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PinkMonkey Online Study Guide-Biology

18.1 Vascular System

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Figure 18.2 Open Circulatory system Figure 18.3 Closed Circulatory System

There are two basic types of transport systems:

(1) In an open (vascular) circulatory system (Fig 18.2) the blood is not completely enclosed within vessels and it flows within blood vessels for only a limited part of its circuit. The blood vessels open into the open fluid spaces (sinuses or hemocoel) so that the circulating fluid (hemolymph) can reach the cells directly. This type occurs in insects, crustaceans and molluscs. Circulation and O2 transport is slower in an open circulatory system. (Smaller or sluggish animals).

(2) In a closed circulatory system (Fig. 18.3) the blood remains within a completely closed (unbroken) system of vessels, and never comes in direct contact with the cells. This occurs in molluscs (squids), annelids (earthworms), echinoderms, and vertebrates (animals and humans). The advantages of a closed circulatory system are : faster transport of oxygen; greater efficiency of blood flow; economy of blood volume and maintenance of sufficient blood pressure for a large body.

A circulatory system, whether open or closed, has several functions such as transportation of dissolved nutrients, hormones, gases, antibodies, control of fluid volume, pH, and regulation of body temperature.

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Table of Contents

18.0 - Introduction
18.1 - Closed Vascular System
18.2 - Heart
18.3 - Arterial Blood Pressure
18.4 - Blood

Chapter 19


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