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Transportation Section 1: Blood • Cardiovascular system – Includes: • Fluid (blood) – Includes ~75 trillion cells • Series of conducting hoses (blood vessels) • Pump (heart) The Components of the Cardiovascular System THE HEART propels blood and maintains blood pressure. Heart BLOOD VESSELS distribute blood around the body. Capillaries permit diffusion between blood and interstitial fluids. Capillaries Arteries carry blood away from the heart to the capillaries. Artery Veins return blood from capillaries to the heart. Vein BLOOD distributes oxygen, carbon dioxide, and blood cells; delivers nutrients and hormones; transports waste products; and assists in temperature regulation and defense against disease. Figure 17 Section 1 1 Section 1: Blood • Functions of blood – Transportation of dissolved gases, nutrients, hormones, and metabolic wastes – Regulation of the pH and ion composition of interstitial fluids – Restriction of fluid loss at injury sites – Defense against toxins and pathogens – Stabilization of body temperature Module 17.1: Blood components • Blood – Is a fluid connective tissue – About 5 liters (5.3 quarts) in body • 5–6 in males, 4–5 in females (difference mainly body size) – Consists of: • Plasma (liquid matrix) • Formed elements (cells and cell fragments) – Properties • Temp is roughly 38°C (100.4°F) • Is 5× more viscous than water (due to solid components) • Is slightly alkaline (average pH 7.4) Module 17.1: Blood components • Whole blood – Term for removed blood when composition is unaltered • May be fractionated or separated – Plasma » 46%–63% of blood volume – Hematocrit (or packed cell volume [PCV]) » Percentage of whole blood contributed by formed elements (99% of which are red blood cells) » Average 47% for male (range 40%–54%) » Average 42% for female (range 37%–47%) Module 17.1: Blood components • Plasma – Composition resembles interstitial fluid in many ways • • • • Exists because exchange of water, ions, and small solutes 92% water 7% plasma proteins 1% other solutes – Primary differences • Levels of respiratory gases (oxygen and carbon dioxide) • Concentrations of dissolved proteins (cannot cross capillary walls) Module 17.1: Blood components • Plasma proteins – In solution rather than as fibers like other connective tissues – Each 100 mL has ~7.6 g of protein • ~5× that of interstitial fluid – Large size and globular shapes prevent leaving bloodstream – Liver synthesizes >90% of all plasma proteins Module 17.1: Blood components • Plasma proteins (continued) – Albumins • ~60% of all plasma proteins • Major contributors to plasma osmotic pressure – Globulins • ~35% of all plasma proteins • Antibodies (immunoglobulins) that attack pathogens • Transport globulins that bind ions, hormones, compounds – Fibrinogen • Functions in clotting and activate to form fibrin strands – Many active and inactive enzymes and hormones Module 17.1: Blood components • Plasma solutes – Electrolytes • Essential for vital cellular activities • Major ions are Na+, K+, Ca2+, Mg2+, Cl–, HCO3–, HPO4–, SO42– – Organic nutrients • Used for cell ATP production, growth, and maintenance • Includes lipids, carbohydrates, and amino acids – Organic wastes • Carried to sites of breakdown or excretion • Examples: urea, uric acid, creatinine, bilirubin, NH4+ Plasma (46–63%) Whole blood consists of Formed elements (37–54%) Figure 17.1 1 Module 17.1: Blood components • Formed elements – Platelets • Small membrane-bound cell fragments involved in clotting – White blood cells (WBCs) • Also known as leukocytes (leukos, white + -cyte, cell) • Participate in body’s defense mechanisms • Five classes, each with different functions – Red blood cells (RBCs) • Also known as erythrocytes (erythros, red + -cyte, cell) • Essential for oxygen transport in blood Module 17.1 Review a. Define hematocrit. b. Identify the two components constituting whole blood, and list the composition of each. c. Which specific plasma proteins would you expect to be elevated during an infection? Module 17.2: Red blood cells • RBCs in blood – Most numerous cell type in blood • Roughly 1/3 of all cells in the body – Red blood cell count (standard blood test) results • • • Adult males: 4.5–6.3 million RBCs/1 µL or 1 mm3 of whole blood Adult females: 4.2–5.5 million RBCs/1 µL or 1 mm3 of whole blood One drop = 260 million RBCs Module 17.2: Red blood cells • RBC characteristics – Biconcave disc – Average diameter ~8 µm – Large surface area-to-volume ratio • Greater exchange rate of oxygen – Can form stacks (rouleaux) • Facilitate smooth transport through small vessels – Are flexible • Allow movement through capillaries with diameters smaller than RBC (as narrow as 4 µm) Stained blood smear LM x 450 Figure 17.2 1 The size and biconcave shape of an RBC 7.2–8.4 μm 0.45–1.16 μm RBCs 2.31–2.85 μm Colorized SEM x 1800 Figure 17.2 2 The advantages of the biconcave shape of RBCs Functional Aspects of Red Blood Cells • Large surface area-to-volume ration. Each RBC carries oxygen bound to intracellular proteins, and that oxygen must be absorbed or released quickly as the RBC passes through the capillaries. The greater the surface area per unit volume, the faster the exchange between the RBC’s interior and the surrounding plasma. The total surface area of all the RBCs in the blood of a typical adult is about 3800 square meters, roughly 2000 times the total surface area of the body. Rouleaux (stacks of RBCs) Blood vessels (viewed in longitudinal section) • RBCs can form stacks. Like dinner plates, RBCs can form stacks that ease the flow through narrow blood vessels. An entire stack can pass along a blood vessel only slightly larger than the diameter of a single RBC, whereas individual cells would bump the walls, bang together, and form logjams that could restrict or prevent blood flow. • Flexibility. Red blood cells are very flexible and can bend and flex when entering small capillaries and branches. By changing shape, individual RBCs can squeeze through capillaries as narrow as 4 μm. Nucleus of endothelial cell Red blood cell (RBC) Sectional view of capillaries LM x 1430 Figure 17.2 3 Module 17.2: Red blood cells • RBC characteristics (continued) – Lose most organelles including nucleus during development • – Cannot repair themselves and die in ~120 days Contain many molecules (hemoglobin) associated with primary function of carrying oxygen • • Each cell contains ~280 million hemoglobin (Hb) molecules Normal whole blood content (grams per deciliter) – • 14–18 dL (males), 12–16 dL (females) ~98.5% of blood oxygen attached to Hb in RBCs – Rest of oxygen dissolved in plasma Module 17.2: Red blood cells • Hemoglobin – – Protein with complex quaternary structure Each molecule has 4 chains (globular protein subunits) • • – 2 alpha (α) chains 2 beta (β) chains Each chain contains a single heme pigment molecule • Each heme (with iron) can reversibly bind one molecule of oxygen – Forms oxyhemoglobin (HbO2) (bright red) » Deoxyhemoglobin when not binding O2 (dark red) Figure 17.2 4 The quaternary structure of hemoglobin β chain 1 α chain 1 β chain 2 Heme α chain 2 Figure 17.2 5 The chemical structure of a heme unit Heme Figure 17.2 6 Module 17.2 Review a. Define rouleaux. b. Describe hemoglobin. c. Compare oxyhemoglobin with deoxyhemoglobin. Section 1: Heart Structure • Location of the heart – Near anterior chest wall, directly posterior to sternum – Center lies slightly to the left of midline – Entire heart is rotated slightly left Section 1: Heart Structure • Gross anatomy – Base (superior surface where major vessels attach) – Apex (inferior pointed tip) – Borders • Superior border (formed by base) • Right border (formed by right atrium) • Left border (formed by left ventricle and small part of left atrium) • Inferior border (formed mainly by inferior wall of right ventricle) The location of the heart in the chest cavity Base 1 2 3 4 5 6 7 8 9 10 1 2 3 Ribs 4 5 Apex 6 7 8 9 10 Figure 18 Section 1 1 An anterior view showing the borders of the heart Superior border Right border Left border Inferior border Figure 18 Section 1 2 Module 18.1: Heart wall and tissue • Layers of heart wall 1. Epicardium (visceral pericardium) • • Covers surface of heart Serous membrane made of exposed mesothelium and underlying areolar tissue (attaching to myocardium) – Parietal pericardium • • Not a heart wall layer but is continuous serous membrane with visceral pericardium Lines pericardial cavity and fibrous pericardial sac Module 18.1: Heart wall and tissue • Layers of heart wall (continued) 2. Myocardium • • Middle, muscular layer forming atria and ventricles Contains cardiac muscle tissue, blood vessels, and nerves – Concentric muscle tissue layers » Form a figure-eight around the atria » Superficial muscle layers wrap both ventricles » Deep muscle layers form figure-eight around ventricles The direction of muscle bundles of the atrial and ventricular musculature Atrial musculature Ventricular musculature Figure 18.1 2 Module 18.1: Heart wall and tissue • Layers of heart wall (continued) 3. Endocardium • • Covering inner surfaces of heart, including valves Composed of simple squamous epithelial tissue and underlying areolar tissue – Forms endothelium continuous with blood vessel endothelium A section of the heart showing its three layers: epicardium, myocardium, and endocardium Parietal Pericardium The serous membrane that forms the outer wall of the pericardial cavity; it and a dense fibrous layer form the pericardial sac surrounding the heart Pericardial cavity (contains serous fluid) Dense fibrous layer Areolar tissue Mesothelium Myocardium Muscular wall of the heart consisting primarily of cardiac muscle cells Epicardium Covers the outer surface of the heart; also called the visceral pericardium Mesothelium Areolar tissue Connective tissues Endocardium Covers the inner surfaces of the heart Endothelium Areolar tissue Figure 18.1 1 Module 18.1: Heart wall and tissue • Cardiac muscle tissue – Compared to skeletal muscle tissue 1. 2. 3. 4. Small cell size Single, centrally located nucleus Branching interconnections Specialized intercellular connections – Intercalated discs A light micrograph showing the histological characteristics of cardiac muscle tissue Intercalated discs Cardiac muscle tissue LM x 575 Figure 18.1 3 Module 18.1: Heart wall and tissue • Cardiac muscle tissue (continued) – Found only in the heart – Cells are striated due to organized myofibrils – Almost totally dependent on aerobic metabolism for ATP • Large numbers of mitochondria and myoglobin to store O2 • Has large number of capillaries to supply nutrients and O2 Module 18.1: Heart wall and tissue • Intercalated discs – Contain: • Desmosomes • Gap junctions – Allow ions and molecules to move directly between cells » Create direct electrical connection so an action potential can pass directly between cells – Stabilize relative positions of adjacent cells – Allow cells to “pull together” for maximum efficiency – All cells to function “as one” (functional syncytium) The structure of cardiac muscle cells Cardiac muscle cells, which feature organized myofibrils, aligned sarcomeres, and numerous mitochondria Size of a typical cardiac muscle cell: 10–20 μm in diameter and 50–100 μm in length Intercalated disc (sectioned) Nucleus Mitochondria Bundles of myofibrils Intercalated disc The connection of cardiac muscle cells by intercalated discs, gap junctions, and desmosomes, forming a functional syncytium Gap junction Intercalated Disc Z lines bound to opposing cell membranes Desmosomes Figure 18.1 4 – 5 Module 18.1 Review a. From superficial to deep, name the layers of the heart wall. b. Describe how the cardiac muscle cells ‘talk’ to one another. c. Why is it important that cardiac tissue be richly supplied with mitochondria and capillaries? Module 18.2: Pericardial cavity • • Heart lies within pericardial cavity, a subdivision of the mediastinum Mediastinum also contains: – – – – • Great vessels (entering and exiting the heart) Thymus Esophagus Trachea Because heart is closely associated with many organs, trauma can lead to fluid accumulation that can restrict heart movement (cardiac tamponade) Two views showing the location of the heart in the chest cavity The position and orientation of the heart relative to the major vessels and the ribs, sternum, and lungs Trachea Thyroid gland A diagrammatic superior view of a partial dissection of the thoracic cavity showing the physical relationships among the components in the mediastinum First rib (cut) Esophagus Posterior mediastinum Aorta (arch segment removed) Base of heart Right lung Left lung Left pulmonary artery Apex of heart Diaphragm Right pleural cavity Anterior view of chest cavity Parietal pericardium (cut) Right lung Left pleural cavity Left lung Left pulmonary vein Bronchus of lung Aortic arch Right pulmonary artery Pulmonary trunk Left atrium Right pulmonary vein Left ventricle Pericardial cavity Superior vena cava Epicardium Right atrium Pericardial sac Right ventricle Anterior mediastinum Figure 18.2 1 – 3 Module 18.2: Pericardial cavity • Pericardial cavity and fluid – Lined with parietal pericardium • Continuous with visceral pericardium (like balloon with fist in it) – Contains 10–15 mL of pericardial fluid secreted by membranes • Acts as lubricant when heart beats – Swelling of pericardial surfaces can occur with infection causing friction (pericarditis) The position and orientation of the heart relative to the major vessels and the ribs, sternum, and lungs Trachea Thyroid gland First rib (cut) Base of heart Right lung Left lung Apex of heart Diaphragm Anterior view of chest cavity Parietal pericardium (cut) Figure 18.2 1 The positions of and relationship between the heart and the pericardial cavity Wrist (corresponds to base of heart) Inner wall (corresponds to epicardium) The relationship between the heart and the pericardial cavity, which can be linked to a fist pressed into the center of a partially inflated balloon Air space (corresponds to pericardial cavity) Outer wall (corresponds to parietal pericardium) Balloon The location of the pericardial cavity relative to the heart Base of heart Cut edge of parietal pericardium Fibrous tissue of pericardial sac Pericardial cavity containing pericardial fluid Parietal Pericardium Areolar tissue Mesothelium Cut edge of epicardium Fibrous attachment to diaphragm Apex of heart Figure 18.2 2 Module 18.2 Review a. Define mediastinum. b. Describe the heart’s location. c. Why can cardiac tamponade be a lifethreatening condition? Module 18.3: Heart surface anatomy • Heart surface anoatomy – Sulci (singular, sulcus) • Surface grooves separating heart chambers – Often with cardiac vessels covered with fat • Anterior interventricular sulcus – Anterior groove separating ventricles • Posterior interventricular sulcus – Posterior groove separating ventricles • Coronary sulcus – Separates atria from ventricles – On posterior surface, contains coronary sinus (collects blood from myocardium and conveys to right atrium) Module 18.3: Heart surface anatomy • Other surface features – Auricles • Expandable extensions of atria – Ligamentum arteriosum • Fibrous remnant of fetal connection between aorta and pulmonary trunk Two views of the anterior surface of the heart A diagrammatic view of the anterior surface of the heart A photograph of an anterior view of a heart from a preserved cadaver Aortic arch Ligamentum arteriosum Ascending aorta Superior vena cava Pulmonary trunk Parietal pericardium Superior vena cava Pulmonary trunk Auricle of right atrium Auricle of left atrium Right atrium Auricle Auricle of left atrium Right atrium Ascending aorta Right ventricle Coronary sulcus Fat Anterior interventricular sulcus Left ventricle Right ventricle Left ventricle Cadaver dissection, anterior view Coronary sulcus Anterior interventricular sulcus Anterior surface Figure 18.3 1 – 3 Module 18.3 Review b. Name and describe the shallow depressions and grooves found on the heart’s external surface. c. Which structures collect blood from the myocardium, and into which heart chamber does this blood flow? Module 18.4: Coronary circulation • Coronary circulation – Provides cardiac muscle cells with reliable supplies of oxygen and nutrients – During maximum exertion, myocardial blood flow may increase to 9× resting levels – Blood flow is continuous but not steady • With left ventricular relaxation, aorta walls recoil (elastic rebound), which pushes blood into coronary arteries Module 18.4: Coronary circulation • Coronary arteries – Right coronary artery (right atrium, portions of both ventricles and conduction system of heart) • • – Marginal arteries (right ventricle surface) Posterior interventricular artery (interventricular septum and adjacent ventricular portions) Left coronary artery (left ventricle, left atrium, and interventricular septum) • • Circumflex artery (from left coronary artery, follows coronary sulcus to meet right coronary artery branches) Anterior interventricular artery (interventricular sulcus) The locations of the arterial supply to the heart Pulmonary trunk Aortic arch An anterior view of the coronary arteries Left Coronary Artery Left atrium Left coronary artery Circumflex artery Right atrium Right Coronary Artery Anterior interventricular artery Right ventricle Right coronary artery in the coronary sulcus Left ventricle Marginal arteries Anterior view Arterial anastomoses between the anterior and posterior interventricular arteries The branches of the coronary arteries on the posterior surface of the heart Circumflex artery Left atrium Marginal artery Right atrium Left ventricle Posterior interventricular artery Right ventricle Posterior view Right coronary artery Figure 18.4 1 – 2 Module 18.4: Coronary circulation • Coronary veins – Great cardiac vein (drains area supplied by anterior interventricular artery, empties into coronary sinus on posterior) – Anterior cardiac veins (drains anterior surface of right ventricle, empties into right atrium) The major collecting vessels on the anterior surface of the heart Aortic arch Left atrium Right atrium Anterior cardiac veins Great cardiac vein Right ventricle Left ventricle Anterior view Figure 18.4 3 Module 18.4: Coronary circulation • Coronary veins (continued) – Coronary sinus (expanded vein, empties into right atrium) – Posterior cardiac vein (drains area supplied by circumflex artery) – Small cardiac vein (drains posterior right atrium and ventricle, empties into coronary sinus) – Middle cardiac vein (drains area supplied by posterior interventricular artery, drains into coronary sinus) The major collecting vessels on the posterior surface of the heart Great cardiac vein Left atrium Coronary sinus Right atrium Left ventricle Posterior cardiac vein Small cardiac vein Right ventricle Posterior view Middle cardiac vein Figure 18.4 4 Module 18.4 Review a. List the arteries and veins of the heart. b. Describe what happens to blood flow during elastic rebound. c. Identify the main vessel that drains blood from the myocardial capillaries. Module 18.5: Internal heart anatomy • Internal heart anatomy – Four chambers • • Two atria (left and right separated by interatrial septum) Two ventricles (left and right separated by interventricular septum) – Left atrium flows into left ventricle – Right atrium flows into right ventricle Module 18.5: Internal heart anatomy • Right atrium – Receives blood from superior and inferior venae cavae and coronary sinus – Fossa ovalis (remnant of fetal foramen ovale) – Pectinate (pectin, comb) muscles (muscular ridges on anterior atrial and auricle walls) • Left atrium – Receives blood from pulmonary veins Module 18.5: Internal heart anatomy • Right ventricle – Receives blood from right atrium through right atrioventricular (AV) valve • Also known as tricuspid (tri, three) – – • Has three flaps or cusps attached to tendinous connective fibers (chordae tendineae) Fibers connect to papillary muscles » Innervated to contract through moderator band which keeps “slamming” of AV cusps Prevents backflow of blood to atrium during ventricular contraction Module 18.5: Internal heart anatomy • Left ventricle – Receives blood from left atrium through right atrioventricular valve • • • – Also known as bicuspid and mitral (mitre, bishop’s hat) valve Prevents backflow of blood to atrium during ventricular contraction Has paired flaps or cusps Trabeculae carneae (carneus, fleshy) • – Muscular ridges on ventricular walls Aortic valve • Allows blood to exit left ventricle and enter aorta The internal anatomy of the heart and the direction of blood flow between the chambers Ascending aorta Pulmonary trunk Superior vena cava Right Atrium Aortic arch Receives blood from the superior and inferior venae cavae and from the cardiac veins through the coronary sinus Left Atrium Receives blood from the pulmonary veins Left pulmonary veins Fossa ovalis Pectinate muscles on the inner surface of the auricle Opening of the coronary sinus Left Ventricle Right Ventricle Thick wall of left ventricle Right atrioventricular (AV) valve (tricuspid valve) Chordae tendineae Papillary muscle Pulmonary valve (pulmonary semilunar valve) Left atrioventricular (AV) valve (bicuspid valve) Inferior vena cava Trabeculae carneae Interventricular septum Moderator band Aortic valve Figure 18.5 1 Module 18.5: Internal heart anatomy • Ventricular comparisons – Right ventricle has relatively thin wall • • – Ventricle only pushes blood to nearby pulmonary circuit When it contracts, it squeezes against left ventricle wall forcing blood out pulmonary trunk Left ventricle has extremely thick wall and is round in cross section • • Ventricle must develop 4–6× as much pressure as right to push blood around systemic circuit When it contracts 1. 2. Diameter of chamber decreases Distance between base and apex decreases A sectional view of the heart showing the thicknesses of the ventricle walls and the shapes of the ventricular chambers Posterior interventricular sulcus The left ventricle has an extremely thick muscular wall and is round in cross section. The relatively thin wall of the right ventricle resembles a pouch attached to the massive wall of the left ventricle Fat in anterior interventricular sulcus Figure 18.5 2 The changes in ventricle shape during ventricular contraction Right ventricle Left ventricle Dilated (relaxed) Contraction of left ventricle decreases the diameter of the ventricular chamber and reduces the distance between the base and apex Contraction of right ventricle squeezes blood against the thick wall of the left ventricle. Contracted Figure 18.5 3 Module 18.5 Review a. Damage to the semilunar valves on the right side of the heart would affect blood flow to which vessel? b. What prevents the AV valves from swinging into the atria? c. Why is the left ventricle more muscular than the right ventricle? d. Name the four cardiac chambers.