Animal Circulatory Systems Flashcards
Very small animals may not need a circulatory
system>
Small size may permit nutrients and other
substances to reach all the body parts by simple
diffusion
What do larger animals without a separate circulatory system have?
The gastrovascular cavity
extends to most areas of the body in these animals and serves as a circulatory
system as well as a digestive cavity.
What are the two types of circulatory system found in larger animals?
Open Circulatory Systems
Closed Circulatory Systems
What circulatory systems do insects have?
Insects have an open circulatory system, with a dorsal tube-shaped heart,
and a fluid-filled body
cavity(haemocoele).
Hemolymph leaves the
heart in short, branched
arteries that open up into
large spaces called sinuses.
Hemolymph percolates
around organs, directly
bathing the cells.
Hemolymph then returns to the heart directly or through short veins.
What are the advantages of Open Circulatory System?
Advantage - Since cells are bathed by hemolymph,
the exchange of materials is direct between the
hemolymph and tissues. There is no diffusion
barrier.
What are the disadvantages for an open circulatory system?
There is little opportunity for fine control over distribution of the hemolymph to body regions. No mechanism for reducing flow to a specific part of an organ.
Where are open circulatory systems usually found?
Open circulatory systems tend to be found in more
inactive animals.
Most molluscs have an open system, but the
highly active cephalopods (squid and octopus)
have evolved a closed system.
What is a closed circulatory system?
The blood is contained within a completely closed system of vessels.
Vessels form a closed loop,
usually with some sort of
pumping organ like a heart or contractile vessels.
Vessels branch into smaller
and smaller tubes that
penetrate among the cells of tissues.
Organs are not in direct
contact with the blood and the blood is under pressure
What are some of the advantages of a Closed Circulatory System?
Fine-scale control over the distribution of blood to
different body regions is possible. Muscular walls of vessels can constrict and dilate to vary the amount of flow through specific
vessels.
Blood pressures are fairly high and the circulation
can be vigorous.
What are the functions of Circulatory Systems
Transportation
Regulation
Protection
What are the Characteristics of arteries
Blood leaves heart through arteries
Arterioles are the finest microscopically-sized
branches of the arterial tree
Blood from arterioles enters capillaries
Capillaries later join to form venules that lead
to larger vessels, veins, that carry blood back to
the heart
What are characteristics of Arteries and Arterioles?
Arteries surrounded by layer of smooth muscle
Contraction of smooth muscle layer of
arterioles results in vasoconstriction which
greatly increases resistance and decreases blood flow.
Relaxation of smooth muscle layer results in
vasodilation decreasing resistance and
increasing blood flow.
What are characteristics of Capillaries
Capillaries are very small,
about the diameter of a red blood cell (8µm or less).
Capillary walls are a single
layer of very thin endothelial
cells, attached at their edges and surrounded by a basement membrane (extracellular matrix).
What are the characteristics Venules and Veins
Made up of same tissue layers as arteries, but
have thinner layer of smooth muscles.
Pressure in veins is only about one-tenth that in
arteries
Venous valves prevent back flow and are
important in return of blood to heart
Skeletal muscles surrounding veins can contract
to move blood by squeezing the veins
