Flashcards in Chapter 18 - The Heart Deck (57)
Function of the Heart
To pump blood. It provides the pressure responsible for moving the blood through the vessels, and then filtering into the capillaries where the tissue fluid bathes the cells.
Anatomy of the Heart
A hollow organ, which consists of 4 chambers. A dual pump. Two sides, a left and a right that each pumps into two distinct pathways, the systemic and the pulmonary pathways.
Size and Shape of the Heart
Cone-shaped with a pointed end called the apex and a broad section called the base. About the size of a clenched fist, and angled towards the left.
Location of the Heart
Lies in a space between the lungs called the mediastinum. The base of the heart lies behind the sternum and the apex points to the left.
A double layer membrane that surround the heart.
-Parietal layer: tough fibrous membrane, outer layer.
-Visceral layer (epicardium): inner layer, a delicate serous layer that adheres to the heart muscle.
Space between the two membranes, filled with pericardial fluid which reduces friction when the heart is beating
Left and right. The two upper chambers, each one empties into the lower chambers, the ventricles.
Left and right. The lower chambers, they pump blood out into the two circuits.
Wall structure of the Heart
3 layers. The endocardium, the myocardium, and the epicardium.
The inner lining of the heart. Consists of a single layer of squamous epithelia. Its continuous with the epithelium that lines the remainder of the circulatory system. It fold over and with connective tissue makes up the valves of the heart.
This is the muscle layer. The thickest of the three layers. It's very thin in the atria, and thicker in the ventricles. The right ventricle has three layers of muscle, while the left ventricle has four layers.
The thin serous membrane which adheres to the myocardium. Also called the pericardium.
Regulate the flow of the blood through the heart.
Regulate flow from the atria to the ventricles, one on each side of the heart. When blood flows into the atria, the pressure of the incoming blood forces the blood open, when the ventricles begin to contract, the pressure causes the valves to swing shut.
Three flaps, located between the right atria and the right ventricle.
Mitral. Two flaps, is separates the left atria from the left ventricle.
These separate the arteries from the ventricles. They prevent the back flow of blood from the arteries into the ventricles during ventricular relaxation.
Pulmonary Semilunar Valve
Separates the right ventricle from the pulmonary trunk
Aortic Semilunar Valve
Separates the left ventricle from the aorta
Path of blood through the heart
sup&inf vena cava and coronary sinus ---> right atrium ---> tricuspid valve ---> right ventricle --->pulmonary semilunar valve ---> pulmonary trunk ---> pulmonary rt&lft arteries ---> lungs ---> pulmonary veins ---> left atrium ---> bicuspid valve ---> left ventricle ---> aortic semilunar valve ---> aorta ---> system
Cardiac muscle is very metabolically active, and requires a constant supply of blood for nourishment. It is supplied by the right and left coronary arteries.
Cellular Organization of Heart Cells
Cardiac muscle is made of branching, striated cells separated by tone another by intercalated discs. They have 2 types of membrane junctions desmosomes and gap junctions.
All or None Response
Because the AP moves across every cell, it contracts with the maximum force with every contraction.
Resting Membrane Potential
A special set of cells located in the wall of the right atrium that always depolarize first. This is where the heartbeat originates, the pacemaker.
Located just above the ventricles.
Conduction in the Heart
SA node --> atrial myocardium --> AV node --> Bundle of His --> left and right bundles --> Purkinje fibers --> ventricular myocardium
Electrocardiogram. Measure of the electrical activity of the heart.
Contraction of the heart. Blood is being expelled from the heart