Unit 3.C. The circulatory system

Index1. Composition of the Circulatory System2. Blood Circulation3. The Working of the Heart4. Some Illnesses of the Circulatory System

1. Composition of the Circulatory System

The human circulatory system consists of:1.1 Blood vessels 1.2 Heart1.3 Blood

1.1 Blood Vessels

ArteryCapillaryVein

Caracteristics of Blood VesselsArteries have thick walls, no valves and carry blood away

from the heartCapillaries link arteries to veins. Their wall is only one cell thick

and this allows substances to pass into and out of the blood.

Veins • have thin walls, • valves, and • carry blood to the heart

http://www.youtube.com/watch?v=CjNKbL_-cwA Types of blood vessels

1.2 Parts of the Heart It is a pump that pushes the blood into the arteries. Is made of cardiac muscle, a special kind of muscle that never

tires. Is divided into two sides by a wall called the septum.

Atria: the two upper chambers (singular: atrium). They have thin walls. They pump blood to the ventricles.

Ventricles: the two lower chambers. They pump blood out of the heart.right ventricle, with thin

wall, pumps the blood to the lungs .

left ventricle, with thicker and stronger wall, pumps the blood to the body.

Chambers of the HeartIt has got four chambers:

Valves

Valves prevent the backflow of blood.

Tricuspid valve and bicuspid valve or mitral valve, between atria and ventricles.

Semilunar valves (aortic valve and pulmonary valve) between ventricles and arteries.

http://vimeo.com/5588613 ==> valves working

THE HEART

http://www.youtube.com/watch?v=jLTdgrhpDCg Cardiac Cycle, systole and diastole

1.3 The BloodEvery person has 4 to 5 litres of blood on average.55% of the blood is plasma 45% consists of blood cells and platelets.

They defend the body from infection

coagulation

(leukocytes)

(erythrocytes)

Composition of Blood

http://www.youtube.com/watch?v=CRh_dAzXuoU blood cells

FUNCTIONS OF THE BLOODTransport of:

NutrientsWaste productsHormones Oxygen and carbon dioxide

Keeping the normal temperature of the body

Defence against disease

2. Blood circulationBlood circulation in human being is double and complete

It has two circuits (general and pulmonary)

The blood in the veins never mixes with the blood in the arteries

3. The working of the heart

The movement of blood through the heart1.Blood from the body enters the right atrium through the vena cava.

The atria contract, the blood is pushed through the tricuspid valve, into the right ventricle.

2.When the right ventricle contracts, the blood is pumped through the semilunar valve into the pulmonary arteries.

3.Blood goes to the lungs. In the lungs, the blood collects up oxygen and gets rid of its carbon

dioxide.4. It then comes back to the heart in the pulmonary vein which enters the

left atrium. When the atria contract, the blood is pushed through the bicuspid o mitral valve into the left ventricle.

5.The ventricles contract and this pushes the blood through the semilunar valve to the main artery of the body, aorta.

6.Blood is pushed out to all around the body.

The stages of heartbeat (cardiac cycle)

Diastole: heart chambers relax. Systole: heart chambers contract.

Heartbeat

http://www.youtube.com/watch?v=jLTdgrhpDCg

4. Some illnesses of the circulatory systemArteriosclerosisAccumulation of substances (fats, calcium…) in the arteries, which causes them to narrow and restricts the blood flow.

http://www.youtube.com/watch?v=qRK7-DCDKEA atherosclerosis (a common form of arteriosclerosis in which fatty substances form a deposit of plaque on the inner lining ofarterial walls)

ThrombosisBlood clots formed in a blood vessel. It is especially dangerous in the brain

or in the heart

http://www.youtube.com/watch?v=OxY4BphpGqo Thrombosis

Heart attack and angina

Angina: narrowing or partial obstruction of the coronary arteries.

Heart attack: total obstruction of the coronary arteries

Arteries which carry blood to the cardiac cells