Cardiorespiratory System & Venous System

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What is the Cardiorespiratory System?

The cardiorespiratory system (also called the cardiopulmonary system) is made up of the heart, blood vessels, and lungs working together to deliver oxygen to the body and remove carbon dioxide.

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Main Components:

1. Heart

• A muscular organ that pumps blood.
• Has four chambers: two atria (upper) and two ventricles (lower).
• Pumps oxygen-poor blood to the lungs and oxygen-rich blood to the rest of the body.

2. Lungs

• Organs responsible for gas exchange.
• Oxygen from the air enters the blood, and carbon dioxide from the blood is expelled when we breathe out.

3. Blood Vessels

• Arteries carry oxygen-rich blood away from the heart.
• Veins carry oxygen-poor blood back to the heart.
• Capillaries are tiny vessels where oxygen and carbon dioxide exchange happens with body tissues.

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How It Works Together:

1. Deoxygenated blood flows from the body → into the right atrium → right ventricle → pumped to the lungs.
2. In the lungs, blood picks up oxygen and releases carbon dioxide.
3. Oxygenated blood flows from lungs → left atrium → left ventricle → pumped out through arteries to the whole body.
4. Oxygen in the blood is delivered to tissues, and carbon dioxide is collected from tissues → blood returns to the heart → cycle repeats.

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Functions:

• Deliver oxygen to cells for energy production.
• Remove carbon dioxide, a waste product of metabolism.
• Help regulate body temperature.
• Maintain acid-base balance and homeostasis.

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Summary:

Component	Function
Heart	Pumps blood throughout body
Lungs	Gas exchange (O₂ in, CO₂ out)
Blood vessels	Transport blood to/from heart and tissues

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What is the Venous System?

The venous system is the part of the circulatory system that carries blood back to the heart, primarily deoxygenated blood (except for the pulmonary veins, which carry oxygenated blood from lungs to heart).

Main Components of the Venous System:

1. Veins

Blood vessels that carry blood toward the heart.

Walls are thinner and less muscular than arteries.

Have valves to prevent backflow of blood, especially important in the limbs.

2. Venules

Small vessels that collect blood from capillaries and drain into larger veins.

3. Valves

One-way valves inside veins keep blood flowing in the correct direction, preventing it from pooling or flowing backward.

Key Venous Pathways:

Superior vena cava: Returns blood from the upper body (head, neck, arms) to the right atrium of the heart.

Inferior vena cava: Returns blood from the lower body (abdomen, legs) to the right atrium.

Functions of the Venous System:

Return deoxygenated blood from body tissues to the heart.

Store a large volume of blood (about 60-70% of total blood volume at rest).

Help regulate blood pressure and blood volume.

Facilitate waste removal by transporting blood to the lungs for oxygenation.

How Blood Flows Through the Venous System:

Blood moves from capillaries → venules → small veins → larger veins → heart.

Muscle contractions (especially in legs) and valves help push blood upward against gravity toward the heart.

Summary:

Component Description/Function

Veins Carry blood back to the heart

Venules Small vessels draining capillaries

Valves Prevent backflow, ensure one-way flow

Vena cavae Large veins draining upper and lower body