Circulatory system
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Circulatory System PowerPoint PPT Presentation

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Circulatory System. Circulatory system consists of:. Heart Blood Vessels Blood. Closed System in Humans. Arteries, Arterioles, Capillaries, Venules , Veins. Heart. Artery. Vein. Capillary. Venule. Arteriole. Portal Vein. Has capillaries at both ends E.g. hepatic portal vein

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Circulatory System

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Circulatory System

Circulatory system consists of:

  • Heart

  • Blood Vessels

  • Blood

Closed System in Humans

Arteries, Arterioles, Capillaries, Venules, Veins







Portal Vein

Has capillaries at

both ends

E.g. hepatic portal vein


  • glucose

  • amino acids

  • minerals

    from intestine to liver

Structure of Arteries, Veins and Capillaries

Thick muscular








Very thin wall

Veins have Valves

Double Circulatory System

Heart Structure

Pulmonary artery


Pulmonary vein

Vena cava

Left Atrium

Right Atrium

Semilunar valve

Tricuspid valve

Right ventricle

Left ventricle


Cardiac Muscle


Human Circulatory System

Structure of Human CirculatorySystem


  • Located in thoracic cavity: area inside rib cage

  • Contains strong double pump

  • Made of a special muscle which does not tire

  • Coronary artery supplies heart itself with blood

Cardiac Cycle

Systole and Diastole

  • Diastole: the filling phase of the heart with blood (the heart is relaxed)

  • Systole: the emptying phase when the heart muscles contract



  • Heartbeat can occur independently of the brain

  • Controlled by a small bundle of specialised tissue called pacemakers (SA and AV nodes) in the right atrium

  • Sinoatrial (SA) node sends out regular electrical impulses causing the atria to contract

  • It also stimulates the atrio-ventricular (AV) node

  • The AV node then stimulates the ventricles to contract

What affects the pacemakers?

  • The pacemaker itself controls the heartbeat

  • Average rate = 75 beats per minute

  • But signals from the brain (via nerves) and hormones can change the rate at which it operates

Factors that can increase the heart rate include:

  • Exercise

  • Temperature

  • Emotions and shock

Factors that decrease the heart rate include:

  • Relaxation

  • Sleep

  • Alcohol


What causes a pulse?

The expansion of an artery due to the pumping of the heart

What is blood pressure?

  • Recall : Pressure = Force/area

  • Blood pressure is the force exerted by blood on the wall of a blood vessel

Effects of External Factors on Heart Rate

To maintain a healthy heart

  • Don’t smoke

  • Eat less fat

  • Eat less salt

  • Exercise regularly

  • Avoid excess stress

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