Blood Vessels Flashcards
What is an open circulatory system?
One in which the blood is not held in vessels instead the organisms blood fluid circulates through the body cavity so that the tissues and cells are bathed directly in blood.
What is an arteriole?
Small blood vessel that distributes blood from an artery to the capillaries.
What are venules?
Small blood vessels that collect blood from capillaries and lead into the veins
Instead of a heart in insects what is there?
A muscular tube that lies just under the dorsal (upper) surface of the body.
What are the pores in an insect called?
Ostia
What is the method that blood in an insect is pumped towards the head?
Peristalsis
What happens when the blood is pumped towards the forward end of the head?
The blood simply pores into the body cavity
How do large insects like locusts differ?
They have tubes at the end of their heart that direct blood towards more important muscles such as the keg and wing muscles
Why must small insects be continually moving?
If they have no heart the way their blood is ‘pumped’ around is through movement.
What are the disadvantages of open circulatory systems?
Blood pressure is low and blood flow is slow
Circulation of blood may be affected by movement or lack of
What is meant by a closed circulatory system?
The blood stays entirely in vessels.
What is the separate fluid that bathes cells called in a closed circulatory system?
Tissue fluid
What are the advantages of an open circulatory system?
Higher pressure
More rapid delivery of oxygen and nutrients
More rapid removal of wastes
Transport is independent of body movement
What is the inner layer of blood vessels called?
Endothelium
Why must artery walls be thick?
To withstand the higher pressure
What are the three layers of the arteries and what do they do?
Inner layer (tunica intima) thin layer of elastic tissue allows the walls to stretch and recoil Middle layer (tunica media) thick layer of smooth muscle Outer layer (tunica adventitia) thick layer of collagen and elastic tissue. Provides strength to withstand pressure
What do arteriole walls contain to restrict the diameter of the arteriole?
Smooth muscle
Why is the constriction of blood flow important with arteriole?
Able to direct blood to regions of the body requiring more oxygen
Capillaries have very thin walls.
What do their single thin layer consist of?
Flattened endothelial cells
Why are capillaries so thin?
To reduce the diffusion distance for the materials being exchanged
Capillary walls can be described as leaky. What does this allow?
Blood plasma and dissolved substances to leave the blood
Where does the blood flow into after capillaries?
Venules
What do venules consist of?
Thin layers of muscle and elastic tissue and a thin outer layer of collagen
Why do veins contain valves?
To stop blood from flowing in the opposite direction
