MECHANISM OF TRANSPORTATION IN HIGHER ANIMALS
Mammals exhibit double circulation, blood passes through the heart twice every time it makes on complete movement round the body.
there are two different circulations
In other words, there are two different circulations.
These are pulmonary and systemic circulation.
in some cases they can be known as open and closed circulation
Types of Circulation
The circulatory system in which the blood flows only once through the heart for
every complete circuit around the body is spoken of as a single circulation. This type
of circulation is found in the fish, insects and other arthropods.
In higher vertebrates,
including most amphibians and all reptiles, the blood passes through the heart twice in
one full circuit around the body. The blood from the heart is pumped into the lungs from
where it returns to the heart before it is finally repumped to the body. This is spoken.
of as a double circulation. To prevent mixing of deoxygenated and oxygenated blood,
the heart is divided into right and left sides. The right side deals with deoxygenated blood
and the left side with oxygenated blood. The heart is further divided into the upper and
lower chambers, the atrium and ventricle.
In insects the only blood vessel as such is a single long tubular heart which
extends through the thorax and abdomen and is expanded in each segmentto form a small
chamber pierced by a pair of ostia. In this case the heart may be regarded as one-
chambered as there are no atria or ventricles (fig. 10.1). In fish, the heart contains one atrium and one ventricle and is said to be two-chambered In the amphibians
and reptiles, the hearts are not fully divided into right and left halves, rather there are two
atria but only one ventricle. This arrangement is spoken of as three-chamberoo;..~e in
the mammals and birds, the heart is four-chambered and has two atria and two ventricles
- Pulmonary circulation:
during the pulmonary circulation, blood is taken from the heart to the lungs through the pulmonary artery and taken back to the heart through the pulmonary vein.
The role of this circulation is to oxygenate the blood and remove carbon dioxide from the blood in the lungs.
Systemic blood circulation:
this circulation takes the blood (oxygenated blood) from the heart to all parts of the body through the arteries and sends the blood back to the heart through the veins. The role of the systemic circulation is to transport products of digestion, oxygen, water, hormones and other substances to all parts of the body and collect excretory products like water, urea, carbon dioxide and mineral salts from the cells of the body to organs that will excrete them.
The Contribution of the Mammalian Blood Circulatory System
Exchange of gases in higher animals
the gases involved in this process are oxygen and carbon dioxide. The blood system has many capillaries in close contact with the air sacs (alveoli) of the lungs. The thin wall of capillaries and air sacs enable oxygen to be exchanged for carbon dioxide through the process of diffusion. Also, in the tissues, carbon dioxide is exchanged with oxygen. The continuous circulation of blood ensures diffusion of oxygen into the blood and carbon dioxide out of the blood in the lungs.
Absorption of digested food in higher animals
the digested food materials are absorbed by the villi of the small intestine. The mesenteric arteries take the food from the small intestine to the liver through the hepatic portal vein. The liver then regulates the amount of food going into the blood. The blood then transports these food materials to capillaries of tissues and organs. With the aid of the lymph, the food substances diffuse into the cells.
Removal of excretory products in higher animals
the blood is able to collect excretory products like urea, nitrogenous materials, carbon dioxide, and water from the cells by simple diffusion. The waste products are then transported to the various organs like skin, liver, lungs, and kidney from where they are removed from the body.
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MECHANISM OF TRANSPORTATION IN PLANTS