cnidarians - gastrovascular cavity ensures that are cells are bathed by a suitable medium and diffusion distances are short In more complex animals, two types of circulatory systems open circulatory system and closed circulatory system muscular pump (the heart) a set of tubes (blood vessels) circulatory fluid (blood

In insects, other arthropods, and most mollusks, open circulatory system. Hemolymph - blood and interstitial fluid One or more hearts pump the hemolymph into interconnected sinuses When the heart relaxes, it draws hemolymph into the circulatory through pores called ostia. Fig. 42.2a

closed circulatory system earthworms, squid, octopuses, and vertebrates, blood is confined to vessels and is distinct from the interstitial fluid. –One or more hearts pump blood into large vessels that branch into smaller ones cursing through organs. –Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells. Fig. 42.2b

cardiovascular system. heart - pump atrium(atria) receiving chamber ventricle(s) that pump blood out of the heart. Vessels - Arteries, veins, and capillaries fluid - blood/lymph Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

A fish heart two chambers one atrium and one ventricle. Ventricle to the gills (the gill circulation) The gill capillaries converge into a vessel that carries oxygenated blood to capillary beds at the other organs (the systemic circulation) and back to the heart. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 42.3a

Frogs and other amphibians have a three- chambered heart with two atria and one ventricle. –The ventricle pumps blood into the pulmocutaneous and systemic circulations. Although the reptilian heart is three-chambered, the ventricle is partially divided.

4 chamber heart - Right vs. Left crocodilians, birds, and mammals Double circulation restores pressure to the systemic circuit and prevents mixing of oxygen-rich and oxygen-poor blood essential for endotherms.. Birds and mammals evolved from different reptilian ancestors - an example of convergent evolution Fig. 42.3c

Fig. 42.4

Cardiac Cycle Cardiac output = heart rate X stroke volume

Cardiac muscle has its own intrinsic contraction rhythm. Initiated by sinoatrial (SA) node, or pacemaker Neural & Hormonal Control

The walls of both arteries and veins have three layers. Tunica externa Tunica media Tunica interna (endothelium) Blood vessels

Venous system - moving blood against gravity one-way valves veins that collapse

Blood Pressure Systolic Diastolic

Capillary flow Neural & Hormonal control

Filtration vs. Absorption Hydrostatic (blood) Pressure - Osmotic Pressure Role of lymphatic system

Blood Liquid - Plasma Cellular- Erythrocytes & Leukocytes