Cardiovascular System

Question 1

How do circulatory systems in multicellular organisms supplement diffusion with bulk transport (convection)?

Answer 1

Through moving gases, nutrients, waste products, hormones, and components of the immune system.

Question 2

What are the necessary components of the circulatory system?

Answer 2

Fluid that carries transported molecules and cells, a pump to move the fluids, and vessels to carry fluid between the pump and body tissues.

Question 3

What is the key difference between open and closed circulatory systems?

Answer 3

The gastrovascular cavities. Capillaries (closed system) are the primary structure distinguishing a closed from an open system.

Question 4

What is key about the open circulatory system?

Answer 4

The hemolymph moves through vessels that open into extracellular spaces. There is no distinction between the hemolymph and interstitial fluid.

Question 5

What is key about the closed circulatory system?

Answer 5

Blood is pumped from a heart through vessels that return blood to the heart; capillaries.

Question 6

What is the Gastrovascular Cavity?

Answer 6

The simplest type of circulatory system. It’s found in cnidarians and relies on water currents to bring nutrients and release waste.

Question 7

What is the basic information about the open circulatory system?

Answer 7

It’s found in many invertebrates, the blood pumped by the heart empties into an open fluid space.
There is the heart, and blood vessels are open to the animal’s body cavity (hemocoel).
Blood + interstitial fluid = heamolymph.

Question 8

What is important about the open circulatory system?

Answer 8

There is the limited ability to alter the velocity or distribution of blood flow, a low rate of oxygen transfer.

Question 9

Why are insects an exception?

Answer 9

Because despite the usual low rate of oxygen transfer in open circulatory systems, their circulatory system is not involved in oxygen transport so insects can maintain high metabolic rates.

Question 10

What are the functions of insect haemolymph?

Answer 10

The transports of nutrients, hormones, waste products, and immune molecules. The haemolymph cells are involved in wound repair and immune response. Hydraulic skeleton (especially in larvae), heat transfer, and important CO2 sink.

Question 11

What is important about the closed circulatory system?

Answer 11

All vertebrates and some invertebrates (cephalopods) have this type of system. It’s ideal for large animals as it allows blood to reach all cells. The blood flows in a continuous circuit of tunes. The capillary beds allow fine control of blood distribution, which can increase the delivery of oxygen to tissue very rapidly.

Question 12

What kind of cardiovascular system design do fish have?

Answer 12

Single circulation.

Question 13

What kind of cardiovascular system design do amphibians have?

Answer 13

Parallel circulation.

Question 14

What kind of cardiovascular system design do mammals, birds, and crocodiles have?

Answer 14

Double circulation.

Question 15

What is Single Circulation?

Answer 15

The ventricles generate relatively low pressure in ventral aorta, which contains deoxygenated blood. There is high gill resistance to blood flow, which means a further drop at gills. The low pressure in dorsal aorta limits the ability to differentially distribute blood to tissues in response to demand.
The heart is always pumping low oxygen blood to the gills, where there is gas exchange; there is a major drop in pressure to the tissues and then back to the heart.
The body of the fish works at a very low pressure, and is a lot less efficient than in humans (low metabolic energy?).

Question 16

What is involved in the Parallel circulation?

Answer 16

Left (oxygenated blood) and right (largely deoxygenated blood) atria, and a single spongy ventricle. It doesn’t need to have equal circulation, which is an adaption that helps organisms live in water (can shut down the artery that sends blood to the lungs); mixing the poorly oxygenated blood with the oxygenated blood allows organisms to adapt to life on land and in water.

Question 17

What is involved in the Single Circulation?

Answer 17

Contains a single atrium and ventricle filled with deoxygenated blood.

Question 18

What is Parallel Circulation?

Answer 18

Where the pulmocutaneous artery has pulmonary and cutaneous branches. There is good flow separation in a single ventricle (laminar flow), which leads to little mixing. The spiral valve in truncus maintains the separation so oxygenated blood goes to tissues in aorta, and relatively deoxygenated blood goes to lungs and skin.

Question 19

What are the advantages of parallel circulation?

Answer 19

The cardiac output (mL/min) can be different in systemic and pulmocutaneous circulations.
Adapted to periodic ventilation, blood is diverted to lung while breathing and away from lung during apnea.

Question 20

What is the disadvantage of parallel circulation?

Answer 20

The single ventricle produces relatively low blood pressure; less capacity to ‘flood’ newly active tissue with blood.

Question 21

What is involved in Double Circulation?

Answer 21

The complete separation of pulmonary and systemic blood; a right and left atrium and a right and left ventricle.

Question 22

What is Double Circulation?

Answer 22

The heart muscle is supplied with oxygen by a branch of the systemic circulation (coronary arteries).
Flow has to be equal in the pulmonary and systemic circulations or else one would become more volume loaded compared to the other.
Fluid transfer across the capillaries depends on hydrostatic pressure and osmotic forces (Starling forces).

Question 23

What is an advantage of double circulation?

Answer 23

Systemic circulation can operate at a high arterial pressure so that flow can be selective to organs and tissues.
Pulmonary circulation is a low pressure, low resistance circuit.

Question 24

How does blood enter the heart?

Answer 24

Left heart blood goes through aorta in the large artery; right heart blood enters through the inferior vena cava, in the large vein.

Question 25

What are Arteries?

Answer 25

Arteries transfer blood to tissues, and serve as a pressure reservoir. They are capable of keeping pressure out due to the properties of the many layers of smooth muscle and connective tissue. They carry blood away from the heart.

Question 26

What are Arterioles?

Answer 26

Small branches of arteries; they deliver blood to capillaries. They control most of the distribution of blood.

Question 27

What are Capillaries?

Answer 27

Site of exchange between blood and fluid; exchange material with interstitial fluid. Located in close proximity to all cells in the body, blood exchange is very slow.

Question 28

What are Venules?

Answer 28

They collect blood from capillaries, and act as a blood reservoir.

Question 29

What are Veins?

Answer 29

They transport blood to the heart, are a blood/volume reservoir, and have thin walls, making them compliant to how much blood is pumping through.

Question 30

What is meant by: The velocity of blood is inversely related to total cross sectional area?

Answer 30

The larger the cross sectional area, the slower the velocity of blood flow. This allows diffusion of products to happen in the capillaries.

Question 31

What is the capillary wall composed of?

Answer 31

A single layer of endothelial cells, which allows diffusion due to the very slow movement of blood.

Question 32

What is the venous return of blood to the heart aided by?

Answer 32

Limb muscle pumps and valves; the valves make sure blood flows in one direction. When muscles contract, they squeeze the vein - the blood moves in both directions, but the valves make sure the blood doesn’t continue going ‘backwards’.

Question 33

What happens to veins due to valve damage?

Answer 33

Varicose veins.