Chapter 12 Circulation The circulatory system connects with all body s In many animals, microscopic blood vessels called capillaries Form an intricate network among the Red blood cell song Figure 23.1A Capillary Nuclei of smooth cells LM 700 Are the sites of exchange between blood and interstitial fluid Land vertebrates have double circulation with separate pulmonary and systemic circuits Birds and mammals have four-chambered hearts Lung capillaries Capillary circuit A A Interstitial fluid Diffusion of molecules V Systemic circuit V Left Tissue cell Figure 23.1B Figure 23.3C Systemic capillaries
3 pulmonary capillaries CO 2 O 2 4 External Respiration 1 At pulmonary capillaries, HCO 3 is converted inside red blood cells to H 2 O and CO 2. CO 2 leaves red blood cells and capillaries. O 2 CO 2 Internal Respiration At systemic capillaries, CO 2 enters red blood cells. Some combine with Hb to form HbCO 2. Most is converted to HCO 3, which is carried in the plasma. Hb now combines with H + to form HHb. CO2 systemic capillaries systemic capillaries O 2 pulmonary vein 2 External Respiration At pulmonary capillaries, O 2 enters red blood cells where it combines with Hb to form HbO 2. CO 2 O 2 pulmonary capillaries Internal Respiration At systemic capillaries, HbO 2 inside red blood cells becomes Hb and O 2. O 2 leaves red blood cells and capillaries. The Mammalian Cardiovascular System The mammalian heart Figure 23.4A Has two thin-walled atria that pump blood into the ventricles Has thick-walled ventricles that pump blood to all other body organs Semilunar valve Atrioventricular (AV) valve atrium ventricle Left ventricle Left atrium Semilunar valve Atrioventricular (AV) valve Blood Flow through the Human Cardiovascular System Figure 23.4B Superior vena cava of right lung vein 3 atrium ventricle Inferior vena cava 9 4 10 9 8 2 7 1 8 Aorta 5 6 2 of head, chest, and arms 4 3 of left lung vein Left atrium Left ventricle Aorta of abdominal region and legs The structure of blood vessels fits their functions A single layer of epithelial cells Forms the walls capillaries Arteries and veins Have smooth and connective Artery Arteriole Smooth Connective Capillary Smooth Connective Basement membrane Venule Vein Valve
The heart contracts and relaxes rhythmically During diastole Blood flows from the veins into the heart chambers During systole Contractions of the atria push blood into the ventricles Stronger contractions of the ventricles propel blood into the large arteries A cardiac cycle 1 2 1 Heart is relaxed. AV valves are open. Diastole 0.4 sec 0.1sec 0.3 sec 2 Atria contract. Systole 3 3 Ventricles contract. Semilunar valves are open. Cardiac output Is the amount of blood/minute pumped into the systemic circuit Heart valves Prevent the backflow of blood The pacemaker sets the tempo of the heartbeat The pacemaker (SA node) generates electrical signals that trigger contraction of the atria The AV node relays these signals to the ventricles Pacemaker (SA node) AV node Specialized fibers atrium ventricle Apex 1 2 3 4 ECG
An electrocardiogram (ECG) Records the electrical changes in the heart Heart rate Adjusts to body needs What is a heart attack? A heart attack is damage to cardiac Usually resulting from a blocked coronary 1 2 3 4 Superior Vena cava coronary Aorta Left coronary Blockage ECG Figure 23.8A Dead In atherosclerosis Plaques develop in the inner walls of arteries and can block blood flow Connective Smooth Plaque Blood exerts on vessel walls Blood Is the force blood exerts on vessel walls Depends on cardiac output and the resistance of vessels LM 160 LM 60 Figure 23.8B
Pressure is highest in the arteries And lowest in the veins Pressure (mm Hg) 120 100 80 60 40 20 0 Relative sizes and numbers of blood vessels Diastolic Systolic Muscle contractions and one-way valves Keep blood moving through the veins to the heart Direction of blood flow in vein Valve (open) Skeletal Figure 23.9A Velocity (cm/sec) 50 40 30 20 10 0 Aorta Arteries Arterioles Venules Veins Venae cavae Figure 23.9B Valve (closed) Measuring blood can reveal cardiovascular problems Blood Is measured as systolic and diastolic s Hypertension (blood consistently above 140/90 mmhg Is a serious cardiovascular problem Blood 110 systolic 70 diastolic (to be measured) Rubber cuff inflated with air Pressure in cuff above 110 110 Pressure in cuff at 110 110 Pressure in cuff at 70 70 Diet and exercise Keep your blood at normal levels Figure 23.10 Artery Artery closed Sounds audible in stethoscope 1 2 3 4 Sounds stop
substances allow through the transfer their walls of Smooth controls the distribution of blood Constriction of arterioles and precapillary sphincters Controls blood flow through capillary beds Precapillary sphincters Thoroughfare channel Capillary wall Iumen Interstitial fluid Arteriole 1 Sphincters relaxed Venule Thoroughfare channel Nucleus of epithelial cell Figure 23.11 Arteriole 2 Sphincters contracted Venule Figure 23.12A TEM 5,000 Muscle cell Cleft between two epithelial cells of the capillary wall The transfer of materials between the blood and interstitial fluid occurs By diffusion By flow through clefts between epithelial cells Blood forces fluid out of the capillary at the arterial end And osmotic draws fluid at the venous end Tissue cells Arterial end of capillary Blood Osmotic Blood Osmotic Venous end of capillary Interstitial fluid Net fluid Movement out Net fluid Movement in
STRUCTURE AND FUNCTION OF BLOOD Blood consists of 45% cells (red and white blood cells, platelets) and 55% plasma Plasma is about 90% water and contains various inorganic ions, proteins, nutrients, wastes, gases, and hormones Plasma (55%) Red blood cells (erythrocytes) transport O 2 bound to hemoglobin White blood cells (leukocytes) function both inside and outside the circulatory system to fight infections and cancer Cell type Cellular elements (45%) Number per µl (mm 3 ) of blood Functions Constituent Water Major functions Solvent for carrying other substances Centrifuged blood sample Erythrocytes (red blood cells) 5 6 million Transport of oxygen (and carbon dioxide) Salts (ions) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Osmotic balance, ph buffering, and nerve and function Centrifuged blood sample Leukocytes (white blood cells) 5,000 10,000 Defense and immunity Plasma proteins Osmotic balance and ph buffering Basophil Lymphocyte Fibrinogen Immunoglobulins (antibodies) Clotting Immunity Eosinophil Neutrophil Monocyte Substances transported by blood Nutrients (e.g., glucose, fatty acids,vitamins) Waste products of metabolism Respiratory gases (O 2 and CO 2 ) Hormones Platelets 250,000 400,000 Blood clotting Too few or too many red blood cells can be unhealthy Anemia Is an abnormally low amount of hemoglobin or red blood cells The hormone erythropoietin Regulates red blood cell production Some athletes Artificially increase their red blood cell production, a dangerous practice Colorized SEM 3,400
Blood clots plug leaks when blood vessels are injured When a blood vessel is damaged Platelets help trigger the conversion of fibrinogen to fibrin, forming a clot that plugs the leak The blood-clotting process 1 Platelets adhere to exposed connective 2 Platelet plug forms 3 Fibrin clot traps blood cells Connective Colorized SEM 3,400 Platelet Figure 23.15A Platelet plug Stem cells offer a potential cure for blood cell diseases Stem cells divide in bone marrow To produce all blood cells And may be used to treat some blood disorders Stem cells Stem cells Erythrocytes Basophils Platelets Eosinophils Lymphocytes Monocytes Neutrophils