Bài giảng Biology 25: Human Biology - Chapter 7

Chapter 7 Biology 25: Human BiologyProf. GonsalvesLos Angeles City CollegeLoosely Based on Mader’s Human Biology,7th edition Blood VesselsInclude arteries, arterioles, capillaries, venules, and veins.Double circuit, closed system:1. Pulmonary circuit: Delivers blood to lungs. Oxygenation of blood.2. Systemic circuit: Delivers oxygenated blood to tissues and organs of body (brain, liver, heart, kidneys, etc). Picks up carbon dioxide produced by tissues.HeartAnatomical Features:Hollow muscular organ, about the size of a human fist.Weighs less than one pound (10 ounces).Rests on diaphragm, near middle of thoracic cavity.Wall is composed of cardiac muscle covered by connective tissue.Pericardium: Membrane that surrounds entire heart and contains a fluid which protects heart and decreases friction. HeartHeart Chambers: Heart is divided into four separate chambers. Both the left and the right side of the heart have a(an):Atrium (Plural atria): Smaller, superior chambers. Receive blood from veins.Ventricle: Larger, inferior chambers. Pump blood into arteries.Two sides of heart have different functions:Right side: Pumps oxygen poor blood.Left side: Pumps oxygen rich blood.Pacemaker (Sinoatrial node): Specialized structure that sends electrical impulses that causes both atria and ventricles to contract.HeartHeart Valves: Heart has several valves made of connective tissue, that prevent backflow of blood as it circulates.Atrioventricular (AV) Valves: Close between atria and ventriclesRight AV Valve: Connects right atrium to the right ventricle.Left AV Valve: Connects left atrium to the left ventricle.Semilunar Valves: Close as blood leaves the ventricles and enters the arteries.Heart murmur: Rushing, gurgling sound created by backflow of blood due to damaged or imperfect heart valves. Fairly common (10% of healthy population). Most are asymptomatic. Heart BeatAverage 70 beats per minute. 100,000 beats every day.Cardiac cycle about every 0.8 sec.Diastole: Heart relaxes and blood flows into chambers (0.4 sec).Systole: Heart contracts. First atria (0.1 sec)Then ventricles (0.3 sec)Pumps about 8000 liters of blood/day.Pacemaker (Sinoatrial node): Controls heart rate.Regulated by nervous and endocrine systems.Two heart beat sounds (“Lub-dupp”):First sound: Ventricles contract, AV valves close.Second sound: Heart relaxes, semilunar valves are closing.Pulse: Arteries expand and contract with each heartbeat.Pacemaker Controls Cardiac Rhythm Blood PressurePressure is highest in arteries; lowest in veins. “Blood pressure” usually refers to arterial pressure.Usually measured at brachial artery in arm.Two measurements:Systolic Blood Pressure: During heart contraction. Normal systolic pressure is about 120 mm Hg. (Range: 110-140 mm Hg).Diastolic Blood Pressure: During heart relaxation. Normal diastolic pressure is about 80 mm Hg. (Range: 70-90 mm Hg)Blood Pressure and Velocity in Blood Vessels Blood Pathway in BodyRight Side of Heart: Right atrium receives oxygen poor blood from body.Right ventricle pumps oxygen poor blood to lungs. Left Side of Heart: Left atrium receives oxygenated blood from lungs.Left ventricle pumps oxygenated blood to body. Blood Pathway:Veins ---> Vena cava ---> Right atrium ---> Right ventricle ---> Pulmonary artery ---> Lungs ---> Left atrium ---> Left ventricle ---> Aorta ---> Arteries ---> Capillaries ---> Veins Cardiovascular DiseaseNumber one cause of death in the U.S. and industrialized nations.Includes hypertension, strokes, heart attacks, and congestive heart failure.Most often caused by complications of: Arteriosclerosis: A condition in which arteries become blocked by calcium and lipid deposits (plaque), losing their elasticity. Heart Attack (Myocardial infarction-MI)Sudden decrease in blood supply to the heart, due to a clot or plaque in arteries. Death of cardiac muscle resulting in insufficient blood supply to rest of body. Heart may stop beating altogether or suffer permanent damage.Over 1.3 million heart attacks every year in U.S.Leading cause of death and disability60% had no previous symptoms. 25% are not recognized when they occur.25% die before receiving medical assistance.In 1995 960,000 deaths in U.S. Heart Attacks are Caused by Blocked Coronary Arteries Heart Attack (Myocardial infarction)Symptoms: Chest pain, pressure, or tightness, sweating, nausea, shortness of breath, dizziness, and fainting.Risk factors:SmokingHigh blood pressureHigh cholesterolHigh LDLs (low density lipoproteins)DiabetesMale genderEmotional stressObesityHereditySedentary lifestyle Hypertension: High blood pressure.Blood pressure over 140/90. Over 20% of U.S. population suffers from blood pressures over 160/95. Another 25% is borderline (above 140/90).Heart must work harder to overcome resistance.Silent killer: May have few or no symptoms.May result in strokes, heart attacks, aneurysms, ischemia (insufficient blood supply to heart) and arteriosclerosis. Risk factors: Heredity, obesity, high salt intake, black race (relative risk 2), smoking, stress, diet high in fat, and lack of exercise. Ischemic Heart Disease:Insufficient blood supply to the heart. Especially during exercise or physical exertion. May cause angina pectoris: sharp chest pain. Congestive Heart Failure:Heart cannot pump enough blood to meet body’s needs.Slow blood flow causes veins to back up causing edema in tissue (legs, tissues, or lungs). Symptoms: Shortness of breath, edema, and fatigue.Causes: Hypertension , arteriosclerosis, heart valve damage, heart attack, etc. Stroke:Third leading cause of death in U.S. after heart disease and cancer.5% of people over 65 have had a stroke.400,000 stroke victims discharged from hospitals every year.Insufficient blood supply to the brain, caused by a blood clot or rupture of a blood vessel. Depending on area affected may cause:Paralysis (usually one side of body).Loss of sensation or motor control.IncontinenceLoss of speech, hearing, or sight.Death