Blood Circulation and Transport

The Transport System in Humans

• All cells in our body need nutrients, oxygen and water. Meanwhile carbon dioxide and other waste materials produces by the cells must be removed.

• An internal transport system is needed to deliver useful materials to the body cells and remove the waste materials from them.

• The internal transport system is often called the circulatory system because useful as well as waste materials circulate the body.

The heart and some major blood vessels

• A circulatory system has four basic characteristics:

a. Circulating fluid – this circulating fluid is called blood. The blood transports useful and waste materials.

b. Pumping device – the pumping device is the heart. Blood is moved through the body by muscular contractions of the heart.

c. Blood vessels – a complex network of blood vessels carries materials to the tissues and back to the heart. There are three main types of blood vessels, namely arteries, veins and capillaries.

d. Valves – valves are present in some blood vessels to prevent backflow and ensure that blood flows in one direction only.

• The human circulatory system is a double circulatory system. This means that in each complete circuit of the body, the blood must flow through the heart twice.

• The human double circulatory system consists of:

a. The pulmonary circulation which transports blood between the heart and the lungs and

b. The systematic circulation which transports blood between the heart and all other parts of the body.

• The advantage of having a double circulatory system is that it increase the pressure of the blood and the rate of flow, thereby speeding up the delivery of materials to the tissues.

The human double circulatory system

Structure of the human heart

• An adult human heart is about the size of a clenches fist.

• The heart lies in the chest between the two lungs.• The heart is a muscular organ with walls made of

cardiac muscles.• The coronary arteries supply nutrients and oxygen

wastes from the muscles.• The heart is divided into four chambers. The two

upper chambers are called auricles and atria ( atrium) and the two lower chambers are called ventricles.

• The septum divides the heart into the right and left halves.

• The auricles have thinner walls than the ventricles. When the auricles contract, blood is pushed into the ventricles below.

• The left ventricle has a much thicker muscular wall than the right ventricle. The right ventricle pumps blood to the lungs , which lie next to the heart. The left ventricle has to pump blood from the heart to the rest of the body.

• The right atrium is connected to the right ventricle by the tricuspid valve. The left atrium is connected to the left ventricle by the bicuspid or mitral valve.

• Semilunar valves are situated at the entrances of the aorta and the pulmonary artery to prevent to backflow of blood into the ventricles.

• The chordae tendineae prevent the valves from turning inside out when the ventricles contract

The structure of the human heart

Function of the human heart

• The heart is made up of two pumps located side by side.

• The right side of the heart pumps deoxygenated blood it receives from the lungs to the rest of the body. Oxygen is removed at the tissues for respiration

Arteriesa. Arteries are blood vessels which carry blood

away from the heart.

b. Arteries deliver oxygenated blood except pulmonary artery.

c. The walls of the arteries are much thicker and stronger than those of veins because they have to withstand the high pressure of blood coming from the heart.

The blood vessels

Artery

Veinsa. Veins are blood vessels which carry blood

back to the heart.b. Veins deliver deoxygenated blood except

pulmonary veins. c. Veins have thinner walls than arteries

because blood pressure in the veins is much lower than that in the arteries. Since the blood in the veins may be moving against gravity, the contain valves to present the blood from flowing back.

Veins

Capillariesa. Capillaries are tiny blood vessels which

connect arteries and veins. They have walls which are only one cell thick.

b. Oxygen and nutrients move from the blood through the capillary walls into the body cells. At the same time carbon dioxide and other waste products move from the cells into the body.

Capillary

Characteristics

Artery Vein Capillary

Cross section

Circular Oval Circular

Size of wall Has thick muscular wall

Has thin muscular wall

Has very thin walls, only one cell- thick

Valves Absent (except in pulmonary artery)

Present Absent

Differences of artery, vein and capillary

Lumen Narrow Fairly wide Very narrow

Colour Red Bluish – red Bluish – red

Oxygen content

Oxygenated blood (except in pulmonary artery)

Deoxygenated blood (except in pulmonary veins)

Oxygenated blood to the tissuesDeoxygenated blood from the tissues

Maintaining a healthy heart• Heart disease is one of the major cause of death in Thailand.

• Factors that increase the risk of getting heart disease:

a. Heredity – the risk is increase if there is a family history of heart disease.

b. Cholesterol and obesity – high cholesterol and obesity are major heart disease risk factor.

c. Lack of exercise – low level of physical activity increase the risk of getting heart disease.

d. Smoking – smoking damages blood vessels and leads to heart disease. Smoking also decreases the amount of oxygen that reaches the heart.

Heridity Cholesterol and obesity

Lack of ExerciseSmoking

e. Stress – people who are stressed are more prone to heart attacks.

f. Alcohol – excessive alcohol intake can elevate blood pressure, thus making heart attacks more likely.

Stress Alcohol

Ways to reduce the risk of getting heart disease:

a. Avoid high cholesterol foods. Eat more fruits and vegetables.

b. Regular aerobic exercises help to keep body weight down. Lower blood pressure and strengthen the heart.

c. Lose weight to a desirable weight range and keep within it with moderate eating and exercise.d. Relax and get enough

sleep.e. Quit smoking.f. Reduce alcohol consumption.

Eat more fruits Aerobics Lose weight

Get enough sleep Quit Smoking Reduce Alcohol