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!

http://www.innerbody.com/anim/heart.html

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 SL 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

Blood Smear

Blood Clot

Heart disease

• Atherosclerosis • Strokes• Blockage• Bypass

How can 1 heartbeat circulate

blood through 2 capillary

beds?

What are the advantages and disadvantages of the amphibian

circulatory system?

• What is the change seen in reptiles that was not present in amphibians?

Why do endotherms have the greatest need for a 4

chambered heart?

Birds and mammals show convergent evolution of 4 chambered heart!