Cardiovascular System DTH22 PDF

Cardiovascular system Module: Biomedical sciences Tutor: Haydee Husain BDS MSc Learning Outcomes At the end of the session students GDC outcomes: will be able to: 1.1.5 Describe relevant and appropriate dental, Describe the heart oral, craniofacia...

Cardiovascular system Module: Biomedical sciences Tutor: Haydee Husain BDS MSc Learning Outcomes At the end of the session students GDC outcomes: will be able to: 1.1.5 Describe relevant and appropriate dental, Describe the heart oral, craniofacial and general anatomy and Explain the structure of the heart explain their application to patient Describe the flow of blood through management the heart 1.1.6 Describe relevant and Understand the conduction system appropriate physiology and explain its of the heart application to patient management Describe blood supply to the heart Describe the components vessels of the circulatory system Heart The heart is a hollow four chambered muscular organ roughly the size of a clenched fist The heart beats around 100 000 times a day It acts as two separate pumps. The right heart pumps blood to the lungs and the left heart pumps blood to the body Heart shape and position The heart is located in the thoracic cavity, in between the lungs, in a region known as the mediastinum It sits behind the breastbone (sternum) Most of the heart lies left of the midline, with its apex pointing downwards The base of the heart is the broad superior end, where the large vessels Image source University of Michigan Feb 2021 attach Heart structure - Pericardium The heart is enclosed and protected by the parietal pericardium (or pericardial sac) which separates the heart from other thoracic organs and forms the wall of the pericardial cavity which contains pericardial fluid The parietal pericardium is composed of an outer fibrous and an inner serous layer The serous layer secretes the pericardial fluid Heart structure – Heart Wall The wall of the heart is comprised of three distinct layers: Epicardium outer layer Myocardium thick middle layer comprised of thick cardiac muscle Endocardium smooth inner layer lining the heart and its internal structures Hear structure – Cardiac muscle Exists only in the heart of animals Controlled by the autonomic nervous system Fibres are branched and arranged in a striated pattern Cardiac muscle cells are and connected by intercalated discs consisting of fascia adherens, gap junctions and desmosomes The regular arrangement and specialised cell junctions allow the muscle to contract smoothly and repeatedly Heart structure - Chambers The heart is divided into four chambers the upper right and left atria and the lower right and left ventricles The atria are receiving chambers which contract and empty into the ventricles. They are separated by a thin muscular interatrial septum The ventricles are pumping chambers are are separated by a thick muscular interventricular septum Grooved depressions on the surface of the heart indicate the partitions between the chambers and also contain cardiac vessels that supply blood to the heart wall Heart structure – right atrium and ventricle The right atrium receives venous blood from the superior vena cava and the inferior vena cava The cardiac cycle consists of a period of relaxation when the heart fills with blood (diastole) followed by a period of contraction (systole) During diastole blood passes from the right atrium to the right ventricle through the atrioventricular triscuspid valve During systole when the right ventricle contracts the tricuspid valve closes preventing backflow of blood into the atrium Question If the atria fail the difference is unlikely to be noticed unless a person exercises. Can you think why this might be?  Heart structure – Left atrium and ventricle After gas exchange in the lung, oxygenated blood is passed to the left atrium from the pulmonary veins During diastole blood passes from the left atrium to the left ventricle through the bicuspid mitral valve During systole when the left ventricle contracts the mitral valve closes preventing backflow of blood into the atrium The left ventricle has thicker walls than the right ventricle Oxygenated blood leaves the left ventricle via the aorta. The aortic semilunar valve prevents backflow from the aorta into the left ventricle Heart sounds When listening to the heart with a stethoscope we are listening to the turbulence created when the heart valves close S1 First heart sound (‘Lub’) S2 Second heart sound (‘Dub’) Problems with the valves may be detected by variations in these sounds known as heart murmurs Heart structure Test your knowledge - can you describe or define these? Interventricular Superior vena Diastole septum cava Interatrial Mediastinum Pericardial septum fluid Aorta Inferior vena cava Parietal Epicardium pericardium Mitral valve Pulmonary Gap junctions Pericardial activity vein Myocardium Systole Intercalated discs Tricuspid Semilunar valve Sternum valve Heart structure – helpful videos https://anatomyzone.com/thorax/heart/heart-structure-and-function- basics/ https://www.youtube.com/watch?v=jBt5jZSWhMI Test your knowledge Ensure you can label a diagram of the heart correctly Conduction system of the heart Consists of: Sinoatrial node Atrioventricular node Bundle of His Purkinje fibres Conduction system of the heart Each heartbeat begins in the heart’s pacemaker known as the the sinoatrial or SA node The SA node is located in the right atrium During diastole the SA node exhibits a spontaneous depolarisation called the pacemaker potential The wave of depolarisation spreads across the atria resulting in atrial systole then converges at the atrioventricular or AV node The AV node delays the impulses to allow the atria time to fully empty into the ventricles The Bundle of His conducts impulses to the Purkinje fibres of the ventricles resulting in ventricular systole Conduction system – Electrocardiogram (ECG) An ECG is an important non-invasive test that provides information about heart rate and rhythm It measures the electrical activity generated when the heart contracts and records this as a trace consisting of: P wave QRS complex T wave ECG can help detect abnormal heart rhythms (arrythmias), an enlarged heart due to high blood pressure (hypertension), heart attacks (myocardial infarction) among other conditions Electrocardiogram (ECG) Conduction system of the heart – useful video https://www.youtube.com/watch?v=NijiLTONHxg BREAK Circulatory system Also known as the cardiovascular system Circulates blood, transports nutrients, oxygen and hormones, removes waste products and controls homeostasis The pulmonary circulation transports blood from the right ventricle to lungs and then the left atrium to the heart The systemic circulation composed of all the remaining vessels of the body that are not part of the pulmonary system Circulatory system – Coronary circulation The heart has its own circulation known as the coronary circulation It consists of the right and left coronary arteries delivering oxygenated blood to the heart From capillaries in the myocardium blood enters the cardiac veins into the right atrium Circulatory system – Foetal circulation In utero the pulmonary circulation is unnecessary because foetal blood is oxygenated by the placenta The umbilical cord serves as the connection between foetus and placenta Systemic venous blood returning to the right atrium is deflected through the foramen ovale to the left atrium Blood from the left ventricle is diverted away from the pulmonary arteries, to the aorta, through the ductus arteriosus Circulatory system – Blood vessels Arteries Arterioles Capillaries Venules Veins Circulatory system - Arteries Carry oxygenated blood (except pulmonary system) away from heart Thick elastic muscular walls Blood flow under high pressure 3 layers Tunica externa Tunica media Tunica intima Circulatory system - Capillaries Smallest and most abundant blood vessels in body 3 types: Walls consist of endothelium only, one Continuous cell layer thick Fenestrated Discontinuous (sinusoidal) Permit rapid rate of exchange of oxygen, nutrients and waste products between blood and tissues Capillary beds are networks of capillaries supplying organs Blood flow through capillaries is determined by precapillary sphincter muscles and the constriction or dilatation of arteries and arterioles Circulatory system - Veins Carry oxygen depleted blood back to the heart Contain valves to prevent backflow/pooling Act as a reservoir of blood Rely on the skeletal muscle pump and respiratory pump Also have 3 layered walls but less muscular/elastic than arteries Circulatory system - the blood brain barrier The blood-brain barrier acts as a boundary between circulating blood and the brain and spinal cord It is highly selective and protects the brain from ‘foreign’ substances and maintains a constant environment for the brain Brain capillaries are not fenestrated and their endothelial cells are very tightly packed so large molecules, immune cells, bacteria and viruses are prevented from passing from the blood to the central nervous system Test your knowledge Ensure you can identify and label these blood vessels correctly Major blood vessels – the great vessels Arteries Pulmonary artery Aorta Aortic arch Ascending and descending aorta The pulmonary arteries carry blood from the right atrium to the lungs for oxygenation The aorta originates from left ventricle as the ascending aorta, forms the aortic arch band becomes the descending aorta as it continues down through body Major blood vessels – the great vessels Veins Pulmonary vein Superior vena cava Inferior vena cava The pulmonary vein returns oxygenated blood from the lungs to the left atrium The supervior vena cava receives deoxygenated blood from the upper body and the inferior vena cava receives the venous return from the lower body. Both drain into the right atrium Blood pressure Blood pressure is the force exerted by circulating blood against the artery walls Measured in millimetres of mercury (mmHg) Systolic/diastolic e.g. 120/80mmHg Question What might cause blood pressure variation? Circulatory system – helpful videos Blood pressure https://www.youtube.com/watch?v=keYtWNAJY64 Capillary exchange https://www.youtube.com/watch?v=dFRa2ECm5pY End Further references/resources: Waugh, A. and Grant, A. (2018) Ross & Wilson Anatomy And Physiology In Health And Illness. 13th ed. Elsevier. Ward, J. and Linden, R. (2017) Physiology At A Glance. 4th ed. Wiley-Blackwell