Circulation and Gas ExchangeChapter 42

Internal Transport

Gastrovascular cavity makes circulatory system unnecessary

Open and closed circulatory systems What are the limits an open circulatory

system places on an organism? What is the difference between an

artery and a vein? Arteries carry blood away from the

heart Veins bring blood back to the heart

Why do veins have valves and arteries do not? Veins move blood against gravity without

benefit of the heart contraction Blood flow:

Heart arteries arterioles capillaries venules veins heart

Which chamber of the heart receives the blood?

Which chamber pumps the blood?

Vertebrate Circulatory Evolution

Fish have 2 chambered heart, one beat circuit: 1 atrium 1 ventricle

Amphibians have 3 chambered heart: 2 atria 1 ventricle

Reptiles have 3 – 4 chambered heart: Septum keeps 2 parts of ventricles separate

Mammals and birds have 4 chambered heart!

The Heart Cardiac muscle Atria have thin walls Ventricles have thick and powerful walls Systole = ventricular contraction blood is

pumped Diastole = ventricular filling Lub dub = heart sounds opening and closing

of the valves Lub = contraction of ventricles (AV closing) Dub = blood recoiling against Semi Lunar valves

Heart murmur = valve defect

CO = cardiac output ; Volume of blood pumped/ minute

SV = stroke volume: Amount of blood pumped by L

ventricle/contraction CO is effected by heart rate and SV Myogenic heart can regulate its own rhythm SA node is the pacemaker of the heart

Arteries and Veins

How do differences between arteries and veins reflect their different functions?

Artery wall is very thick to absorb pulsation from heart

Veins are wider in diameter and are not as muscular

Veins have valves Capillaries have only single layer of

endothelium

Blood Pressure

The force that blood exerts against vessel walls

BP is greater in arteries than veins Pulse is measure of BP Exact BP is measured as systolic/diastolic

pressures Constricted blood vessels have higher BP

than dilated vessels In veins heart has little effect on BP How, then does blood move in veins?

Blood Flow

Velocity

Blood Flow Through Capillary

Beds

Capillary Movement of Fluids

Lymphatic System

Lymphatic system returns lost blood to circulatory system

Lymph nodes filter the lymph Help fight infection

How can 1 heartbeat circulate

blood through 2 capillary

beds?

What are the advantages and disadvantages of the amphibian circulatory system?

Why do endotherms have the greatest need for a 4 chambered heart?

Birds and mammals show convergent evolution of 4 chambered heart!