Chapter 20: The Heart- Anatomy of the Hearto Size of fisto Location: Sits on mediastinum, an atomical region that extends from the sternum to the vertebral column  About 2/3 lies to the left of the body’s midlineo Apex of heart – bottom of heart Formed by the tip of left ventricle and rests on the diaphragmo Heart Layers: 3 layers Pericardium membrane = outer layer- Membrane that surrounds and protects the heart- 2 main parts: fibrous pericardium & serous pericardium- has freedom to contract- pericarditis = inflammation of the pericardium o leads to a build-up of pericardial fluid that compresses the heart and makes it hard to fill up pericardial fluid helps reduce friction between layers1. Epicardium = contains coronary vasculature - Has adipose tissue that houses the major coronary and cardiac vessels of heart 2. Myocardium- Responsible for the pumping action of the heart - Composed of cardiac muscle tissue o have striated, involuntary fibers3. Endocardium = smooth and helps minimize friction - Innermost layero Heart Structures: 4 chambers:- 2 superior receiving chambers = atriao right and left atrium- 2 inferior pumping chambers = ventricleso right and left ventricles Arteries: carry blood away from heart- Coronary artery = main supply of blood- Aorta = splits off and goes to various systemic arteries that supply body Veins: carry blood to heart- Superior vena cava & inferior vena cava = both dump into right atrium- Coronary sinus dumps into right atrium o From blood actually supplying hearto The Heart Highway Right atrium  goes thru tricuspid valve  to right ventricle  thru pulmonary valve  to pulmonary trunk/arteries  go to lung  then pulmonary veins  goes to left atrium  thru bicuspid valve  to left ventricle  thru aorta valve  to aorta  goes to aorta arteries  capillaries  veins, vena cavao Myocardial Wall Thickness = pressure and work done by chamber- High blood pressure is bad bc the heart has to pump harder  Ventricle walls are thicker than atria - Left ventricle is much thicker because the blood is going to the whole body - Circulationo Principal types: Pulmonary (right)- Receives dark-red deoxygenated blood from systemic circulationo From body to lung- R ventricle  pulmonary valve  pulmonary trunk/arteries  lungs pulmonary veins  left atrium Systemic (left)- Receives red oxygenated blood from the lungso Pumps blood at higher pressure- Blood enters systemic arteries that carry it to all organs throughout the bodyo Except for the air sacs (alveoli)- Give rise to smaller-diameter arterioles  lead into extensive beds of systemic capillaries- Left ventricle  aortic valve  aorta  capillaries  vena cava, coronary artery  right atrium o The output of one becomes the input of the othero YOU TRI BEFORE YOU BIo Right to left- Atrioventricular Valveso Also known as tricuspid and bicuspid valve Because located between atrium and ventricleo Blood flow is unidirectionalo When open= relaxed because chordae tendineae are slack = blood moves from a higher pressure in the atria to a lower pressure in the ventricles o When closed= papillary muscle contracts, tighten up to prevent the blood from flowing back into the atria - Semilunar Valveso Also known as the aortic and pulmonary valveso When ventricles are relaxed = closed blood flows back toward the heart blood backflow caught by cuspo When the ventricles contract = the open because the pressure builds up within the chamber that exceeds the pressure in the arteries(aorta)- Coronary Blood Flow (3rd circulation)o Cardiac fibers do not fatigue because  they have a well-established network of blood vessels that supply oxygen and nutrients to it the majority of heart stays in a relaxed stateo prevent substrate depletion/metabolite accumulation due to large vessels that are supplying the heartCoronary arteries- Left and right coronary arteries supply the oxygenated blood to the myocardiumo Heart looks after itself- soon as blood leaves ventricle, it goes back to the heart- Circumflex branch = lies in the coronary sulcus and distributes oxygenated blood to the walls of the left ventricle and left atrium o Wraps around to get back side of heartCoronary Veins- Veins pick up and drain coronary arteries - Collect deoxygenated blood- All veins drain back into vena cavao Vena cava goes to rt atria back into pulmonary circulation- Heart attack (MI)o A disruption of coronary artery blood flow Not receiving the nutrients or oxygen it needs Becoming ischemico Inhibit the amount of blood flow going into tissue that puts stress/strain on cardiac fiberso Energy substrates for heart: Fats  burn thru aerobic glycolysis  Lactate acid- Waste product from skeletal muscleo Risk factors: Atherosclerosis = hardening of the blood vessels Obesity Having a Y-chromosome (males) Affect older people Physical inactivity- Sitting around, not moving aroundo Which coronary artery would be the biggest concern for blockage in artery? Left coronary because it provides blood to the left ventricle = the walls are thicker in left ventricle and supplies a stronger amount of blood- no blood to the left ventricle = no blood to the rest of the body (brain, vital organs, muscles, etc..)o if we kill all tissues = cardiac output will be diminished more fibers affect = more fibers die = no contraction- Heart Tissue Death & Regenerationo Not all heart attacks are fatal o The more tissue affected = poor cardiac function/outputo Muscle is post-mitotic = no longer able to divide Once heart is matured, no fibers can be replacedo If heart tissue is damaged, tissue can be regenerated Transplant cases- Study where male receives heart transplant from female donor- Organ transplant- NMJo Nervous system and heart communicate thru the ANSo Dual innervationo Adjust rate at nodes SA, VA, and ventricle o Parasympathetic slows HR down Vagus nerveo Sympathetic increases HR Cardiac nerves Harder contraction = moves more blood- Autorhythmicityo Cells self-excite/depolarize spontaneously on their owno Generate action potential o SA & AV nodes have pacemaker cells During embryonic development, only 1% of the cardiac muscle fibers become autorhythmic fiberso Fibers also form cardiac conduction system (heart contraction)  5 partsSinoatrial (SA) node- In right ventricular wall, top of atria- They repeatedly