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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