Lesson 6 - Circulatory System

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.

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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 (via norepinephrine) speeds up the heart rate, while the parasympathetic system (via acetylcholine) slows it down post-exercise.
• Stress activates the sympathetic nervous system, releasing adrenaline (epinephrine).

• 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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Sinoatrial (SA) Node: This specialized group of cells located in the right atrium initiates the electrical impulse that begins the heartbeat. It acts as the natural pacemaker of the heart.

Atrioventricular (AV) Node: Located between the atria and ventricles, the AV node delays the electrical signal to allow the ventricles time to fill with blood from the atria.

Bundle of His and Purkinje Fibers: The electrical impulse travels from the AV node through the Bundle of His and down the Purkinje fibers to the ventricles. This causes the ventricles to contract, pumping blood to the lungs (right ventricle) and to the rest of the body (left ventricle).

Ventricular Contraction (Systole): The contraction of the ventricles forces blood into the pulmonary arteries (right ventricle) and the aorta (left ventricle).

Relaxation (Diastole): After contraction, the heart relaxes, allowing the chambers to refill with blood in preparation for the next beat.

Atria Contraction (both atriums): The electrical signal from the SA node spreads across the atria, causing them to contract and push blood into the ventricles.

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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.

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Drag and drop the correct component to the correct system.

Circulatory System

Lymphatic System

Descriptors

Function: Transports oxygen, nutrients, hormones, and waste products. It also plays a role in immune responses, temperature regulation, and the maintenance of homeostasis.

Vessels: Arteries, veins, and capillaries.

Blood: Carries oxygen, carbon dioxide, nutrients, waste products, and immune cells.

Function: The lymphatic system helps to maintain fluid balance by draining excess interstitial fluid from tissues, filters and removes pathogens, and is an integral part of the immune system.

Vessels: Lymphatic vessels transport lymph, a fluid containing white blood cells, throughout the body.

Lymph Nodes: These are distributed throughout the body and act as filtration points for lymph, removing pathogens and debris.

Heart

Blood Vessels

Blood

Lymph

Lymphatic Vessels

Lymph Nodes

Spleen

Thymus

Tonsils

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.