Component 3

Gas exchange in animals, animal transport, nerves, kidney

Open circulatory system

the blood is not always held within the blood vessels and can circulate through the body cavity so that cells are immersed directly in the blood

What happens in insects circulatory system?

the heart will pump blood towards the head by peristalsis; it re-enters the heart through pores called ostia.

Open circulatory system features

Little control over direction of circulation. Movement of muscles assist with the movement of blood back to the head region.

No respiratory pigment - insect blood does not carry oxygen

Blood pumped at low pressure into a fluid-filled cavity - the haemocoel

Closed circulatory system

The blood is enclosed within the blood vessels.

Tissues are not in direct contact with the blood, a separate fluid called tissue fluid exits the capillaries and bathes the cells.

This allows the heart to pump at a higher pressure.

Advantages of the closed circulatory system

The blood flow is more rapid and efficient

Blood flow ca be directed to where it is needed by vasoconstriction and vasodilation e.g. more to working muscles or to the body surface if hot.

More efficient delivery of oxygen and nutrients (glucose) and removal of waste products such as CO2

Singe closed circulatory system

Fish have a single closed circulatory system which means the blood stays in blood vessels on a single pathway around the body.

Blood only passes through the heart once before returning to the gills.

Heart → Gills → Body → Heart

Double circulatory system

Heart pumps the blood and it goes twice through the heart

What are the two components of the double circulatory system?

Pulmonary circulatory system:

Heart → Lungs → Heart

Systemic circulatory system:

Heart → Body → Heart

Why do mammals have the double circulatory system?

Mammals are endothermic so have a high metabolic rate and high energy requirement.

Therefore, their cells need a large amount of glucose and oxygen and the removal of waste products such as CO2

Advantages of the double circulatory system

The heart increases the pressure after it has passed through the lungs so the blood flows more quickly to the body tissues.

More efficient delivery of oxygen and nutrients to the body tissues.

The oxygen supply to heart muscles is better.

The systemic circulation can carry blood at higher pressure than the pulmonary circulation.

The Mammalian heart

4 chambered pumps for both pulmonary and systemic circulatory systems.

Double pump working synchronously keeping oxygenated blood separated.

Cardiac muscle - myogenic - beats from within the muscle itself therefore it never gets tired.