HUMAN HEART PDF S
INTRODUCTION. The heart is a muscular pump that serves two functions: (1) to collect blood from the tissues of the body and pump it to the lungs and (2) to. The heart is a cone-shaped, muscular organ about the size of a fist. 4. The human heart contracts (beats) about 70 times a minute ( billion times in a. PDF | Molecular and genetic studies around the turn of this century While the primary heart tube is growing by addition of cells, it does not.
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of left ventricular twisting is the earliest sign of heart failure . myocardial fibers in human embryo at 10 and 14 weeks, respectively;. In many ways, the human heart is a very simple The centerpiece of the exhibit is the giant walkthrough model of the human heart, described below. The Normal Heart and How It Works. The normal heart is a strong, hard-working pump made of muscle tissue. It's about the size of a person's fist. The heart has.
The physiology of the heart basically comes down to "structure, electricity and plumbing," Phillips told Live Science. The human heart has four chambers: The right atrium and right ventricle together make up the "right heart," and the left atrium and left ventricle make up the "left heart. A double-walled sac called the pericardium encases the heart, which serves to protect the heart and anchor it inside the chest.
Between the outer layer, the parietal pericardium, and the inner layer, the serous pericardium, runs pericardial fluid, which lubricates the heart during contractions and movements of the lungs and diaphragm.
The heart's outer wall consists of three layers.
Human heart anatomy
The outermost wall layer, or epicardium, is the inner wall of the pericardium. The middle layer, or myocardium, contains the muscle that contracts. The inner layer, or endocardium, is the lining that contacts the blood. The tricuspid valve and the mitral valve make up the atrioventricular AV valves, which connect the atria and the ventricles. The pulmonary semi-lunar valve separates the right ventricle from the pulmonary artery, and the aortic valve separates the left ventricle from the aorta.
The heartstrings, or chordae tendinae, anchor the valves to heart muscles. The heart circulates blood through two pathways: In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.
In the systemic circuit, oxygenated blood leaves the body via the left ventricle to the aorta, and from there enters the arteries and capillaries where it supplies the body's tissues with oxygen. Deoxygenated blood returns via veins to the venae cavae, re-entering the heart's right atrium.
Of course, the heart is also a muscle, so it needs a fresh supply of oxygen and nutrients, too, Phillips said. The left main coronary artery, on one side of the aorta, branches into the left anterior descending artery and the left circumflex artery.
The right coronary artery branches out on the right side of the aorta. A heart attack is distinct from cardiac arrest, which is a sudden loss of heart function that usually occurs as a result of electrical disturbances of the heart rhythm. This has three cusps which are not attached to any papillary muscles.
When the ventricle relaxes blood flows back into the ventricle from the artery and this flow of blood fills the pocket-like valve, pressing against the cusps which close to seal the valve. The semilunar aortic valve is at the base of the aorta and also is not attached to papillary muscles. This too has three cusps which close with the pressure of the blood flowing back from the aorta.
A small amount of blood from the coronary circulation also drains into the right atrium via the coronary sinus , which is immediately above and to the middle of the opening of the inferior vena cava. In addition to these muscular ridges, a band of cardiac muscle, also covered by endocardium, known as the moderator band reinforces the thin walls of the right ventricle and plays a crucial role in cardiac conduction.
It arises from the lower part of the interventricular septum and crosses the interior space of the right ventricle to connect with the inferior papillary muscle. The pulmonary trunk branches into the left and right pulmonary arteries that carry the blood to each lung.
The pulmonary valve lies between the right heart and the pulmonary trunk.
The left atrium has an outpouching called the left atrial appendage. Like the right atrium, the left atrium is lined by pectinate muscles.
Like the right ventricle, the left also has trabeculae carneae , but there is no moderator band. The left ventricle pumps blood to the body through the aortic valve and into the aorta. Two small openings above the aortic valve carry blood to the heart itself, the left main coronary artery and the right coronary artery.
The heart: All you need to know
The heart wall is made up of three layers: the inner endocardium , middle myocardium and outer epicardium. These are surrounded by a double-membraned sac called the pericardium.
The innermost layer of the heart is called the endocardium. It is made up of a lining of simple squamous epithelium and covers heart chambers and valves.
It is continuous with the endothelium of the veins and arteries of the heart, and is joined to the myocardium with a thin layer of connective tissue.
The cardiac muscle pattern is elegant and complex, as the muscle cells swirl and spiral around the chambers of the heart, with the outer muscles forming a figure 8 pattern around the atria and around the bases of the great vessels and the inner muscles, forming a figure 8 around the two ventricles and proceeding toward the apex. This complex swirling pattern allows the heart to pump blood more effectively.
These contractile cells are connected by intercalated discs which allow a rapid response to impulses of action potential from the pacemaker cells. The intercalated discs allow the cells to act as a syncytium and enable the contractions that pump blood through the heart and into the major arteries. They are generally much smaller than the contractile cells and have few myofibrils which gives them limited contractibility. Their function is similar in many respects to neurons. The tough outer surface of the pericardium is called the fibrous membrane.
This is lined by a double inner membrane called the serous membrane that produces pericardial fluid to lubricate the surface of the heart.
The pericardium is present in order to lubricate its movement against other structures within the chest, to keep the heart's position stabilised within the chest, and to protect the heart from infection. This is achieved by the coronary circulation , which includes arteries , veins , and lymphatic vessels.
Blood flow through the coronary vessels occurs in peaks and troughs relating to the heart muscle's relaxation or contraction. These are the left main coronary artery and the right coronary artery. The left main coronary artery splits shortly after leaving the aorta into two vessels, the left anterior descending and the left circumflex artery.
The left anterior descending artery supplies heart tissue and the front, outer side, and the septum of the left ventricle. It does this by branching into smaller arteries—diagonal and septal branches.
The left circumflex supplies the back and underneath of the left ventricle. The right coronary artery supplies the right atrium, right ventricle, and lower posterior sections of the left ventricle.
The right coronary artery runs in a groove at the back of the heart and the left anterior descending artery runs in a groove at the front. There is significant variation between people in the anatomy of the arteries that supply the heart  The arteries divide at their furtherst reaches into smaller branches that join together at the edges of each arterial distribution. It receives blood from the great cardiac vein receiving the left atrium and both ventricles , the posterior cardiac vein draining the back of the left ventricle , the middle cardiac vein draining the bottom of the left and right ventricles , and small cardiac veins.
These networks collect into a main left and a main right trunk, which travel up the groove between the ventricles that exists on the heart's surface, receiving smaller vessels as they travel up.
These vessels then travel into the atrioventricular groove, and receive a third vessel which drains the section of the left ventricle sitting on the diaphragm. The left vessel joins with this third vessel, and travels along the pulmonary artery and left atrium, ending in the inferior tracheobronchial node.Blood vessels There are three types of blood vessels: Arteries: carry oxygenated blood from the heart to the rest of the body.
Human Heart: Anatomy, Function & Facts
For more information see: But without functioning atria, venous flow becomes pulsatile, and the overall circulation rate decreases significantly. Fathers to be: What is the Cardiac Cycle? The heart is located in between the two lungs. This blood will again return back to the heart through the veins and the cycle continues.