Lesson 9 - Circulatory System

• Animal Science
• Further Education (Key Stage 5)

These are specialized cells that carry oxygen from the lungs to the tissues and return carbon dioxide to the lungs for exhalation. They contain hemoglobin, a protein that binds oxygen.

Part of the immune system, these cells protect the body against infections and foreign substances. There are several types, including neutrophils, lymphocytes, and monocytes.

These are small cell fragments that are crucial in blood clotting, helping to prevent excessive bleeding after injury.

Click on the Hotspots

Click on the Hotspots

Inferior Vena Cava

Right Ventricle

Left Ventricle

Left Ventricle

Pulmonary Valve

Right Ventricle

Aortic Valve

Aorta

Superior Vena Cava

Left Pulmonary Artery

Right Pulmonary Vein

Inferior Aorta

Left Pulmonary Vein

Right Pulmonary Artery

Tricuspid Valve

Septum

Bicupsid Valve / Mitral Valve

• The heart is a muscular organ that pumps blood through the circulatory system. It is divided into four chambers: two atria (upper chambers) and two ventricles (lower chambers).

• The right side of the heart pumps deoxygenated blood to the lungs for oxygenation (pulmonary circulation), while the left side pumps oxygenated blood to the rest of the body (systemic circulation).

• Valves between the chambers ensure unidirectional blood flow and prevent backflow during contraction.
• During physical activity, the body's demand for oxygen and nutrients increases, prompting the heart rate to increase to deliver more blood to muscles. The sympathetic nervous system speeds up the heart rate, while the parasympathetic system slows it down post-exercise.

• In cold environments, blood vessels constrict to preserve heat, which increases blood pressure and can slightly decrease heart rate.
• In hot environments, blood vessels dilate to release heat, which can lower blood pressure and increase heart rate to maintain adequate circulation.

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Carry oxygenated blood away from the heart to the body, except for the pulmonary artery, which carries deoxygenated blood to the lungs. Arteries have thick, muscular walls to withstand high-pressure blood flow.

Capillaries: These are tiny blood vessels that connect arteries and veins. Capillaries are where the exchange of oxygen, nutrients, and waste products takes place between the blood and tissues.

Carry deoxygenated blood back to the heart, except for the pulmonary vein, which carries oxygenated blood from the lungs. Veins have thinner walls and contain valves to prevent backflow.

Click on each image to learn more about their circulatory system

Circulatory System: Closed, double circulatory system (two circuits—pulmonary and systemic).

Heart: Four-chambered heart (two atria and two ventricles).

Blood Flow: Oxygenated and deoxygenated blood are kept separate in the heart.

Circulatory System: Closed, double circulatory system, but with partial separation of oxygenated and deoxygenated blood (except for some primitive reptiles).

Heart: Three-chambered heart (two atria and one ventricle, with a septum that partially separates the ventricles).

Blood Flow: The partial separation allows some mixing of oxygenated and deoxygenated blood, but it is more efficient than in amphibians.

Circulatory System: Closed, double circulatory system, similar to mammals.

Heart: Four-chambered heart.

Blood Flow: Oxygenated and deoxygenated blood are completely separated, allowing efficient oxygen delivery during flight.

Circulatory System: Closed, double circulatory system, but with more significant mixing of oxygenated and deoxygenated blood in the heart.

Heart: Three-chambered heart (two atria and one ventricle).

Blood Flow: Blood flows from the heart to the lungs for oxygenation and then to the body, but the heart does not fully separate oxygenated and deoxygenated blood.

Circulatory System: Open circulatory system (blood is not confined to blood vessels).

Heart: Typically a single-chambered heart, or in some cases, no distinct heart.

Blood Flow: Hemolymph (a fluid analogous to blood) flows freely in the body cavity, with limited control over direction. Hemolymph is not used to transport oxygen (except in some species that use a form of hemoglobin).

Circulatory System: Closed, single circulatory system (only one circuit—systemic).

Heart: Two-chambered heart (one atrium and one ventricle).

Blood Flow: Blood flows from the heart to the gills (for oxygenation) and then directly to the rest of the body.