Key Takeaways
- The cardiovascular system consists of the heart, blood vessels (arteries, veins, capillaries), and blood
- The heart has 4 chambers: right atrium, right ventricle, left atrium, left ventricle
- Blood flow path: body → right atrium → right ventricle → lungs → left atrium → left ventricle → body
- Arteries carry blood AWAY from the heart; veins carry blood TOWARD the heart (remember: Arteries = Away)
- Blood components: plasma (55%), red blood cells (carry oxygen), white blood cells (immune defense), platelets (clotting)
- The respiratory system facilitates gas exchange: oxygen in, carbon dioxide out
- Air pathway: nose/mouth → pharynx → larynx → trachea → bronchi → bronchioles → alveoli
- Gas exchange occurs in the alveoli through diffusion — O2 moves into blood, CO2 moves out
- The diaphragm is the primary muscle of breathing — it contracts to inhale and relaxes to exhale
Cardiovascular & Respiratory Systems
The cardiovascular and respiratory systems work together to deliver oxygen to every cell in the body and remove carbon dioxide — a process essential for life. These systems are heavily tested on the NEX.
The Heart
The heart is a muscular organ about the size of a fist, located in the mediastinum (center of the chest, slightly left).
Four Chambers
| Chamber | Location | Receives Blood From | Sends Blood To |
|---|---|---|---|
| Right Atrium (RA) | Upper right | Body (via superior/inferior vena cava) | Right ventricle |
| Right Ventricle (RV) | Lower right | Right atrium | Lungs (via pulmonary artery) |
| Left Atrium (LA) | Upper left | Lungs (via pulmonary veins) | Left ventricle |
| Left Ventricle (LV) | Lower left | Left atrium | Body (via aorta) |
Key fact: The left ventricle has the thickest wall because it pumps blood to the entire body (systemic circulation).
Heart Valves
| Valve | Location | Function |
|---|---|---|
| Tricuspid | Between RA and RV | Prevents backflow into right atrium |
| Pulmonary | Between RV and pulmonary artery | Prevents backflow into right ventricle |
| Mitral (bicuspid) | Between LA and LV | Prevents backflow into left atrium |
| Aortic | Between LV and aorta | Prevents backflow into left ventricle |
Path of Blood Flow
Deoxygenated blood from body → Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Artery → LUNGS (picks up O₂, drops off CO₂) → Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta → BODY
Blood Vessels
| Vessel Type | Direction | Wall Thickness | Blood Pressure | Oxygen Level |
|---|---|---|---|---|
| Arteries | Away from heart | Thick, muscular | High | Usually oxygenated* |
| Capillaries | Connect arteries to veins | Very thin (1 cell thick) | Low | Exchange site |
| Veins | Toward the heart | Thinner, have valves | Low | Usually deoxygenated* |
*Exception: Pulmonary arteries carry deoxygenated blood TO the lungs; pulmonary veins carry oxygenated blood FROM the lungs.
Blood Components
| Component | Percentage | Function |
|---|---|---|
| Plasma | ~55% | Liquid portion; carries nutrients, hormones, waste |
| Red Blood Cells (RBCs) | ~44% | Carry oxygen (hemoglobin); carry CO₂ |
| White Blood Cells (WBCs) | < 1% | Immune defense; fight infection |
| Platelets | < 1% | Blood clotting (hemostasis) |
The Respiratory System
Air Pathway
| Structure | Function |
|---|---|
| Nose/Mouth | Entry point; nose warms, moistens, filters air |
| Pharynx (throat) | Passageway for air and food |
| Larynx (voice box) | Contains vocal cords; protects airway |
| Trachea (windpipe) | Conducts air; lined with cilia and mucus |
| Bronchi | Two main branches into left and right lungs |
| Bronchioles | Smaller branches within the lungs |
| Alveoli | Tiny air sacs where gas exchange occurs |
Gas Exchange
Gas exchange occurs in the alveoli through diffusion (molecules move from high to low concentration):
- Oxygen (O₂): Moves from alveoli → blood (into RBCs, binds to hemoglobin)
- Carbon dioxide (CO₂): Moves from blood → alveoli → exhaled
The alveoli have very thin walls (one cell thick) and are surrounded by dense capillary networks, maximizing the surface area for gas exchange.
Breathing Mechanics
| Phase | Diaphragm | Rib Cage | Lung Volume | Air Pressure | Result |
|---|---|---|---|---|---|
| Inhalation | Contracts (moves down) | Expands | Increases | Decreases | Air flows IN |
| Exhalation | Relaxes (moves up) | Contracts | Decreases | Increases | Air flows OUT |
The diaphragm is the primary muscle of breathing. The intercostal muscles between the ribs assist.
Which chamber of the heart has the thickest muscular wall?
Arteries carry blood:
Where does gas exchange occur in the respiratory system?
Arrange the structures of the respiratory system in the correct order that air travels during INHALATION.
Arrange the items in the correct order
During inhalation, the diaphragm:
The protein in red blood cells that binds to and carries oxygen is called _____.
Type your answer below
Match each blood component to its primary function.
Match each item on the left with the correct item on the right
The pulmonary artery is unique because it:
Which heart valve separates the left atrium from the left ventricle?
Which component makes up the largest percentage of blood by volume?