Cardiovascular System

Introduction

The heart pumps blood Blood vessels provide the conduits within

which blood circulates to all body tissues

Main function: ◦ Transportation

Function Preview

The HeartThe main organ of the circulatory system

Location and Size Coverings and Wall Chambers Valves

Page 329 in book

Anatomy of the Heart

The relative size and weight of the heart give a few hints to the incredible strength the heart has

Size: ◦ approx. size of fist

Shape: ◦ Hollow, Cone-shaped

Weight:◦ Less than a pound

Size

Apex points toward the left hip and rests on the diaphragm ◦ Approx. where the left intercoastal space is

Where you would place a stethoscope to hear the heart beats Base – broader posterosuperior aspect, from where the

great vessels of the body emerge, points toward the right shoulder and lies beneath the 2nd rib

Location

Pericardium: ◦ double sac of serous membrane

The thin visceral pericardium, or epicardium tightly hugs the external surface of the heart and part of the heart wall

A lot of connective tissue There is a fibrous layer helps protect the heart and anchors it to

surrounding structures such as the diaphragm and the sternum A slippery lubricating fluid (serious fluid) is produced by the

pericardial membranes ◦ The fluid allows the heart to beat easily in a relatively frictionless

environment as the pericardial layers slide smoothly across each other

Myocardium:◦ Consists of think bundles of cardiac muscle twisted around and

actually contracts Endocardium:

◦ Thin, glistening sheet of endothelium that lines the heart chambers

Coverings and Wall

Two atria Two ventricles

Each of these is lined with endocardium, which helps blood flow smoothly through the heart

The superior atria are typically the receiving chambers ◦ They are not important in the actual pumping activity ◦ Blood flows into the atria under low pressure from the veins of the

body and then continues to fill the ventricles The inferior, thick-walled ventricles are the discharging

chambers, or actual pumps of the heart

Video

Chambers

Read information on page 331-332Chambers and Valves

CirculationCardiac Circulation/ Operation

Circulation Song Pg 333

Circulation

1. Once the deoxygenated red blood cell (RBC) returns to the heart, it enters either through the superior vana cava or the inferior vena cava. The superior vena cava returns deoxygenated blood from the upper part of the body to the heart. The inferior vena cava returns deoxygenated blood from the lower part of the body to the heart. These large veins lead into the right atrium.

2. The RBC passes through the tricuspid valve into the right ventricle. 3. The RBC is then pumped through the pulmonary valve into the pulmonary artery

and on to the lungs. There the RBC gives off carbon dioxide and picks up oxygen. 4. The RBC returns to the heart through a pulmonary vein, enters the left atrium,

passes through the mitral valve, and flows into the left ventricle. 5. The left ventricle pumps the fully oxygenated RBC through the aortic valve, into

the aorta, the body's main artery, and out to the body. 6. From the aorta, the RBC flows into one of the many arteries of the body, through

the arterioles, and then to the capillaries, where the RBC will deliver oxygen and nutrients to the cells and remove wastes and carbon dioxide. Next it moves through the venules, veins, and on to the vena cava in a deoxygenated state, and returns to the heart, only to begin its repetitive journey once again. This whole process has taken approximately 20 seconds!

That single RBC will travel about 950 miles (more than 1500 kilometers) in its brief 4-month lifetime!

Life Span of a RBC