The Circulatory System(a.k.a. The Cardiovascular System)

Consists of the heart, blood vessels, and blood

Function:

◦Transports oxygen and nutrients to body cells

◦Transports carbon dioxide and metabolic materials away from body cells

The Heart

Muscular hollow organOften called the pump of the bodyWeighs less than one poundAbout the size of a closed fistContracts about 100,000 times each day

to pump the equivalent of 2,000 gallons of blood through the body

Located in the medial to the lungs, deep to the sternum, and superior to the diaphragm

Three layers of tissue form the heart

Endocardium◦Smooth layer of cells◦Lines the inside of the heart◦Allows for smooth flow of blood

Myocardium◦Thickest layer◦Muscular middle layer

Pericardium◦Double layered membrane or sac◦Covers outside of heart◦Fluid fills space between two layers and prevents friction

and damage to membranes as the heart beats, or contracts

The Septum

Muscular wallSeparates heart into a right and left

sidePrevents blood from moving

between the right and left side of the heart

Heart Chambers

Heart is divided into four parts (chambers)

Two upper chambers are called atria

Two lower chambers are called ventricles

Heart ChambersRight atrium receives blood as it returns

from the bodyRight ventricles

◦Receives blood from the right atrium(Pushes blood into the pulmonary artery, which

carries the blood to the lungs for oxygen)Left atrium receives oxygenated blood

from the lungs by way of pulmonary veinLeft ventricle

◦Receives blood from the left atrium◦Pushes blood into the aorta so it can be carried

to the body

ValvesOne way valves in the chambers of the heart keep blood flowing in the proper direction

TRICUSPID VALVE

Located between the right atrium and right ventricle

Closes when right ventricle contracts and pushes blood into the lungs

Prevents blood from flowing back into the right atrium

Pulmonary Valve

Located between right ventricle and pulmonary artery (blood vessel that carries blood to lungs)

Closes when right ventricle has finished contracting and pushing blood into pulmonary artery

Prevents blood from flowing back into right ventricle

Mitral Valve

Located between left atrium and left ventricle

Closes when left ventricle is contracting and pushing blood into aorta so blood can be carried to the body

Prevents blood from flowing back into left atrium

Aortic Valve

Located between left ventricle and aorta, largest artery in the body

Closes when left ventricle is finished contracting and pushing blood into aorta

Prevents blood from flowing back into left ventricle

The right and left sides of the heart work together in a

cyclic manner even though they are separated by the

septum.

The Cardiac CycleElectrical impulse originating in heart

causes myocardium to contract in cyclic manner

Cycle consists of brief period of rest, called diastole, followed by of ventricular contraction called systole

Is the blood in the right side of the heart oxygenated or deoxygenated?

Left?

Conductive Pathway

Electrical impulses originating in the heart triggers cyclic

contraction of muscles.

Sinoatrial (SA) Node

Electrical impulse starts in the SA nodeGroup of nerve cells located in right atriumAlso called the “pacemaker”Sends out electrical impulse that spreads

out over muscles in atriaAtrial muscles then contract and push

blood into ventriclesAfter electrical impulse passes through

atria it reaches atrioventricular (AV) node

Atrioventricular (AV) node

Group of nerve cells located between atria and ventricles

AV node sends electrical impulse through nerve fibers in the septum called the bundle of HIS

Bundle of HIS

Nerve fibers in septumDivides into a right and left bundle branch

Right and Left Bundle Branches

Pathways that carry the impulse down through ventricles

Bundles continue to subdivide into network of nerve fibers throughout ventricles called Purkinje fibers

Purkinje Fibers

Final fibers on conduction pathway

Spread electrical impulse to all muscle tissue in ventricles

Ventricles then contract

Electrical conduction pattern occurs approximately every 0.8 seconds

Movement of electrical impulse can be recorded on an ECG/EKG and used to detect abnormal activity or disease

Arrhythmias

Interference with normal electrical conduction pattern

of the heart which causes abnormal heart rhythms

Arrythmias can be mild to life-threatening

◦Premature atrial contraction (PAC), an early contraction of the atria, can occur in anyone and usually goes unnoticed

◦Ventricular fibrillation, in which ventricles contract at random without coordination decreases or eliminates blood output and causes death if not treated

Cardiac monitors and electrocardiograms (ECG) are used to diagnose arrythmias

Treatment of arrythmias

Life-threatening fibrillations are treated with a defibrillator

◦Device that shocks the heart with an electrical current

◦Stops uncoordinated contraction◦Allows SA node to regain control

Internal Artificial PacemakerSmall battery-powered device with

electrodesElectrodes are threaded through a vein

and positioned in right atrium and in apex of right ventricle

Pacemaker monitors heart’s activity and delivers electrical impulse through electrodes to stimulate contraction

Educate your patients with pacemakers to not store cell phones in shirt pocket. It could alter signals sent from the pacemaker.

Blood Vessels

Blood leaving the heart is carried throughout the body in blood vessels

Heart and blood vessels form a closed system for flow of blood

Three main types of blood vessels are:◦Arteries◦Capillaries◦Veins

Arteries

Carries blood away from the heartAorta

◦Largest artery in the body◦Receives blood from left ventricle of the heart◦Branches off into all other arteries that supply

blood to the bodyArterioles

◦Smallest branches of arteries◦Join with capillaries

Capillaries

Connect arterioles with venules, the smallest veins

Located in close proximity to almost every cell in the body

Have thin walls that contain only one layer of cells

Allow oxygen and nutrients to pass through the cells

At the same time, carbon dioxide and metabolic products from the cells enter the capillaries

Veins

Blood vessels that carry blood back to the heart

Venules-◦Smallest branches of veins◦Connect with capillaries◦Venules join together and become larger to

form veins

VeinsSuperior and Inferior Vena Cava

◦Two largest veins◦Superior vena cava brings blood from upper

part of the body◦Inferior vena cava brings blood from lower part

of the body◦Both vena cava empty blood into right atrium

**Most veins contain valves that keep blood from flowing backward**

Blood Composition

Blood is often called a tissue because it contains many kind of cells

About four to six quarts of blood are in the average adult

Blood circulates throughout the body continually

Blood transports many substances

◦Oxygen from lungs to the body cells◦Carbon dioxide from body cells to lungs◦Nutrients from digestive tract to cells◦Metabolic waste products from cells to organs of excretion

◦Hormones produced by endocrine glands to organs in the body

Plasma

Plasma is the fluid or liquid portion of blood (Plasma makes up 55% of our blood)

About 90% of plasma is waterMany substances are dissolved or suspended in

the water◦Blood proteins◦Nutrients◦Mineral salts or electrolytes◦Gases◦Wastes◦Hormones◦Enzymes

Blood Cells

Blood cells are the solid elements of blood

Three main kinds of blood cells◦Erythrocytes◦Leukocytes◦Thrombocytes

Erythrocytes (red blood cells)

Produced in the red bone marrow at a rate of about 1 million per minute

Live about 120 days before being broken down by the liver and spleen

There are 4.5-5.5 million erythrocytes per cubic ml (one gtt) OR 25 trillion in the body

Erythrocytes contain a protein called Hemoglobin

Composed of a protein molecule called globin and an iron compound called heme

Carries both oxygen and carbon dioxideWhen hemoglobin carries oxygen, it gives

blood its characteristic red colorIf blood contains a lot of oxygen it is

bright redWhen there is less oxygen and more

carbon dioxide, blood is a much darker red

Leukocytes (white blood cells)

Not as numerous as erythrocytesFormed in the bone marrow and lymph

tissue and usually live about 3-9 daysNormal count is 5000-9000 leukocytes per

cub ml of bloodLeukocytes can pass through capillary

walls and enter body tissueMain function is to fight infection

Leukocytes continued…Phagocytosis- process by which some

leukocytes engulf, ingest, and destroy pathogens, or germs