The Circulatory System

Chapter 4: The Circulatory System

1. Heart

2. Lungs

3. Blood vessels (tubes)-Through which blood flows

It is known as the circulatory system as the blood flow around your body in a never-ending cycle.

1. Transportation

2. Protection against infection

3. Clotting

Blood transports many important substances around your body
For Example it transports oxygen to your cells from your lungs and brings glucose from your intestines to your cells
However, blood also removes harmful substances from your body to be excreted
For Example, it removes carbon dioxide from your cells to the lungs to be excreted. It also transports urea from your liver to the kidneys

We are under constant attack from micro-organsims such as bacteria and it is up to our imune system to stop such "attacks"

When we cut ourselves our blood spills out but after a short period of time this blood flow stops-This is clotting. If clottting did not occur when cut you would lose all blood and die

1. Red blood cells

2. White blood cells

3. Platelets

These cells are involved in fighting infection and are also fromed in the bone marrow
They have no definite shape but they do have a nucleus
They fight infection in 2 ways

1. They create antibodies which stick to the dangerous organisms and makes them inactive

2. The white blood cells attack and eat the micro-organism.

1. Arteries: Carries blood away from the heart

2. Veins: Carries blood towards the heart

3. Capilleries: Connects arteries and veins

The atrium is the upper part of the heart
The ventricle is the lower part
Valves allow blood flow in only one direction
The septum is the wall of muscle seperating left from right
Rule to Remember: Blood enter the heart in the atrium and leaves it from the ventricle

Blood enters the heart from the inferior vena (blood from lower body) and the superior vena cava (upper body)
The blood from the vessels is pushed through the heart when the heart pulses (a pulse is caused by a surge of blood in the artery after a heart beat) into the right ventricle and then from there into the pulmonary artery which brings it to the lungs to be oxygenated
It then returns to the heart through the pulmonary veins and into the left atrium
From here it enters through a valve into the left ventricle and is squeezed (when the heart beats) into the aorta and transported around the body

The walls of the heart consist of muscle which squeezes the blood out of the heart
The wall of the left side of the heart is three times quicker than the right side as the aorta which transports blood all over the body is on the left side. Therefore it needs to be stronger
The pumping action of a heart is known as a heartbeat-average is 70 beats a minute
Your heartbeat increasea and decreases depending on what you are doing. The increase of a heartbeat means blood is being pumped faster and more oxygen is required (increases breathing rate
Heartbeat increases: Excercising/Smoking/Shock/excitement
Heartbeat Decreases: Clinical shock/rest

An artery has a thicker wall than a vein as pressure is higher in arteries than in veins
The Lumen or opening of a vein is much wider than that an arteries as the walls of a vein are not as thick
Blood in arteries travels in spurts with the beat of the heart but in veins blood flows freely
Veins require valves to prevent the free-flowing blood from flowing backwards. These valves are not required in arteries as the blood does not flow freely
Arteries tend to have oxygenated blood in them while veins normally have de-oxygentaed blood. The exception to this is the pulmonary vein which contains oxygenated blood and the pulmonary artery which contains de-oxygenated blood.