Overview
This lecture covers the transport system in animals, focusing on the structure and function of circulatory systems, blood components, and the differences between open and closed circulatory systems.
Components of the Circulatory System
- The main transport medium in animals is blood.
- Blood consists of red blood cells, white blood cells, and platelets.
- The heart pumps blood throughout the body.
- Blood vessels contain and direct the flow of blood.
Types of Circulatory Systems
- Animals have two main types of circulatory systems: open and closed.
- In the open circulatory system, blood flows in open spaces called sinuses.
- In the closed circulatory system, blood flows through vessels only.
- The open system uses a fluid called hemolymph, contained in the body cavity (hemocoel).
- Closed systems have a muscular heart that pumps blood at high pressure.
Differences: Open vs. Closed Circulatory System
- Open system: low blood velocity, low pressure, organs are in direct contact with hemolymph.
- Closed system: high blood velocity and pressure, blood is separated from organs by vessels.
- Open system: slow circulation, less active organisms, not regulated to activity level.
- Closed system: rapid circulation, more active organisms, blood flow regulated as needed.
Types of Circulation
- Single circulation: blood passes through the heart once per cycle (e.g., fish).
- Double circulation: blood passes through the heart twice per cycle (e.g., mammals, amphibians, reptiles).
Pulmonary and Systemic Circulation
- Pulmonary circulation: blood goes from the right heart to lungs via pulmonary artery, returns via pulmonary vein at low pressure.
- Systemic circulation: blood goes from heart to body and back at high pressure for efficient function and tissue fluid formation.
Advantages and Disadvantages
- Open system advantages: direct contact with cells, fluid mixing, less energy required, low oxygen needs.
- Open system disadvantages: slow waste and nutrient movement, unregulated flow, less active animals.
- Closed system advantages: rapid nutrient/waste transport, high activity, high pressure, no cell interference.
- Closed system disadvantages: high energy need, risk of vessel rupture, heart disease risk, susceptible to pathogens.
Key Terms & Definitions
- Red blood cell — carries oxygen in the blood.
- White blood cell — defends the body against disease.
- Platelet — helps blood clotting.
- Open circulatory system — system where blood flows freely in body cavities.
- Closed circulatory system — system where blood flows within vessels.
- Hemolymph — the transport fluid in an open circulatory system.
- Hemocoel — body cavity containing hemolymph in open systems.
- Single circulation — blood passes through the heart once per cycle.
- Double circulation — blood passes through the heart twice per cycle.
- Pulmonary circulation — movement of blood between heart and lungs.
- Systemic circulation — movement of blood between heart and body.
Action Items / Next Steps
- Prepare for the next class discussion on the mammalian circulatory system.