Circulatory Systems

exam 4

What are the two main types of circulatory systems

• Open Circulatory System: Blood (hemolymph) bathes the organs directly. Example: Insects, most mollusks.  

• Closed Circulatory System: Blood is confined to vessels and is distinct from the interstitial fluid. Example: Vertebrates, earthworms, cephalopods and humans

Which organisms have single circulation, and which have double circulation?

 

• Single Circulation: Blood passes through the heart only once in each complete circuit of the body. Found in bony fishes, rays, and sharks.  

• Double Circulation: Blood flows through the heart twice in each circuit: once to the lungs (pulmonary) and once to the rest of the body (systemic). Found in amphibians, reptiles, and mammals.  

Which organisms have a two-chambered heart?

Bony fishes, rays, and sharks.

Which organisms have a three-chambered heart?

Amphibians and most reptiles (except birds and crocodilians).

Which organisms have a four-chambered heart?

Birds and mammals

What is the pulmonary circuit?

• Heart → Lungs: Oxygen in, CO₂ out.

• Lungs → Heart: Oxygenated blood returns.

What is the systemic circuit

• Heart → Body: Oxygen & nutrients delivered, CO₂ picked up.

• Body → Heart: Deoxygenated blood returns.

Where does blood come from that enters the human heart?

• Body → Vena Cava → Right Atrium (Deoxygenated Blood).  

• Lungs → Pulmonary Veins → Left Atrium (Oxygenated Blood)

Where does blood go after it leaves the human heart?

• Deoxygenated blood is pumped from the right ventricle to the lungs via the pulmonary arteries.

• Oxygenated blood is pumped from the left ventricle to the rest of the body via the aorta

What happens during diastole in the cardiac cycle?

The heart muscle relaxes, and the chambers fill with blood.

What happens during systole in the cardiac cycle?

The heart muscle contracts, and the chambers eject blood into the arteries.

What is a heart attack?

Damage to the heart muscle resulting from a blockage of blood supply to the heart, often due to a blood clot in a coronary artery

What is the pacemaker (or SA node), and what does it do?

The sinoatrial (SA) node is a region of specialized cardiac muscle cells in the right atrium that initiates the electrical impulses that control the heart rate. It sets the rhythm of the heart.  

What is the basic structure of the different blood vessels?

• Arteries: Thick walls with smooth muscle and elastic fibers to withstand high pressure; carry blood away from the heart.  

• Veins: Thinner walls than arteries, contain valves to prevent backflow; carry blood towards the heart.  

• Capillaries: Very thin walls (single layer of cells) to allow for exchange of gases, nutrients, and wastes between blood and tissues.  

How do blood pressure and blood velocity change in arteries, capillaries, and veins?

• Arteries: High blood pressure, high blood velocity.

• Capillaries: Blood pressure drops significantly, blood velocity is slowest (allowing for exchange).  

• Veins: Low blood pressure, blood velocity increases as blood returns to the heart.  

What causes heart attack, stroke, and atherosclerosis?

• Heart Attack: Blockage of coronary arteries (often by blood clots forming on plaques).  

• Stroke: Blockage or rupture of blood vessels in the brain.

• Atherosclerosis: Buildup of fatty deposits (plaques) in the walls of arteries, narrowing the vessels and reducing blood flow.  

What are the similarities and differences among arteries, veins, and capillaries?

All are part of the closed circulatory system and carry blood. Their walls have layers of tissue (though the thickness varies).

diff- Wall thickness, presence of valves (veins), diameter, blood pressure, blood velocity, and function (carrying blood to, within, or away from tissues).

Where is blood pressure highest, lowest, and where does it decrease significantly?

• Highest: Arteries (especially near the heart).

• Lowest: Veins (especially furthest from the heart).

• Significant Decrease: Arterioles (small arteries) and capillaries.

What are precapillary sphincter muscles, and what happens to blood flow when they are relaxed and contracted?

Small bands of smooth muscle located at the entrance to capillary beds.  

Relaxed: Blood flow into the capillary bed increases.

Contracted: Blood flow into the capillary bed is reduced or stopped, diverting blood to other areas.

What are the major components of our blood and what are their functions?

• Plasma: Liquid matrix containing water, salts, proteins (e.g., antibodies, clotting factors), nutrients, wastes, and hormones; transports substances.

• Red Blood Cells (Erythrocytes): Contain hemoglobin and transport oxygen.  

• White Blood Cells (Leukocytes): Involved in the immune system, defending against pathogens.  

• Platelets (Thrombocytes): Cell fragments involved in blood clotting.

How do blood clots form (what’s involved with the clotting process)?

1. Damage to a blood vessel wall exposes collagen fibers.

2. Platelets adhere to the collagen and release signaling molecules.  

3. These molecules attract more platelets, forming a platelet plug.  

4. A cascade of reactions involving clotting factors in the plasma leads to the formation of fibrin.

5. Fibrin forms a meshwork that traps blood cells and platelets, creating a blood clot.  

pulmonary circuit vs systemic circuit

• Pulmonary: Heart ↔ Lungs (gas exchange)

• Systemic: Heart ↔ Body (O₂ delivery, CO₂ pickup)