8 Transport systems in animals
8.1 Overview
Introduction DUMMY
All living organisms require oxygen and nutrients, and a method of removing carbon diox-
ide and waste products. However, the circulatory system is not limited to the delivery of
nutrients, gas exchange, and waste removal. Hormones, too, rely on the circulatory system
to reach target organs, and the immune system depends on the transport of white blood cells
and antibodies. This chapter discusses transport systems found in mammalian systems, with
a focus on transport systems found in humans.Key concepts- There are open and closed circulatory systems. In an open circulatory system blood
enters a cavity, in a closed circulatory system blood remains in vessels. - A double closed circulation system consists of the pulmonary and systemic circulatory
systems. - The direction of blood flow is significant. In the systemic circulatory system oxy-
genated blood is transported to the body and deoxygenated returns to the heart. In
the pulmonary circulatory system, deoxygenated blood is sent to the lungs, and oxy-
genated blood is returned to the heart. - Specialised cells (sinoatrial node) send signals to the atrioventricular node to cause the
atria and ventricles to contact and control the cardiac cycle and heart rate. - The structure of blood vessels such as arteries, veins and capillaries are suited to their
function. - The lymphatic system transports lymph around the body and returns fluid to the blood
circulatory system. - The lymphatic system also plays an important role in immunity.
- Conditions and diseases of the heart and circulatory system include high and low
blood pressure, heart attacks and strokes. Treatments include stents, valve replace-
ments, bypass surgery, pacemakers, and heart transplants.
8.2 Circulatory systems in animals
Transport systems are crucial to survival. Unicellular organisms rely on simplediffusionfor
transport of nutrients and removal of waste. Multicellular organisms have developed more
complexcirculatorysystems.220 8.1. Overview