Cardiovascular System PDF

Heart orientation heart is rotated in quadripeds and tipped sternal view us. Vertebral view side of the heart is on Right the left Aurides-top extension...

Heart orientation heart is rotated in quadripeds and tipped sternal view us. Vertebral view side of the heart is on Right the left Aurides-top extension Cardiovascular System The heart is a pump. It fills with blood then the cardiac muscle contracts and squeezes the blood out of the chambers and into the vessels of the body. The blood carrying oxygen to the tissues and removing waste products of cellular respiration are carried through the body, propelled by the heart through a closed system of blood vessels. The heart is surrounded by the lungs and protected by the ribs. Mediastinum in veterinary species the heart is located in a space between the pleural cavities of the lungs called the mediastinum. The trachea, esophagus, vessels and of lymph nodes also run through the mediastinum. "Pluck"-removal trachea esophagus lungs , , and heart for examination The Heart Wall The pericardium is the “sac” that suspends the heart within the mediastinum o The pericardium has an outer fibrous layer ▪ This layer protects the heart and loosely cardiac attaches it to the diaphragm preventstorsion o The inner portion of the pericardium is made up of two layers of serous pericardium ▪ The outer, parietal layer between the fibrous pericardium and the epicardium ▪ The inner, visceral layer is closely adherent to the heart muscle and is called the epicardium cannot pericardu epicannot separatevisceral remove ois Myocardium is the thickest layer of heart tissue, made up of cardiac muscle Between the myocardium and the chambers of the heart is the thin membranous lining called the  endocardium Hardware Disease appears fuzzy velvety or Septic pericarditis is a bacterial infection and inflammation of the fibrous pericardium Septic pericarditis can occur in any species, but in cattle it is frequently caused by hardwire Hardware disease is also known as traumatic reticulopericarditis Cattle may consume pieces of wire in the farm yard that are then pushed through the wall of the first chamber of the stomach, the reticulum, by its muscular contractions bacteriafrom introduced to percardium the rumen As the reticulum contracts and the infection spreads it may penetrate the diaphragm into the pericardium The disease may be prevented by bolusing cattle with prevents a magnet to prevent migration of any ingested magnet wires from penetration hardware. Pericardial Effusion/ Cardiac Tamponade When the space between the fibrous pericardium and the epicardium fills with fluid, pericardial effusion, pericardial causing the heart to be unable to fill between effusion leads to tamponade the heart-"Tamponade" contractions compression of The fibrous pericardium cannot stretch and as the sac fills there is less and less space for the heart to expand between contractions When the heart is unable to expand it cannot fill with blood causing blood pressure to drop and heart rate after high heart rate observed and to go up Diagnosedultrasound. (black fluid around the heart) The Flow of Blood Blood fluid hemangiosarcoma in Deoxygenated blood is received from the body via the cranial and caudal vena cava (e) into the right atrium The blood then passes through the right Hemangiosarcoma Blood vessel tumor aurice starts in spleen and spreads to right atrium or Bleeds and fills pericardium , leads to tamponade  atrioventricular valve (tricuspid valve) into the right ventricle During systole the right AV valve closes and the right ventricle pushes the deoxygenated blood out the pulmonic valve into the pulmonary arteries and finally to the alveoli where the blood is oxygenated The blood then returns to the heart via the pulmonary named because Oxygenateo veins to the left atrium It is carrying Blood from the left atrium flows through the left atrioventricular valve (mitral /bicuspid valve) into the left ventricle During systole the mitral valve closes and the left ventricle contracts pushing blood through the aortic valve into the coronary arteries and the aorta and then the arteries of the body External Structures of the Heart The heart is roughly triangle shaped, the base is the portion with the atria, located on the top of the heart The apex is the point of the triangle, in this case the bottom, made up of the two ventricles The right and left sides of the heart can be identified by the orientation of the auricles (auricle means ear, and they look like ears on the base of the heart). The right auricle is above the right atrium and the left is over the left atrium. When examining the heart grossly, you should be able to “shake hands” with the right atrium- try it in lab! The right auricle is also a common place to find a vascular tumor known as hemangiosarcoma. This tumor may hemorrhage and result in cardiac tamponade. The borders of the ventricles can be seen as grooves, or sulci filled with fat on the surface of the heart Blood Flow & & & ↑ & Aorta cranial venar ~ pulmonaryis > cava J pulmonary vein ~ & Left Atrium ↓ Right Atrium & Left Atrioventricular value (mitral J > Aortic valueemilunar) pulmonaryis · Left j Atrioventricular Right valueTricuspid) X ventricle & I ventricle Right L Caudal vena Cava block oxygenated b Deoxygenate  veing The vessels returning to the heart from the body are under low pressure and have thinner walls than the aorta and arteries carrying blood away from the heart under high pressure that have thick, muscularoften walls. arteriesare not placed Internal Structures of the Heart superficially The tricuspid valve has three flaps, or leaflets, that arise from a fibrous ring called the annulus of the valve supports the leaflets Chordae tendineae (heart strings) allow the valve to function in one direction only, so blood must flow in the direction previously described preventsbloodfromPow aressure The chordae tendineae connect the free edges of the valve leaflets to the papillary muscles which attach ↳ function to the wall between the two ventricles and the only anchor as an for interventricular septum chordae tendineae In the right ventricle there is a band of tissue that runs between the interventricular septum and the right ventricular free wall called the moderator band which lends structural support to the right ventricle The pulmonary valve prevents backflow from the pulmonary arteries into the right ventricle The pulmonary valve also has three leaflets that attach to a fibrous ring, it ensures the blood flows only out of the right ventricle into the pulmonary arteries during contraction After the blood becomes oxygenated in the lungs it reenters the heart through the pulmonary vein into the left atrium namedforsmar shape to miter hat cony, i The mitral valve has two leaflets (also known as the bicuspid valve) that work in one direction (because of their chordae tendineae) that prevent backflow of blood into the left atrium when the ventricle contracts  The thick walled left ventricle does not have a moderator band onlyinrightvene connects right > - vene wall e Finally, blood leaves the left ventricle through the aortic valve lackChordeneae half moon The aortic and pulmonic valves are both semilunar blood cupe empty when is valves that lack chordae tendineae The Cardiac Cycle pumpe intopulmonaryare into ventricles by bloc Each complete contraction and relaxation of the heart filling value cups in is called the cardiac cycle Systole is when the heart muscle contracts and blood is ejected from the atria to the ventricles and from the when ventricles to the arteries "Squeeze" high , number pressure bloodensure high - This19 in the heart Diastole is when the heart muscle relaxes and fills muscler blood with blood "Dilate" of number lower blood - low - blood pressure pressure gets The impulse for the heartbeat comes from the sinoatrial node (SA node) not visible to the naked eye o The SA node is an area of specialized cardiac muscle cells capable of automatically generating the electrical impulses that trigger the beating of the heart o The SA node generates an electrical current by the movement of the positively charged cations Na+, K+, Ca++ and negatively charged anions Cl- Anion Cl : ▪ Cations are pumped across the cell CICI Depolarization "rechargingthetery" as s des KT Nat KT Nat membrane in a process called polarization KTNaT I Nat Nat Nat KT ▪ When the gates of the cell membrane are W V W W W a opened, cations flow out of the cell to polarization equalize the charge in a process called v v v V & at depolarization "battery discharge" Xa ▪ Depolarization generates an electrical current that causes the heart muscle to contract  & W Sinatra 7 Purkinje Ifibers Atrioventricular Node (AV) I S > Bundeis J A r S  The electrical current generated by the SA node travels by two routes on its way from the base to the apex of the heart o The speedy route is through the specialized cardiac muscle cells of the SA node to the AV node, bundle of His and the Purkinje fibers SA Node o The slower, local route through the rest of the cardiac muscle fibers ▪ Unlike other muscle cells, the cardiac cells can transmit an electrical impulse from one cell to the next (skeletal muscle requires an & electrical message from a nerve) Av Node o After the electrical impulse leaves the SA node it travels quickly to the AV node ▪ There is a slight delay in conduction through the AV node ▪ The AV node is the only route of conduction of the electrical impulse from the atria to the ventricles ▪ This delay allows the atria to complete their systolic contraction before ventricular systole begins ⑲ ▪ If the atrial and ventricular systole occurred at the same time the pressure of the contracting ventricles would too high for the Bundle of His blood to flow from the atria into the ventricles o After the delay at the AV node the electrical impulse travels through specialized fibers in the ventricles called the bundle of His and the Purkinje fibers Durkinje Fibers ▪ The fibers of the bundle of His travel down the interventricular septum to the apex of the right and left ventricles  ▪ The Purkinje fibers carry the impulses up the from the bundle of His into the ventricular myocardium ▪ Even though the impulse starts at the heart base, the contraction of the ventricles begins at the apex, facilitating the ejection of blood from the ventricles During ventricular systole the atria have entered diastole and are filling with blood in preparation for the next contraction Fetal Circulation The fetus receives oxygen from the blood of its mother Since gas exchange does not occur in the lungs of the fetus, only enough blood to support the growing lung tissue is required Fetal circulation allows most of the blood to bypass the pulmonary circulation Oxygenated blood from the placenta flows through the umbilical vein o Oxygenated blood from the umbilical vein flows by pagges liver through the ductus venosus which allows some of the blood to bypass the liver into the caudal vena cava portosystemic Shunt-ductus venogus doesn't o In the fetus the blood can bypass the pulmonic close circulation by two routes: ▪ Foramen ovale directly connects the right and left atria allows blood to skip the lungs ▪ The blood that does not flow directly into the left atrium, enters the pulmonary artery and may flow into the lungs or bypass the lungs into the aorta via the ductus arteriosus pulmonary artery aortaSupplied - During the first breath the lungs inflate and the pulmonary Hegveg neonate begins to oxygenate its own blood used path of least resistance when lungs are , It opens a  Normally, the ductus venosus constricts so that blood no longer bypasses the liver and the foramen ovale and ductus arteriosus close so that blood may no longer bypass the lungs blood - is going from pulmonary PDA- Patent Ductus Arteriosus is when the ductus to aorta artery want 2 arteriosus does not close at birth and continues to close ligatures allow blood to bypass the lungs, resulting in cyanosis to arteries to prevent “blue baby” and a pronounced “washing machine” aneurysm murmur. The PDA must be surgically ligated to notblood oxygenating formation establish normal circulation through the lungs. properly Heart Sounds Listening to the heart, or to lungs or GI sounds, is called auscultation The normal cardiac cycle results in two sounds: lub (S1) and the dub (S2) ventricle contraction S1 is generated by the simultaneous closure of the S right AV (tricuspid) and left AV (mitral) valves at the beginning of ventricular systole end of ventricle S2 is generated by the closure of the aortic and contraction pulmonic (semilunar) valves at the beginning of ventricular diastole The heart sounds should be evaluated from both sides of the chest, but are typically loudest on the left (or along the right sternal border in cats) In large animals the stethoscope must be placed against the chest wall near the level of the elbow and as a far cranially as possible In small animals the stethoscope is placed on the chest wall just caudal to the elbow Also, in large animals a third heart sound (S3) may be ausculted due to rapid ventricular filling and a fourth sound (S4) due to contraction of the atria  S3 and S4 are not usually heard in dogs and cats Heart rate and Cardiac Output The heart must move blood to the tissues to deliver oxygen and nutrients and to remove waste In order to maintain tissue perfusion the heart must ↳ deliver oxygen and nutrients maintain cardiac output and removing waste CO2 and water Cardiac output is determined by two factors: stroke Kidneys volume and heart rate brain retinas sensitive o Stroke volume is the amount of blood ejected to lack of howmuch delivered. preload is with each cardiac contraction how much heartIs is oxygen o Heart rate is how often the heart contracts Afterload contracthow much : systemic o CO=SV x HR cardiac output Stroke volume x heart rate Vascular resistance Increased o The fact that a large animal’s stroke volume is so pressure much larger explains why they can survive with a much lower heart rate than and small animal Stroke volume Heart rate is determined, in part, by the rate of high heart ratee versalow and spontaneous SA node depolarization but is influenced by other factors o Exercise increases oxygen demand resulting in increased rate increased heart rate (positive chronotropy) and when we stretch increased contractility (positive inotropy) which more increased the heart reaps are increases stroke volume squeeze thehearts Starling’s Law: states that increased filling of the renin-angiotensin heart (increased preload) results in increased cardiac fluid retention blood vessels constrict contraction. Stretching of the ventricular muscle telling increases the force of its contraction ter Kidneys are heart that it is not Short > - termlong asready getting enoughto Changes in blood pressure may affect stroke failing heart more pressure cardacoutput : of volume and heart rate Blood pressure 19 meanarterial cular best indicator resistance Issue perforation o Shock is a rapid drop in blood pressure from any of a number of reasons o Low blood pressure results in decreased preload and therefore decreased stroke volume, heart palemucus membranes  extreme pain can cause rate must increase to maintain cardiac output shock The autonomic nervous system can influence cardiac output by releasing epinephrine during a fight or flight response, which results in increased stroke volume vasoconstriction and therefore increased cardiac output blood pressure Increases General anesthesia can stimulate the parasympathetic portion of the autonomic nervous system, releasing acetylcholine that decreases stroke volume, heart rate and thus decreases cardiac output vasodilates blood pressure decreases IV fluids increases o It is for this reason medications that block the stroke volume gives drugg to raise parasympathetic response are given prior to blood pressure general anesthesia anticholinergics Atropine Electrocardiogram glycopyrrolate An instrument called an electrocardiograph measures the electrical activity in the heart and produces an electrocardiogram (ECG or EKG) a graphical representation of the depolarization and repolarization of the heart muscle The normal electrical activity of the heart is represented: The P wave represents the depolarization of the atria, followed by the QRS complex representing  atria repolarization ventricular depolarization and finally, the T wave represents repolarization of the ventricles Vascular Anatomy and Physiology thicker and higher Arteries carry blood Away from the heart pressure and Veins carry blood towards the heart thinnerpressure lower Blood going into the systemic circulation is under higher pressure than the blood in the pulmonary or coronary circulation Because of the high pressure, the aorta is the largest diameter vessel with the thickest vessel wall The aortic wall has a fibrous outer layer, a middle layer of smooth muscle and elastic connective tissue and a smooth inner layer of endothelium (simple squamous epithelial tissue) curve of aorta cancause aneurysms mostly in As the aorta leaves the heart there are branches that horses form the carotids, subclavians, then caudal to the spine and abdominal organs and then branches again to the iliac and femoral arteries for the hind limbs The arteries continue to branch into smaller arterioles so that the tissue may be supplied with oxygen and nutrients through the thin-walled capillaries From the capillaries blood begins its route back to the heart through venules that merge to form veins The blood in veins is under less pressure and valves in small and medium sized veins ensure blood travels the frog horses help only in the direction of the heart in force blood up the legs Veins travel towards the heart next to an artery when putting their leg down carrying blood away from the heart As the veins merge, those in the forelimbs become the brachiocephalic veins and those in the hind limbs the iliac veins while the jugulars drain blood from from the head draw bloodveing to prevent hematomas in arteries  Most blood vessels have smooth muscle in their walls which allows constriction and dilation o This allows blood to be shunted to specific portions of the body o During fight or flight response the sympathetic nervous system constricts vessels that supply the extremities and digestive system and redirects blood to the vital organs: heart, brain and muscles o Blood vessels may also constrict to maintain blood pressure when blood volume or cardiac output is decreased Congestive Heart Failure (CHF) Occurs in animals whose hearts have lost their pumping ability, reducing forward flow of blood, Jam" "traffic resulting in congestion CHF can be right or left sided o Right sided heart failure results in congestion of the blood returning from the systemic fluid accumulation - circulation often associated with ascites and inperitoneum blood backs up into limb edema body o Left sided heart failure decreases venous blood backs heartworms , into return from the heart and congestion of blood inup lungs cyanosis the pulmonary circulation and pulmonary edema coughing exercise The reduced cardiac output associated with heart intolerance failure may reduce perfusion to other organs, lungsfilledavid especially the kidneys orthoped Medications used to treat heart failure include holdingbos a breath them o Positive inotropes to increase the strength of cardiac contractions o Diuretics to eliminate edema o Vasodilators to enhance blood flow to organs  o Congestive heart failure cannot be cured, but can be medically managed to improve quality of life 7