Thorax

Thorax

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

Cardiovascular SystemThe HeartAnatomy

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






This allows the atria to contract simultaneously while the ventricles are relaxed; then the ventricles contract simultaneously while the atria relax
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

External Features

Auricles
Coronary sulcus – contains the coronary sinus
Anterior interventricular sulcus – contains coronary vessels
Posterior interventricular sulcus – contains coronary vessels

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

Rt Atrium

Lt Atrium

Pectinate muscles

SVC
IVC
Coronary sinus (opening)
Deoxygenated blood
Pulmonary veins
Oxygenated blood
Tricuspid valve


Bicuspid (mitral) valve

Chordae tendoneae

Papillary muscle

Chordae tendoneae

Papillary muscle

Interatrial septum

Fossa ovalis

Atrioventricular (AV) valves

Tricuspid
Bicuspid

Rt ventricle

Lt ventricle

Interventricular septum

Trabeculae carneae

Aorta

Aortic semilunar valve

Pulmonary semilunar valve

Pulmonary trunk

Pulmonary artery

Ligamentum arteriosum


Brachiocephalic trunk

Left 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