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Cardiovascular System (Heart (Layers of the heart wall (Epicardium-upon…
Cardiovascular System
Heart
Pericardial Membrane
Fibrous pericardium is the large "sak" that holds the heart in the pericardial cavity. Keeps the heart in place and keeps it from overfilling. It is comprised of dense irregular tissue. Extends from the diaphragm to the roots of the large vessels.
Serous pericardium lies deep to the fibrous pericardium. It is a serous membrane (simple squamous epithelium and areolar connective tissue); Superficial is called the parietal pericardial membrane, deep is the visceral pericardial membrane. In between these layers is pericardial cavity which is filled with serous fluid. This lubricates the tissue to withstand movement of the organ.
Layers of the heart wall
Epicardium-upon the heart. Visceral peridcardium serous membrane (simple squamous epithelium and areolar connective tissue.
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Endocardium-lines the heart and covers the valves. Comprised of simple squamous epitheoum and areolar connective tissue.
Anatomy of myocardium
The myocardium, or heart muscle, is spiral shaped and wraps around the atria and ventricles. This shape helps the muscle "wring" the blood out of the chambers.
Myocardium is comprised of cardiac muscle fibers connected by intercalated discs. Cardiac muscle fibers are similar in anatomy to skeletal muscle except for the intercalated discs. They have sarcoplasmic reticulum and transverse T tubules in between each myofibril with in the cell. The intercalated discs are like a zipper; held together by facia adherens. These are desmosome like structures. The intercalated discs have gap junctions which function to pass electrical signals from one cell to the next.
Heart Valves
Atrioventricular valves-located between atria and ventricle chambers. When ventricles contract these valves close. This is the first heart sound of a heart beat.
Semilunar valves-located at the start of the aortic arch and pulmonary branch. These are forced open with contraction of the ventricles. There is a moment of rest (diastole) after this in which they close. The second heart sound of a heart beat happens when they close.
Conduction system
Intrinsic electrical system in the heart. Begins at the sinoatrial node (SA) located in the right atrium. It is unique muscle tissue that can generate an electrical signal autonomically.
Steps: 1) SA node sends out signal which travels cell to cell via gap junctions. Atria contract. Signal reaches atrioventricular node (AV). 2) There is a slight delay of signal here while the ventricles fill with blood. 3) Signal reaches the AV bundle at the top of the interventricular septum. 4) Bundle branches bring the electrical signal to the papillary muscles, apex and through the heart muscle in the walls of the ventricles. 5) Signal reaches the purkinje fibers.
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Blood
Plasma-mostly water (90%) which includes over 100 different molecules (ions, sugar, hormones, vitamins, amino acids and lipids).
Cells
Erythrocytes-"bags" of hemoglobin which has iron making red blood cells heavier. Hemoglobin binds to oxygen. These cells are created in the red bone marrow. The shape increases the surface area for oxygen to bind to hemoglobin.
Leukocytes or white blood cells are part of the immune system-include neutrophils, eosinophil, basophil, lymphocyte and monocytes.
Platelets or thrombocytes which are pieces of larger cells called megakaryocytes. Play a role in stopping bleeding and clott formation.