Download The Circulatory System and Heart Circulatory System is composed

The Circulatory System and Heart
 Circulatory System is composed of the Cardiovascular System and Lymphatic System
o It transports blood and lymph through the body of organisms to distribute nutrients and remove waste
o Moves blood to a site where it can be oxygenated & wastes to a site where they can be disposed of.
 The heart functions as the pump of the circulatory system
1) Systematic Loop: blood circulates into the body’s systems, bringing oxygen to all its organs; collects
carbon dioxide and waste; controlled by left side of the heart
2) Pulmonary Loop: the blood circulates to and from a respiratory surface to release carbon dioxide and pick
up new oxygen; controlled by the right side of the heart
 Animals with multiple layers of cells are unable to obtain nutrients by simply exchanging materials with their
environment through diffusion, so they need a circulatory system to ensure nutrients reach all cells. This
circulatory system needs a heart to power it.
 Features of the heart the circulatory system depends upon to function:
1) Arteries, capillaries, and respiratory surface
2) Veins, valves, and skeletal muscle contractions
3) Lymphatic System
 How Organisms without Hearts accomplish Circulation
o Unicellular organisms can exchange nutrients directly with their environment by diffusion; the cell
surface is the point of exchange with the environment
 Eg. Bacteria
o Plants absorb water and nutrients through their roots. Xylem is vascular tissue that transports water and
minerals up from the roots and phloem transports sugar molecules, amino acids, and hormones. They are
propelled up the plant by the forces of osmotic potential and water pressure.
 Eg. Flowers
o Animals with gastrovascular cavities have two cell layers. The inner layer has direct access to nutrients
by diffusion and the second layer is close enough that the nutrients can diffuse into them also so a
circulatory system is not needed.
 Eg. Hydra
 Evolutionary Trends of the Heart
o Simplest heart is a muscular tube with a rhythmic pump
o Fishes contain two chambers in their hearts, one atrium and two ventricles
o Amphibians and reptiles have hearts with two atria and one ventricle
o Mammals and birds have hearts with two ventricles and two atria
o Arthropods and molluscs have an open circulatory system
o Earthworms, squids, octopuses, and vertebrates have a closed circulatory system
o The evolution of double circulation, a divided ventricle, and a closed system increases the efficiency of
the heart
 Lungs, and the skin of animals that use their skin as respiratory surface, have a dense net of capillaries just under
the epithelium. Carbon dioxide and oxygen exchange take place in the capillary vessels, which have alveoli that
hold the gases. The respiratory surface (skin or lungs) must remain moist in order for exchange to occur. The
skin does not have as much surface area as lungs do so animals that use their skin to obtain oxygen usually have
lungs as well.
 The Circulatory System Depends on Other Systems
o Respiratory
o Digestive
o Excretory
Disease
Atherosclerosis
Aortic Aneurysm
Description
Plaque builds up in
the arteries, causing
them to become
narrow. Platelets
adhere to the inside of
the arteries and can
cause clotting.
When the aorta is
damaged it will bulge
and eventually tear,
causing severe
internal bleeding.
Cause
A diet high in LDL ,
fat , and calcium.
Symptoms
Occasional chest pain
Weakness could be
present at birth or
caused by
Atherosclerosis,
obesity, or high blood
pressure.
Chest pain, heart
murmur, hoarseness,
trouble breathing or
swallowing.
Treatment
Avoid smoking,
exercise regularly,
and eat a balanced
diet. The condition
cannot be reversed but
progression can be
slowed or prevented.
Medicine may be able
to slow the growth of
the aneurysm, but
surgery might be
necessary.