Introduction
The lungs major function is to offer uninterrupted exchange of gas between the blood in circulation and inspired air, as well as taking out carbon dioxide through expiration and bringing in oxygen (Roberts, 2000). This process is known as respiration and is managed by the brain areas comprised of apneustic, pheumotaxic and medullary inspiratory Centre that “stimulate the contraction of the diaphragm and the intercostal muscles” (Roberts, 2000).
Circulation is “the movements of body fluids inside the animals from the place of formation to the place of its utilization” in a one-celled animal (unicellular), cells exchange materials directly with the environment; this implies that it has no circulatory system and the cells have to be close to the immediate medium of exchange (Universereview.ca, 2010). On the other hand, large multi-cellular animals have circulatory system to carry oxygen and nutrients to the body tissues and to carry away waste products; blood and lymph are the key body fluids used in circulation of materials (Universereview.ca, 2010).
The following section shows the similarities and differences amongst the worms, insects, fish, and human in anatomy and physiology of circulation and respiration.
Anatomy and Physiology of circulation and respiration in;
Worms
Worms such as earthworms usually have a closed circulation system while flatworms and roundworms have no circulation system. This means that they have no respiratory organ thus oxygen is taken in through the skin, body cavity or osmosis (Chandra, 2010).
The earthworm uses its skin as breathing organ; this is enabled by its moist skin which allows effective absorption of oxygen. The oxygen diffuses through the body and enters into the blood contained in the dense capillary network that is positioned next to the skin. The blood transport oxygen to other body cells (Universereview.ca, 2010). In the body cells the carbon dioxide diffuses to the blood and it is then transported to the capillaries on skin where it finally diffuses to the body surface. Therefore, skin is an efficient respiratory organ in worms which have a “high surface area to volume ratio” (Universereview.ca, 2010). Worms have no heart chamber except earthworms which have five hearts that pair off (Chandra, 2010).
Flatworms mostly lives in water thus remove waste through osmosis and they have organ that get rid of surplus water in the body. This organ contains series of intersecting canals, which are on each side of the body and usually run through the length of the worm while roundworms have single opening for digestion that act as mouth as well as anus (Chandra, 2010). On the other hand, earthworms have two Nephridia openings; one gathers coelomic fluid and the other act as exit to the body wall and between these two openings waste is removed from the blood vessels (Chandra, 2010).
Insects
Insects have open circulation system in which circulation fluid in the body cavity known as hemocoel directly feeds the organs and thus no difference between interstitial fluid and the blood. The collective fluid is known as haemolyph or hemolymph (Chandra, 2010). An insect usually has one chamber of heart implying that its circulation system is not very well developed (Universereview.ca, 2010).
Tracheae are used to allow the oxygen in to the body tissue (Chandra, 2010). These tracheae have pores known as spiracles which allow the air to enter the insect’s body. The spiracles are located on the sides of the abdomen and each section of abdomen contains pair of spiracles (Farabee, 2001). The air from the atmosphere passes through the tracheae which stem into lesser and lesser tubes, similar to human bronchioles found in the lungs. These tracheae ends into the respiring body tissues, the oxygen is taken in and the carbon dioxide is taken out of the tissue and it’s expelled out of the body through the tracheae. The breathing process for the insects is very slow but very active and large insects thrust their abdomen to assist the quickening of the air movement (Farabee, 2001).
The excretory system of terrestrial type conserves water; malphighian tubules gather waste in the blood and absorb water again to make sure that only material that is dry is removed (Chandra, 2010).
Fish
Fish uses closed circulation system meaning that blood is contained in the blood vessels system implying that blood does not leave the blood vessels system (Chandra, 2010). Fish usually has two heart chambers meaning that it has a single circulation system. The water passes through the mouth to the gills and the oxygen is absorbed. The oxygenated blood in the gills is transported to the body tissues and carbon dioxide is taken out of the tissues to the blood and transported to the gills and as the water passes through the gills carbon dioxide is removed (Chandra, 2010).
Waste is filtered from blood by the kidney and removed through anal fin or external opening to reproductive tract and digestive urinary (Chandra, 2010). The kidney is very significant in modifying salt and water concentrations in the body of the fish, thus allowing specific species of fish to live in saltwater or freshwater or both (Farabee, 2001).
Humans
Human beings have closed circulation system implying that blood does not leave the blood vessels system which consists of veins, arteries and capillaries (Universereview.ca, 2010). Humans have four heart chambers resulting to a two circuits that is pulmonary and systemic (Double circulation system).
The air enters through the nostrils to lungs then to the heart, is absorbed in the blood arteries which transports oxygen (apart from pulmonary arteries) to the body (Chandra, 2010). The carbon dioxide from the body tissues is carried by blood through the veins (except pulmonary veins) to the heart to the lungs and finally to nostrils (Chandra, 2010).
The major excretory organ for humans is the kidney. It separates toxin, urea and other forms of waste out of the blood, at the same time salt, electrolytes and water are regulated at suitable levels; the kidney has nephrons which filter wastes (Chandra, 2010).
In conclusion, survival is reliant on process of respiration, circulation, excretion and digestion, therefore, these processes which together form part of the body system must be consistent, continuous and efficient, under all environmental conditions or when suffering from a disease.
References
Chandra, D. (2010). Circulatory system. Web.
Farabee, M. (2001). The blood circulation system. Web.
Roberts, F. (2000). Respiratory Physiology. Web.
Universereview.ca. (2010).Anatomy of animals. Web.