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Lecture 20

ANAT 103 Lecture 20: Ch20 ANAT103

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ANAT 103
Mary Flynn

Ch 20 ANAT Heart - Located in the mediastinum in the thoracic cavity - Anterior and posterior is the sternum and vertebral bodies - Diaphragm is the floor - Rib cage is the top - Base of the heart is the broader part (top) where the vessels come out - Apex is the bottom, narrow part (toward left) - Fibrous skeleton: - 4 dense connective tissue rings surrounding the valves of the heart - Functions: - Prevent valves from overstretching - Point of insertion for cardiac muscle bundle - Electrical insulator between atria and ventricles Pericardium - Encloses the heart and holds it in place - Two Main Parts: separated by serous cavity (fluid filled space) - Fibrous Pericardium - Superficial layer: protection and anchorage - Serous Pericardium - Deep layer: secretes serous fluid for friction reduction - Two Layers: - Visceral layer/ epicardium is clinging to the heart - Parietal layer (outer) is farther away and separated by the serous cavity - Pericardial fluid: - Between the visceral and parietal layer and within the serous cavity - Reduce friction between parietal layers Wall of Heart Layers 1) Epicardium (external) a) Visceral layer of serous pericardium b) Contains Blood vessels on other side (deep) that supply the myocardium and connective tissue (fat) 2) Myocardium (middle) a) The cardiac muscle part of the heart i) Involuntary ii) Components: (1) Nucleus (2) mitochondria (3) Cardiac myocytes (cells) (a) Form branches to increase chance of contracting in a group (4) Intercalated disk: (a) Area of contact between one cardiac myocyte to another (b) The zig-zag interlocking (c) Creates a lot of surface contact area for simultaneous squeezing and contracting (5) Gap Junctions: (a) Electronic communication b) Pumping action 3) Endocardium (internal) a) Innermost layer b) Squamous epithelium (thin, single layer of cells) lining the chambers of the heart and vessels c) Minimize surface friction Chambers of the Heart (4) Upper (receiving) - Right atrium - Rough Pectinate muscle inside the anterior wall - Receive blood from the: - superior & inferior vena cava - coronary sinus - Has an auricle to accepts overfill from the atrium - Left atrium - Gets blood from the pulmonary veins → biscuspid/ mitral valve → left ventricle - Has an auricle to to accepts overfill from the atrium Inferior (pumping) - Right ventricles - Gets blood from right atrium and tricuspid valve and sends it to the lungs through the left pulmonary artery - Little muscle ridge network (trabeculae carnae) - Papillary muscles (large ridges) - Anchor the tricuspid valve via cordae tendineae - Prevents regurgitation by not allowing valve to go inside out - Blood passes through the pulmonary semilunar valve + pulmonary trunk → pulmonary arteries → lungs - Left ventricle - Thicker myocardium muscle than right ventricle - Blood passes through the aortic semilunar valve → ascending aorta → arch of aorta (brachiocephalic trunk, left subclavian, left carotid artery) and descending aorta → body Connective tissue valve (atrioventricular valve) between the RA and RV and LA and LV - Makes sure blood only flows in one direction - Prevents backflow/ reguritation (should go atrium to ventricles) - When the valve is open, papillary muscles are relaxed, cordae tendineae is slack and blood goes from high → low pressure - Ventricles contract, the pressure makes the cups close and papillary muscles contract Semilunar Valves - Open when the pressure in the ventricles > pressure in arteries (pulmonary trunk and aorta) - Close when the ventricles relax and blood flows back to the heart, fills the cusps abd causes the semilunar valve to contract Sulci - On the surface of the heart - Contains coronary blood vessels and fat Coronary Sulcus: Boundary between the superior atria and inferior ventricles Anterior Interventricular Sulcus: - Boundary between the right and left ventricle on the anterior side Posterior Interventricular sulcus: - Boundary between the right and left ventricles on the posterior side Interatrial Septum: - Thin partition between the R and L atrium Fetus Parts - Fossa Ovalis: - opening in the interatrial septum (foramen ovalley) where blood can go from the right atrium to the left atrium which closes up on your first breath - Becomes the fossa ovalis (indentation) and keeps pulmonary from systemic side - Ligamentum arteriosum (Connective tissue in adults ): - Blood vessel called the ductus arteriosus connects blood from the pulmonary trunk to the aorta and becomes the Ligamentum arteriosum after birth Right Side → Pulmonary side - Receive deoxygenated blood from superior vena cava (head), inferior vena cava (below heart extremedies) and coronary sinus) and sends it to lungs to get oxygenated - 3 entrances → Right atrium → Right ventricle → pulmonary trunk → pulmonary artery → lungs - Goes to systematic side Left Side → Systemic side - Receive oxygenated blood from lungs and sends to whole system - Pulmonary veins bring blood to left atrium → left ventricle → aorta → brachiocephalic trunk (head and upper right extremedies), left common carotid artery (left side of head), left subclavian artery (left upper extremedies) → body - Valve between LV and aorta (aortic semilunar valve) Atrium squeezes as a group → ventricle squeezes as a group → both rest - Atrium and ventricle never squeeze at once (due to connective tissue valve) Coronary Circulation - Coronary arteries branch from the ascending aorta - Supply oxygenated blood and nutrients to the myocardium - Feed oxygenated blood to heart: - Right coronary artery - Comes off aorta → front of heart → right marginal branch (right front side) and posterior interventricular branch (right back side) - Left coronary artery - Comes off aorta → anterior interventricular branch/ Left Anterior Descending artery LAD (supplies oxy blood to both ventricles) and circumflex branch (bends around the left back side) - When the heart is relaxed, blood from the aorta goes through the arteries, capillaries and into the coronary veins - Coronary Veins remove CO2 and waste from myocardium - Coronary Sinus receives deoxy blood from the myocardium and takes it to the right atrium Cardiac Muscle - Has 1-2 nucleus - Muscle fibers connect to another by intercalcted discs which contain desmosomes (hold fibers together) and gap junctions (allow myocradium to contract as one unit) Autorhythmic Fiber - generate their own action potential/ self-excitable (open and close ion gates in their own way) and trigger heart contractions - Acts as pacemakers (set rhythm of heart contraction) - Form the cardiac conductive system - Network of cardiac muscle fibers that provide a path for cardiac excitation and contract in a coordinated manner - Artia squeeze, ventricle squeeze, both relax (heartbeat) - Depolarization = contraction - From resting (negative) to excited state (positive) - Repolarization = constriction The Conductive System - Sinoatrial Node (SA) in right atrium self fires (action potential/ depolarization) and sends pace a
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