Difference Between Secretion and Excretion

Main Difference – Secretion vs Excretion

Secretion and excretion are involved in the movement or passage of materials in the body. Both processes are important in maintaining the homeostasis of the body. The main difference between secretion and excretion is that secretion is the movement of materials from one part of the body to the other part of the body whereas excretion is the removal of waste material, which has no further use for living organisms. Secretion is an active process and excretion is a passive process. Tears, sweat, carbon dioxide, urine, and feces are excreted from the animal body while saliva, hormones, and enzymes are secreted.

Key Areas Covered

1. What is Secretion
     – Definition, Glands and Organs Involved, Function
2. What is Excretion
      – Definition, Glands and Organs Involved, Function
3. What are the similarities between Secretion and Excretion
     – Outline of Common Features
4. What is the difference between Secretion and Excretion
     – Comparison of Key Differences

Key Terms: Carbon Dioxide, Enzymes, Excretion, Hormones, Kidneys, Liver, Lungs, Saliva, Skin, Secretion, Wastes

What is Secretion

Secretion is a process by which substances are produced and discharged from a cell, gland or organ. Substances like hormones, enzymes, and saliva are the secretory products of humans. Hormones are secreted by endocrine glands while enzymes are secreted by gastric glands in the lining of the stomach. Hormones are secreted into the blood in order to be transported to their site of action. Hormones and enzymes facilitate and regulate biochemical processes. Saliva provides lubrication, moisture, and protection. Golgi apparatus is involved in the production and release of secretory substances within the cells. Secretion by glands is shown in figure 1.

Difference Between Secretion and Excretion

Figure 1: Secretion

What is Excretion

Excretion is the process by which metabolic waste products like urea and carbon dioxide are eliminated from the body. Excretion helps to control osmotic pressure by balancing inorganic ions and water and by maintaining acid-base balance. Thus, the main purpose of excretion is to maintain homeostasis in the internal environment of an organism. Protozoans like Amoeba throw out their wastes by diffusion. In contrast, higher multicellular organisms comprise specialized organs for excretion. Kidneys are the major excretory organs in vertebrates, which maintain water balance while excreting urine. Skin, lungs, and liver are also involved in the excretion in humans. A small amount of urea, water, and salts are excreted from the skin along with sweat. Liver excretes cholesterol and bile. Lungs remove carbon dioxide, which is produced as a by-product of cellular respiration. Eccrine sweat glands are the major type of sweat glands in the human body.

Main Difference - Secretion vs Excretion

Figure 2: Sweat Glands

Similarities Between Secretion and Excretion

Both secretion and excretion are involved in the movement or passage of materials in the body.

Organs in the body are involved in both secretion and excretion in animals.

Both are important for the maintenance of the homeostasis in the body.

Definition

Secretion: Secretion is the movement of material from one part of the body to another part of the body.

Excretion: Excretion is the removal of waste material from living organisms.

Active/Passive

Secretion: Secretion is an active process.

Excretion: Excretion is a passive process.

Materials

Secretion: Materials like saliva, enzymes, and hormones are secreted from the body.

Excretion: Materials like tears, sweat, carbon dioxide, urine, and feces are excreted from the body.

Organs

Secretion: Salivary glands, digestive glands, endocrine glands, pancreas, liver, and gallbladder are involved in secretion.

Excretion: Rectum, lungs, tear ducts, and skin are involved in the excretion.

Role

Secretion: Secreted substances are involved in the metabolism of the body.

Excretion: Excretion is mainly involved in the elimination of body wastes.

Conclusion

Secretion and excretion are two methods, which are involved in the movement of materials in the body. Metabolically important substances are produced and secreted by glands and organs in the body. Excretion is mainly involved in the elimination of wastes like urea and carbon dioxide from the body. Therefore, the main difference between secretion and excretion is their role in the body.

Reference:

1. “Secretion.” Encyclopædia Britannica. Encyclopædia Britannica, inc., 14 Feb. 2011. Web. Available here. 21 June 2017.
2. Ramsay, James Arthur, and Fenton Crosland Kelley. “Excretion.” Encyclopædia Britannica. Encyclopædia Britannica, inc., 04 June 2014. Web. Available here. 21 June 2017.
3. “Excretion in Animals, Humans and Plants (with diagram).” Biology Discussion. N.p., 27 Aug. 2015. Web. Available here. 21 June 2017.

Image Courtesy:

1. “405 Modes of Secretion by Glands Merocine” By CFCF – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “508 Eccrine gland” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia