Cardiovascular System-Cardiovascular System-The HeartThe Heart

Anatomy Chap. 21Anatomy Chap. 21

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

Heart Anatomy Overview

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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”

Layers of Heart Wall Epicardium (a.k.a. visceral pericardium)

Myocardium

Endocardium

Cardiac muscle tissue

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

Atrioventricular (AV) valves

Tricuspid

Bicuspid

Rt ventricleLt ventricle

Interventricular septum

Trabeculae carneae

Aorta (ascending)

Aortic semilunar valve

Pulmonary semilunar valve

Pulmonary trunk

Pulmonary artery

Semilunar valves

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

Anatomy

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