the heart Flashcards
what is the heart
a transport pump that pumps blood through a system of blood vessels to body tissues
what is the hearts role
to ensure the delivery of oxygen rich blood to the cells, tissues and organs of the body and the return of poorly oxygenated blood to the lungs
where is the heart located
the heart is located in the mediastinum which is the medial cavity of the thorax slightly off centre to the left.
what is the structure of the pericardium and the functions
it is a double walled membranous sac that the heart is enclosed in. Made of 2 main layers
- fibrous pericardium- superficial layer of dense, fibrous CT that protects, anchors to the surrounding tissue and prevents the heart from overfilling with blood
- serous pericardium- deep layer of smooth, thin, slippery epithelium which allows the heart to constantly move without causing friction. it is made of 2 layers and a space
- partiel layer- lines inner surface of fibrous pericardium
- visceral layer- lines external surface of the heart and forms the outermost layer of the heart
- pericardial cavity between the 2 layers. filled with serous fluid which lubricates and allows for frictionless movement
what are the three layers of the heart wall
- epicardium- outermost layer. it is a visceral layer of the serous pericardium
- myocardium- middle layer mostly composed of cardiac muscle tissue
- endocardium- deepest layer that is continuous with the lining of blood vessels
what are the chambers of the heart
the heart has 4 chambers- 2 atria (receiving chambers) and 2 ventricles (pumping chambers)
what are the valves of the heart
the heart has 4 valves, which control the flow of blood into or out of the heart chambers- 2 atrioventricular valves and 2 semilunar valves. valves can facilitate blood flow through chambers of the heart in only one direction
what are the great vessels of the heart
they are continuous with the chambers of the heart. arteries carry blood away from the heart and veins carry blood to the heart
how does blood flow through the heart
oxygen poor blood from the body returns to the right atrium, blood from the upper body returns through the superior vena cava and blood from the lower body through the inferior vena cava. as the right atrium fills with blood it contracts and the tricuspid valve opens and blood is pumped into the right ventricle. when the right ventricle is full the tricuspid valve closes to prevent blood from flowing back into the atrium. the right ventricle contracts and the pulmonary valve opens and blood is pumped into the pulmonary artery (lungs). the pulmonary valve then closes to stop blood from flowing back. pulmonary artieries take oxygen poor blood to the lungs where pulmonary circulation takes place and pulmonary veins return the oxygen rich blood from the lungs to the left atrium. as the left atrium fills with blood it contracts and the mitral valve opens up and blood is pumped into the left ventricle. the mitral valve then closes and the aortic valve opens as the left ventricle contracts and the oxygen rich blood is pumped through the aorta to reach all parts of your body. the aortic valve closes to prevent blood from flowing back to the heart. then systemic circulation takes place. the left and right side are working and pumping blood at the same time and the cycle continues to repeat itself
what is systemic circulation
delivers blood to and from body tissues so those body tissues can extract oxygen and release carbon dioxide into the blood.
- receives blood from the left ventricle
- delivers highly oxygenated blood to body tissues
- returns poorly oxygenated blood to heart
- empties blood into the right atrium
what is the coronary circulation and key vessels of this circuit
coronary circulation is when blood vessels deliver and take blood to and from the heart tissue because the walls of the heart are too thick for oxygen and nutrients to diffuse through from the blood pumping through the heart chambers.
coronary arteries from the aorta deliver highly oxygenated blood to the heart walls through the myocardium. cardiac veins return poorly oxygenated blood from the myocardium into the coronary sinus which empties directly into the right atrium.
what is the structure of cardiac muscle
they are cylindrical and have bundles of myofibrils called fascicles consisting of sarcomeres. they are relatively short and branched, connecting with each other via intercalated discs. they have one or two nuclei and contain lots of mitochondria which supplies continuous energy. they rely exclusively on oxygen and energy metabolism
what is the cardiac conduction system of the heart
to maintain an ongoing and steady cycle of contractions and therefore heart rate, some cardiac muscle fibers create a conduction system throughout the myocardium of the heart. these cells are non contractile and can generate and distribute action potentials without requiring neural stimulation
order and explain the events of the cardiac conduction cycle
the SA node of the heart is the pacemaker of the heart, it initiates heart beat and determines heart rate. electrical impulses from the SA node spread throughout both atria and stimulate them to contract. The AV node receives signals from the SA node and delays the passage of electrical impulses to the ventricles to ensure the atria has ejected all the blood before into it before it contracts. the impulses are then sent to the AV bundle which is divided into left and right bundle branches which conduct the impulse towards the apex of the heart. the signals are then passed to the purkinje fibers, turning upwards and spreading throughout the myocardium.
what is cardiac output
the volume of blood pumped out of the left ventricle every minute
