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. 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


Heart

Artery

Vein

Capillary

Venule

Arteriole


Portal Vein

Has capillaries at

both ends

E.g. hepatic portal vein

Carries:

  • glucose

  • amino acids

  • minerals

    from intestine to liver


Structure of Arteries, Veins and Capillaries

Thick muscular

wall

Thin

wall

Large

lumen

Small

lumen

Very thin wall


Veins have Valves


Double Circulatory System


Heart Structure

Pulmonary artery

Aorta

Pulmonary vein

Vena cava

Left Atrium

Right Atrium

Semilunar valve

Tricuspid valve

Right ventricle

Left ventricle

Septum

Cardiac Muscle


Valves


Human Circulatory System


Structure of Human CirculatorySystem


Heart

  • 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


Pacemakers


Pacemakers

  • 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


Pulse

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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