystemA closed system of the heart and blood vesselsThe heart pumps bloodBlood vessels allow blood to circulate to all parts of the body
- Functions of the cardiovascular systemTransport oxygen, nutrients, cell wastes, hormones to and from cells
- Coverings of the heart§ Pericardium—a double-walled sac§ Fibrous pericardium is loose and superficial§ Serous membrane is deep to the fibrous pericardium and composed of two layers1. Parietal pericardium: outside layer that lines the inner surface of the fibrous pericardium2. Visceral pericardium: next to heart; also known as theepicardium§ Serous fluid fills the space between the layers of pericardium, called the pericardial cavity
- Anatomy of the Heart§ Size of a human fist, weighing less than a pound§ Located in the thoracic cavity, between the lungs in the inferior mediastinum§ Orientation§ Apex is directed toward left hip and rests on the diaphragm§ Base points toward right shoulder
- Functions of the PERICARDIUMKeeps the heart contained within the chest cavityPrevents the heart from over expanding when blood volume increasesLimits heart motionReduces friction between the heart and surrounding tissuesProtects the heart against infection
- Walls of the heart1. Epicardium (Pericardium)Outside layer; the visceral pericardium2. MyocardiumMiddle layer; thickest layerMostly cardiac muscleThe layer that contracts3. EndocardiumInner layer known as endotheliumLines the inner heart chambers, covers heart valves and continuous with the endothelium of large blood vessels
- § Four chambers of the heart§ Atria (right and left)§ Receiving chambers§ Assist with filling the ventricles§ Blood enters under low pressure§Ventricles (right and left)§ Discharging chambers§ Thick-walled pumps of the heart§ During contraction, blood is propelled into circulation
- Heart functions as a double pumpArteries carry blood away from the heartVeins carry blood toward the heartDouble pumpRight side works as the pulmonary circuit pumpLeft side works as the systemic circuit pump
- Pulmonary circulation-Blood flows from the right side of the heart to the lungs and back to the left side of the heart-Blood is pumped out of right side through the pulmonary trunk, which splits into pulmonary arteries and takes oxygen-poor blood to lungs-Oxygen-rich blood returns to the heart from the lungs via pulmonary veins
- Systemic circulation§ Oxygen-rich blood returned to the left side of the heart is pumped out into the aorta§ Blood circulates to systemic arteries and to all body tissues§ Left ventricle has thicker walls because it pumps blood to the body through the systemic circuit§ Oxygen-poor blood returns to the right atrium via systemic veins, which empty blood into the superior or inferior vena cava
- Cardiac Circulation§ Blood in the heart chambers does not nourish the myocardium§ The heart has its own nourishing circulatory system consisting of:§ Coronary arteries—branch from the aorta to supply the heart muscle with oxygenated blood§ Cardiac veins—drain the myocardium of blood§ Coronary sinus—a large vein on the posterior of the heart; receives blood from cardiac veins§ Blood empties into the right atrium via the coronary sinus
- Semilunar valves—between ventricle and artery§ Pulmonary semilunar valve§ Aortic semilunar valve§ Function:§ Closed during heart relaxation§ Open during ventricular contraction
- Heart Valves§ Allow blood to flow in only one direction, to prevent backflow§ Valves open and close in response to pressure changes in the heart§ Atrioventricular (AV) valves—between atria and ventricles§ Left AV valve: bicuspid (mitral) valve§ Right AV valve: tricuspid valve§ Function:§ Anchored the cusps in place by chordae tendineae to the walls of the ventricles§ Open during heart relaxation, when blood passively fills the chambers§ Closed during ventricular contraction
- Cardiac Circulation§ Blood in the heart chambers does not nourish the myocardium§ The heart has its own nourishing circulatory system consisting of:§ Coronary arteries—branch from the aorta to supply the heart muscle with oxygenated blood§ Cardiac veins—drain the myocardium of blood§ Coronary sinus—a large vein on the posterior of the heart; receives blood from cardiac veins§ Blood empties into the right atrium via the coronary sinus
- What makes the heart beat?§ Intrinsic conduction system (nodal system) of the heart§ Built into the heart tissue and sets its basic rhythm§ Composed of specialized tissue§ Causes heart muscle depolarization in one direction only (atria to ventricles)§ Heart rate 75 beats per minute§ Cardiac muscle contracts spontaneously and independently of nerve impulses§ Spontaneous contractions occur in a regular and continuous way§ Atrial cells beat 60 times per minute§ Ventricular cells beat 20−40 times per minute
- Physiology of the Heart§ Intrinsic conduction system of the heart§ Components include:§ Sinoatrial (SA) node§ Located in the right atrium§ Serves as the heart’s pacemaker§ Atrioventricular (AV) node is at the junction of the atria and ventricles§ Atrioventricular (AV) bundle (bundle of His) and bundle branches are in the interventricular septum§ Purkinje fibers spread within the ventricle wall muscles
- Physiology of the Heart§ Intrinsic conduction system of the heart pathway§ The sinoatrial node (SA node) starts each heartbeat§ Impulse spreads through the atria to the AV node§ Atria contract§ At the AV node, the impulse is delayed briefly§ Impulse travels through the AV bundle, bundle branches, and Purkinje fibers§ Ventricles contract; blood is ejected from the heart
- Homeostatic Imbalance§ Heart block – damage to AV node causes ventricles to beat at their own rate, which is much slower, some or all of the time§ artificial pacemakers can be installed if damage to SA node§ Ischemia – lack or adequate blood supply to the heart muscles§ Fibrillation – rapid, uncoordinated quivering of the ventricles; makes the heart unable to pump blood, major cause of death from heart attacks in adult§ Tachycardia—rapid heart rate, over 100 beats per minute§ Bradycardia—slow heart rate, less than 60 beats per minutes
- 5 Events of Cardiac cycle(1) Atrial diastole (ventricular filling)§ Heart is relaxed§ Pressure in heart is low§ Atrioventricular valves are open§ Blood flows passively into the atria and into ventricles§ Semilunar valves are closed
- Cardiac cycle and heart sounds§ The cardiac cycle refers to one complete heartbeat, in which both atria and ventricles contract and then relax§ Systole = contraction§ Diastole = relaxation§ Average heart rate is approximately 75 beats per minute§ Cardiac cycle length is normally 0.8 second
- 5 Events of Cardiac cycle(2) Atrial systole§ Ventricles remain in diastole§ Atria contract§ Blood is forced into the ventricles to complete ventricular filling
- 5 Events of Cardiac cycle(3) Isovolumetric contraction§ Atrial systole ends; ventricular systole begins§ Intraventricular pressure rises§ AV valves close§ For a moment, the ventricles are completely closed chambers
- 5 Events of Cardiac cycle(4) Ventricular systole (ejection phase)§ Ventricles continue to contract§ Intraventricular pressure now surpasses the pressure in the major arteries leaving the heart§ Semilunar valves open§ Blood is ejected from the ventricles§ Atria are relaxed and filling with blood
- 5 Events of Cardiac cycle(5) Isovolumetric relaxation§ Ventricular diastole begins§ Pressure falls below that in the major arteries§ Semilunar valves close§ For another moment, the ventricles are completely closed chambers§ When atrial pressure increases above intraventricular pressure, the AV valves open
- Heart sounds§ Lub—longer, louder heart sound caused by the closing of the AV valves§ Dup—short, sharp heart sound caused by the closing of the semilunar valves at the end of ventricular systole§ Heart murmurs – sounds during heartbeat cycle (whooshing or swishing) made by turbulent blood in or near your heart§ Not a disease but may/can indicate an underlying heart problem
- Regulation of stroke volume§ 60 percent of blood in ventricles (about 70 ml/2 ounces) is pumped with each heartbeat§ Starling’s law of the heart§ The critical factor controlling SV is how much cardiac muscle is stretched§ The more the cardiac muscle is stretched, the stronger the contraction§ Venous return is the important factor influencing the stretch of heart muscle§ Muscular pump plays a major role in increasing the venous return
- Physiology of the HeartFactors modifying basic heart rate1. Neural (ANS) controls§ Sympathetic nervous system speeds heart rateextreme physical and emotional stress can cause the nerves of the sympathetic and sympathetic of the ANS to strongly stimulate the SA and AV nodes§ Parasympathetic fibersoprimarily vagus nerve fibers, slow and steady the heart rate
- Factors modifying basic heart rate2. Hormones and ions§ Epinephrine and thyroxine speed heart rate§ Excess or lack of calcium, sodium, and potassium ions also modify heart activity
- Factors modifying basic heart rate3. Physical factors§ Age, gender, exercise, body temperature influence heart rateA. Age- Resting heart rate in fetus (140 – 160 beats per minute)b. Gender- Ave. adult females (72 – 80); male (64 – 72)C. ExerciseD. Body temperature
- Blood Vessels§ Blood vessels form a closed vascular system that transports blood to the tissues and back to the heart§ Vessels that carry blood away from the heart§ Arteries and arterioles§ Vessels that play a role in exchanges between tissues and blood§ Capillary beds§ Vessels that return blood toward the heart§ Venules and veins
- Application of changes in the heart rate§ Cardiac output (CO)§ Amount of blood pumped by each side (a ventricle) of the heart in 1 minute§ Stroke volume (SV)§ Volume of blood pumped by each ventricle in one contraction (each heartbeat)§ About 70 ml of blood is pumped out of the left ventricle with each heartbeat§ Heart rate (HR)§ Typically 75 beats per minuteCO = SV x HRCO = SV (70 mL/beat) x HR (75 beats/min)CO = 5250 mL/minCO = 5.25 L/min
- Microscopic Anatomy of Blood Vessels§ Structural differences in arteries, veins, and capillaries§ Arteries have a heavier, stronger, stretchier tunica media than veins to withstand changes in pressure§ Veins have a thinner tunica media than arteries and operate under low pressure§ Veins also have valves to prevent backflow of blood§ Lumen of veins is larger than that of arteries§ Skeletal muscle ―milks‖ blood in veins toward the heart
- Microscopic Anatomy of Blood Vessels§ Three layers (tunics) in blood vessels (except the capillaries)§ Tunica intima forms a friction-reducing lining§ Endothelium§ Tunica media§ Smooth muscle and elastic tissue§ Controlled by sympathetic nervous system§ Tunica externa forms protective outermost covering§ Mostly fibrous connective tissue§ Supports and protects the vessel
- Gross Anatomy of Blood Vessels§ Major arteries of systemic circulation§ Aorta§ Largest artery in the body§ Leaves from the left ventricle of the heart§ Regions§ Ascending aorta—leaves the left ventricle§ Aortic arch—arches to the left§ Thoracic aorta—travels downward through the thorax§ Abdominal aorta—passes through the diaphragm into the abdominopelvic cavity
- Microscopic Anatomy of Blood Vessels§ Structural differences in arteries, veins, and capillaries (continued)§ Capillaries§ Only one cell layer thick (tunica intima)§ Allow for exchanges between blood and tissue§ Form networks called capillary beds that consist of:§ A vascular shunt§ True capillaries§ Blood flow through a capillary bed is known asmicrocirculation
- Blood Pressure§ The pressure the blood exerts against the inner walls of the blood vessels§ The force that causes blood to continue to flow in the blood vessels
- Blood Pressure§ Blood pressure gradient§ When the ventricles contract:§ Blood is forced into elastic arteries close to the heart§ Blood flows along a descending pressure gradient§ Pressure decreases in blood vessels as distance from the heart increases§ Pressure is high in the arteries, lower in the capillaries, and lowest in the veins
- Blood Pressure§ Measuring blood pressure§ Two arterial blood pressures are measured§ Systolic—pressure in the arteries at the peak of ventricular contraction§ Diastolic—pressure when ventricles relax§ Expressed as systolic pressure over diastolic pressure in millimeters of mercury (mm Hg)§ For example, 120/80 mm Hg§ Auscultatory method is an indirect method of measuring systemic arterial blood pressure, most often in the brachial artery
- Blood Pressure§ Variations in blood pressure§ Normal human range is variable§ Systolic pressure ranges from 110 to 140 mm Hg§ Diastolic pressure ranges from 70 to 80 mm Hg
- Blood Pressure§ Effects of various factors on blood pressure§ Arterial blood pressure (BP) is directly related to cardiac output and peripheral resistance§ Cardiac output (CO; the amount of blood pumped out of the left ventricle per minute)§ Peripheral resistance (PR; the amount of friction blood encounters as it flows through vessels)BP = CO × PR