Anatomy & Physiology II Lecture Exam Blood, Cardiovascular System PDF PDF

Anatomy & Physiology II: Lecture Exam \# 2 Chapters 19, 20, & 21 Chapter 19: Blood An Introduction to Blood and the Cardiovascular System Cardiovascular system consists of... - A pump (the heart) - Series of conducting hoses (blood vessels) - Fluid connective tissue (blood) 19-1 Blood,...

Anatomy & Physiology II: Lecture Exam \# 2 Chapters 19, 20, & 21 Chapter 19: Blood An Introduction to Blood and the Cardiovascular System Cardiovascular system consists of... - A pump (the heart) - Series of conducting hoses (blood vessels) - Fluid connective tissue (blood) 19-1 Blood, composed of plasma and formed elements, provides transport, regulation, and protective services to the body. **[Blood:]** specialized connective tissue that contains cells suspended in a fluid matrix. **Functions of blood** - Transporting dissolved gases, nutrients, hormones, and metabolic wastes. - Regulating pH, ion composition of interstitial fluids. - Restricting fluid losses at injury sites. - Defending against toxins and pathogens. - Stabilizing body temperature. **Characteristics of blood** - 38ºC (100.4ºF). - High viscosity. - Slightly alkaline (pH of 7.35--7.45). - Blood volume (liters) = 7 percent of body weight (kilograms). - A 75-kg (165-lb) person would have approximately 5.25 liters (5.4 quarts) of blood. **Whole blood** - **[Plasma ]** - Fluid containing many proteins. - **[Formed elements ]** - Cells and cell fragments. **[Fractionation:]** process of separating whole blood into plasma and formed elements. **Plasma** - Makes up about 55% of blood volume. - More than 90% of plasma is water. - Also contains dissolved plasma proteins and other solutes. - Similar in composition to interstitial fluid. - Because water, ions, and small solutes are exchanged across capillary walls. **Plasma Proteins** **Albumins (60%)** - Major contributors to plasma osmolarity. - Transport fatty acids, thyroid hormones, some steroid hormones, etc. **Globulins (35%)** - Antibodies (immunoglobulins). - Transport globulins including hormone-binding proteins, metalloproteins, apolipoproteins (lipoproteins), and steroid-binding proteins. **Fibrinogen (4%)** - Soluble protein that functions in clotting. - Converted to insoluble fibrin. - Conversion of fibrinogen to fibrin leaves serum (fluid) in blood sample. **Other plasma proteins (1%)** - Varying concentrations of enzymes and hormones. **Origins of plasma proteins** - More than 90% made in liver. - Including all albumins, fibrinogen, most globulins, and various proenzymes. - Antibodies made by plasma cells. - Peptide hormones made by endocrine organs. **Formed elements** - Red blood cells- **erythrocytes** - White blood cells- **leukocytes** - Cell fragments (platelets)- **thrombocytes** **[Hemopoiesis:]** process of producing formed elements. 19-2 red blood cells, formed by erythropoiesis, contain hemoglobin that transports respiratory gases. **Red blood cells (RBCs)** - Also called **[erythrocytes]**. - Make up 99.9 percent of formed elements. - **[Hemoglobin:]** red pigment that gives whole blood its color. - Binds and transports oxygen and carbon dioxide. **[RBC count:]** number of RBCs per microliter of whole blood. - Adult male: 4.5--6.3 million - Adult female: 4.2--5.5 million **[Hematocrit:]** percentage of formed elements in blood, packed cell volume (PCV). - Adult male: 46 - Adult female: 42 **Structure of RBCs** - Small, highly specialized cells. - **[Biconcave discs:]** thin central region and thicker outer margin. **Important effects of RBC structure on function** - Large surface-area-to-volume ratio. - Quickly absorb and release oxygen. - **[Rouleaux:]** formed stacks. - Smooth blood flow through narrow blood vessels. - Bend and flex when entering small capillaries. - 7.8-µm RBC can pass through a 4-µm capillary. **Mature RBCs** - **[Anucleate:]** lack nuclei. - Lack mitochondria and ribosomes. - Unable to divide, synthesize proteins, or repair damage. - Live about 120 days. **Hemoglobin (Hb or Hgb)** - Protein in RBCs that transports respiratory gases. - Normal hemoglobin - Adult male: 14--18 g/dL whole blood - Adult female: 12--16 g/dL whole blood - Complex quaternary structure. - Four globular protein subunits. - Two alpha (α) chains and two beta (β) chains. - Each with one molecule of **[heme]**. - Each heme contains one iron ion. - Iron interacts with oxygen to form **[oxyhemoglobin, HbO2]**. - Dissociate easily to form **[deoxyhemoglobin]**. **Fetal hemoglobin** - Form of hemoglobin in embryo or fetus. - Binds oxygen more readily than does adult hemoglobin. - Takes up oxygen from maternal blood at placenta. **Hemoglobin function** - Each RBC contains about 280 million Hb molecules. - Each RBC can carry over a billion molecules of O2. - In peripheral capillaries, where O2 is low, hemoglobin. - Releases O2. - Binds CO2, forming **[carbaminohemoglobin]**. - At the lungs, where O2 is high, hemoglobin. - Binds O2. - Releases CO2. **[Anemia:]** results when hematocrit or Hb content of RBCs is reduced. - Interferes with oxygen delivery to peripheral tissues. **RBC formation and turnover** - 1 percent of circulating RBCs are replaced per day. - About 3 million new RBCs enter bloodstream each second. **[Erythropoiesis:]** red blood cell formation. - In embryos, embryonic blood cells move from bloodstream to liver, spleen, thymus, bone marrow. - Differentiate into **[stem cells]**. - That divide to produce blood cells. - In adults, occurs only in **[myeloid tissue:]** red bone marrow. **[Hemocytoblasts]**, also called hematopoietic stem cells (HSCs) - Stem cells in myeloid tissue that divide to produce... - **[Myeloid stem cells:]** become RBCs and some WBCs. - **[Lymphoid stem cells:]** become lymphocytes. Hematologists have identified several stages of RBC maturation... - Myeloid stem cell - Proerythroblast - Erythroblast stages - Reticulocyte - Mature RBC **[Erythropoietin (EPO):]** hormone that stimulates erythropoiesis. - Secreted by kidneys and liver when oxygen in peripheral tissues is low (**[hypoxia]**). **[Blood doping:]** re-infusing packed RBCs to elevate hematocrit. - A dangerous practice used by some athletes. Erythropoiesis requires amino acids, iron, folic acid, and vitamins B12 and B6. **[Pernicious anemia:]** lack of vitamin B12. **Hemoglobin recycling** - Macrophages of spleen, liver, and red bone marrow... - Engulf aged RBCs. - Remove Hb molecules from hemolyzed RBCs. - Break Hb into components. - Only the iron of each heme unit is recycled. **[Hemoglobinuria:]** red or brown urine due to abnormally high hemolysis in bloodstream. **[Hematuria:]** whole RBCs in urine due to kidney or blood vessel damage. Iron is removed from each heme unit, forming green **[biliverdin]**. - Converted to orange-yellow **[bilirubin]**. - Bilirubin is excreted by liver in bile. **[Jaundice:]** caused by buildup of bilirubin. - Converted by intestinal bacteria and oxygen to urobilins and stercobilins. - Urobilins make urine yellow. - Stercobilins make feces brown. **Iron recycling** - Iron removed from heme. - Is bound and stored in phagocytic cell. - Or released into bloodstream. - In bloodstream, iron is bound to **[transferrin]**. - Developing RBCs in red bone marrow absorb transferrins and use them to synthesize Hb. - Excess transferrins are removed in liver and spleen, storing iron in **[ferritin]** and **[hemosiderin]**. 19-3 The ABO and Rh blood groups are based on antigen-antibody responses. **[Surface antigens:]** substances on plasma membranes that identify cells to immune system. - Normal cells are ignored and foreign cells are attacked. Blood type is determined by presence or absence of surface antigens on RBCs: A, B, and Rh (or D). **Four blood types** - **[Type A]** (surface antigen A) - **[Type B]** (surface antigen B) - **[Type AB]** (antigens A and B) - **[Type O]** (neither A nor B) **Rh blood group** Based on presence or absence of Rh antigen. - **[Rh positive (Rh+) ]** - Rh surface antigen is present (e.g., Type O+). - **[Rh negative (Rh--) ]** - Rh antigen is absent (e.g., Type O--). **[Agglutinogens:]** surface antigens on RBCs. - Screened by immune system. **[Agglutinins:]** antibodies in plasma. - Attack antigens on foreign RBCs. - Causing **[agglutination]** (clumping) of foreign cells. **Agglutinins** - Type A blood - Anti-B antibodies - Type B blood - Anti-A antibodies - Type O blood - Both anti-A and anti-B antibodies - Type AB blood - Neither anti-A nor anti-B antibodies - Only **sensitized** Rh-- blood has anti-Rh antibodies **[Cross-reaction (transfusion reaction)]** may occur in a transfusion of blood or plasma from one person to another. - Occurs if donor and recipient blood types are **NOT COMPATIBLE**. - Plasma antibody meets its specific surface antigen. - RBCs agglutinate and may hemolyze. **Compatibility testing** - Performed in advance of transfusions. **[Cross-match testing:]** reveals cross-reactions between donor's RBCs and recipient's plasma. **Type O- is the universal donor.** **Type AB+ is the universal recipient.** - But cross-reactions can still occur. - Because at least 48 surface antigens exist besides A and B. 19-4 The various types of white blood cells contribute to the body's defense. **[White blood cells (WBCs)]**, also called ***leukocytes***. - Have nuclei and other organelles. - Lack hemoglobin. **WBC functions** - Defending body against pathogens. - Removing toxins and wastes. - Attacking abnormal or damaged cells. **Most WBCs are in...** - Connective tissue proper - Organs of lymphatic system A small fraction of WBCs circulates in blood about 5000 to 10,000 per microliter. **Characteristics of circulating WBCs** - All can migrate out of bloodstream. - All are capable of amoeboid movement. - **[Positive chemotaxis:]** all are attracted to specific chemical stimuli. - Some are phagocytic. **Types of WBCs** - Neutrophils - Eosinophils - Basophils - Monocytes - Lymphocytes The WBCs are grouped into 2 classes: granulocytes and agranulocytes. **Granulocytes** **Neutrophils** (neutral pH stain) - Also called ***polymorphonuclear leukocytes*** - 50--70% of circulating WBCs. - Pale cytoplasmic granules containing... - Lysosomal enzymes. - Bactericidal (bacteria-killing) compounds. - Very active, phagocytic cells. - Attack and digest bacteria. - **[Degranulation:]** reduction in number of cytoplasmic granules. - Occurs when vesicle containing pathogen fuses with lysosomes containing enzymes and defensins. - Release prostaglandins and leukotrienes. - Live in bloodstream for 10 hours or less. - Dead neutrophils contribute to pus. **Eosinophils** (acidic pH stains them reddish) - Also called ***acidophils*** - 2--4% of circulating WBCs. - Engulf bacteria, protozoa, and cellular debris. - Attack large parasites by releasing toxic compounds. - Nitric oxide. - Cytotoxic enzymes. - Sensitive to allergens. - Release enzymes that reduce inflammation caused by mast cells and neutrophils. **Basophils** (basic pH stains them blue-blackish) - Less than 1% of circulating WBCs. - Cross capillary endothelium and accumulate in damaged tissues. - Release... - **[Histamine:]** dilates blood vessels. - **[Heparin:]** prevents blood clotting. **Agranulocytes** **Monocytes** - Large, spherical cells. - 2--8% of circulating WBCs. - Remain in bloodstream for 24 hours. - Then enter peripheral tissues to become macrophages. - Aggressive phagocytes that engulf large pathogens. - Release chemicals that attract other phagocytic cells and fibroblasts to injured area. **Three Classes of Lymphocytes** **[T cells (T lymphocytes):]** cell-mediated immunity. - Attack foreign cells or control other lymphocytes. **[B cells (B lymphocytes):]** humoral immunity. - Differentiate into plasma cells, which synthesize antibodies. **[Natural killer (NK) cells:]** detect and destroy abnormal cells. **[Differential count]** of WBC population - Can detect infection, inflammation, and allergic reactions. **WBC Disorders** **[Leukopenia:]** low WBC count. **[Leukocytosis:]** high WBC count. **[Leukemia:]** cancer of WBCs indicated by extreme leukocytosis. **[Leukopoiesis:]** WBC production. - Hemocytoblasts produce myeloid stem cells and lymphoid stem cells. - Myeloid stem cells - Divide to produce **[progenitor cells.]** - Give rise to all formed elements ***except*** lymphocytes. **[Lymphocytopoiesis:]** production of lymphocytes from lymphoid stem cells. **WBC development** Some lymphoid stem cells remain in red bone marrow. - Differentiate into B cells or natural killer cells. Others migrate from red bone marrow to peripheral lymphatic tissues. - Thymus, spleen, and lymph nodes. - Produce lymphocytes. - T cells are produced in thymus. **[Colony-stimulating factors (CSFs):]** hormones that regulate WBC populations. - **[Multi-CSF:]** accelerates production of granulocytes, monocytes, platelets, and RBCs. - **[GM-CSF:]** stimulates granulocyte and monocyte production. - **[G-CSF:]** stimulates granulocyte production. - **[M-CSF:]** stimulates monocyte production. 19-5 Platelets, disc-shaped cell fragments, function in the clotting process. **[Platelets (*thrombocytes*):]** cell fragments involved in clotting system. - Circulate for 9--12 days. - Removed by phagocytes, mainly in spleen. - 150,000 to 500,000 per microliter of blood. - One-third of platelets in body are stored in vascular organs like the spleen. - Mobilized during a circulatory crisis. **Functions of Platelets** - Release important clotting chemicals. - Temporarily patch damaged vessel walls. - Reduce size of break in vessel wall. **[Thrombocytopoiesis:]** platelet production. - Occurs in red bone marrow. **[Megakaryocytes:]** giant cells in red bone marrow. - Produce platelets by shedding membrane-enclosed packets of cytoplasm. **Hormonal Control of Platelet Production** - Thrombopoietin (TPO) - Interleukin-6 (IL-6) - Multi-CSF 19-6 The process of blood clotting, or hemostasis, stops blood loss. **[Hemostasis:]** cessation of bleeding. Hemostasis has three phases... - Vascular phase - Platelet phase - Coagulation phase **Vascular Phase** - A cut triggers **[vascular spasm]**. - Contraction of smooth muscle fibers of vessel wall. - Lasts about 30 minutes. - Changes in endothelium during vascular phase. - Endothelial cells contract and expose basement membrane to bloodstream. - Endothelial cells release chemical factors and local hormones. - ADP, tissue factor, and prostacyclin. - **[Endothelins]** (peptide hormones). - Cause smooth muscle contraction and cell division. - Endothelial plasma membranes become "sticky". - Seal off tear and prevent blood flow. **Platelet Phase** - **[Platelet adhesion:]** platelets attach to exposed surfaces. - **[Platelet aggregation:]** platelets stick to each other. - Begins within 15 seconds after injury. - Forms **platelet plug** that closes small breaks. - Activated platelets release clotting compounds including... - Adenosine diphosphate (ADP) - Thromboxane A2 and serotonin - Clotting factors - Platelet-derived growth factor (PDGF) - Calcium ions **Factors that Limit Growth of Platelet Plug** - Prostacyclin inhibits platelet aggregation. - Inhibitory compounds released by WBCs. - Circulating enzymes break down ADP. - Negative feedback from serotonin, etc. - Blood clot isolates area from general circulation. **Coagulation Phase** (blood clotting) - Begins 30 seconds or more after injury. - Depends on **[clotting factors]** **(*procoagulants*)**. - Ca2+ and 11 different proteins. - **[Proenzymes:]** inactive enzymes. - Converted to active enzymes that direct reactions in clotting response. - Involves chain reactions of three pathways... - Extrinsic pathway - Intrinsic pathway - Common pathway **Extrinsic pathway** - Damaged endothelial cells or peripheral tissues release **[Factor III]** (tissue factor). - Enzyme complex activates **[Factor X]**. **Intrinsic pathway** - Begins with activation of proenzymes exposed to collagen fibers at injury site. - Platelets release **[PF-3]**. - Enzyme complex activates **[Factor X]**. **Common pathway** - Begins with activation of Factor X. - Factor X activates prothrombin activator. - Converts **[prothrombin]** (proenzyme) to **[thrombin]**. - Thrombin converts **[fibrinogen]** to insoluble **[fibrin]**. - Producing a **[blood clot]**. Thrombin generated in common pathway... - Stimulates formation of tissue factor. - Stimulates release of PF-3 by platelets. Forms **positive feedback loop** that accelerates clotting process. **Feedback control of blood clotting** - Anticoagulants (enzymes that inhibit clotting) - Antithrombin-III - Heparin - Accelerates activation of antithrombin-III. - Thrombomodulin - Activates protein C, which inactivates clotting factors and stimulates formation of plasmin. - Prostacyclin - Inhibits platelet aggregation and opposes factors. **Calcium ions and vitamin K** - Essential to clotting process. - All three pathways require Ca2+. - Vitamin K is required for synthesis of four clotting factors. **Bleeding and clotting extremes** - Thrombocytopenia - Hemophilia - Thrombophilia - Deep vein thrombosis (DVT) **[Clot retraction:]** pulls torn edges of vessel closer together. - Reduces residual bleeding. - Stabilizes injury site. - Reduces size of damaged area. - Making it easier for fibroblasts, smooth muscle cells, and endothelial cells to complete repairs. Chapter 20: The Heart **An Introduction to the Heart** The cardiovascular system includes... - Heart - Blood - Blood vessels The heart... - Beats approximately 100,000 times each day. - Pumping about 8000 liters of blood per day. 20-1 The heart is a four-chambered organ that pumps blood through the systemic and pulmonary circuits. The heart pumps **oxygen-poor blood** to the **lungs** within the **pulmonary circuit** and **oxygen-rich blood** to the **rest of the body** within the **systemic circuit**. **Overview of Heart Functions: The Pulmonary and Systemic Circuits** **[Pulmonary circuit:]** carries blood to and from gas exchange surfaces of lungs. **[Systemic circuit:]** carries blood to and from the rest of the body. Each circuit begins and ends at the heart. - Blood travels through these circuits in sequence. **Types of Blood Vessels** **[Arteries:]** carry blood away from heart. **[Veins:]** return blood to heart. **[Capillaries (*exchange vessels*):]** interconnect smallest arteries and smallest veins. - Exchange dissolved gases, nutrients, and wastes between blood and surrounding tissues. **Four Chambers of the Heart** **[Right atrium:] receives** blood from **systemic** circuit. **[Right ventricle:]** **pumps** blood into **pulmonary** circuit. **[Left atrium:]** **receives** blood from **pulmonary** circuit. **[Left ventricle:]** **pumps** blood into **systemic** circuit. **Heart Location and Position** - Great vessels connect at **[base]** (superior). - Pointed tip is **[apex]** (inferior). - Sits between two pleural cavities in mediastinum. **[Pericardium:]** surrounds heart. - Outer **fibrous** pericardium - Inner **serous** pericardium - Outer **parietal** layer - Inner **visceral** layer - **[Pericardial cavity:]** between parietal and visceral layers. - Contains **[pericardial fluid]**. **[Pericarditis:]** caused by pathogens in pericardium. - Inflamed pericardial surfaces rub against each other. - Producing **distinctive scratching sound**. - **[Cardiac tamponade:]** restricted movement of the heart. - Due to excess fluid in pericardial cavity. **Heart Superficial Anatomy, Heart Wall, and Cardiac Skeleton** **[Atria:]** two thin-walled top right and left chambers of the heart. - Each with an expandable outer **[auricle]**. **[Sulci:]** grooves that contain fat and blood vessels. **[Coronary sulcus:]** marks border between atria and ventricles. **[Anterior interventricular sulcus and posterior interventricular sulcus:]** mark boundary between left and right ventricles. The heart wall consists of three distinct layers... **[Epicardium:]** covers outer surface of heart. - **[Visceral layer of serous pericardium:]** covers surface of heart. - **[Parietal layer of serous pericardium:]** covers the visceral layer. **[Myocardium:]** cardiac muscle tissue. **[Endocardium:]** covers inner surface of heart. **Connective Tissues of the Heart** - Physically support cardiac muscle fibers, blood vessels, and nerves of myocardium. - Distribute forces of contraction. - Add strength and prevent overexpansion of heart. - Provide elasticity that helps return heart to original size and shape after contraction. **[Cardiac skeleton:]** four dense bands of tough elastic tissue. - Encircle heart valves and bases of pulmonary trunk and aorta. - Stabilize positions of heart valves and ventricular muscle cells. - Electrically insulate ventricular cells from atrial cells. **Heart Chambers, Valves, and Great Vessels** The chambers of the heart are separated by muscular partitions called **[septa]**. **[Interatrial septum:]** separates atria. **[Interventricular septum:]** separates ventricles. - Much **thicker** than interatrial septum. **Atrioventricular (AV) Valves** **\*\*\* They separate the atria from the ventricles, hence the name. \*\*\*** There are two AV valves: tricuspid and mitral valves. - Folds of fibrous tissue that extend into openings between atria and ventricles. - Permit blood flow in one direction. - From right atrium to right ventricle. - From left atrium to left ventricle. **Semilunar Valves** There are two semilunar valves: aortic and pulmonary valves. - Prevent backflow of blood into ventricles. **The Vena Cavae, Right Atrium, and Tricuspid Valve** **Right Atrium** Right atrium receives blood from... - **[Superior vena cava:]** carries blood from head, neck, upper limbs, and chest. - **[Inferior vena cava:]** carries blood from trunk, viscera, and lower limbs. **[Foramen ovale:]** before birth, the opening through interatrial septum, which connects the two atria of fetal heart. - Closes at birth, eventually forming **[fossa ovalis]**. **[Pectinate muscles:]** prominent muscular ridges. - On anterior atrial wall and inner surface of auricle Blood flows from the **right atrium** to the **right ventricle** through the... **Tricuspid Valve (*Right Atrioventricular Valve*)** - Has three cusps (hence its name). - Prevents backflow of blood. - Free edges of valve attach to **[chordae tendineae]** from **[papillary muscles]** of ventricle. - Prevent valve from opening backward. **The Right Ventricle, Pulmonary Valve, and Pulmonary Trunk** **Right Ventricle** **[Trabeculae carneae:]** muscular ridges on internal surface. - Of both, right and left ventricles. **[Moderator band:]** muscular ridge that delivers stimulus for contraction to papillary muscles. **[Conus arteriosus:]** at superior end of right ventricle. - Ends at **[pulmonary valve]**. **Pulmonary Valve** - Three semilunar cusps. - Leads to pulmonary trunk. - Start of pulmonary circuit, - Divides into left and right pulmonary arteries. **The Pulmonary Veins, Left Atrium, and Mitral Valve** **Left Atrium** **[Left atrium]** receives blood from **[left and right pulmonary veins]**. Blood flows from the left atrium to the left ventricle passes to left ventricle through... **Mitral Valve (Left Atrioventricular Valve or Bicuspid Valve)** - Two cusps **The Left Ventricle, Aortic Valve, and Ascending Aorta** **Left Ventricle** Similar to right ventricle but, does **NOT** have moderator band. Blood leaves left ventricle through aortic valve into ascending aorta. **[Aortic sinuses:]** saclike expansions at base of ascending aorta. - **[Ascending aorta]** turns to become **[aortic arch]**, - Becomes **[descending aorta]**. Compared to left ventricle, the right ventricle... - Holds and pumps the **SAME** amount of blood. - Has thinner walls. - Develops less pressure. - Is more pouch-shaped than round. **Blood Flow through the Heart Valves** The heart valves prevent backflow of blood. **The AV Valves: Atria to Ventricles** **[Atrioventricular (AV) valves:]** between atria and ventricles. There are two AV valves: tricuspid and mitral valves. - When ventricles contract, - Blood pressure closes valves - Papillary muscles contract and tense chordae tendineae, - Prevents regurgitation of blood into atria. - **[Regurgitation:]** backflow of blood. **The Semilunar Valves: Ventricles to Great Vessels** **[Semilunar valves:]** prevent backflow of blood into ventricles. There are two semilunar valves: pulmonary and aortic valves. - No muscular braces - **[Valvular heart disease (VHD):]** deterioration of valve function. - May develop after **[carditis:]** inflammation of heart. - May result from **[rheumatic fever:]** inflammatory autoimmune response to streptococcal bacteria. **The Blood Supply to the Heart** **Coronary Circulation** **\*\*\* Coronary circulation will supply blood FIRST to muscle tissue of heart before the blood goes anywhere else. \*\*\*** **Coronary Arteries** **[Coronary arteries:]** originate at aortic sinuses. - Elevated blood pressure and elastic rebound of aorta maintain blood flow through coronary arteries. **[Right coronary artery (RCA) ]** Supplies blood to... - Right atrium - Portions of both ventricles - Portions of electrical conducting system of heart Gives rise to... - Marginal arteries - Posterior interventricular artery **[Left coronary artery (LCA)]** Supplies blood to... - Left atrium - Left ventricle - Interventricular septum Gives rise to... - Circumflex artery - Anterior interventricular artery **[Arterial anastomoses:]** interconnect anterior and posterior interventricular arteries. - Maintain constant blood supply to cardiac muscle. **Cardiac Veins** **[Great Cardiac Vein ]** - Drains blood from region supplied by anterior interventricular artery. - Returns blood to coronary sinus, - Opens into right atrium. **[Posterior Vein of Left Ventricle, Middle Cardiac Vein, and Small Cardiac Vein]** - Empty into great cardiac vein or coronary sinus. **Anterior Cardiac Veins** - Empty into right atrium. **[Coronary artery disease (CAD):]** areas of partial or complete blockage of coronary circulation. - Cardiac muscle cells need a constant supply of oxygen and nutrients, - Reduction in blood flow to heart muscle reduces cardiac performance. **[Coronary ischemia:]** reduced circulatory supply from partial or complete blockage of coronary arteries. **Coronary Artery Disease** - Usual cause is formation of a fatty deposit, or atherosclerotic plaque, in wall of coronary vessel. - The plaque, or an associated thrombus (clot), narrows passageway and reduces blood flow. - Spasms in smooth muscles of vessel wall can further decrease or stop blood flow. **[Angina pectoris:]** chest pain. - Commonly one of the first symptoms of CAD. - A temporary ischemia develops when workload of heart increases - Individual may feel comfortable at rest - Exertion or emotional stress can produce sensations of pressure, chest constriction, and pain - Pain may radiate from sternal area to arms, back, and neck. **[Myocardial infarction (MI):]** part of coronary circulation becomes blocked, also called heart attack. - Cardiac muscle cells die from lack of oxygen. - Death of affected tissue creates a nonfunctional area known as an **[infarct]**. - Most commonly results from severe CAD. **[Coronary thrombosis:]** thrombus formation at a plaque. - Most common cause of an MI. Consequences depend on site and nature of circulatory blockage... - If near the start of one of the coronary arteries, - Damage will be widespread and heart may stop beating. - If blockage involves small arterial branch, - Individual may survive the immediate crisis. - But may have complications such as reduced contractility and cardiac arrhythmias. Myocardial infarctions... - Causes intense, persistent pain, even at rest, - BUT pain is not always felt. - May go undiagnosed and untreated. - **Often diagnosed with ECG and blood studies.** - Damaged myocardial cells release enzymes into circulation, - **[Cardiac troponin T]** - **[Cardiac troponin I]** - A form of **[creatinine phosphokinase, CK-MB]** **Risk Factor Modification** - Stop smoking - Treat high blood pressure - Adjust diet to lower cholesterol and promote weight loss - Reduce stress - Increase physical activity **Noninvasive Surgery** **[Atherectomy:]** long, slender catheter is inserted into coronary artery to remove plaque. **[Balloon angioplasty:]** tip of catheter contains inflatable balloon. - Inflated balloon presses plaque against vessel walls, - Plaques commonly redevelop. - A **[stent]** may be inserted to hold vessel open. **[Coronary artery bypass graft (CABG):]** small section of another vessel is removed. - Used to create detour around obstructed portion of coronary artery. - Up to four coronary arteries can be rerouted during a single operation, - Single, double, triple, or quadruple coronary bypasses. 20-2 The cells of the conducting system distribute electrical impulses through the heart, causing cardiac contractile cells to contract. **Cardiac Physiology: Electrical Impulses Leading to the Contractions Making Up a Heartbeat** **[Heartbeat:]** a single cardiac contraction. All heart chambers contract in series... - First the atria, - Then the ventricles. **Two Types of Cardiac Muscle Cells** **[Autorhythmic cells:]** control and coordinate heartbeat. **[Contractile cells:]** produce contractions that propel blood. **The Conducting System: Pacemaker and Conducting Cells** **[Conducting system:]** consists of specialized cardiac muscle cells. - Initiate and distribute electrical impulses that stimulate contraction. **[Autorhythmicity:]** cardiac muscle tissue contracts without neural or hormonal stimulation. **Components of the Conducting System** Pacemaker cells are found in the... - **[Sinoatrial (SA) node:]** in wall of right atrium. - **[Atrioventricular (AV) node:]** at junction between atria and ventricles. Conducting cells are found in the... - **[Internodal pathways of atria]** - **[Atrioventricular (AV) bundle]** - **[Bundle branches]** - **[Purkinje fibers]** of ventricles **[Pacemaker potential:]** gradual depolarization of pacemaker cells. - Do NOT have a stable resting membrane potential. **Rate of Spontaneous Depolarization** - SA node is 60--100 action potentials per minute. - AV node is 40--60 action potentials per minute. SA node depolarizes first, which establishes **[sinus rhythm]**. **Impulse Conduction through the Heart** 1. SA node activity and atrial activation begin. 2. Stimulus spreads across atria and reaches AV node. 3. Impulse is delayed for 100 msec at AV node, - Atrial contraction begins. 4. Impulse travels in AV bundle to left and right bundle branches in interventricular septum. - To Purkinje fibers, - And to papillary muscles via moderator band. 5. Purkinje fibers distribute impulse to ventricular myocardium. - Atrial contraction is completed. - Ventricular contraction begins. **Cardiac Arrythmias** **[Arrythmias:]** disturbances in heart rhythm. **[Bradycardia:]** abnormally slow heart rate. **[Tachycardia:]** abnormally fast heart rate. **[Ectopic pacemaker:]** abnormal cells generate high rate of action potentials. - Bypasses conducting system. - Disrupts timing of ventricular contractions. **The Electrocardiogram (ECG)** **[Electrocardiogram (ECG or EKG):]** a recording of electrical events in the heart. - Obtained by placing electrodes at specific locations on body surface. - Abnormal patterns are used to diagnose damage. **Features of an ECG** **ECG Waves** **[P wave:]** depolarization of atria. **[QRS complex:]** depolarization of ventricles. - Ventricles begin contracting shortly after R wave. **[T wave:]** repolarization of ventricles. **ECG Intervals** The time intervals are between ECG waves. **[P--R interval:]** from start of atrial depolarization to start of QRS complex. **[Q--T interval:]** time required for ventricles to undergo a single cycle of depolarization and repolarization. **[Cardiac contractile cells:]** form bulk of atrial and ventricular walls. - Receive stimulus from Purkinje fibers. **Resting Membrane Potential** - Of ventricular cell is about --90 mV. - Of atrial cell is about --80 mV. **[Intercalated discs:]** interconnect cardiac contractile cells. - Membranes of adjacent cells are, - Held together by desmosomes. - Linked by gap junctions. - Transfer force of contraction from cell to cell, - Propagate action potentials. **Characteristics of Cardiac Contractile Cells** - Small size - Single, central nucleus - **[Intercalated discs:]** branch interconnections between cells. **Action Potential in Cardiac Contractile Cells** **[Rapid depolarization:]** massive influx of Na+ through **fast sodium channels**. **[Plateau:]** extracellular Ca2+ enters cytosol through **slow calcium channels**. **[Repolarization:]** K+ rushes out of cell through **slow potassium channels**. **Refractory Period** **[Absolute refractory period (200 msec):]** cardiac contractile cells cannot respond. **[Relative refractory period (50 msec):]** cells respond only to strong stimuli. **Action Potential in a Ventricular Contractile Cell** - 250--300 msec. - 30 times longer than that in skeletal muscle fiber. - Prevents summation and tetany. **Role of Calcium Ions in Cardiac Contractions** - Extracellular Ca2+ crosses plasma membrane during plateau phase, - Provides roughly 20% of Ca2+ required for contraction. - Entry of extracellular Ca2+ triggers release of additional Ca2+ from sarcoplasmic reticulum (SR). **Cardiac Muscle Tissue** - Very sensitive to extracellular Ca2+ concentrations. - As slow calcium channels close, - Intracellular Ca2+ is pumped back into SR or out of cell. **Energy for Cardiac Contractions** **[Aerobic energy:]** from mitochondrial breakdown of fatty acids and glucose. - Oxygen is delivered by circulation. - Cardiac contractile cells store oxygen in myoglobin. 20-3 The contraction-relaxation events that occur during a complete heartbeat make up a cardiac cycle. **Cardiac Cycle** **[Cardiac cycle:]** from start of one heartbeat to beginning of next heartbeat. - Includes alternating periods of contraction and relaxation There are two phases of the cardiac cycle within each chamber. - **[Systole:]** contraction. - **[Diastole:]** relaxation. The blood pressure in each chamber... - **Rises** during **systole**. - **Falls** during **diastole**. Blood flows from an area of higher pressure to one of lower pressure... - Controlled by timing of contractions. - Directed by one-way valves. **Cardiac Cycle and Heart Rate** - At 75 beats per minute (bpm), - Cardiac cycle lasts about 800 msec. When heart rate increases... - All phases of cardiac cycle shorten, particularly diastole. There are four phases of cardiac cycle... - Atrial systole - Atrial diastole - Ventricular systole - Ventricular diastole **Atrial Systole** 1. Atrial contraction begins. - Right and left AV valves are open. 2. Atria eject blood into ventricles. **Ventricular Systole and Atrial Diastole** 3. Atrial systole ends - Atrial diastole begins. - Ventricles contain maximum blood volume, - Known as, **[end-diastolic volume (EDV)]**. 4. Ventricles contract and build pressure - Closing AV valves - Producing **[isovolumetric contraction]**. **Ventricular Systole** 5. ​Ventricular ejection - Ventricular pressure exceeds arterial pressure - Opens semilunar valves, allowing blood to exit. - Amount of blood ejected = **[stroke volume (SV)]**. 6. Semilunar valves close - As ventricular pressure falls, - Ventricles contain **[end-systolic volume (ESV)]**. - About 40 percent of end-diastolic volume. **Ventricular Diastole** 7. **[Isovolumetric relaxation]** - All heart valves are closed. - Ventricular pressure is higher than atrial pressure, - Blood cannot flow into ventricles. 8. AV valves open; ventricles fill passively. - Atrial pressure is higher than ventricular pressure. Individuals can survive severe atrial damage, BUT ventricular damage can lead to **[heart failure]**. **Heart Sounds** - Detected with a stethoscope **[S1:]** loud sound as AV valves close. \*\*\* LUBB \*\*\* **[S2:]** loud sound as semilunar valves close. \*\*\* DUPP \*\*\* **[S3, S4:]** soft sounds as blood is flowing into ventricles and atrial contraction. **[Heart murmur:]** sounds produced by regurgitation through valves. 20-4 Cardiac output is determined by heart rate and stroke volume. **Cardiac Output** **[Cardiac output (CO):]** the amount of blood pumped by left ventricle in one minute. **CO = HR × SV** - CO = cardiac output (mL/min) - HR = heart rate (beats/min) - SV = stroke volume (mL/beat) **Stroke Volume** **[Stroke volume (SV):]** the amount of blood pumped out of a ventricle during each contraction. **SV = EDV -- ESV** **[End-diastolic volume (EDV):]** amount of blood in each ventricle at end of ventricular diastole. **[End-systolic volume (ESV):]** amount of blood remaining in each ventricle at end of ventricular systole. **[Ejection fraction (EF):]** percentage of EDV ejected during contraction. Factors affecting heart rate... - Autonomic activity - Circulating hormones **Autonomic Innervation** - Cardiac plexus innervates heart. - Vagus nerves (CN X) carry parasympathetic fibers to small ganglia in cardiac plexus. - Cardiac centers of medulla oblongata. - **[Cardioacceleratory center:]** controls sympathetic neurons that increase heart rate. - **[Cardioinhibitory center:]** controls parasympathetic neurons that slow heart rate. **Cardiac Reflexes** - Cardiac centers - **[Baroreceptors:]** monitor blood pressure. - **[Chemoreceptors:]** monitor arterial oxygen and carbon dioxide levels. - Adjust cardiac activity. **Autonomic Tone** - Maintained by dual innervation and release of ACh and NE. - Fine adjustments meet needs of other systems. **Effects on Pacemaker Cells of SA Node** - Membrane potentials of pacemaker cells, - Are closer to threshold than those of cardiac contractile cells. - Any factor that changes the rate of spontaneous depolarization or the duration of repolarization, - Will alter heart rate by changing time required to reach threshold. - **ACh** released by **parasympathetic neurons**, - **Decreases** heart rate. - **NE** released by **sympathetic neurons**, - **Increases** heart rate. **[Bainbridge reflex (*atrial reflex*):]** adjustments in heart rate in response to increase in venous return. - **[Venous return:]** amount of blood returning to heart through veins. Stretch receptors in right atrium trigger increase in heart rate by stimulating sympathetic activity. **Hormonal Effects on Heart Rate** Heart rate is increased by... - Epinephrine (E) - Norepinephrine (NE) - Thyroid hormone (T3) **Factors affecting Stroke Volume** - Changes in EDV or ESV affect stroke volume, - And thus cardiac output. There are two factors that affect EDV... - **[Filling time:]** duration of ventricular diastole. - Venous return **[Preload:]** degree of ventricular stretching during ventricular diastole. - Directly proportional to EDV - Affects ability of muscle cells to produce tension **EDV and Stroke Volume** - At rest, - EDV is low. - Myocardium is stretched very little. - Stroke volume is relatively low. - With exercise, - Venous return increases. - EDV increases. - Myocardium stretches more. - Stroke volume increases. **[Frank--Starling Principle:]** as EDV increases, stroke volume increases. **Physical Limits** Ventricular expansion is limited by... - Myocardial connective tissues - Cardiac skeleton - Pericardium **Three Factors affect ESV** **[Preload:]** ventricular stretching during diastole. **[Contractility:]** force produced during contraction at a given preload. - Affected by autonomic activity and hormones. **[Afterload:]** tension that must be produced by ventricle to open semilunar valve and eject blood. **Effects of Autonomic Activity on Contractility** **Sympathetic Stimulation** - NE released by cardiac nerves, - E and NE released by adrenal medullae, - Causes ventricles to contract with more force. - Increases ejection fraction, decreases ESV. **Parasympathetic Stimulation** - ACh released by vagus nerves, - Reduces force of cardiac contractions. **Hormones** Many hormones affect heart contractility. - Pharmaceutical drugs mimic hormone actions, - Stimulate or block alpha or beta receptors. - Block calcium channels. **[Afterload:]** increased by any factor that restricts blood flow. - As afterload increases, stroke volume decreases. **[Summary: The Control of Cardiac Output]** **Control Factors of Heart Rate** **Autonomic Nervous System** - Sympathetic and parasympathetic **Circulating Hormones** - Venous return and stretch receptors **Stroke Volume Control Factors** - EDV---filling time and rate of venous return - ESV---preload, contractility, and afterload **[Cardiac reserve:]** difference between resting and maximal cardiac outputs. **Heart and Vessels of Cardiovascular System** **Cardiovascular Regulation** - Ensures adequate circulation to body tissues. **Cardiac Centers** - Control heart rate and peripheral blood vessels. **Cardiovascular System Responds to...** - Changing activity patterns. - Circulatory emergencies. Chapter 21: Blood Vessels and Circulation **Introduction to Blood Vessels and Circulation** Blood vessels are... - Classified by size and histological organization. - Instrumental in overall cardiovascular regulation. The great, or largest blood vessels attach directly to the heart... - **[Pulmonary trunk:]** carries blood from right ventricle to pulmonary circulation. - **[Aorta:]** carries blood from left ventricle to systemic circulation. 21-1 Arteries, which are elastic or muscular, and veins, which contain valves, have three-layered walls; capillaries have thin walls with only one layer. **[Arteries:]** carry blood away from heart. **[Arterioles:]** smallest branches of arteries that lead to capillary beds. **[Capillaries:]** smallest blood vessels with thin walls. - Location of exchange between blood and interstitial fluid. **[Venules:]** smallest branches of veins that collect blood from capillaries. **[Veins:]** return blood to heart. **Vessel Wall Structure in Arteries and Veins** The vessel walls have three layers... - Tunica intima - Tunica media - Tunica externa **[Tunica intima:]** inner layer. Includes... - The endothelial lining - Connective tissue layer - **[Internal elastic membrane]** (in arteries), - Elastic fibers in outer margin of tunica intima. **[Tunica media:]** middle layer. Contains... - Concentric sheets of smooth muscle in loose connective tissue - Encircles the endothelium that lines the lumen. - **[Lumen:]** interior space of the blood vessel. - Binds to inner and outer layers - **[External elastic membrane]**, - Separates tunica media from tunica externa. **[Tunica externa:]** outer layer, that anchors vessel to adjacent tissues. Contains... - Collagen fibers - Elastic fibers - Smooth muscle cells (in veins) **[Vasa vasorum ("vessels of vessels"):]** small arteries and veins in walls of large arteries and veins. - Serve cells of tunica media and tunica externa. **Differences between Arteries and Veins** - Arteries have thicker walls and higher blood pressure than veins. - A constricted artery has a small, round lumen. - A vein has a large, irregular lumen. - The endothelium of a constricted artery is folded. - Arteries are more elastic than veins. - Veins have valves. **Arteries** Elasticity allows arteries to absorb pressure waves that come with each heartbeat. **[Contractility:]** arteries change diameter. - Controlled by sympathetic division of ANS. - **[Vasoconstriction:]** contraction of arterial smooth muscle. - **[Vasodilation:]** relaxation of arterial smooth muscle. - Enlarges the lumen. **Vasoconstriction and Vasodilation** Affect... - Afterload on heart. - Peripheral blood pressure. - Capillary blood flow. From heart to capillaries, arteries change... - From elastic arteries, - To muscular arteries, - To arterioles. **Elastic Arteries** **[Elastic arteries:]** conducting arteries. - Large vessels Ex. *pulmonary trunk and aorta*. - Tunica media has many elastic fibers and few muscle cells. - Elasticity evens out pulse force. **Muscular Arteries** **[Muscular arteries:]** distribution arteries. - **Most arteries are medium-sized muscular arteries.** - Tunica media has many muscle cells. **Arterioles** **[Arterioles:]** resistance vessels. - Small vessels. - Have little or no tunica externa. - Have thin or incomplete tunica media. **[Aneurysm:]** a bulge in an arterial wall. - Caused by weak spot in elastic fibers. - Pressure may rupture vessel. **Capillaries** **[Capillaries:]** smallest vessels with thin walls. - Microscopic capillary networks permeate all active tissues. **Capillary Function** - Location of all exchange functions of cardiovascular system. - Materials diffuse between blood and interstitial fluid. **Capillary Structure** - Endothelial tube, inside thin basement membrane. - No tunica media. - No tunica externa. - Diameter is similar to that of a red blood cell. **[Continuous capillaries:]** have complete endothelial lining. - Found in all tissues except epithelia and cartilage. - Permit diffusion of water, small solutes, and lipid-soluble materials. - Block blood cells and plasma proteins. - Specialized continuous capillaries in CNS and thymus. - Have very restricted permeability. - Ex. *blood brain barrier*. **[Fenestrated capillaries:]** have pores in endothelial lining. - Permit rapid exchange of water and larger solutes - Found in... - Choroid plexus - Endocrine organs - Kidneys - Intestinal tract **[Sinusoids (*sinusoidal capillaries*):]** have gaps between adjacent endothelial cells. - Permit free exchange of water and large plasma proteins. - Found in... - Liver - Spleen - Bone marrow - Endocrine organs - Phagocytic cells monitor blood at sinusoids. **Capillary Beds** **[Capillary beds (*capillary plexus*):]** connect one arteriole and one venule. **[Precapillary sphincter:]** guards entrance to each capillary. - Opens and closes, causing capillary blood to flow in pulses. **[Thoroughfare channels:]** direct capillary connections between arterioles and venules. **[Collaterals:]** multiple arteries that contribute to one capillary bed. - Allow circulation if one artery is blocked. **Anastomoses and Angiogenesis** **[Arterial anastomosis:]** fusion of two collateral arteries. **[Arteriovenous anastomoses:]** direct connections between arterioles and venules. - Bypass the capillary bed. **[Angiogenesis:]** formation of new blood vessels. - Stimulated by **[vascular endothelial growth factor (*VEGF*)]**. - Occurs in the embryo as organs develop. - Occurs in response to factors released by cells that are **[hypoxic:]** oxygen-starved. - Most important in cardiac muscle, in response to a chronically constricted or occluded vessel. **Veins** **[Veins:]** collect blood from capillaries and return it to heart Compared to arteries, veins have... - Larger diameters - Thinner walls - Lower blood pressure **Types of Veins** **[Venules:]** very small veins that collect blood from capillaries. **[Medium-sized veins]** - Thin tunica media and few smooth muscle cells - Tunica externa contains longitudinal bundles of elastic fibers **[Large veins]** - Have all three tunica layers - Thick tunica externa - Thin tunica media **Venous Valves** **[Venous valves:]** prevent blood from flowing backward. - Folds of tunica intima. - Compression of veins pushes blood toward heart. - When walls of veins near the valves weaken, **[varicose veins]** or **[hemorrhoids]** may result. **The Distribution of Blood** - Heart, arteries, and capillaries - 30--35% of blood volume. - Venous system - 65--70% of blood volume. - One-third of venous blood is in large venous networks of the liver, bone marrow, and skin. **[Capacitance:]** the ability to stretch. - Relationship between blood volume and pressure. - Veins (capacitance vessels) stretch more than arteries, - Act as blood reservoirs. Systemic veins constrict ***(venoconstriction)*** in response to blood loss, - Increasing amount of blood in arterial system and capillaries. 21-2 Pressure and resistance determine blood flow and affect rates of capillary exchange. **Introduction to Pressure and Flow in Blood Vessels** **[Total capillary blood flow:]** equals cardiac output. - Is determined by, - Pressure (P) and resistance (R) in the cardiovascular system. **[Pressure (P):]** generated by the heart to overcome resistance. - Absolute pressure is less important than pressure gradient **[Pressure gradient (∆P):]** the difference in pressure from one end of a vessel to the other. **[Flow (F):]** is proportional to the pressure gradient (∆P) divided by resistance (R). **Measuring Pressure** **[Blood pressure (BP):]** arterial pressure (mmHg). **[Capillary hydrostatic pressure (CHP):]** pressure within the capillary beds. **[Venous pressure:]** pressure in the venous system. **Circulatory Pressure** - Must overcome total peripheral resistance, - R of entire cardiovascular system. - ∆P across the systemic circuit is about 85 mmHg. **Total Peripheral Resistance** Total peripheral resistance is affected by... - Vascular resistance - Blood viscosity - Turbulence **[Vascular resistance:]** due to friction between blood and vessel walls. - Depends on vessel length and vessel diameter. - Adult vessel length is constant. - Vessel diameter varies by vasodilation and vasoconstriction. - R increases exponentially as vessel diameter decreases. **Blood Viscosity** - R caused by molecules and suspended materials in a liquid. - Whole blood viscosity is about four times that of water. **[Turbulence:]** swirling action that disturbs smooth flow of liquid. - Occurs in heart chambers and great vessels. - Atherosclerotic plaques cause abnormal turbulence. **Overview of Cardiovascular Pressures** - Vessel luminal diameters - Total cross-sectional areas - Pressures - Velocity of blood flow **Arterial Blood Pressure** **[Systolic pressure:]** peak arterial pressure during ventricular systole. **[Diastolic pressure:]** minimum arterial pressure at end of ventricular diastole. **[Pulse pressure:]** difference between systolic and diastolic pressure. **[Mean arterial pressure (MAP):]** diastolic pressure + one-third pulse pressure. Normal blood pressure is 120/80. **[Hypertension:]** abnormally high blood pressure. - Greater than 140/90 **[Hypotension:]** abnormally low blood pressure. **Elastic Rebound in Arteries** Arterial walls... - Stretch during systole. - Rebound (recoil to original shape) during diastole. - Keep blood moving during diastole. **Pressures in Muscular Arteries and Arterioles** - MAP and pulse pressure decrease with distance from heart. - MAP declines as arterial branches become smaller and more numerous. - Pulse pressure decreases due to elastic rebound in arteries. **[Venous pressure:]** determines the amount of blood arriving at right atrium each minute (venous return). - Low effective pressure and low resistance in venous system. Return of blood to the heart is assisted by... - Skeletal muscular compression of veins. - When leg muscles are immobilized, blood supply to the brain is reduced, and fainting may result. - **[Respiratory pump:]** thoracic cavity expands during inhalation, decreasing venous pressure in the chest. **Capillary Exchange and Capillary Pressures** - Vital to homeostasis. - Materials move across capillary walls by... - Diffusion - Filtration - Reabsorption **Diffusion** **[Diffusion:]** movement of ions or molecules from areas of high concentration to lower concentration along the concentration gradient. **Diffusion Routes** - Water, ions, and small molecules - Diffuse between endothelial cells or through pores. - Some ions (Na+, K+, Ca2+, Cl−) - Diffuse through channels in plasma membranes. - Large, water-soluble compounds - Pass through fenestrated capillaries. - Lipids and lipid-soluble materials such as O2 - Diffuse through endothelial plasma membranes. - Plasma proteins cross endothelium of sinusoids. **Filtration** **[Filtration:]** the removal of solutes as a solution flows across a porous membrane. - Driven by hydrostatic pressure. - Water and small solutes forced through capillary wall, - Leaves larger solutes in bloodstream. **Reabsorption** **[Reabsorption:]** the result of osmosis. Higher solute concentration leads to higher **[osmotic pressure (OP)]** of a solution. **[Blood colloid osmotic pressure (BCOP):]** pressure required to prevent osmosis. - Caused by suspended blood proteins that are too large to cross capillary walls. **Interplay between Filtration and Reabsorption** - Ensures that plasma and interstitial fluid are in constant communication and mutual exchange. - Accelerates distribution of nutrients, hormones, and dissolved gases throughout tissues. - Assists in the transport of insoluble lipids and tissue proteins that cannot cross capillary walls. - Carries bacterial toxins and other chemical stimuli to lymphatic tissues and organs. Filtration and reabsorption are affected by... - **[Net capillary hydrostatic pressure]** - **[Net capillary colloid osmotic pressure]** Factors that contribute to net capillary hydrostatic pressure... - **[Capillary hydrostatic pressure (CHP)]** - **[Interstitial fluid hydrostatic pressure (IHP) ]** - Tends to push water and solutes, - Out of capillaries into interstitial fluid. **[Net capillary colloid osmotic pressure:]** is the difference between BCOP and ICOP. - Pulls water and solutes, - Into a capillary from interstitial fluid. **[Net filtration pressure (NFP):]** the difference between net hydrostatic pressure and net osmotic pressure. **NFP = (CHP -- IHP) -- (BCOP -- ICOP)** Capillary Exchange - At arterial end of capillary, - Fluid moves from capillary to interstitial fluid. - At venous end of capillary, - Fluid moves into capillary from interstitial fluid. - Transition point between filtration and reabsorption, - Is closer to venous end than arterial end. - Capillaries filter more than they reabsorb, - Excess fluid enters lymphatic vessels. **Capillary Dynamics** - Hemorrhaging reduces CHP and NFP, - Increases reabsorption of interstitial fluid or, **[recall of fluids]**. - Dehydration increases BCOP, - Accelerates reabsorption. - If CHP rises or BCOP declines - Fluid moves out of blood. - **[Edema:]** build up of fluid in peripheral tissues. 21-3 Blood flow and pressure in tissues are controlled by both autoregulation and central regulation. **Tissue Perfusion** **[Tissue perfusion:]** blood flow through the tissues. - Carries O2 and nutrients to tissues and organs. - Carries CO2 and wastes away. Affected by... - Cardiac output. - Peripheral resistance. - Blood pressure. When certain cells become active, circulation to that region must increase. Cardiovascular regulation ensures that blood flow changes occur... - At an appropriate time. - In the right area. - Without changing blood pressure and blood flow to vital organs. **[Vasomotion:]** contraction and relaxation cycle of precapillary sphincters. - Causes blood flow in capillary beds to constantly change routes. **Controlling Cardiac Output and Blood Pressure** **[Autoregulation:]** causes immediate, localized homeostatic adjustments. **[Neural mechanisms:]** respond quickly to changes at specific sites. **[Endocrine mechanisms:]** direct long-term changes. **Autoregulation of Blood Flow within Tissues...** - Adjusted by peripheral resistance while cardiac output stays the same. - Precapillary sphincters are stimulated to constrict or dilate, altering blood flow. - **[Vasoconstrictors:]** reduce blood flow by constricting precapillary sphincters. - Local vasoconstrictors include... - Endothelins released by damaged endothelial cells - Prostaglandins - Thromboxanes - **[Vasodilators:]** promote dilation of precapillary sphincters, increasing blood flow. - Local vasodilators include... - Low O2 or high CO2 levels - Lactate - Nitric oxide (NO) - High K+ or H+ concentrations - Chemicals released by inflammation Ex. *Histamine* - Elevated local temperature **Neural Mechanisms** **[Cardiovascular (CV) center]** of the medulla oblongata consists of cardiac centers and vasomotor center. **Cardiac Centers** **[Cardioacceleratory center:]** increases cardiac output. **[Cardioinhibitory center:]** reduces cardiac output. **Vasomotor Center** **Control of Vasoconstriction** - Controlled by adrenergic nerves (NE). - Stimulate contraction in arteriole walls. **Control of Vasodilation** - Controlled by cholinergic nerves (NO). - Relax smooth muscle. **[Vasomotor tone:]** produced by constant action of sympathetic vasoconstrictor nerves. **Reflex Control of Cardiovascular Function** Cardiovascular centers monitor arterial blood... **[Baroreceptor reflexes:]** respond to changes in blood pressure. **[Chemoreceptor reflexes:]** respond to changes in chemical composition, particularly pH and dissolved gases. **Baroreceptor Reflexes** Stretch receptors in walls of... - ​**[Carotid sinuses:]** maintain blood flow to brain. - ​**[Aortic sinuses:]** monitor start of systemic circuit. - **[Right atrium:]** monitors end of systemic circuit. Changes in blood pressure in the ascending aorta trigger the aortic reflex. - Adjusts blood pressure and flow in systemic circuit. When blood pressure rises, CV centers... - Decrease cardiac output, - Cause peripheral vasodilation. When blood pressure falls, CV centers... - Increase cardiac output, - Cause peripheral vasoconstriction. **[Atrial baroreceptors:]** monitor blood pressure at the end of the systemic circuit. - Bainbridge reflex responds to stretching of the wall of the right atrium. **Chemoreceptor Reflexes** Peripheral chemoreceptors in carotid bodies and aortic bodies monitor blood. - Central chemoreceptors below medulla oblongata... - Monitor cerebrospinal fluid. - Control respiratory function - Control blood flow to brain - Respond to changes in pH, O2, and CO2. - Coordinate cardiovascular and respiratory activities. **Cardiovascular Center and CNS Activities** Thought processes and emotional states can elevate blood pressure by... - Cardiac stimulation and vasoconstriction. **Endocrine Mechanisms** Hormones have short-term and long-term effects on cardiovascular regulation. Ex. *E and NE from adrenal medullae stimulate cardiac output and peripheral vasoconstriction.* **Antidiuretic hormone (ADH)** - Released by neurohypophysis (posterior lobe of pituitary). - Elevates blood pressure. - Reduces water loss at kidneys. - ADH responds to... - Low blood volume - High plasma osmotic concentration - Circulating angiotensin II - **[Angiotensin II:]** released in response to a decrease in renal blood pressure. - Stimulates... - Aldosterone production - ADH secretion - Thirst - Cardiac output and peripheral vasoconstriction **Erythropoietin (EPO)** - Released by kidneys. - Responds to low blood pressure or low O2 content in blood. - Stimulates vasoconstriction and red blood cell production. **Natriuretic Peptides** **Atrial Natriuretic Peptide (ANP)** - Produced by cells in right atrium. **Brain Natriuretic Peptide (BNP)** - Produced by ventricular muscle cells. - Respond to excessive diastolic stretching. - Reduce blood volume and blood pressure by several means. 21-4 The cardiovascular system adapts to physiological stress while maintain a special vascular supply to the brain, heart, and lungs. **Vascular Supply to Special Regions** - Some organs have separate mechanisms to control blood flow. - Three important examples... - Brain - Heart - Lungs **Blood Flow to the Brain** - Is top priority - Brain has high oxygen demand - When peripheral vessels constrict, cerebral vessels dilate, normalizing blood flow **[Cerebrovascular accident (CVA):]** blockage or rupture that stops blood flow in a cerebral artery. **Blood Flow to the Heart** - Through coronary arteries, - Oxygen demand increases with activity. Lactic acid and low O2 levels - Dilate coronary vessels. - Increase coronary blood flow. Epinephrine (E) - Dilates coronary vessels. - Increases heart rate. - Strengthens contractions. **[Heart attack:]** a blockage of coronary blood flow. Can cause... - Angina (chest pain) - Tissue damage - Heart failure - Death **Blood Flow to the Lungs** - Regulated by O2 levels in alveoli. - High O2 content, - Vessels dilate. - Low O2 content, - Vessels constrict. **The Cardiovascular Response to Exercise** - Light exercise - Extensive vasodilation occurs, increasing circulation - Venous return increases with muscle contractions - Cardiac output rises in response to - Venous return (Frank--Starling principle) - Atrial stretching - Heavy exercise - Activates sympathetic nervous system - Cardiac output increases to maximum - About four times resting level - Restricts blood flow to "nonessential" organs (e.g., digestive system) - Redirects blood flow to skeletal muscles, lungs, and heart - Blood supply to brain is unaffected **Exercise and Cardiovascular Disease** Regular, moderate exercise... - Moves low-density lipoproteins from blood to the liver, where they are converted to bile and excreted. - Slows the formation of plaques. - Reduces the risk of myocardial infarction by almost half. - Speeds recovery after a heart attack. - Reduces symptoms of coronary artery disease, such as angina. **The Cardiovascular Response to Hemorrhaging and Shock** Entire cardiovascular system adjusts to... - Maintain blood pressure. - Restore blood volume. - Short-term elevation of blood pressure. **Carotid and Aortic Reflexes** - Increase cardiac output (increasing heart rate), - Cause peripheral vasoconstriction. **Sympathetic Nervous System** - Further constricts arterioles, - Venoconstriction improves venous return. **Hormonal Effects** - Increase cardiac output. - Increase peripheral vasoconstriction. **Shock** - Short-term responses compensate after blood losses of up to 20 percent of total blood volume. - Failure to restore blood pressure results in shock. - Long-term restoration of blood volume. - Recall of fluids from interstitial spaces. - Aldosterone and ADH promote fluid retention and reabsorption, - Thirst increases. - Erythropoietin stimulates red blood cell production. 21-5 The vessels of the cardiovascular system make up both pulmonary and systemic circuits. **Three General Functional Patterns** - Peripheral artery and vein distribution is the same on right and left, except near the heart. - The same vessel may have different names in different locations. - Tissues and organs usually have multiple arteries and veins. - Vessels may be interconnected with anastomoses. 21-6 In the pulmonary circuit, deoxygenated blood enters the lungs in arteries, and oxygenated blood leaves the lungs by veins. Deoxygenated blood arrives at the heart from the systemic circuit. - Passes through right atrium and right ventricle, - Enters pulmonary trunk. - At the lungs, - CO2 is removed. - O2 is added. Oxygenated blood is returned to the heart from the pulmonary circuit. **[Pulmonary arteries:]** carry **deoxygenated** blood. - Pulmonary trunk - Branches into left and right pulmonary arteries. - Pulmonary arteries - Branch into pulmonary arterioles. - Pulmonary arterioles - Branch into capillary networks that surround alveoli. **[Pulmonary veins:]** carry **oxygenated** blood. - Capillary networks around alveoli, - Join to form venules. - Venules - Join to form four pulmonary veins. - Pulmonary veins - Empty into left atrium. 21-7 The systemic circuit carries oxygenated blood from the left ventricle to tissues and organs other than the lungs, and returns deoxygenated blood to the right atrium. **The Systemic Circuit** - Contains 84 percent of blood volume. - Supplies entire body, - Except for pulmonary circuit. **Systemic Arteries** - Carry blood from left ventricle, - Into **ascending aorta**. **Coronary Arteries** - Branch from aortic sinus. **The Aorta** - The ascending aorta, - Rises from the left ventricle. - Curves to form **aortic arch**, - Turns downward to become **descending aorta**. **Branches of the Aortic Arch** The aortic arch delivers blood to the head, neck, shoulders, and upper limbs. - ​**Brachiocephalic trunk (*innominate artery*)** - **​Left common carotid artery** - **​Left subclavian artery** Brachiocephalic trunk gives rise to... - **Right subclavian artery** - **Right common carotid artery** - Subclavian arteries - Supply blood to arms, chest wall, shoulders, back, and CNS - Give rise to - **Internal thoracic artery** - **Vertebral artery** - **Thyrocervical trunk** After leaving thoracic cavity, the subclavian artery... - Becomes **axillary artery**, - And **brachial artery** distally - The brachial artery divides at coronoid fossa of humerus, - Into **radial artery** and **ulnar artery**. - Fuse at wrist to form... - **Superficial** and **deep palmar arches**, - Which supply **digital arteries**. **The Common Carotid Arteries** Each common carotid divides into... - **External carotid artery** - Supplies blood to structures of the neck, lower jaw, and face. - **Internal carotid artery** - Enters skull and delivers blood to brain. **Internal Carotid Artery** Divides into three branches... - ​**Ophthalmic artery** - **​Anterior cerebral artery** - **​Middle cerebral artery** **The Vertebral Arteries** The vertebral arteries also supply brain with blood. Divides into two branches... - **Left** and **right vertebral arteries** - Arise from subclavian arteries. - Enter cranium through foramen magnum. - Fuse to form **basilar artery**, - Branches to form **posterior cerebral arteries**, - Become **posterior communicating arteries**. **Anastomoses** The **[cerebral arterial circle (*circle of Willis*)]** interconnects... - Internal carotid arteries - Basilar artery **[Cerebrovascular accidents (CVAs):]** interruptions of vascular supply to a portion of the brain, also called stroke. - Most commonly occur in middle cerebral artery. **The Descending Aorta** **Thoracic aorta** - Supplies organs of the chest. - **Bronchial arteries** - **Pericardial arteries** - **Esophageal arteries** - **Mediastinal arteries** - Supplies chest wall. - **Intercostal arteries** - **Superior phrenic arteries** **Abdominal Aorta** Divides at terminal segment into... - **Left common iliac artery** - **Right common iliac artery** Three unpaired branches - To visceral organs. Paired branches - To body wall, kidneys, adrenal glands, gonads, and structures outside abdominopelvic cavity. **Unpaired Branches of Abdominal Aorta** - ​​**Celiac trunk** - Which gives rise to... - **Left gastric artery** - **Splenic artery** - **Common hepatic artery** - **​Superior mesenteric artery** - **​Inferior mesenteric artery** **Paired Branches of Abdominal Aorta** - ​**Inferior phrenic arteries** - **​Adrenal arteries** - **​Renal arteries** - **​Gonadal arteries** - **​Lumbar arteries** **Arteries of the Pelvis and Lower Limbs** - **Median sacral artery** - **Right** and **left common iliac arteries** give rise to... - **Internal iliac artery** - **External iliac artery** - External iliac becomes **femoral artery**, - Gives rise to **deep femoral artery**. - **Femoral artery** becomes **popliteal artery** posterior to knee. - Branches to form... - **Posterior** and **anterior tibial arteries**. - **Anterior tibial artery** - Becomes **dorsalis pedis artery**. - **Posterior tibial artery** - Gives rise to **fibular artery** - Forms **medial** and **lateral plantar arteries** in foot - Connect to **dorsalis pedis artery** - To form **dorsal arch** and **plantar arch**. **Systemic Veins** - Complementary arteries and veins. - Run side by side. - Branching patterns of peripheral veins are variable. In neck and limbs... - One set of arteries (deep). - Two sets of veins (one deep, one superficial). \*\*\* Venous system controls body temperature. \*\*\* The **superior vena cava (SVC)** - Receives blood from the tissues and organs of... - Head - Neck - Chest - Shoulders - Upper limbs **The Dural Sinuses** The superficial cerebral veins and small veins of the brainstem empty into a network of **[dural sinuses]**. - **Superior and inferior sagittal sinuses** - **Petrosal sinuses** - **Occipital sinus** - **Left and right transverse sinuses** - **Straight sinus** **Cerebral Veins** - **Great cerebral vein** - Drains to straight sinus. - **Other cerebral veins** - Drain to cavernous sinus, - Which drains to petrosal sinus. - Each transverse sinus drains into a **sigmoid sinus** **Vertebral Veins** - Empty into **brachiocephalic veins** of chest. **Superficial Veins of the Head and Neck** - Converge to form... - **Temporal vein** - **Facial vein** - **Maxillary vein** **Temporal and Maxillary Veins** - Drain to **external jugular vein**. **Facial Vein** - Drains to **internal jugular vein**. **Veins of the Hand** **Digital Veins** - Empty into **superficial** and **deep palmar veins**, - Which interconnect to form **palmar venous arches**. **Superficial arch** empties into... - **Cephalic vein** - **Median antebrachial vein** - **Basilic vein** - **Median cubital vein** **Deep palmar veins** drain into... - **Radial** and **ulnar veins**, - Which fuse above elbow to form **brachial vein**. **The Brachial Vein** - Merges with **basilic vein** to become **axillary vein**. - **Cephalic vein** joins **axillary vein** to form **subclavian vein**. - Merges with **external** and **internal jugular veins** to form **brachiocephalic vein** - Which enters thoracic cavity. **Veins of the Thoracic Cavity** **Brachiocephalic vein** receives blood from... - **Vertebral vein** - **Internal thoracic vein** - Merge to form the **superior vena cava (SVC)**. **Tributaries of the Superior Vena Cava** **Azygos vein** and **hemi-azygos vein** receive blood from... - **Intercostal veins** - **Esophageal veins** - Veins of other mediastinal structures **The Inferior vena cava (IVC)** The IVC collects blood from organs inferior to the diaphragm. **Veins of the Foot** - Capillaries of the sole. - Drain into a network of **plantar veins**, - Which supply the **plantar venous arch**, - Drains into deep veins of leg... - **Anterior tibial vein** - **Posterior tibial vein** - **Fibular vein** - All three join to become **popliteal vein**. **Dorsal Venous Arch** Collects blood from... - Superior surface of foot - **Digital veins** Drains into two superficial veins... - **Great saphenous vein** - Drains into **femoral vein**. - ​**Small saphenous vein** - Drains into **popliteal\ vein**. **The Popliteal Vein** - Becomes the **femoral vein**. - Before entering abdominal wall, receives blood from... - **Great saphenous vein** - **Deep femoral vein** - **Femoral circumflex vein** - Inside the pelvic cavity, - Becomes the **external iliac vein**. **The External Iliac Veins** - Are joined by **internal iliac veins**, - To form **right** and **left common iliac veins**. **The Right and Left Common Iliac Veins** - Merge to form the inferior vena cava. **Major Tributaries of the Abdominal Inferior Vena Cava** - ​**Lumbar veins** - **​Gonadal veins** - **​Hepatic veins** - **​Renal veins** - **​Adrenal veins** - **​Phrenic veins** **The Hepatic Portal System** - Connects two capillary beds. - Delivers nutrient-laden blood from capillaries of digestive organs to liver for processing. - After processing in liver sinusoids (exchange vessels), - Blood collects in hepatic veins and empties into inferior vena cava. **Tributaries of the Hepatic Portal Vein** - ​**Inferior mesenteric vein** - Drains part of large intestine. - ​**Splenic vein** - Drains spleen, part of stomach, and pancreas. - ​**Superior mesenteric vein** - Drains part of stomach, small intestine, and part of large intestine. - ​**Left** and **right gastric veins** - Drain part of stomach. - ​**Cystic vein** - Drains gallbladder. 21-8 Modifications of fetal and maternal cardiovascular systems promote exchange of materials; the fetal cardiovascular system changes to function independently after birth. **Fetal and Maternal Cardiovascular Systems** - Embryonic lungs and digestive tract are nonfunctional. - Respiratory functions and nutrition are provided by placenta. **Placental Blood Supply** - Blood flows to the placenta. - Via umbilical cord, - Through a pair of **umbilical arteries** that arise from **internal iliac arteries**. - Blood returns from placenta. - Through a single **umbilical vein** that drains into **ductus venosus**, - Empties into **inferior vena cava**. Before birth... - Fetal lungs are collapsed. - O2 is provided by placental circulation. Fetal pulmonary circulation bypasses... **Foramen Ovale (interatrial opening)** - Covered by valve-like flap. - Directs blood from right to left atrium. - Becomes fossa ovalis. **Ductus Arteriosus** - Short vessel. - Connects pulmonary trunk to aorta. - Becomes ligamentum arteriosus. **Cardiovascular Changes at Birth** - Newborn breathes air and the lungs expand. - Pulmonary vessels expand. - Reduced resistance increases blood flow. - Rising O2 causes ductus arteriosus constriction. - Rising left atrium pressure closes foramen ovale. - Pulmonary circulation provides O2.