Lecture 20: 3 Chambered Hearts

Question 1

What needs to be transported by the circulation?

Answer 1

Nutrients
Respiratory gases
Intracellular waste
Protective agents
Regulatory molecules
Heat

Question 2

What selective forces selected against diffusion as the main mode of transport?

Answer 2

Increase in body size
Endothermy
Flight

Question 3

How do we overcome the limitations of diffusion?

Answer 3

Within the cells there is cytoplasmic streaming

Convective transport of extracellular fluid

Question 4

What is an open circulatory system?

Answer 4

There is no separation between the blood and interstitial fluid, have haemolymph

Question 5

Animals with an open circulatory system usually have a ______________ because their bodies are ____________________________________________.

Answer 5

Hard exoskeleton

Pressurised to enable haemolymph movement

Question 6

What is a closed circulatory system?

Answer 6

Blood is confined to vessels

Question 7

What are the disadvantages of an open circulatory system?

Answer 7

Sluggish

Can’t circulate fluid rapidly

Question 8

What are the disadvantages of a closed circulatory system?

Answer 8

Requires lots of energy to overcome the resistance of the vasculature

Question 9

What are the advantages of a closed circulatory system?

Answer 9

• Blood is conveyed directly to the organs
• Can regulate blood flow
• Blood return to the heart is rapid

Question 10

Describe circulation in the Hagfish?

Answer 10

• Partially open with sinuses
• Heart pumps blood to the gill baskets –> systemic circulation
• Accessory hearts are under neural control but main heart isn’t
• Main heart responds to increased venous return (due to accessory heart pumping) by increasing contraction

Question 11

Describe the fish heart:

Answer 11

• 4 chambered but a single circuit

- has a sinus venosus where the blood is drained into

Question 12

Describe the Lungfish heart:

Answer 12

• 2 chambered with the atrium and ventricle partially separated
• Get mixing of blood but there are 2 circuits
• the most posterior branch of the aortic arch provides flow to the lungs

Question 13

What is the Bulbis Cordis?

Answer 13

A system of spiral folds that keep the oxygenated and deoxygenated blood fairly separated within the ventricle

Question 14

Describe the amphibian heart:

Answer 14

• 3 chambered heart
• atria are completely separated
• ventricle is partially (functionally) divided by dense trabeculation of spongy myocardium
• spiral folds in the conus arteriosus separates oxygenated and deoxygenated outflow from the ventricle

Question 15

What is the main problem with the amphibian circulatory system?

Answer 15

Oxygenated blood from the skin returns to the right atrium and mixes with deoxygenated blood

Question 16

Describe the reptilian heart:

Answer 16

• Atria are completely divided

- Ventricle is functionally but not completely divided into 3 chambers

Question 17

How does blood flow through the reptilian heart?

Answer 17

During ventricular systole the pressure in the pulmonary artery –> blood flows from the CP and CV to PA

Question 18

Why have reptiles retained their heart structure?

Answer 18

When they dive the pulmonary pressure increases which shuts off the passage to the lungs (Right-to-Left cardiac shunt)

Question 19

Describe the Crocodile heart:

Answer 19

• 4 chambered heart
• Formaen of Panizza (FoP) joins the 2 systemic arteries
• FoP is usually kept shut by high pressures in the left artery
• FoP allows the crocodiles to bypass the lungs when diving