Secretion and Excretion

Many of the processes we encounter in the body have definitions that are similar. We frequently use these terms interchangeably. We won’t be able to use the terms correctly until we understand what they mean. In this article, we will look at two of these terms, excretion and secretion, which are frequently used interchangeably. Both of these processes involve material movement within the body. However, the distinction between excretion and secretion is that excretion is the removal of waste from the body, whereas secretion is the movement of materials within the body.

What is secretion?

In biology, secretion is the production and release of a useful substance by a gland or cell; it is also the substance produced. Body tissues secrete a variety of substances that provide lubrication and moisture, in addition to enzymes and hormones that facilitate and regulate complex biochemical processes. The Golgi apparatus and its associated secretory granules are thought to be the structures responsible for secretory substance production and release within a single cell.

The majority of secretions are internal, but some are both external and visible, such as tears and sweat. The gastric glands that line the stomach contain four different types of cells that secrete digestive substances. Hormones are secreted directly into the bloodstream by endocrine glands and carried to their sites of action.

What is excretion?

Excretion is the process by which animals eliminate waste products and nitrogenous byproducts of metabolism. Organisms control osmotic pressure (the balance of inorganic ions and water) and maintain acid-base balance through excretion. As a result, the process promotes homeostasis, or the consistency of the organism’s internal environment.

Every organism must eliminate potentially harmful byproducts of its own vital activities. This process is known as elimination in living things, and it can be thought of as encompassing all of the various mechanisms and processes by which life forms dispose of  toxic substances, and dead portions of the organism. The nature of the process and the specialised structures developed for waste disposal vary greatly depending on the organism’s size and complexity.

Kidney excretion: the functions of the kidney

The kidneys are excretory organs that produce urine by performing three main functions: filtration, reabsorption, and secretion. They are located in the peritoneal cavity at the back.

A cross-section of the kidney reveals an outer layer (renal cortex), a middle layer (renal medulla), and an inner area (renal pelvis) where the ureter joins the kidney.

Each kidney contains approximately one million nephrons, each of which functions as an independent filter and urine-processing unit. A nephron is made up of a renal corpuscle, which is located in the cortex, and a renal tubule, which is a long tube that collects and processes the filtered fluid.

The glomerulus, a network of very small-diameter blood capillaries, comes into close contact with the closed end of the tubule, which is composed of a single layer of epithelial cells – the Bowman’s capsule – at the renal corpuscle.

Tubular secretion and risk of kidney

Kidney function is most commonly assessed using estimated glomerular filtration rate and albuminuria, both of which are glomerular function markers. Tubular secretion is an important nonglomerular kidney function that is required for toxin excretion as well as non filtered endogenous metabolites excretion. 

Because creatinine is filtered by the glomerulus and secreted by the proximal tubule, creatinine clearance overestimates GFR by 10% to 20%. It is unclear whether measuring secretory function provides additional information about kidney tubule health. The difference between measured CLcr and GFR represents creatinine clearance due to tubular secretion . We performed a post-hoc analysis of the MDRD Study to see if TScr could be used to assess the impact of secretion on long-term clinical outcomes.

Animals and humans excretion

Different metabolic wastes are excreted by animals and humans via specialised organs such as our skin, lungs, liver, kidneys, and intestines. Let’s take a look at each one.

Sweat and oils are excreted by humans through sweat glands, which are specialised glands in the skin. Sweat isn’t always a metabolic waste, but it does help to lower our body temperature by evaporation when it gets too hot. 

Amphibians, such as salamanders and frogs, expel carbon dioxide via their skin rather than their lungs. Carbon dioxide, a gaseous waste, is excreted by mammals, birds, and reptiles through the tissues of their lungs and out into the environment through exhalations. Fish use their gills to expel carbon dioxide into their watery environment in the same way that humans do.

Conclusion

Many of the processes we encounter in the body have definitions that are similar. However, the distinction between excretion and secretion is that excretion is the removal of waste from the body, whereas secretion is the movement of materials within the body. In biology, secretion is the production and release of a useful substance by a gland or cell; it is also the substance produced. The majority of secretions are internal, but some are both external and visible, such as tears and sweat. Excretion is the process by which animals eliminate waste products and nitrogenous byproducts of metabolism