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Transport in Animals

Updated on February 16, 2016

Transport in Animals

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According to Biological study, there are two broad divisions of living things; they are the Plant and Animal kingdoms. Also, man is believed to be a member of the Animal Kingdom but that is referred to as higher animal. There are many religious people that argued that man is not an animal and should be treated with good respect. Biology stands its ground in the categorization process notwithstanding these arguments. In this text, the transport that takes place in animals will be discussed in details for more understanding of Biology, which is neutral subject that both Art and Science students offer. Note that as there is transport in animals, there exists transport in plants also.

Transport can be defined as the movement of materials from one location to the other. There are transport in plants but this topic is solely on the transport in animals systems. Materials are transported in animals for their survival and proper working of their systems. The materials in this discussion can be gases that are taken in or out of the organisms. This can also be the food nutrients which are carried out from one part of the organisms to the other by the responsible organs of the animals. These transported materials help to keep the internal part of animals and at equilibrium state. The materials are transported by specific organs of the organisms.

Transport in animals is the means through which materials move from area where they are produced to areas where they are needed in the system of the animals. This is very important study in animal systems. Without transport in animals, there will be nothing like digestion, absorption or excretion in animals. It is when materials are transported from the mouth or area of abundance in the animals to other areas that they are of good use that all these processes can take place. In animals, there are medium and mechanisms of transportation. The medium of transportation in mammals is not the same with that in some other animals. The medium of transportation in blue green algae is not the same in monkey or spider.

Materials Transported in Animals

There are eight principal materials transported in the system of animals. These materials transported are as follow:

  • Carbon (IV) Oxide which has chemical formula of CO2;

  • Oxygen which has chemical formula of O2;

  • Hormone;

  • Urea and urine;

  • Glucose;

  • Amino acid;

  • Water; and

  • Amonia.

Carbon (IV) Oxide

Animals breathe in oxygen and breaths out CO2. Metabolic process of respiration going on in the body cells constantly releases carbon (IV) Oxide and water. These diffuse in exchange of oxygen across the capillary wall into the blood stream. The release of carbon (IV) Oxide from the body of animals helps to maintain the adequate internal body temperature of animals. Release of CO2 is successful because of the proper operation of animals’ lungs. Carbon IV Oxide is transported from the lungs to the external environment. Itis absorbed by plants when animals breathe it out.

Oxygen (O2)

Remove Oxygen from animals and what will be left is nothing but a “dead thing”. Oxygen is the principal gas that holds the lives of animals. The red blood cells contain haemoglobin. This haemoglobin combines with oxygen to form what is called Oxyhaemoglobin. The oxyhaemoglobin assists in distributing oxygen to cells and tissues where they are needed in the body.


Hormone is produced by the endocrine glands of the animal body. It is transported by blood to the action sites. These action sites are where these hormones are needed and used. Human endocrine system is a group of ductless glands that regulate body processes by secreting chemical substances called hormones. They act on nearby tissues or are carried in the bloodstream to act on specific target organs and distant tissues. Diseases of the endocrine system can result from the oversecretion or undersecretion of hormones or from the inability of target organs or tissues to respond to hormones effectively.

Urea and Urine

Urea is mainly associated with the excretory products of birds. The urine is the excretory products of higher animals like mammals. Waste products arising from body metabolism of animals are carried by blood to the kidney, skin and so on for excretion. In the other words, urine is transported from the kidney to the bladder and then excreted from the body through the possible part of the body.


In aerobic respiration, the glucose in the body of animals is broken into CO2, H2O and Energy. These are transported to parts of the body where they are needed. Glucose in the body of animals supplies energy to the body system of the animals.

Amino acid

The transport of amino acid in animals is carried out by various distinct transport systems. The affinities of the neutral amino acids clustered into two groups, indicating the presence of at least two distinct heavily overlapping mediated systems identified as the A and the L transport systems. System A (alanine-preferring) serves mainly for such amino acids as alanine, glycine, and serine while System L (leucine-preferring) shows a preference for the branched chain and aromatic amino acids. Straight chain amino acids such as methionine have a high affinity for both systems. The body does not have a store for amino acids. This means that dietary amino acids, in excess of those required for protein synthesis, are rapidly catabolised.


Water is a universal solvent. It is highly needed in good proportion in the system of both plants and animals. All living things both plants and animals needs water for survival. Do you know the percentage of water in the human body? Arthur Guyton 's Textbook of Medical Physiology states that "the total amount of water in a man of average weight (70 kilograms) is approximately 40 litres, averaging 57 percent of his total body weight. Water is transported from one part of human body to the other. Water is also released as sweat through the skin pores. It is a very important class of food needed by animals.


Amonia has the molecular formula of NH3. It is formed during metabolism of amino acids in the system of animals which include both vertebrates and invertebrates. The ammonium or ammonia when transported can lead to predictable intracellular and extracellular pH changes. One important toxic effect of ammonia/ammonium is an increased demand for maintenance energy, caused by the need to maintain ion gradients over the cytoplasmic membrane. Amonia is transported across the cell membranes of animals.

Importance of Transportation in Animals

Transport in animals is of very good importance to the whole animal kingdom. I wonder how animals can live without transport in the body system. Thus, the importances of transportation in animals are shown below:

  • Transportation helps to take digested materials to where they are needed.

  • Transportation keeps the body warm during distribution of materials.

  • It helps in the excretion of toxic materials from the body.

Medium of Transportation

Transportation in animals occurs through some medium. This simply mean the means through which transportation in animals occur. These media of transportation in animals are blood, lymph and haemolymph.

The Blood

Blood is a liquid tissue which is made up of cells suspended in freely in a watery medium called the plasma. The plasma appears as pale-yellow liquid and suspended cells under mild configuration. There are Red Blood Cells and White Blood Cells. Red Blood Cells (RBCs) are also known as the Erythrocytes. They are formed by special cells of bones, marrows of ribs, sternum (breast bone) and vertebrae. The red blood cells transport oxygen from the lungs to the cells of the body. The red blood cells are able to do this because they contain haemoglobin. The haemoglobin is an iron compound which combines with oxygen to form a bright red compound called Oxyhaemoglobin.

The White Blood Cells are also known as Leucocytes. The proportion of these cells is more when compared with the red blood cells. The cells feed like Amoeba and they take the shape of Amoeba as well. The overall function of the Leucocytes is to protect the body against infections. The white blood cells are “disease fighters”. They build stronger immune system in animals.

In general, the blood as a medium of transportation in higher or multicellular animals performs many activities during transportation processes. The blood transports oxygen in the animal system. Oxyhaemoglobin formed when oxygen combines with the haemoglobin in the red blood cells assists in the distribution of oxygen to the cells and tissues in the body. The blood also helps in the transportation of Carbon IV Oxide (CO2) to the external environment. It helps to control the internal temperature of the body through distribution of heat. Waste products that results from the body metabolisms of animals are carried by the blood to the kidney and other parts of the body where they are needed. In a nutshell, the blood helps in the transportation of excretory products. The transportation of hormones by the blood is not overlooked in any way. Hormones produced by the endocrine glands are transported by the blood to the action sites where they are needed.

The lymph

The lymph capillaries and lymphatic vessels make up the lymphatic system. Lymph flows quite slowly like venous blood. Venous blood is deoxygenated blood that flows from tiny capillary blood vessels within the tissues into progressively larger veins to the right side of the heart. All the lymph collected from the entire left side of the body, those from digestive tract and right side of the lower body part enter into a single major vessel called the thoracic duct. The lymph produced in the right side of the head, neck and check is collected by the right lymphatic duct.

The lymph as a medium of transportation in animals transports proteins to different parts of the body where they are needed for the body system to perform and work effectively. Proteins are body building foods and this is needed by animals for growth and development. It is lymph that transports these proteins to the areas that demands for them. The lymphatic system has an important role in transporting body fluids and particulate materials to include proteins, fat particles, etc. Large proteins and certain cells (lymphocytes) pass from the blood plasma into the tissue fluid and it is the major role of the lymph to return these important components to the blood circulation.

Mechanisms of Transportation in Animals

Transportation has means through which they occur. These are mechanisms through which transportation takes place in animals. These mechanisms of transportation in animals are summarized under the following points:

  • Diffusion;

  • Osmosis;

  • Phagocytosis;

  • Pinocytosis;

  • Facilitated transport; and

  • Active transport.

The step-by-step explanations of the mechanisms of transportation in animals are explained thus:


This is the movement of materials from a region of higher concentration to a region of lower concentration until equilibrium of two sides is maintained. It can also be defined as the movement of ions or molecules from the region of higher concentration to the region of lower concentration, without involving any permeable membrane. Materials are transported in the body system of animals from the area where they are abundant to areas where they are less abundant, and this process or mechanism of transportation in these animals is termed diffusion. Diffusion occurs in exchange of gases like oxygen (O2) or Carbon IV Oxide (CO2) during respiration in animals. Also, diffusion takes place during distribution of nutrients and digested foods in the blood stream of animals. In earthworms, the major blood vessels are the artery, capillaries and veins. The arteries connect the veins through the capillaries while they supply nutrients to the cells and take away waste from the cell. This medium of transportation in earthworm takes place through diffusion because the capillaries, arteries and veins are thin and small so that diffusion can easily occur through them.


This is the movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane. In the other words, it can be said to be the movement of water molecules from the region of higher concentration but lower osmotic pressure through a semi-permeable membrane. It is a special case of diffusion. In these definitions, examples of semi-permeable membranes are Cells membrane and pigs bladder. These membranes allow transportation of water through them. Note that notwithstanding the fact that they allow transportation of water through them, they do not permit the passage of sugar or salt molecules because they are solutes. Osmosis occurs when water moves down its activity gradient across the semi-permeable membrane. In osmosis, movement is strictly a random process.


This is the movement of particulate matter from outside of the environment into the body of the organism across the cell membrane. This mechanism of transportation is found in Amoeba where the feeding material that is attached to the membrane is transported into the cells of the organism. Phagocytosis is also known as Cell eating. It is the process of engulfing and ingestion of particles by the cell or a phagocyte (e.g. macrophage and amoeba) to form a phagosome (or food vacuole). This process is used by the organisms to obtain nutrients which they need in order to succeed in their living. Phagocytosis is found in unicellular organisms such as Paramecia and by specialized phagocytes in multicellular organisms.


This is also known as Cell Drinking. It is the process through which liquid droplets are passed into the cells of lower organism like amoeba across its membrane. Pinocytosis is the means of taking in fluid together with its contents into the cell by forming narrow channels through its membrane that pinch off into vesicles, and fuse with lysosome that hydrolyze or break down contents. When amoeba gets close to the liquid fluid it wants to feed on, it engulfs them with its pseudopodia. This leads to the formation of a vesicle in the cytoplasm. With this vesicle (a pocket-like structure), the fluids are absorbed into the cells of the amoeba. Note that this is one of the endocytosis processes. Endocytosis is the external process through which unicellular organisms feed. Another form or type of endocytosis is the phagocytosis which was explained above.

Facilitated Transport

This involves the movement of materials across a cell that can attach to a carrier molecule. Facilitated diffusion allows polar and charged molecules, such as carbohydrates, amino acids, nucleosides, and ions, to cross the plasma membrane through diffusion process. The two types of proteins that encourages facilitated transport in animals are the carrier proteins and channel proteins. The carrier proteins bind specific molecules to be transported on one side of the membrane. They then undergo conformational changes that allow the molecule to pass through the membrane and be released on the other side. Channel proteins form open pores through the membrane and they allow the free diffusion of any molecule of the appropriate size and charge. Also, specific channel proteins allow the passage of Na+, K+, Ca2+, and Cl- across the membrane of animals.

Active Transport

In this transportation mechanism, materials are transported into the cells of organisms or animals against a concentration gradient. Energy is needed to facilitate the movement of materials in this mechanism. In active transport, energy provided by coupled reaction (such as the hydrolysis of ATP) is used to drive the uphill transport of molecules in the energetically unfavourable direction. The ion pumps that are responsible for maintaining gradients of ions across the plasma membrane provide important examples of active transport driven directly by ATP hydrolysis. The concentration of Na+ is approximately ten times higher outside than inside of cells, whereas the concentration of K+ is higher inside than out. These ion gradients are maintained by the Na+-K+pump (also called the Na+-K+ATPase), which uses energy derived from ATP hydrolysis to transport Na+ and K+ against their electrochemical gradients.

Transport in Insects

Insects practice open circulation system. This is because blood flows through the vessel and the body cavity in one complete circulation. The circulation is referred to as open circulation because blood is exposed to the environment of the body when it passes through the body cavity. Transportation of Oxygen in insects does not depend on blood flow but on the mesh work of the tubular trachea system which gets exposed through opening called spiracles. Oxygen from outside the environment gets into the trachea system through the spiracles. The Oxygen (O2) is then exposed to the cells through this trachea system. Carbon IV Oxide from the cells leaves through the trachea. The Carbon IV Oxide is finally released to the environment through the cell spiracles.


Animals cannot live without transportation taking place in them. Transportation in animals is one of the fundamental topics in Biology.Evidence, observation and proof have shown that animals cannot do without transportation in their systems. How will you feel if the food you eat on daily basis do not digest and distributed to the area where they are needed? In fact without transportation process in your system, you stand the chance to bargain for price with that enemy called “death”. So, transportation in living things, both animals and plants, is very important and cannot be done without.

Finally, transportation in animals has been discussed in details. The materials transported in animals have been discussed as well. The medium and mechanisms of transportation is animals have been thoroughly dealt with.

•Amino Acid Transport and Binding Activity from Membrane Preparation of Animal Cells by D. L Oxender, G. Cecchini, M. Lee and P. Moore.

•Interorgan amino acid transport and its regulation by Brosnan JT, Department of Biochemistry, Memorial University of Newfoundland, St. John's, NF Canada.

•Mechanisms of ammonia and ammonium ion toxicity in animal cells: transport across cell membranes by Martinelle K and Haggstrom L, Department of Biochemistry and Biotechnology, Royal Institute of Technology, Stockholm, Sweden.

•Advanced General Biology by Ezugwu E. N, Chukwu C. E, Arinzeagu C. C, Department of Basic Science in Institute of Management and Technology, Enugu, Nigeria.

•MediaLab Incorporated text book.

•Lymphatic transport of proteins after s.c. injection: implications of animal model selection by Porter CJ, Edwards GA and Charman SA, Department of Pharmaceutics, Victorian College of Pharmacy, Monash University, Australia.

•Lymphatic delivery methods by Nicola Christy, Stanley S. Davis, Lisbeth Illum and Moein Moghimi .

•Animal Osmoregulation by Timothy J. Bradley, Oxford University Press, 2009.

Feel free to drop your comments if you need more explanations on this topic.


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