Many biological processes take place inside a living organism. All these processes have different and specific role to play. These processes are vital for the survival of living organisms.
Scientists have researched a lot to understand many such processes and two of such processes are excretion and secretion.
Excretion vs Secretion
The difference between excretion and secretion is that excretion is a biological process in which the body releases waste materials that cannot be used further whereas secretion is a biological process in which the body releases unwanted materials that can be used further.
Also, excretion is an external process whereas secretion is an internal process.
|Parameter of Comparison||Excretion||Secretion|
|Type of materials released||In excretion, waste materials are released that cannot be used further.||In secretion, unwanted materials are released that can be used further.|
|Process type||It is a passive process.||It is an active process.|
|Materials released||The materials which are excreted from the body are carbon dioxide, sweat, tears, feces, and urine.||The materials which are secreted in the body are hormones, enzymes, and saliva.|
|Body parts involved||The parts involved in the process are:|
3) Tear ducts
|The parts which are involved in the process are:|
1) Endocrine glands
2) Digestive glands
3) Salivary glands
|Released Materials||The materials released are tears, sweat, and urine.||The materials released are saliva and hormones.|
What is Excretion?
The cells which are present in an organisms’ body has to do some biochemical reactions to survive and when these reactions take place some by-products are formed and these by-products are lethal and toxic to the cell if the accumulate, therefore in the process of excretion all these wastes are thrown out of the body.
In short, excretion is a process in which the waste products are thrown out of the body.
Excretion is also essential for many other things like Osmoregulation and osmoregulation is essential because it is responsible for providing a suitable environment for the cells so that they can do the required reactions properly.
All the organisms have a different method of secretion depending upon their species and type. Some examples of excretion in different organisms are:
- Excretion in Unicellular Organisms: This process is simple in unicellular organisms. They mostly feed through the process of phagocytosis. During this process the cell membrane gets folded inwards to create a food vesicle, then this folded thing is taken into the cytoplasm of the cell where digestive enzymes perform their task. After the food gets digested, the remains also known as waste present in the vesicle are then removed by the process of exocytosis.
- Excretion in Animals: The smallest and thinnest organisms excrete through their skin, which later diffuses away over time and the other big animals have specialized organs and systems especially for excretion.
- Excretion in Plants: Just like animals plants also undergo excretion. Small plants simply excrete wastes over their surfaces’ cells whereas the larger vascular plants have the method of excretion in which the leaves play an important part.
The stoma which is the series of openings in the leaves lets oxygen (the waste product) out and brings in fresh carbon dioxide which is required by the plants.
What is Secretion?
Secretion is the process in which the organisms actively move molecules manufactured within a cell to space outside of the cell. The substances which are secreted are functional proteins, also many non-proteins such as steroids.
Secreted substances are sometimes useful and sometimes useless for the body. Secretion occurs via many pathways depending upon the cell type and also the substance being transported.
Some of the major secretory pathways are:
- The ER-Golgi Pathway and Porosomes: In this type of pathway, the secretory products are first produced in the endoplasmic reticulum which is then inserted into spherical containers like vesicles, known as transport vesicle, made up of lipid bilayer. These products then pass through the Golgi apparatus where they are modified and then packaged into specialized secretory vesicles.
- Membrane Transports: In some cases, the proteins in the cytosol move across the cell membrane through transporter proteins and not via exocytosis. In this case, the products are not packaged in vesicles, but instead, get transported individually by specialized proteins present in the cell membrane.
- Lysosomes: These are organelles that are generally thought to be important only for dehydration but in reality, they also play important role in secretion. The lysosomal secretory pathway is frequently used in certain specialized cell types like pigment cells and blood stem cells.
Just like secretary vesicles, lysosomes are also capable of fusing with the cell membrane to release their contents but a different kind of protein is used for the fusion process.
Main Differences Between Excretion and Secretion
- In excretion, waste materials are released that cannot be used further whereas, in secretion, unwanted materials are released that can be used further.
- Excretion is a passive process whereas secretion is an active process.
- The materials which are excreted from the body are carbon dioxide, sweat, tears, feces, and urine whereas, the materials which are secreted in the body are hormones, enzymes, and saliva.
- The parts involved in the excretion are lungs, skin, tear ducts, and rectum whereas, the parts which are involved in the secretion are Endocrine glands, digestive glands, salivary glands, liver, pancreas, and gallbladder.
- The materials released through the process of excretion are tears, sweat, and urine whereas, the materials released through the process of secretion are saliva and hormones.
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