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Equine Cardiovascular System - Horse Anatomy (view source)
Revision as of 21:50, 18 November 2012
, 21:50, 18 November 2012no edit summary
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==Heart==
The heart is located in the thoracic cavity in between the [[Lungs - Anatomy & Physiology|lungs]], 60% of it lying to the left of the median plane. Most of the heart’s surface is covered by the [[Lungs - Anatomy & Physiology|lungs]] and in juveniles it is bordered cranially by the [[Thymus - Anatomy & Physiology|thymus]]. Caudally the heart extends as far as the [[Diaphragm - Anatomy & Physiology|diaphragm]]. The heart makes direct contact with the [[Ribs and Sternum - Anatomy & Physiology|ribs]], through the cardiac notches of the lungs to the 3rd-4th intercostal space on the right.
The heart is cone-shaped, with a broad base at the top from which the large blood vessels enter and exit. The tip, known as the apex, points downwards and lies close to the [[Ribs and Sternum - Anatomy & Physiology|sternum]]. In the horse, the apex is blunted during diastole. The longitudinal axis of the heart is tilted , resulting in the base facing craniodorsally and the apex caudoventrally.
The heart has a right and left lateral surface, which meet cranially at the right ventricular border and caudally at the left ventricular border. The auricles of the atria are visible on the left side, surrounding the root of the aorta and the pulmonary trunk, whilst the large veins and the main parts of the atria are situated on the right. The free border of the left auricle is usually notched.
Grooves on the surface represent the divisions of the internal structure of the heart. The right surface of the heart is marked by the '''subsinusoidal groove''', which extends from the coronary groove to the apex of the heart. The '''paraconal groove''' runs over the left surface of the heart from the coronary groove to the distal end of the cranial margin. The '''coronary groove''' contains the coronary blood vessels and marks the separation of the atria and ventricles.
==Pericardium==
The pericardium is the membrane that surrounds and protects the heart. It is composed of two layers separated by a narrow cavity. The inner layer is firmly attached to the heart wall and is known as the visceral layer or epicardium. The outer layer is composed of relatively inelastic connective tissue and is termed the parietal layer. This fibrous layer prevents distension of the heart, thus preventing excessive stretching of the heart muscle fibres. The cavity between the two layers contains a small volume of fluid which serves as a lubricant, facilitating the movement of the heart by minimising friction. The '''sternopericardiac ligament''' connects the parietal layer to the sternum.
==Great Vessels==