Introduction

• The heart pumps 7,000 liters of blood through the body each day• The heart contracts 2.5 billion times in an average lifetime•It takes approximately 1 minute for a blood cell to circulate through the body (at rest)• The heart and all blood vessels make up the cardiovascular system• The blood vessels make up two circuits:• Pulmonary circuit• Systemic circuit

SIZE AND LOCATION OF

HEART

The heart is located in the mediastinum in a cavity called the pericardial cavity.

The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth

and fifth ribs near their articulation with the costal cartilages

Diaphragm

Base of heart

Apex of heart

Heart

Sternum

Coverings of the heart

The heart is separated from other structures by a tough membrane known as the pericardium, or pericardial sac.

The percardium is the serous membrane lining the cavity.

• The pericardium is a continuous membrane but the part that attaches to the surface of the heart is the visceral pericardium (a.k.a. epicardium) and the part that lines the outer wall of the cavity is the parietal pericardium

The outer surface of the parietal pericardium is reinforced by a layer of dense, irregular connective

tissue called the fibrous pericardium.

Walls of the heart

Structure of Heart Wall 

• The heart wall can be divided into three layers:1. Epicardium (visceral pericardium) described

previously2. Myocardium consists of multiple interlocking layers

of cardiac muscle tissue with associated connective tissue, blood vessels and nerves.

3. Endocardium is the inner lining of the heart. It is continuous with the endothelium that lines the blood vessels.

`Epicardium (outer layer)Myocardium (middle layer)Endocardium(inner layer)

Heart Chambers and

valves

Internal Heart Structures

Atrium (single) Atria (plural)- collect blood from incoming veins; pass blood into ventricles

Ventricles- pump blood out of heart through outgoing arteries

• The common wall between the atria is the interatrial septum and the common wall between the ventricles is theinterventricular septum.

• a septum (plural = septa) refers to a wall or partition that divides the heart into chambers– word septum is derived from the Latin for “something

that encloses;”

Path of blood

Right Atrium 

• The right atrium receives deoxygenated blood from superior vena cava, inferior vena cava

Right Ventricle • The deoxygenated blood from right atrium enters

the right ventricle through the right atrioventricular (tricuspid) valve.

• This valve has three “flaps” or “cusps”• The edges of the cusps are attached to strings of

connective tissue called the chordae tendineae. • The chordae tendineae are anchored to the

ventricular wall by papillary muscles.• These help reinforce the valves and prevent

backflow

Left Atrium

• The left (2) and right (2) pulmonary veins drain oxygenated blood from the lungs into the left atrium.

• The oxygenated blood enters the left ventricle through a valve with two flaps, the left atrioventricular (a.k.a. bicuspid, mitral) valve.

Left Ventricle

• The left ventricle, has a thicker wall than the right. • As oxygenated blood is ejected from the left

ventricle is passes through the aortic semilunar valve and enters the ascending aorta.