Black Belt
DEVELOPMENT CLASSES
THE CARDIOVASCULAR SYSTEM
Hand-Out
2009
DEVELOPMENT CLASSES
THE CARDIOVASCULAR SYSTEM
THE HEART
The heart is the center of the cardiovascular system. Cardio meaning heart, and vascular refers to the blood vessels. The heart propels blood (1800 gallons per day and 1.3 million gallons a year), through an estimated 60,000 miles of blood vessels and it is magnificently designed for the task. The unique properties of the heart muscle that permits a lifetime of pumping with never a minute’s rest.
LOCATION and SIZE OF THE HEART
For all its might, the hollow, cone-shaped heart is relatively small, about the size of the owner’s clenched fist, and weighs only about 300-330 g (10-11 ounces). In an adult. The heart is slightly smaller in females than males.
The heart sits in a space in the thorax between the lungs called the MEDIASTINUM
LAYERS OF THE HEART
ENDOCARDIUM…………………Inner Layer
MYOCARDIUM…………………..middle (Heart Muscle)
PERICARDIUM…………………..Outer layer (Fibro-serous bag)
ENDOCARDIUM
This lines the inner aspect of the myocardium and heart valves. It makes these surfaces very smooth and prevents blood sticking to the walls of the chambers of the
heart, and clogging the entrance to valves.
MYOCARDIUM
This is the muscular tissue of the heart and it’s responsible for the heart’s contraction. It is composed of specialized muscle tissue called Cardiac Muscle. This muscle is found exclusively in the heart and varies in thickness between the four chambers. The thickest is around the left ventricle.
PERICARDIUM
This is a fibro-serous bag that completely surrounds the heart and prevents over distension. There is a medical condition in which the bag fills with blood and the build up of pressure prevents the heart beating. This is called a CARDIAC TAMPONADE.
THE CARDIOVASCULAR SYSTEM
CHAMBERS AND VALVES
RIGHT and LEFT ATRIUM…………………..Upper collecting chambers
RIGHT and LEFT VENTRICLES…………….Lower pumping chambers
SEPTUM…………Muscular wall that separates the right/left sides of the heart
VALVES
There are four valves within the heart. These work like automatic doors, they open to let blood through during a contraction (one way) and close at the end of it. They help maintain blood pressure and also prevent backflow of blood.
THE CARDIOVASCULAR SYSTEM
TRICUSPID VALVE …………..Between the right atrium/ventricle.
BICUSPID VALVE (MITRAL)..Between the left atrium/ventricle
PULMONARY VALVE …….. In right ventricle at entrance to the
Pulmonary Trunk.
AORTIC VALVE ……………. In the left ventricle at the entrance to the
Aorta.
CHORDAE TENDINEAE
These are fibrous cords extending from the Papillary Muscles in the ventricular walls to the atrio-ventricular valves (tricuspid and mitral). These prevent the cusps of the valves inverting into the atria during a contraction.
PULMONARY AND SYSTEMIC CIRCULATIONS
Deoxygenated blood is pushed through the tricuspid valve from the right atrium into the right ventricle. From here it is pumped up through the pulmonary trunk and into the left and right pulmonary arteries to the lungs where carbon dioxide is given off and oxygen is taken up. Oxygenated blood is retuned to the heart via 4 pulmonary veins to the left atrium. Where it is collected and pushed under contraction, through the bicuspid or mitral valve into the left ventricle. From here the blood is pumped up the largest artery in the body, the aorta and on to all the body’s tissues and organs. Eventually returning via the inferior and superior vena cavas to the heart to start the cycle over again.
THE PORTAL CIRCULATION
A branch of the systemic circulation, which carries blood to and from the liver. The Hepatic Artery supplies the liver with oxygenated blood. The Hepatic Portal Vein carries blood rich in nutrients to the liver from the digestive organs. Deoxygenated blood is carried from the liver to the inferior vena cava by the hepatic veins.
CARDIOVASCULAR SYSTEM
BLOOD SUPPLY TO THE HEART
CORONARY CIRCULATION
Two major arteries provide the blood supply to the heart,
· THE LEFT CORONARY ARTERY
· THE RIGHT CORONARY ARTERY
The myocardium receives its own blood supply via the coronary arteries. These are the first arteries to branch off the aorta as it leaves the left ventricle. The right and left coronary arteries transverse the heart and supply the whole myocardium. Venous return is via the circumflex veins and coronary sinus that returns deoxygenated blood to the right atrium.
CARDIOVASCULAR SYSTEM
THE ELECTRICAL CONDUCTIVE SYSTEM
THE STRUCTURES OF THE CONDUCTION SYSTEM
- THE SINOATRIAL NODE (known as the Pacemaker)
- THE ATRIOVENTRICULAR NODE
- THE BUNDLE OF HIS
- THE Right/Left BUNDLE BRANCHES
- THE PURKINJE FIBRES
CARDIOVASCULAR SYSTEM
ELECTRICAL CONDUCTION SYSTEM (Continued)
An impulse from the SINOATRIAL NODE situated in the upper right aspect of the right atrium is then passed over both atria, like ripples in a pond; this causes the atria to contract (0.1 sec.). The impulse is pick up by the ATRIOVENTRICULAR NODE, in the lower left aspect of the right atrium; there is a slight delay before the impulse is passed on to THE BUNDLE OF HIS situated in the atrio-ventricular septum. The impulse is then channeled down the R-L BUNDLE BRANCHES in the intro-ventricular septum and into the fine network of PURKINJE FIBRES in the walls of the ventricles to cause them to contract (0,3 sec.). Now the heart has a wee rest (0.4 sec.), total cardiac cycle (0.8 sec.).
THE CARDIAC CYCLE
This is the sequence of events that constitutes one heartbeat. There are three stages,
ATRIAL SYSTOLE (0.1 sec.) - Contraction of the atria during which
Blood passes into the ventricles.
VENTRICULAR SYSTOLE (0.3 sec.) - Contraction of the ventricles where
blood is forced into the Pulmonary
trunk and Aorta.
COMPLETE CARDIAC DIASTOLE (0.4 sec.) – The heart rests.
THE CARDIOVASCULAR SYSTEM
ELECTROCARDIOGRAM
The electrocardiogram or ECG, is a way of recording the pattern of electrical activity, which takes place during each cardiac cycle.
A normal ECG trace shows five deflections that are named P.Q.R.S. and T. These deflections correspond to the electrical changes in the atria and ventricles during one cardiac cycle.
P wave (Depolarization)…………this triggers a contraction of the atria QRS complex (Depolarization)…this triggers a contraction of the ventricles
T wave (Repolarisation) …………..The heart rests. (Recharges)
CARDIAC OUTPUT
CARDIAC OUTPUT
The amount of blood expelled by the left ventricle into the aorta in one minute, (5.25 litres)
STROKE VOLUME
The amount of blood pumped from a ventricle during each systole (70ml).
FORMULA
Cardiac Output (CO)
=Stroke Volume (SV) x Heart rate (HR)
=70ml x 75 beats per minute
=5250ml = 5.25 litres per minute
THE CARDIOVASCULAR SYSTEM
BLOOD VESSELS
Types: -
· ARTERIES
· ARTERIOLES
· VEINS
· VENULES
· CAPILLARIES
THE CARDIOVASCULAR SYSTEM
ARTERIES
Carry blood away from the heart, and have thick muscular walls to withstand the high pressure of oxygenated blood (except pulmonary arteries) being forced along by the beat of the heart.
Both arteries and veins are made up of the same three layers, the only difference is the middle layer, being muscle is thicker in an artery than a vein. This is due to the higher forces placed upon the artery walls by the blood being pumped by the contraction of the left ventricle.
VEINS
These take deoxygenated blood to the heart (except the pulmonary veins). In some veins (particularly in the arms and legs) possess valves or cusps in their walls to prevent the backflow of blood en-route to the heart.
ARTERIOLES ……………………..These are small arteries.
VENULES …………………………..These are small veins
CAPILLARIES
The walls of the capillary are composed of a single layer of cells, which are very thin and permit the passage of water and other small molecules (diffusion and osmosis).
The capillaries form a large network of tiny vessels which link the smallest arterioles to the smallest venules. Their diameter is approximately that of a red blood cell (7.5microns).
BLOOD PRESSURE
BLOOD PRESSURE - The pressure exerted by blood on the wall of a blood
Vessel.
Blood pressure is measured on the wall of an artery at ventricular sytole (contraction) and at ventricular diastole. A brachial artery is normally used.
The instrument used to take a blood pressure is a sphygmomanometer.
THE CARDIOVASCULAR SYSTEM
PULSE
A pulse can be described as pressure of blood being exerted on the walls of an artery by the force of contraction of the left ventricle.
A pulse can be felt anywhere an artery crosses over a bone or dense tissue. The average adult’s pulse rate is between 50 – 100 beats per minute at rest.
PULSE SITES
bravenet.com