cardiovascular system- the heart anatomy chap. 21
TRANSCRIPT
The Cardiovascular system is comprised of the heart, blood vessels, & blood
The heart acts as a “pump”, creating pressure which causes blood to move through the blood vessels of the body, allowing O2 & nutrients to be distributed to, & wastes removed from, body tissues
Anatomical Features of the Heart The heart lies within the
mediastinum of the thoracic cavity Hollow muscular organ with four
internal chambers(2) atria (lt. atrium & rt. atrium)-
receive blood from veins(2) ventricles (lt. ventricle & rt.
ventricle)- pump blood into arteries
Superior aspect of heart is the “base” (3rd intercostal space/sternal angle), where the blood vessels attach; Inferior is the “apex” (5th intercostal space), which rests on the relaxed diaphragm
Pericardium The heart lies enclosed within pericardial
membranes Fibrous pericardium (pericardial sac) – outer layer
of dense CT that protects & anchors Serous pericardium – double layered membrane
with “pericardial fluid” between Parietal pericardium – lines the pericardial sac Visceral pericardium – covers the heart; also known as
the “epicardium”
Because of the characteristics of cardiac muscle tissue & the arrangement of connective tissue (fibrous skeleton) within the heart, the heart basically has two functional units:
the myocardium of the atria (upper chambers) act as one functional unit
the myocardium of the ventricles (lower chambers) act as the other
This allows the atria to contract simultaneously while the ventricles are relaxed; then the ventricles contract simultaneously while the atria relax
External Features
Auricles
Coronary sulcus – contains the coronary sinus
Anterior interventricular sulcus – contains coronary vessels
Posterior interventricular sulcus – contains coronary vessels
Rt AtriumLt Atrium
Pectinate muscles
SVC
IVC
Coronary sinus (opening)
Deoxygenated blood
Pulmonary veins
Oxygenated blood
Tricuspid valve
Bicuspid (mitral) valve
Chordae tendineae
Papillary muscle
Chordae tendineae
Papillary muscle
Interatrial septumFossa ovalis
Rt ventricleLt ventricle
Interventricular septum
Trabeculae carneae
Aorta (ascending)
Aortic semilunar valve
Pulmonary semilunar valve
Pulmonary trunk
Pulmonary artery
Rt ventricleLt ventricle
Interventricular septum
Trabeculae carneae
Aortic Arch
Aortic semilunar valve
Pulmonary semilunar valve
Pulmonary trunk
Pulmonary artery
Ligamentum arteriosumBrachiocephalic trunkLeft common carotid artery Left subclavian artery
Coronary Circulation Myocardium receives oxygenated blood from the left & right Coronary arteries – branches off the ascending aorta
left coronary artery anterior interventricular branch & circumflex branch right coronary artery marginal branch & posterior interventricular branch
Deoxygenated blood is drained through Cardiac veins (Great, posterior, middle & small cardiac veins), which all eventually merge and drain into the coronary sinus
Conducting System Intrinsic regulating system that generates “heartbeat”
comprised of functionally specialized “autorhythmic (conducting) cells” – which can spontaneously generate action potentials
SA node (“pacemaker”) AV node AV bundle (of His) Bundle branches Purkinje fibers
The activity of the conduction system results in the contraction (systole) & relaxation (diastole) of the heart chambers
atria will contract as ventricles remain relaxed (atrial systole/ventricular diastole). Blood moves from atria to ventricles
as atria relax, ventricles begin to contract (atrial diastole/ventricular systole). The AV valves (tricuspid & bicuspid/mitral) snap shut to prevent backflow of blood into atria. The closing of the valves makes a sound – “Lub”
as blood moves from ventricles to arteries (pulmonary trunk & aorta), pressure will increase in the arteries and decrease in the ventricles. Semilunar valves will then shut “Dupp” as ventricles relax
all 4 chambers will be in diastole, and then cycle begins again
Movement of blood through heart & heart sounds