Anatomy and Physiology
Anatomy and Physiology BIOH 113 - 01
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BIOH 112 - 01
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This 5 page Bundle was uploaded by Meaghan Raw on Sunday March 13, 2016. The Bundle belongs to BIOH 113 - 01 at University of Montana taught by Heather Dawn Labbe (P) in Spring 2016. Since its upload, it has received 12 views. For similar materials see Human Form and Function II in Biological Sciences at University of Montana.
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Date Created: 03/13/16
Chapter 19: Cardiovascular System, the Heart Location: - Superior surface of the diaphragm - A tad left of midline - Anterior to the vertebral column - Posterior to the sternum Size: - Approximately the size of your fist - 12cm long, 9cm wide at its base, 6cm thick Anatomy: Pericardium: - Surrounds and protects the heart - Double walled sac o Superficial fibrous (tough dense irregular CT) o Two-layer serous (the pericardial cavity separates and contains pericardial fluid) Parietal: lines the internal surface Visceral: (epicardium) lines the outer surface - Protects and anchors the heart - Prevents overfilling of the heart with blood - Allows the heart to work/pump in a mostly friction free environment Layers of the Heart Wall: 1. Epicardium - Visceral layer of serous pericardium - Thin, transparent outer layer of the heart - Contains blood vessels and lymphatic vessels that supply the myocardium 2. Myocardium - Makes up 95% of the heart wall - Made of cardiac muscle tissue - Responsible for the heart’s pumping 3. Endocardium - Thin layer of endothelium and connective tissue - Minimizes friction as blood passes through the heart Four Chambers of the Heart: - Two upper atria = entry halls/chambers - Two lower ventricles = little bellies/chambers that are larger than the atria 1. Right Atrium - Receives blood from 3 veins: Superior vena cava, Inferior vena cava, Coronary sinus - The posterior wall is smooth - The anterior wall is rough due to the pectinate muscles (muscular ridges) - Blood passes from the right atrium to the tricuspid valve into the right ventricle 2. Right Ventricle - Forms most of the anterior surface of the heart - The interior right ventricle contains a series of ridges formed by raised bundles of cardiac muscle fibers called trabeculae carnae - The right ventricle is separated from the left ventricle by a partition called the interventricular septum 3. Left Atrium - Receives oxygenated blood from the lungs through 4 pulmonary veins - Blood passes from the left atrium into the left ventricle and through the bicuspid mitral valve 4. Left Ventricle - The thickest chamber of the heart (10-15mm) and forms the apex - Has a similar structure to that of the right ventricle - Blood passes from the left ventricle through the aortic valve Valves: - Atrioventricular: Lie between the atria and the ventricles Blood moves from higher pressure in the atria to lower pressure in the ventricles through open AV valves When the ventricles contract the pressure of the ventricular blood drives the cusps upward until their edges meet and close the valve opening - Semilunar: Allow for ejection of blood from the heart into arteries but prevent arterial blood from flowing back into the ventricles When walls of the ventricles contract the blood pressure in the ventricles exceeds the pressure in the arteries and forces SL valves to open This permits ejection of blood through SL valves into the pulmonary trunk and aorta Fetal Structures: - Foramen ovale becomes Fosssa ovalis Functionally closes at birth (first breath) Structurally closes in about one year - Ductus Arteriosus becomes Ligamentum ateriosus Functionally closes at birth Structurally closes within one day after birth Systemic and Pulmonary Circulation: Pulmonary: Right side of the heart Receives dark reeed deoxygenated blood returning from systemic circulation and delivers it to the right ventricle The right ventricle pumps it into the pulmonary trunk The pulmonary trunk divides into pulmonary arteries that carry blood to the lungs The blood deposits CO2 (exhaled) and picks up O2 (inhaled) Systemic: Bright red oxygenated blood is taken from the lungs into the left atrium which passes into the left ventricle The left ventricle ejects blood into the aorta where systemic arteries take the blood to all of the organs in the body Blood deposits O2 to the cells and picks up CO2 from the cells Coronary Circulation: - Functional blood supply to the heart muscle itself - Collateral routes ensure blood delivery to the heart even if major vessels are occluded Heart Physiology: - Heart muscle is stimulated by nerves and is self-excitable (automaticity) - The muscle contracts as a unit Sequence of Excitation: 1. Sinoatrial (SA) node generates impulses about 100 times/minute 2. Atrioventricular (AV) node delays the impulse about 0.1 second 3. Impulse passes from the atria to the ventricle via the atrioventricular bundle (bundle of His) 4. The AV bundle splits into 2 pathways in the interventricular septum (bundle branches) 5. Bundle branches carry impulse toward the apex 6. Purkinje fibers carry the impulse to the heart apex and ventricular walls Electrocardiography: - ECG or EKG - Measures electrical activity of the heart P wave corresponds to the depolarization of the atria QRS complex corresponds to ventricular depolarization T wave corresponds to ventricular repolarization Atrial repolarization is masked by the larger QRS complex Cardiac Cycle: - Refers to all events associated with blood flow through the heart - Systole is the contraction of the heart muscle - Diastole is the relaxation of the heart muscle Heart Sounds: - Associated with the closing of valves - First sound (S1) occurs as AV valves close and signifies the beginning of systole - Second sound (S2) occurs when SL valves close at the beginning of ventricular diastole - Third sound (S3) is too quiet to hear but is due to blood turbulence as the ventricles fill - Fourth sound is too quiet to hear but is due to blood turbulence during atrial systole 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 Atrial systole occurs - Isovolumetric relaxation Early diastole Ventricles relax Backflow of blood in the aorta and pulmonary trunk closes SL valves - Dicrotic notch A brief rise in aortic pressure caused by backflow of blood rebounding off of SL valves - Ventricular Systole Atria relax Rising ventricular pressure results in the closing of AV valves Isovolumetric contraction phase Ventricular ejection phase opens SL valves Cardiac Output (CO) and Reserve: - CO is the amount of blood pumped by each ventricle in one minute - CO is the product of heart rate (HR) (beats per minute) and stroke volume (SV) ( amount of blood pumped out by a ventricle with each beat) - Cardiac Reserve is the difference between resting and maximal CO Regulation of Heart Rate: Nervous System: - Sensory input from the proprioceptors, chemoreceptors, baroreceptors that stimulate the cardiac centers in the medulla oblongata of the brain stem Autonomic Nervous System: - Sympathetic nervous system (SNS) is activated by stress, anxiety, excitement, or exercise - Parasympathetic nervous system (PNS) is mediated by acetycholine and opposes the SNS - PNS dominates the autonomic stimulation, slowing heart rate and causing vagal tone
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