Open and Closed Circulatory Systems

Question 1

Open circulatory system

Answer 1

Open circulatory system (insects - invertebrates): One in which the blood is not held in vessels. Instead the
blood fluid circulates through the body cavity, so tissues and cells are bathed directly in blood.

Note: The open circulatory system in insects transports nutrients and hormones around the body. It doesn’t transport O2 as this is done by the tracheal system.
In insects there is a long, segmented heart. Blood from the body enters through ostia (pores). The heart then pumps the blood towards the head by peristalsis (contraction in a wave of heart muscle segments). At the forward end of the heart, the blood simply pours out into the body cavity, and flows around the organs before re-entering the heart through valves.
Some larger and more active insects (locusts) have open ended tubes attached to the heart. These direct the blood towards active parts of the body (e.g. leg and wing muscles).

Disadvantages:
- Low blood pressure, blood flow is slow.
- Circulation may be affected by body movements or lack of body movements (in animals without
hearts circulation is reliant on body movements).

Question 2

Closed circulatory system

Answer 2

Closed circulatory system (fish/mammals): One is which blood is always held in vessels. A separate fluid – tissue fluid, bathes the tissues and cells
Advantages:
- Higher pressure, faster blood flow – more rapid delivery of O2 and nutrients and removal of wastes. - Transport is independent of body movements.