Cardiovascular System

Anatom y Pr ac t i c a l [ PH L 212 ]

The Cardiovascular System· A closed system of the heart and blood vessels• The heart pumps blood• Blood vessels allow blood to circulate to all parts of

the bodya. Pulmonary circuit—flow of blood through the lungs.

Pulmonary arteries—carry O2-poor blood from right ventricle to the lungs.

Pulmonary veins—carry O2-rich blood from lungs to the left atrium.

b. Systemic circuit—flow of blood through the rest of the body. Aorta—carries O2-rich blood to all body tissues.

Vena cava—returns O2-poor blood to the right atrium.· The function of the cardiovascular system is to deliver

oxygen and nutrients and to remove carbon dioxide and other waste products

The Heart: Size & Location· The heart is a hollow, cone-shaped, muscular pump · Nine (9) inches long x three (3) inches wide. · Located in the centre of Thorax between the lungs

posteriorly by the backbone, and anteriorly by the sternum & resting upon the diaphragm.

· Base--attached to several large blood vessels and lies beneath the second rib.

· Pointed apex at the fifth intercostal space directed toward left

Location of Heart in thorax

The Heart: Coverings· The heart and the proximal ends of the large blood

vessels are enclosed by the pericardium. · Consists of an outer fibrous pericardium which

surrounds a more delicate double-layered sac. · Inner layer of this sac--visceral pericardium

(epicardium) covers the heart. · At the base of the heart the visceral pericardium

turns back on itself to become the parietal pericardium.

· Between the parietal and visceral layers is the pericardial cavity which contains serous fluid--pericardial fluid.

The Heart: Heart Wall· Three layers

· Epicardium (Outer layer)· consists of connective tissue covered by epithelium · Functions as an outer protective layer

· Myocardium (Middle layer)· Relatively thick · Consists largely of cardiac muscle tissue responsible for forcing blood

out of the heart chambers · Pumps 70 ml blood with each contraction

· Endocardium (Inner layer)· Relatively thin sheet consists of epithelial and connective tissue that

contains many elastic and collagenous fibers. · Lines all of the heart chambers and covers heart valves

Heart Wall

The Heart: Associated Great Vessels

· Aorta· Leaves left ventricle

· Pulmonary arteries· Leave right ventricle

· Vena cava· Enters right atrium

· Pulmonary veins· Enter left atrium

External Heart Anatomy

The Heart: Chambers· Four chambers

· The AtriumUpper two chambersDivided into the Left Atria and the Right AtriaBrings in Blood from the VeinsReceiving chambers

· VentriclesLower two chambersDivided into Left Ventricle and Right VentriclePumps in Blood into the arteriesDischarging chambers

The Heart: Valves

· Allow blood to flow only in one direction· Four valves· Atrioventricular valves – between atria and

ventricles· Bicuspid or Mitral valve (left)· Tricuspid valve (right)

· Semilunar valves between ventricle and artery· Pulmonary semilunar valve· Aortic semilunar valve

Right Heart Chambers• Right Atrium

– Receives O2-poor blood from body via Superior and Inferior vena cava

• Right Ventricle– Receives O2-poor blood from right atrium through tricuspid valve

– Pumps blood to lungs via Pulmonary Semilunar Valve in pulmonary trunk

Left Heart Chambers• Left Atrium

– Receives O2-rich blood from lungs via 4 Pulmonary Veins

• Left Ventricle (forms apex of heart)– Receives blood from Left Atrium via bicuspid valve (Mitral valve )– Pumps blood into aorta via Aortic Semilunar Valve to body

Heart Chambers and Valves

Blood Circulation

Two circulatory paths

Pulmonary

Systemic

Walls of Arteries and Veins• Tunica externa

– Outermost layer– Connective tissue with varying

quantities of elastic fibers and collagen fibers

• Tunica media– Middle layer– Circular Smooth Muscle– Vaso-constriction/dilation

• Tunica intima– Innermost layer– Simple squamous epithelium

(endothelium). – Minimize friction

• Lumen

Differences Between Artery & Vein

Arteries Veins Direction of flow Blood Away from Heart Blood to Heart

Walls THICKER: Tunica media thicker than tunica externa

THINNER: Tunica externa thicker than tunica media

Lumen Smaller Larger

Pressure Higher Lower

Valves No valves Valves

1. Blood transported by the pulmonary veins returns to theleft atrium.right atrium. right ventricle.left ventricle.

2. The valve between the left ventricle and the blood vessel leaving the left ventricle is thebicuspid valve.tricuspid valve.pulmonary semilunar valve.aortic semilunar valve.

3. The valve located between the right atrium and the right ventricle is thetricuspid valve.bicuspid valve.mitral valve.semilunar valve.