• 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 convergeinto a vessel that carriesoxygenated blood to capillarybeds 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 intothe pulmocutaneousand systemiccirculations.

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 externaTunica mediaTunica interna (endothelium)

Blood vessels

Venous system - moving blood against gravityone-way valvesveins that collapse

Blood PressureSystolicDiastolic

Capillary flow

Neural & Hormonalcontrol

Filtration vs. AbsorptionHydrostatic (blood) Pressure - Osmotic Pressure

Role of lymphatic system

BloodLiquid - PlasmaCellular- Erythrocytes & Leukocytes