Cardiovascular System - Heart and Great Vessels Flashcards
Describe the position of the heart in the thorax.
Heart is located within the mediastinum
Superior to the diaphragm
Anterior to the vertebral column
Posterior to the sternum
Medial to the hilum of the lungs.
What is the pericardium?
Membranous sac enclosing the heart
Pericardial cavity - space between serous layers
Pericardial fluid - secreted by serous layers to reduce friction .
Describe the fibrous aspect of the pericardium.
Attached by sternopericardial ligaments
Physical barrier for protection
Fuses with the tunica adventitia of the great vessels
Lots of fibroblasts and collagen
Exterior
Protects against sudden overfilling.
Describe the serous aspect of the pericardium.
Interior
A closed sac made of a
parietal layer - lines fibrous pericardium
visceral layer - covers the heart.
What are the 5 layers of the heart wall starting with exterior?
Epicardium - formed by visceral layer of pericardium
Subepicardial layer - joins myocardium and epicardium
Myocardium - cardiac muscle, thickest layer
Subendocardium - loose connective tissue, small blood vessels, conducting system of the heart
Endocardium - innermost layer, endothelium.
What are the distinctive features of cardiac muscle?
Striated - actin and myosin filaments
Nucleus positioned centrally
Branched cells joined by intercalated discs - desmosome, gap junctions, fascia adherens.
Explain the flow of blood through the heart.
Deoxygenated blood enters the right atrium of the heart during diastole.
Right atrium contracts during systole which opens tricuspid valve allowing blood to flow from the right atrium into the right ventricle.
Once the right ventricle is filled with blood, it contracts during systole.
This contraction forces the tricuspid valve to close, preventing the backflow of blood into the right atrium.
The contraction also causes the pulmonary valve to open, allowing deoxygenated blood to be pumped out of the heart and into the pulmonary artery.
Deoxygenated blood travels to the lungs.
Oxygenated blood from the lungs returns to the heart via the pulmonary veins and fills left atrium.
When the left atrium contracts during systole, the mitral valve opens, allowing blood to flow from the left atrium into the left ventricle.
The left ventricle contracts during systole, forcing the mitral valve to close and preventing blood from flowing back into the left atrium.
The aortic valve, located between the left ventricle and the aorta, opens, allowing oxygenated blood to be pumped out of the heart and into the aorta.
What makes up the conducting system of the heart?
Sinoatrial node - pacemaker, located in wall of the right atrium, own blood supply
Atrioventricular node - located in septum
Bundle of His - divides into 2 branches of Purkinje fibres
Purkinje fibres - occurs in dense connective tissue of endocardium, specialised cardiac muscle fibres.
Name the 2 major heart valves and how they function.
Atrioventricular valves: tricuspid valve (RA -> RV) + bicuspid (LA -> LV)
Right AV valve has 3 cusps and left has 2
Chord tendineae connect AV valves to papillary muscles
Semilunar valves: pulmonary (RV -> pulmonary trunk) and aortic valve (LV -> aorta). Control flow of blood into great arteries
Prevent the back flow of blood.
Describe pulmonary circulation.
Pulmonary circulation is the portion of the circulatory system that involves the movement of blood between the heart and the lungs. Its primary function is to facilitate gas exchange, where carbon dioxide is removed from the bloodstream and oxygen is absorbed into the blood.
Describe systemic circulation
Systemic circulation refers to the portion of the circulatory system that is responsible for delivering oxygenated blood from the heart to the body’s tissues and organs and returning deoxygenated blood back to the hear
