C IRCULATION AND G AS E XCHANGE Chapter 42

I NTERNAL T RANSPORT 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?

V ERTEBRATE C IRCULATORY E VOLUTION 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!

T HE H EART 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

A RTERIES AND V EINS 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

B LOOD P RESSURE 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

L YMPHATIC S YSTEM 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!