University of Belize Cardiovascular System: Heart PDF

UNIVERSITY OF BELIZE CARDIOVASCULAR SYSTEM: HEART COURSE CODE – ALHL2021 WEEK FACULTY OF HEALTH SCIENCES 4 PATRICIA LOPEZ...

UNIVERSITY OF BELIZE CARDIOVASCULAR SYSTEM: HEART COURSE CODE – ALHL2021 WEEK FACULTY OF HEALTH SCIENCES 4 PATRICIA LOPEZ TIME FRAME (75 MINUTES) Copyright© 2020 University of Belize. All rights reserved Not to be reproduced or disseminated without permission from the University of Belize.  Objectives Describe the structure of the heart (wall, chambers, great vessels and valves) Trace the pathway of blood through the heart Describe the pulmonary and systemic circulations Name the components of the conduction system and trace the conduction pathway Describe the events of the cardiac cycle  Heart Anatomy Approximately the size of your fist Location – Superior surface of diaphragm – Left of the midline – Anterior to the vertebral column, posterior to the sternum Heart Anatomy  Coverings of the heart The pericardium: – Protects and anchors the heart – Prevents overfilling of the heart with blood – Allows for the heart to work in a relatively friction-free environment Pericardial layers of the heart  Heart Wall Epicardium – visceral layer of the serous pericardium Myocardium – cardiac muscle layer forming the bulk of the heart Fibrous skeleton of the heart – crisscrossing, interlacing layer of connective tissue Endocardium – endothelial layer of the inner myocardial surface  Major vessels of the heart Vessels returning blood to the heart include: – Superior and inferior venae cavae – Right and left pulmonary veins Vessels conveying blood away from the heart include: – Pulmonary trunk, which splits into right and left pulmonary arteries – Ascending aorta (three branches) – brachiocephalic, left common carotid, and subclavian arteries Vessels that supply/drain the heart Arteries – right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular arteries Veins – small cardiac, anterior cardiac, and great cardiac veins External heart (anterior view)  Major vessels of the heart (Posterior view) Vessels returning blood to the heart include: – Right and left pulmonary veins – Superior and inferior venae cavae Vessels conveying blood away from the heart include: – Aorta – Right and left pulmonary arteries Vessels that supply/drain the heart (posterior view) Arteries – right coronary artery (in atrioventricular groove) and the posterior interventricular artery (in interventricular groove) Veins – great cardiac vein, posterior vein to left ventricle, coronary sinus, and middle cardiac vein External heart (posterior view) Gross anatomy of heart (frontal section)  Let’s Review 1. Where is the heart located? 2. Name the chambers of the heart. 3. Name the blood vessels that connect to the heart. 4. Name the layers that make up the heart wall. 5. Which side of the heart has thicker wall? Why?  Atria of the heart Atria are the receiving chambers of the heart Each atrium has a protruding auricle Pectinate muscles mark atrial walls Blood enters right atria from superior and inferior venae cavae and coronary sinus Blood enters left atria from pulmonary veins  Ventricles of the heart Ventricles are the discharging chambers of the heart Papillary muscles and trabeculae carneae muscles mark ventricular walls Right ventricle pumps blood into the pulmonary trunk Left ventricle pumps blood into the aorta Pathway of blood through the heart and lungs Right atrium 🡪 tricuspid valve 🡪 right ventricle Right ventricle 🡪 pulmonary semilunar valve 🡪 pulmonary arteries 🡪 lungs Lungs 🡪 pulmonary veins 🡪 left atrium Left atrium 🡪 bicuspid valve 🡪 left ventricle Left ventricle 🡪 aortic semilunar valve 🡪 aorta Aorta 🡪 systemic circulation Pathway of blood through the heart and lungs  Group activity In groups, trace the pathway of blood through the heart  Coronary circulation Coronary circulation is the functional blood supply to the heart muscle itself Collateral routes ensure blood delivery to heart even if major vessels are occluded Coronary circulation (arterial supply) Coronary circulation (venous supply)  Heart valves 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  Heart valves Aortic semilunar valve lies between the left ventricle and the aorta Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk Semilunar valves prevent backflow of blood into the ventricles Heart valves Atrioventricular valve function Semilunar valve function  Microscopic anatomy of heart muscles Cardiac muscle is striated, short, fat, branched, and interconnected Intercalated discs anchor cardiac cells together and allow free passage of ions Microscopic anatomy of heart muscles  Time to review again! Write down three new things you learned about the heart. Heart physiology—conduction system  Conduction system 1 Sinoatrial (SA) node generates impulses about 75 times/minute Atrioventricular (AV) node delays the impulse approximately 0.1 second Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)  Conduction system 2 AV bundle splits into two pathways in the interventricular septum (bundle branches) – Bundle branches carry the impulse toward the apex of the heart – Purkinje fibers carry the impulse to the heart apex and ventricular walls Heart excitation related to ECG Electrocardiography  Electrocardiography Electrical activity is recorded by electrocardiogram (ECG) P wave corresponds to depolarization of SA node QRS complex corresponds to ventricular depolarization T wave corresponds to ventricular repolarization Atrial repolarization record is masked by the larger QRS complex  Cardiac cycle Cardiac cycle refers to all events associated with blood flow through the heart – Systole – contraction of heart muscle – Diastole – relaxation of heart muscle  Phases of the cardiac cycle Ventricular filling – mid-to-late diastole – Heart blood pressure is low as blood enters atria and flows into ventricles – AV valves are open, then atrial systole occurs  Phases of cardiac cycle Ventricular systole – Atria relax – Rising ventricular pressure results in closing of AV valves – Isovolumetric contraction phase – Ventricular ejection phase opens semilunar valves  Phases of cardiac cycle Isovolumetric relaxation – early diastole – Ventricles relax – Backflow of blood in aorta and pulmonary trunk closes semilunar valves Dicrotic notch – brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves  Heart sounds Heart sounds (lub-dup) are associated with closing of heart valves – First sound occurs as AV valves close and signifies beginning of systole – Second sound occurs when SL valves close at the beginning of ventricular diastole  Cardiac output and reserve CO is the amount of blood pumped by each ventricle in one minute CO is the product of heart rate (HR) and stroke volume (SV) HR is the number of heart beats per minute SV is the amount of blood pumped out by a ventricle with each beat Cardiac reserve is the difference between resting and maximal CO Chemical regulation of the heart The hormones epinephrine and thyroxine increase heart rate Intra- and extracellular ion concentrations must be maintained for normal heart function Homeostatic imbalance of the heart In small groups, describe a homeostatic imbalance of the heart.  References Marieb, E. N., & Hoehn, K. (2013). Human Anatomy and Physiology ( 9th ed.). San Francisco, CA: Benjamin Cummings  The End Recorded Lecture Policy: Students who are unable to attend virtual classes or consultation sessions have the right to download and view recorded lectures and consultation sessions for their personal study only. Lectures recorded for this purpose may not be shared with other people without the consent of the instructor. The recorded lectures may not be published without the express consent of the instructor and without giving proper identity and credit to the instructor. Students who use screen-recording softwares are required to adhere to the recording guidelines stated above. Copyright© 2020 University of Belize. All rights reserved Not to be reproduced or disseminated without permission from the University of Belize.