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8/27/2011 Chapter 23: The Circulatory System 1. The Heart 2. The Blood Vessels 3. Blood & Lymph 4. Cardiovascular Health Organs of the Circulatory System Heart pumps the blood Blood vessels Blood veins, arteries, capillaries red & white blood cells, blood plasma (we’ll also look at lymph and lymphatic vessels) Roles of the Circulatory System • deliver O2, remove CO2 • transport nutrients, wastes, hormones • regulate temperature & pH • immune protection (antibodies, white blood cells) 1. The Heart 1 8/27/2011 left atrium right atrium The Human Heart semilunar valve semilunar valve atrioventricular (AV) valve atrioventricular (AV) valve left ventricle right ventricle 2 1 Semilunar valves Heart is closed relaxed. Atria contract. The Cardiac Cycle 0.1 sec Systole AV valves are open. 0.4 sec 0.3 sec 3 Ventricles contract. Semilunar valves are open. Diastole AV valves closed Control of the Heartbeat The synchronous contraction of cardiac muscle cells is controlled by the sinoatrial (SA) & atrioventricular (AV) nodes. 1 Signals from the SA node spread through the atria. SA node (pacemaker) 2 Signals are delayed at the AV node. AV node 3 Specialized muscle fibers pass signals to the heart apex. 4 Signals spread throughout the ventricles. Specialized muscle fibers Right atrium Apex ECG • ea beat starts at the SA node atrial contraction • signal spreads to AV node, ventricles ventricular contraction 2 8/27/2011 superior vena cava capillaries of head, chest, and arms 8 pulmonary artery pulmonary artery aorta 9 capillaries of right lung 2 capillaries of left lung 7 2 3 3 5 4 10 pulmonary vein 4 right atrium pulmonary vein 6 1 9 left atrium left ventricle right ventricle aorta inferior vena cava Blood Circulation 8 capillaries of abdominal region and legs 2. The Blood Vessels Blood Vasculature Arteries, arterioles: • conduct blood flow away from the heart • usually oxygenated blood Veins, venules: • conduct blood flow toward the heart • usu. deoxygenated blood Capillaries: • smallest vessels • where “exchange” occurs 3 8/27/2011 Types of Blood Vessels Epithelium Capillary Basal lamina Valve Epithelium Epithelium Smooth muscle Connective tissue Smooth muscle Connective tissue Artery Vein Venule Arteriole Capillaries Red blood cell Capillary Nuclei of smooth muscle cells • allows diffusion of gases (O2, CO2), nutrients, and wastes between blood & tissues Capillary Interstitial fluid Tissue cell Unlike larger vessels, capillary walls are only 1 cell thick, barely wide enough for RBCs to pass through Diffusion of molecules • some fluid (plasma) “leaks out” as well 3. Blood and Lymph 4 8/27/2011 What does Blood consist of? Plasma (55%) Constituent Major functions Water Solvent for carrying other substances Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Plasma proteins Osmotic balance, pH buffering, and maintaining ion concentration of interstitial fluid Cellular elements (45%) Cell type Centrifuged blood sample Red blood cells (erythrocytes) White blood cells (leukocytes) Osmotic balance and pH buffering Fibrinogen Clotting Immunoglobulins (antibodies) Defense Number per L (mm3) of blood) Functions 5–6 million Transport of O2 and some CO2 5,000–10,000 Defense and immunity Lymphocytes Basophils Eosinophils Substances transported by blood Nutrients (e.g., glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O2 and CO2) Hormones Monocytes Neutrophils Platelets 250,000– 400,000 Blood clotting Where do Blood Cells come from? Multipotent stem cells (in bone marrow) Lymphoid stem cells Myeloid stem cells Basophils Erythrocytes Platelets Lymphocytes Eosinophils Monocytes Neutrophils Oxygen Transport Oxygen is transported by red blood cells (RBCs) • aka erythrocytes • don’t have a nucleus! • vast majority of blood cells (~99%) are RBCs Oxygen binds to hemoglobin in RBCs • each hemoglobin molecule binds 8 O2 • vast majority of protein in RBCs is hemoglobin 5 8/27/2011 The Lymphatic System A vascular system distinct from the circulatory system • conducts fluid “leaked” from the blood called lymph • returned to blood at vena cava • lymph is filtered through structures called lymph nodes • full of immune cells, important part of the immune response • also transports fats from digestion in small intestine Lymphatic Vessels Fluid leaked from capillaries is taken up by “lymph capillaries” • lymph is conducted into larger lymphatic vessels • lymph passes through lymph nodes before being “dumped” into the blood at the vena cava 4. Cardiovascular Health 6 Pressure (mm Hg) 8/27/2011 120 100 80 60 40 20 0 Systolic pressure Blood Pressure Diastolic pressure Relative sizes and numbers blood of bloodTypical pressure vessels 120 systolic Veins Venules Arterioles Capillaries Artery closed Venae cavae 1 Pressure in cuff at 70 Pressure in cuff at 120 120 70 Arteries Artery Pressure in cuff above 120 120 Rubber cuff inflated with air Aorta Velocity (cm/sec) 70 diastolic 50 40 30 20 10 0 2 Sounds audible in stethoscope 3 Sounds stop 4 Artificial Pacemakers Wire leading to SA node Artificial pacemaker Heart Coronary Arteries & Heart Attacks Superior vena cava Pulmonary artery Right coronary artery Aorta Left coronary artery Blockage Dead muscle tissue 7 8/27/2011 Key Terms for Chapter 23 • atrium, ventricle, aorta, vena cava • sinoatrial, atrioventricular nodes • hemoglobin, white blood cells, platelets, plasma • arteries, arterioles, veins, venules, capillaries • lymph, lymph nodes • stem cell, heart attack Relevant Review Questions: 1, 2, 4, 5 8