Cardiovascular System Part 2 of 3 PDF

CARDIOVASCULAR SYSTEM: HEART AND BLOOD VESSELS 2 PUMPS OF THE HEART ¡ PULMONARY CIRCULATION ¡ Carries blood to the lungs ¡ SYSTEMIC CIRCULATION ¡ Delivers oxygen and nutrients to all the remaining tissues of the body FUNCTIONS OF THE HEART 1. GENERATING BLOOD PRESSURE – fro...

CARDIOVASCULAR SYSTEM: HEART AND BLOOD VESSELS 2 PUMPS OF THE HEART ¡ PULMONARY CIRCULATION ¡ Carries blood to the lungs ¡ SYSTEMIC CIRCULATION ¡ Delivers oxygen and nutrients to all the remaining tissues of the body FUNCTIONS OF THE HEART 1. GENERATING BLOOD PRESSURE – from the contractions of the heart and responsible for moving blood through the vessels 2. ROUTING BLOOD – ensures that the blood flowing has adequate oxygen 3. ENSURING ONE-WAY BLOOD FLOW – valves of the heart ensure no back flow will happen 4. REGULATING BLOOD SUPPLY – rate and force of heart contractions change to meet the needs of the tissues  ¡ Shaped like a blunt cone and the size of a closed fist ¡ APEX – blunt, rounded point of the heart HEART ¡ BASE – larger, flat part of the opposite end ¡ Located in the mediastinum (midline of the thoracic cavity) HEART LOCATION Anterior to the vertebral column, posterior to the sternum Left of the midline Deep to the second to fifth intercostal spaces Superior surface of diaphragm ANATOMY OF THE HEART: PERICARDIUM ¡ Double layered, closed sac that surrounds the heart 1. FIBROUS PERICARDIUM – tough, fibrous connective tissue the prevents overdistention of the heart 2. SEROUS PERICARDIUM – divided into PARIETAL and VISCERAL PERICARDIUM (Epicardium) that allows a friction-free environment ¡ PERICARDIAL CAVITY – space between the parietal and visceral that contains a thin layer of serious fluid called PERICARDIAL FLUID ANATOMY OF THE HEART: HEART WALLS LAYER DESCRIPTION EPICARDIUM Superficial layer Thin, serous membrane that constitutes the outer surface of the heart MYOCARDIUM Thick, middle layer Composed of cardiac muscle cells Responsible for heart contraction ENDOCARDIUM Deep to the myocardium Simple squamous epithelium over a connective tissue Forms the inner surface of the heart chambers and covering of the valves Allows blood to move easily ANATOMY OF THE HEART: HEART WALLS ¡ PECTINATE MUSCLES – muscular ridges formed by the myocardium ¡ CRISTA TERMINALIS – separates the pectinate muscles in the right atrium ¡ TRABECULAE CARNEAE – larger, muscular ridges on the ventricles that help with forceful ejection of blood ANATOMY OF THE HEART: HEART WALLS ANATOMY: HEART CHAMBERS ¡ The heart consists of 2 Atria and 2 Ventricles ATRIA VENTRICLES Forms the superior and Forms the inferior and anterior posterior parts of the heart portion Has AURICLES (flaplike Discharging chambers of the heart extensions that protrudes from Papillary muscles and trabeculae the atria) carneae on the walls Pectinate muscles on the walls EXTERNAL ANATOMY Each atrium has a flap called an auricle The coronary sulcus separates the atria from the ventricles The interventricular grooves separate the right and left ventricles The interatrial septum separates the atria from each other The fossa ovalis is the former location of the foramen ovalis through which blood bypassed the lungs in the fetus The interventricular septum separates the ventricles CORONARY CIRCULATION ¡ The major arteries supplying the blood to the tissue of the heart lie within the coronary sulcus and interventricular grooves on the surface ¡ Right and left coronary arteries exit the aorta ¡ Left coronary artery has 3 branches 1) anterior intraventricular artery (supplies the anterior part of the heart) 2) left marginal artery (supplies the lateral wall of the left ventricle) and 3) circumflex artery (supplies the posterior wall of the heart) ¡ Right coronary artery has 2 branches 1) right marginal artery (supplies the lateral wall of the right ventricle and 2) posterior intraventricular artery (supplies the posterior and inferior part of the heart) CORONARY CIRCULATION ¡ The coronary arteries forms different connections through anastomoses so even if one artery becomes blocked, the areas may still receive some blood through other branches ¡ VEINS – carry blood from the heart walls to the right atrium ¡ GREAT CARDIAC VEIN – drains the left side of the heart ¡ SMALL CARDIAC VEIN – drains the right margin of the heart ¡ CORONARY SINUS – large venous cavity and empties into the right atrium ¡ Blood flow through coronary blood is not continuous. During contraction, blood vessels are compressed preventing flow ANATOMY OF THE HEART:VALVES Ensure unidirectional blood flow through the heart Atrioventricular (AV) valves lie between the atria and the ventricles AV valves prevent backflow into the atria when ventricles contract Chordae tendineae anchor AV valves to papillary muscles Tricuspid valve: separates the right atrium and ventricle Bicuspid valve: separates the left atrium and ventricle ANATOMY OF THE HEART: VALVES Semilunar valves prevent backflow of blood into the ventricles Aortic semilunar valve: lies between the left ventricle and the aorta Pulmonary semilunar valve: lies between the right ventricle and pulmonary trunk HEART SKELETON ¡ Consist of a plate of fibrous connective tissue between the atria and the ventricles ¡ Forms fibrous rings around the AV and Semilunar valves and reinforces valve openings ¡ Serve as electrical insulation between atria and ventricles ¡ Site for attachment of the cardiac muscles ROUTE OF BLOOD FLOW THROUGH THE HEART Blood from the body flows through the right atrium into the right ventricle and then to the lungs Blood returns from the lungs to the left atrium, enters the left ventricle, and is pumped back to the body CARDIAC MUSCLES ¡ Cells are elongated, branching cells with one or 2 centrally located nuclei ¡ Contains actin and myosin myofilaments organized as sarcomeres ¡ Striations are less regularly arranged and less numerous than skeletal muscle HISTOLOGY OF THE HEART CARDIAC MUSCLES ¡ Onset of contraction is longer and prolonged since it has a smooth sarcoplasmic reticulum and no dilated cisternae ¡ T-tubules are larger in diameter and not as closely associated with SR making the depolarization not as efficient as skeletal muscles ¡ Sources for calcium includes extracellular fluid, T-tubules and SR ¡ ATP production depends on O2 availability and provides for energy for contraction ¡ Will not maintain steady contraction and relaxation without oxygen ¡ Connected by desmosomes and gap junctions allow for cytoplasm to flow freely between cells CONDUCTING SYSTEM ¡ Relays action potentials through the heart ¡ Consists of modified cardiac muscle cells that form 2 nodes and a conducting bundle ¡ Sinoatrial Node (SA Node) medial to the opening of the superior vena cava ¡ AV Node (medial to the right AV valve ¡ AV Bundle (bundle of His) CONDUCTING SYSTEM ¡ The Bundle of His passes through the fibrous skeleton to reach the interventricular septum and divides into right and left bundle branches ¡ Purkinje fibers are the inferior terminal branches that are large-diameter cardiac muscle fibers ¡ Well-developed intercalated disks allows action potential to travel much more rapidly to other cardiac tissue ¡ Cardiac muscle cells have the intrinsic capacity to generate action potential ¡ SA node generate action potential at greater frequency than other cells and termed as PACEMAKER of the heart ACTION POTENTIAL CONSISTS OF: ELECTRICAL ACTIVITY OF THE HEART Action Potentials 1. After depolarization and partial repolarization, a plateau phase is reached, during which the membrane potential only slowly repolarizes 2. The opening and closing of voltage-gated ion channels produce the action potential The movement of Na+ through Na+ channels causes depolarization During depolarization, K+ channels close and Ca2+ channels begin to open Early repolarization results from closure of the Na+ channels and the opening of some K+ channels The plateau exists because Ca2+ channels remain open The rapid phase of repolarization results from the closure of the Ca2+ channels and the opening of many K+ channels ELECTRICAL ACTIVITY OF THE HEART Refractory Periods Absolute refractory period Cardiac muscle cells are insensitive to further stimulation Relative refractory period Stronger than normal stimulation can produce an action potential Cardiac muscle has a prolonged depolarization and thus a prolonged absolute refractory period, which allows time for the cardiac muscle to relax before the next action potential causes a contraction AUTO RHYTHMICITY OF THE CARDIAC MUSCLES ¡ Stimulates to contract at regular intervals ¡ Pacemaker cells generate action potentials spontaneously and at regular intervals ¡ The action potential spread through the conducting system causing voltage-gated Na channels to open and cardiac muscle cells contract ¡ Depolarization is dependent of Na, K, and Ca AUTO-RHYTHMICITY OF THE HEART ¡ Changes in the ion movement into and out of the cells cases the pacemaker potential: ¡ Sodium causes depolarization by moving into cells ¡ Decreasing permeability to K causes depolarization as K moves out of the cells ¡ Voltage gated Ca channels open and moves the Ca into the cells causing further depolarization ¡ Normally, SA node controls the rhythm of the heart (70-80 beasts per minute) ¡ Ectopic Focus is any part of the heart other than the SA node that generates a heartbeat ¡ AV node produces a heart beat of 40-60 bpm ¡ AV Bundle produces a heart rate of only 30bpm ¡ Inflammation or lack of adequate blood flow can injure muscle cells that can be a source of ectopic focus ELECTROCARDIOGRAM (ECG) ¡ Electrical currents from the action potential can be measured on the body surface ¡ ECG detect a summation of all the action potentials transmitted by the cardiac muscle cells through the heart at a given time ¡ It is a record of the electrical activity of the heart ¡ Each deflection correlates with a subsequent mechanical event in the heart ¡ Useful in diagnosing abnormal cardiac rhythms ALTERATIONS IN ECG CARDIAC CYCLE ¡ The left and right halves of the heart can be viewed as two pumps working together ¡ The Primer pump (atrium) and the power pump (ventricles) ¡ Cardiac Cycle – refers to the repetitive pumping process that begins with the onset of cardiac contraction and ends with the beginning of the next contraction ¡ Systole – Contract ¡ Diastole – Dilate CARDIAC CYCLE ¡ Beginning of the cardiac cycle: ¡ Atria and ventricles are relaxed ¡ AV valves are open ¡ Semilunar valves are closed ¡ At rest, movement of blood into the atria to the ventricles are passive due to (PASSIVE VENTRICULAR FILLING): ¡ AV valves are open ¡ Atrial pressure is greater than the ventricular pressure CARDIAC CYCLE 1. ACTIVE VENTRICULAR FILLING/ ATRIAL SYSTOLE ¡ SA node generates action potential that stimulates atrial contraction. ¡ This begins the cardiac cycle. ¡ P wave of the ECG ¡ As the atria contract, it pushes the blood into the ventricles CARDIAC CYCLE 2. VENTRICULAR SYSTOLE ¡ Action potential passes to the AV node > AV Bundle > Bundle Branches > Purkinje Fibers ¡ Represented by the QRS complex ¡ Ventricles contract and increases in pressure causing AV valve closure. ¡ Semilunar valves are also closed ¡ PERIOD OF ISOVOLUMETRIC CONTRACTION – volume of blood in the ventricles do not change even if it is contracting CARDIAC CYCLE 3. VENTRICULAR SYSTOLE ¡ Contraction continues and pressure builds until it overcomes pressure in the pulmonary trunk and aorta ¡ Semilunar valves open and blood flows to the arteries ¡ PERIOD OF EJECTION – when blood flows from the ventricles to the arteries  4. VENTRICULAR DIASTOLE ¡ Ventricular repolarization represented by the T wave in the ECG ¡ The ventricles relax, and pressure decreases CARDIAC CYCLE ¡ Blood flows back towards the ventricles causing semilunar valves to close ¡ All heart valves are closed and no blood flows in to the ventricles ¡ PERIOD OF ISOVOLUMETRIC RELAXATION CARDIAC CYCLE 5. VENTRICULAR DIASTOLE ¡ Atrial diastole began during ventricular systole ¡ Ventricles continue to relax, pressures drop below the atrial pressure and AV valves open ¡ PASSIVE VENTRICULAR FILLING EVENTS OCCURRING DURING THE CARDIAC CYCLE EVENTS OCCURRING DURING THE CARDIAC CYCLE EVENTS OCCURRING DURING THE CARDIAC CYCLE HEART SOUNDS EVENTS OCCURRING DURING THE CARDIAC CYCLE HEART SOUNDS ¡ Pumping heart produces distinct sounds and best heard using the stethoscope ¡ FIRST HEART SOUND – low pitched sound described as lubb ¡ Occurs during the beginning of the ventricular systole ¡ Caused by the closure of the AV valves ¡ SECOND HEART SOUND – higher pitched sound described as dupp ¡ Occurs at the beginning of ventricular diastole ¡ Caused by the closure of the aortic and pulmonary semilunar valves AORTIC PRESSURE CURVE ¡ The elastic walls of the aorta are stretches as blood is ejected into the aorta ¡ Sudden change in the aortic pressure results in a DICROTIC NOTCH (incisura) in the aortic pressure curve ¡ The term dicrotic means “double beating” when increased pressure caused by recoil is large ¡ Blood pressure measurements reflect the pressure changes that occur in the aorta ¡ Systolic pressure around 120 mmHg ¡ Diastolic pressure around 80 mmHg MEAN ARTERIAL PRESSURE ¡ Average blood pressure in the aorta ¡ Proportional to cardiac output times peripheral resistance ¡ Cardiac Output (minute volume) is the amount of blood pumped by the heart per minute ¡ Peripheral Resistance is the total resistance against which blood must be pumped MEAN ARTERIAL PRESSURE ¡ CARDIAC OUTPUT = Heart Rate x Stroke Volume ¡ Heart Rate = number of times the heart beats per minute ¡ Stoke Volume = volume of blood pumped during each heartbeat ¡ Equal to the end-diastolic volume (125 mL) – end-systolic volume (55mL) (around 70 mL) ¡ EDV – amount of blood collected in a ventricle during diastole ¡ ESV – amount of blood remaining in a ventricle after contraction MEAN ARTERIAL PRESSURE Venous return is the amount of blood returning to the heart Increased venous return increases stroke volume by increasing end- diastolic volume Increased force of contraction increases stroke volume by decreasing end-systolic volume Cardiac reserve is the difference between resting and maximal CO REGULATION OF THE HEART: INTRINSIC ¡ PRELOAD – extent to which the ventricular walls are stretched ¡ An increase in preload increases cardiac output ¡ Decrease in preload decreases cardiac output ¡ STARLING LAW OF THE HEART – described the relationship between preload and stroke volume ¡ An increased preload causes the cardiac muscle fibers to contract with a greater force and produce a greater stroke volume ¡ AFTERLOAD – the pressure the contracting left ventricle must produce to overcome the pressure in the aorta and move blood into the aorta REGULATION OF THE HEART: EXTRINSIC Extrinsic Regulation Modifies heart rate and stroke volume through nervous and hormonal mechanisms The cardioregulatory center in the medulla oblongata regulates the parasympathetic and sympathetic nervous control of the heart Epinephrine and norepinephrine are released into the blood from the adrenal medulla as a result of sympathetic stimulation. They increase the rate and force of heart contraction REGULATION OF THE HEART: EXTRINSIC Parasympathetic stimulation is supplied by the vagus nerve Decreases heart rate. Postganglionic neurons secrete acetylcholine, which increases membrane permeability to K. Hyperpolarization of the plasma membrane increases the duration of the prepotential Sympathetic stimulation is supplied by the cardiac nerves Increases heart rate and the force of contraction (stroke volume) Postganglionic neurons secrete norepinephrine, which increases membrane permeability to Ca2+. Depolarization of the plasma membrane decreases the duration of the prepotential HEART AND HOMEOSTASIS Effect of Blood Pressure Baroreceptors monitor blood pressure and the cardioregulatory center modifies heart rate and stroke volume In response to a decrease in blood pressure, the baroreceptor reflexes increase heart rate and stroke volume When blood pressure increases, the baroreceptor reflexes decrease heart rate and stroke volume HEART AND HOMEOSTASIS Effect of pH, Carbon Dioxide, and Oxygen Carotid body and aortic chemoreceptor receptors monitor blood oxygen levels Medullary chemoreceptors monitor blood pH and carbon dioxide levels Chemoreceptors are not important for the normal regulation of the heart, but are important in the regulation of respiration and blood vessel constriction HEART AND HOMEOSTASIS Effect of Ions and Body Temperature Increased extracellular K+ decrease heart rate and stroke volume Decreased extracellular K+ decrease heart rate Increased extracellular Ca2+ increase stroke volume and decrease heap rate Decreased extracellular Ca2+ levels produce the opposite effect Heart rate increases when body temperature increases, and it decreases when body temperature decreases EFFECTS OF AGING ON THE HEART Aging results in gradual changes in the function of the heart, which are minor under resting conditions but are more significant during exercise Some age-related changes to the heart are the following Decreased cardiac output and heart rate Increased cardiac arrhythmias Hypertrophy of the left ventricle Development of stenoses or incompetent valves Development of coronary artery disease and heart failure Exercise improves the functional capacity of the heart at all ages. CARDIOVASCULAR SYSTEM: BLOOD VESSELS THE CIRCULATORY SYSTEM ¡ Organized into 2 sets: ¡ Pulmonary Vessels – transport blood from the right ventricle, through the lungs and back to the left atrium ¡ Systemic Vessels - transport blood from the left ventricle, through all parts of the body and back to the right atrium FUNCTIONS OF THE CIRCULATORY SYSTEM 1. Carries blood 2. Exchanges nutrients, waste products and gases with tissues 3. Transport substances 4. Helps regulate blood pressure 5. Directs blood flow to tissues STRUCTURAL FEATURES OF BLOOD VESSELS ¡ Blood vessels are hollow tubes that conduct blood through the tissues of the body ¡ 3 types: ¡ Arteries - carry blood away from the heart toward capillaries, where exchange between the blood and interstitial fluid occurs ¡ Capillaries – smallest blood vessels that form networks ¡ Veins - carry blood from the capillaries toward the heart ¡ Form continuous passageway for blood flow from the heart, through the tissues and back BLOOD VESSELS ¡ 3 TISSUE LAYERS/ TUNICS ¡ TUNICA INTIMA (Tunica Interna) - most internal layer ¡ Consists of an endothelium, basement membrane, lamina propria (connective tissue) and internal elastic membrane (fenestrated elastic fibers) ¡ TUNICA MEDIA – middle layer ¡ Consists of smooth muscle cells, with variable amounts of elastic and collagen fibers ¡ Regulates the contraction and relaxation of the blood vessels ¡ External elastic membrane separates the media from the next layer ¡ TUNICA ADVENTITIA - tunica externa ¡ Composed of dense and loose connective tissue ¡ Contains vasa vasorum – nourish the external tissues of the blood vessel wall TYPES OF ARTERIES ELASTIC ARTERIES ¡ Largest diameters and are often called conducting arteries ¡ Blood pressure in these arteries fluctuate between higher systolic and lower diastolic values ¡ Has greater amount of elastic tissue to allow recoil preventing drastic decreases in BP ¡ Features a thick tunica intima MUSCULAR ARTERIES ¡ Referred as such due to the thick tunica media ¡ Called distributing arteries that allows partial regulation of blood flow to different body regions by constricting and dilating ARTERIOLES ¡ Smallest arteries ¡ Transport blood to capillaries ¡ Features no observable internal elastic membrane ¡ Capable of vasodilation and constriction CAPILLARIES ¡ Most common type and the thinnest of all blood vessels Capillaries consist only of endothelium RBCs travel in a single file and may sometimes bend depending on the diameter of the capillary Pericapillary cells – scattered cell that lie between the basement membrane and endothelial cells Thoroughfare channel – vessel within the capillary network that carries blood from arterioles to venules Precapillary sphincters which are smooth muscle cells that regulate the blood flow into the capillaries Capillaries in the skin functions in thermoregulation and nutrient and waste product exchange CAPILLARIES TYPES OF CAPILLARIES TYPES OF CAPILLARIES TYPES OF CAPILLARIES ARTERIOVENOUS ANASTOMOSES ¡ Specialized vascular connections that allow blood to flow directly from arterioles to small veins without passing through capillaries ¡ Glomus – AV anastomoses that consists of arterioles with abundant smooth muscle and present in the sole, palms, terminal phalanges and nail beds VEINS Classified as: 1) Venules 2) Small Veins 3) Medium/ Large Veins  ¡ VENULES – smallest.Veins ¡ Tubes composed of endothelium resting on a delicate basement membrane ¡ Collect blood from the capillaries and transport it to small veins VEINS ¡ Nutrient exchange occurs through the wall ¡ As the venule walls increases in thickness, the degree of nutrient exchange decreases VEINS ¡ Medium veins collect blood from small veins and deliver it to large veins ¡ Large veins transport blood back to the heart ¡ The tunica intima is thin and consists of endothelial cells, with collagenous connective tissue and few elastic fibers VEINS ¡ PORTAL VEINS ¡ Connects 2 capillary network ¡ No pumping mechanism ¡ 3 portal veins are found in the human body: ¡ Hepatic portal vein (GI tract & spleen to dilated capillaries in the liver) ¡ Hypothalamo-hypophysial portal veins (hypothalamus to anterior pituitary gland) ¡ Renal nephron portal system (urine forming structures in the kidney) VEINS ¡ VALVES ¡ Allow blood to flow toward the heart but not in the opposite direction ¡ Found in veins greater than 2 mm ¡ Consist of folds in the tunica intima that form 2 flaps that overlap in the middle of the vein ¡ VASA VASORUM ¡ Small blood vessels that supply nutrients to arteries and veins NEURAL INNERVATION OF BLOOD VESSELS ¡ Innervated by unmyelinated sympathetic nerve fibers ¡ Sympathetic stimulation causes blood vessels to constrict ¡ Parasympathetic stimulation cause blood vessels in the penis and clitoris to dilate ¡ Some neurons function as baroreceptors that monitor stretch in the blood vessel wall and detect changes in pressure AGING OF THE ARTERIES ¡ ARTERIOSCLEROSIS – hardening of the arteries ¡ Consists of degenerative changes in the arteries that make them less elastic ¡ Become more severe with advancing age ¡ Increases resistance to blood flow, reduces the normal circulation of the blood and greatly increases the work performed by the heart ¡ Involves general hypertrophy of the tunica intima and media ¡ May involve the formation of calcium deposits in the tunica media of the arteries and reduces the vessel’s elasticity AGING OF THE ARTERIES ¡ ATHEROSCLEROSIS ¡ Deposition of material in the walls of arteries to form distinct plaques ¡ Affects primarily medium and larger arteries, including coronary arteries ¡ Plaques form when macrophages containing cholesterol accumulate in the media PULMONARY CIRCULATION ¡ Moves blood to and from the lungs ¡ Pulmonary trunk arises from the right ventricle and divides to form the pulmonary arteries, which project to the lungs ¡ From the lungs, four pulmonary veins return blood to the left atrium SYSTEMIC CIRCULATION: ARTERIES ¡ System of vessels that carries blood from the left ventricle to the tissues of the body and back to the right atrium AORTA ¡ Leaves the left ventricle to form the ¡ Ascending aorta ¡ Aortic arch ¡ Descending aorta ¡ Consists of the thoracic aorta and the abdominal aorta ¡ Coronary arteries branch from the aorta and supply the heart ARTERIES OF THE HEAD AND NECK ¡ The following arteries branch from the aortic arch to supply the head and the upper limbs ¡ Brachiocephalic ¡ Divides to form the right common carotid and the right subclavian arteries ¡ Left common carotid ¡ Left subclavian ¡ Vertebral arteries branch from the subclavian arteries ARTERIES OF THE HEAD AND NECK ¡ The common carotid arteries and the vertebral arteries supply the head ¡ The common carotid arteries divide to form the ¡ external carotids: supply the face and mouth ¡ internal carotids: supply the brain ¡ Vertebral arteries join within the cranial cavity to form the basilar artery, which supplies the brain ¡ The internal carotids and basilar arteries contribute to the cerebral arterial circle MAJOR ARTERIES OF THE HEAD AND THORAX CEREBRAL ARTERIAL CIRCLE (CIRCLE OF WILLIS) ARTERIES OF THE UPPER LIMB ¡ The subclavian artery continues (without branching) as the axillary artery and then as the brachial artery. The brachial artery divides into the radial and ulnar arteries ¡ The radial artery supplies the deep palmar arch ¡ The ulnar artery supplies the superficial palmar arch ¡ Both arches give rise to the digital arteries BRANCHES OF THE AORTA  THORACIC AORTA/ BRANCHES ¡ The thoracic aorta has ¡ Visceral branches that supply the thoracic organs ¡ Parietal branches that supply the thoracic wall ABDOMINAL AORTA/ BRANCHES ¡ The abdominal aorta has ¡ Visceral branches that supply the abdominal organs ¡ Parietal branches that supply the abdominal wall ABDOMINAL AORTA/ BRANCHES ¡ The visceral branches are paired and unpaired ¡ The unpaired arteries supply the stomach, spleen, and liver (celiac trunk); the small intestine and upper part of the large intestine (superior mesenteric); and the lower part of the large intestine (inferior mesenteric) ¡ The paired arteries supply the kidneys, adrenal glands, and gonads MAJOR ARTERIES OF THE ABDOMEN AND PELVIS  ARTERIES OF THE PELVIS ¡ The common iliac arteries arise from the abdominal aorta, and the internal iliac arteries branch from the common iliac arteries ¡ The visceral branches of the internal iliac arteries supply the pelvic organs ¡ The parietal branches supply the pelvic wall and floor and the external genitalia MAJOR ARTERIES OF THE LOWER LIMB SYSTEMIC CIRCULATION:VEINS ¡ The three major veins returning blood to the heart are the ¡ Superior vena cava (head, neck, thorax, and upper limbs) ¡ Inferior vena cava ( abdomen, pelvis, and lower limbs) ¡ Coronary sinus (heart) ¡ Veins are of three types: ¡ Superficial veins ¡ Deep veins ¡ Sinuses VEINS OF THE HEAD AND NECK ¡ The internal jugular veins drain the dural venous sinuses and the veins of the anterior head, face, and neck ¡ The external jugular veins and the vertebral veins drain the posterior head and neck VEINS OF THE UPPER LIMB ¡ The deep veins are the small ulnar and radial veins of the forearm, which join the brachial veins of the arm. The brachial veins drain into the axillary vein ¡ The superficial veins are the basilic, cephalic, and median cubital ¡ The basilic vein becomes the axillary vein, which then becomes the subclavian vein. The cephalic vein drains into the axillary vein ¡ The median cubital connects the basilic and cephalic veins at the elbow VEINS OF THE THORAX ¡ The left and right brachiocephalic veins and the azygos veins return blood to the superior vena cava VEINS OF THE ABDOMEN AND PELVIS ¡ Ascending lumbar veins from the abdomen join the azygos and hemiazygos veins ¡ Veins from the kidneys, adrenal glands, and gonads directly enter the inferior vena cava ¡ Veins from the stomach, intestines, spleen, and pancreas connect with the hepatic portal vein ¡ The hepatic portal vein transports blood to the liver for processing. Hepatic veins from the liver join the inferior vena cava VEINS OF THE ABDOMEN AND PELVIS VEINS OF THE LOWER LIMB ¡ The deep veins are the fibular (peroneal), anterior tibial, posterior tibial, popliteal, femoral, and external iliac veins ¡ The superficial veins are the small and great saphenous veins DYNAMICS OF BLOOD CIRCULATION ¡ Blood movement through the vessels is determined by: 1. Flow 2. Resistance 3. Pressure LAMINAR AND TURBULENT FLOW IN VESSELS ¡ LAMINAR FLOW – fluids tend to flow through long, smooth-walled tubes in a streamlined fashion ¡ Consist of movement of concentric layers, with the outer layer moving most slowly and the layer at the center moving most rapidly ¡ TURBULENT FLOW – where laminar flow is interrupted ¡ When the rate of flow exceeds a critical velocity or when the fluid passes a constriction, a sharp turn or rough surface ¡ Caused by numerous small currents flowing at an angle to the long axis of the vessels ¡ Causses the sounds heard during blood pressure measurement and partially responsible for heart sounds BLOOD PRESSURE ¡ A measure of the force exerted by blood against the blood vessel wall. Blood moves through vessels because of blood pressure ¡ Can be measured by listening for Korotkoff sounds produced by turbulent flow in arteries as pressure is released from a blood pressure cuff BLOOD FLOW ¡ Reported in either mL/ min or L/min ¡ Blood flows from an area of higher to lower pressure area ¡ The greater the pressure difference the greater the rate of flow ¡ The resistance increases, the blood flow decreases ¡ Resistance is affected by blood viscosity, vessel length and diameter PHYSIOLOGY OF THE CIRCULATION ¡ Blood Flow Through a Blood Vessel ¡ The amount of blood that moves through a vessel in a given period. ¡ Directly proportional to pressure differences and is inversely proportional to resistance ¡ Resistance is the sum of all the factors that inhibit blood flow. Resistance increases when blood vessels become smaller and viscosity increases ¡ Viscosity is the resistance of a liquid to flow. Most of the viscosity of blood results from red blood cells. The viscosity of blood increases when the hematocrit increases or plasma volume decreases POISEUILLE’S LAW CRITICAL CLOSING PRESSURE AND LAPLACE’S LAW ¡ CRITICAL CLOSING PRESSURE - lowest pressure at which the vessel remains open ¡ Allows the vessel to collapse and blood flow through the vessel stops (i.e. shock states) ¡ Dependent on 2 factors: 1) diameter and 2) blood pressure ¡ LAPLACE’S LAW – states that the force that stretches the vessel wall is proportional to the diameter of the vessel times the blood pressure (i.e. aneurysm) VASCULAR COMPLIANCE ¡ Compliance – tendency for blood vessel volume to increase as blood pressure increases ¡ The more easily the vessel wall stretches, the greater its compliance PHYSIOLOGY OF SYSTEMIC CIRCULATION ¡ Blood Flow Through the Body ¡ Mean arterial pressure equals cardiac output times peripheral resistance ¡ Vasomotor tone is a state of partial contraction of blood vessels.Vasoconstriction increases vasomotor tone and peripheral resistance, whereas vasodilation decreases vasomotor tone and peripheral resistance ¡ Blood pressure averages 100 mm Hg in the aorta and drops to 0 mm Hg in the right atrium. The greatest drop occurs in the arterioles and capillaries PHYSIOLOGY OF CIRCULATION ¡ Pulse Pressure and Vascular Compliance ¡ Pulse pressure is the difference between systolic and diastolic pressures. Pulse pressure increases when stroke volume increases or vascular compliance decreases ¡ Vascular compliance is a measure of the change in volume of blood vessels produced by a change in pressure ¡ Pulse pressure waves travel through the vascular system faster than the blood flows. Pulse pressure can be used to take the pulse PHYSIOLOGY OF SYSTEMIC CIRCULATION ¡ Capillary Exchange and Regulation of Interstitial Fluid Volume ¡ Capillary exchange occurs through or between endothelial cells ¡ Diffusion, which includes osmosis, and filtration are the primary means of capillary exchange ¡ Filtration moves materials out of capillaries and osmosis moves them into capillaries ¡ A net movement of fluid occurs from the blood into the tissues. The fluid gained by the tissues is removed by the lymphatic system CAPILLARY TRANSPORT MECHANISMS CONTROL OF BLOOD FLOW IN TISSUES CONTROL OF BLOOD FLOW IN TISSUES CONTROL OF BLOOD FLOW IN TISSUES NERVOUS REGULATION REGULATION OF MEAN ARTERIAL PRESSURE Peripheral Resistance – resistance to blood flow in all the blood vessels Pulse pressure – difference between the systolic and diastolic pressure As long as arterial pressure is adequate, local control of blood flow is appropriately matched to tissues’ metabolic needs REGULATION OF MAP ¡ SHORT TEM REGULATION ¡ Baroreceptors are sensory receptors sensitive to stretch ¡ Located in the carotid sinuses and the aortic arch ¡ The baroreceptor reflex changes peripheral resistance, heart rate, and stroke volume in response to changes in blood pressure REGULATION OF MAP ¡ SHORT TERM REGULATION ¡ Epinephrine and norepinephrine are released from the adrenal medulla as a result of sympathetic stimulation. They increase heart rate, stroke volume, and vasoconstriction ¡ Peripheral chemoreceptor reflexes respond to decreased oxygen, leading to increased vasoconstriction ¡ Central chemoreceptors respond to high carbon dioxide or low pH levels in the medulla, leading to increased vasoconstriction, heart rate, and force of contraction (CNS ischemic response) HORMONAL REGULATION ON BP REGULATION OF MAP ¡ LONG-TERM REGULATION: ¡ Through the renin-angiotensin-aldosterone mechanism ¡ Renin is released by the kidneys in response to low blood pressure ¡ Promotes the production of angiotensin II, which causes vasoconstriction and an increase in aldosterone secretion ¡ Aldosterone helps maintain blood volume by decreasing urine production ¡ The vasopressin (ADH) mechanism causes ADH release from the posterior pituitary in response to a substantial decrease in blood pressure ¡ ADH causes vasoconstriction and helps maintain blood volume by decreasing urine production RENIN- ANGIOTENSIN- ALDOSTERONE MECHANISM (RAAS) VASOPRESSIN (ADH) MECHANISM) REGULATION OF MAP ¡ Long-Term Regulation of Blood Pressure ¡ The atrial natriuretic mechanism causes atrial natriuretic hormone release from the cardiac muscle cells when atrial blood pressure increases. It stimulates an increase in urinary production, causing a decrease in blood volume and blood pressure ¡ The fluid shift mechanism causes fluid shift, which is a movement of fluid from the interstitial spaces into capillaries in response to a decrease in blood pressure to maintain blood volume CARDIOVASCULAR REGULATION ¡ Exercise ¡ Local control mechanisms increase blood flow through exercising muscles, which lowers peripheral resistance ¡ Cardiac output increases because of increased venous return, stroke volume, and heart rate ¡ Vasoconstriction in the skin, the kidneys, the gastrointestinal tract, and skeletal muscle (non- exercising and exercising) increases peripheral resistance, which helps prevent a drop in blood pressure ¡ Blood pressure increased despite an overall decrease in peripheral resistance because of increased cardiac output CARDIOVASCULAR REGULATION ¡ Circulatory Shock ¡ Baroreceptor reflexes and the adrenal medullary response increase blood pressure ¡ The renin-angiotensin-aldosterone mechanism and the vasopressin mechanism increase vasoconstriction and blood volume. The fluid shift mechanism increases blood volume ¡ In severe shock, the chemoreceptor reflexes increase vasoconstriction, heart rate, and force of contraction ¡ In severe shock, despite negative-feedback mechanisms, a positive- feedback cycle of decreasing blood pressure can cause death