TRANSPORT IN ANIMALS
Circulatory Systems
OPEN CIRCULATORY SYSTEM-
- In invertebrates (e.g. insects), blood isn’t held within vessels always
- It’s free to circulate the body cavities (spaces)
- Only works for insects because they’re small
- Cannot contain any pressure, blood pressure is low, blood flow is slow, not directed to particular organs and wouldn’t meet demand of large animals
CLOSED CIRCULATORY SYSTEM-
- In vertebrates (e.g. fish & mammals), blood is never released into the body cavity
- Blood circulates through series of blood vessels- artery, vein, capillary
- Blood can be pumped under pressure, blood flows quickly, can be directed to specific organs
- More responsive to changes in demand e.g. by increasing pressure to carry more oxygen
- Dilate and constrict vessels to other organs
Single and double circulatory systems:
- In a single circulatory system, blood flows through the heart once in one circuit
- In a double circulatory system, blood flows through the heart twice in one circuit (CIS 1.6)
