Biology - The Heart and Blood Vessels

Open Circulatory System

blood leaves vessels and flows around the cells of the animal’s body before re-entering blood vessels again

Closed Circulatory System

blood remains in a continuous system of blood vessels

Arteries

carry blood away from the heart

Veins

carry blood to the heart

Capillaries

tiny vessels that link arteries and veins

Arteries

• carry blood away from the heart

• blood under high pressure

• thick wall

• small lumen

• blood flows in pulses

• valves absent

• blood high in oxygen (except pulmonary artery)

Veins

• carry blood to the heart

• blood under low pressure

• thin wall

• large lumen

• blood flows smoothly (no pulses)

• valves present

• blood low in oxygen (except pulmonary vein)

Blood Pressure

the force the blood exerts against the wall of a blood vessel

Valves

control the direction of blood flow

Septum

divides the heart in two

Atria

the upper chambers of the heart

Ventricles

pump blood out of the heart

Tricuspid Valve

valve on the right-hand side of the heart

Bicuspid Valve

valve on the left-hand side of the heart

Semilunar Valves

allow blood to flow out of the heart into the two main arteries

Vena Cava

through where deoxygenated blood enters the heart

Pulmonary Vein

through where oxygenated blood enters the heart

Pulmonary Artery

an artery that is low in oxygen

Pulmonary Vein

a vein that is high in oxygen

Pulmonary Circuit

heart → lungs → heart

Systemic Circuit

heart → body → heart

Double Circulation System

• allows oxygen-rich and oxygen-poor blood to be kept separate

• ensures that the blood pressure is high enough to reach all parts of the body

Portal System

a blood pathway that begins and ends in capillaries

Hepatic Portal Vein

example of a portal system, connects the stomach and intestines to the liver

Heartbeat

1. SA node causes atria to contract

2. Electrical impulse from SA node stimulates the AV node

3. AV node sends an impulse down special muscle fibres located in the septum

4. Impulses cause the ventricles to contract

Atrioventricular Node

sends electrical impulses down the septum

Sinoatrial Node

causes the atria to contract

Atrioventricular Node

located between the septum / between the ventricles

Sinoatrial Node

located in the right atrium

Diastole

when the heart chambers relax

Systole

when the heart chambers contract

Cardiac Cycle

• diastole: blood enters the atria

• atrial systole: blood is pumped to the ventricles

• ventricular systole: blood is pumped out of the heart

Pulse

the alternate expansion and contraction of the arteries

Blood Pressure

the force exerted by the blood against the walls of the blood vessels (mainly the arteries)

Pulmonary Vein

carries blood richest in oxygen

Hepatic Portal Vein

carries blood between the intestine and liver

Renal Vein

carries blood lowest in metabolic waste

Vena Cava

carries blood into the right atrium of the heart

Cardiac Muscle

specialised muscle of the heart, never tires