Osmoregulation

Kidneys are responsible for maintaining the process of excretion and osmoregulation in humans. Alongside the kidneys, there is a whole excretory system that is responsible for maintaining the osmoregulation of the body. The kidney, ureter, urinary bladder, and urethra are a part of the excretory system. 

Osmoregulation meaning that it is the maintenance of the concentration of salts and water in the body is known as osmoregulation. In different organisms, different organs are responsible for this process. Osmoregulation meaning in biology or chemistry is the same as it is mentioned above. We will learn more about what is osmoregulation and the roles of various organs that help us to achieve this process. 

Kidneys

Understanding the kidneys will help us understand what is osmoregulation. They are reddish-brown in colour and are two in number in human beings. They are in the shape of a bean and are situated in the abdominal cavity. The right kidney is slightly lower than the left kidney because of the liver occupying a great amount of space. Inside the kidneys, we have the nephrons that are mainly responsible for the formation of urine and also for maintaining the osmotic balance or osmoregulation of the body. The kidneys are covered by three layers that are: 

• Renal Capsule: It is the innermost layer and is the tough protective covering. It is made up of white fibrous connective tissue. Some elastic fibres and muscles are also present.

• Adipose Capsule: It is the middle covering and as the name suggests it has the presence of adipose tissue. It acts as a shock-absorbing layer. 

• Renal Fascia: It is the outermost layer and it helps to link the abdominal wall. 

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Nephron

Here we will understand more about the phenomenon of what is osmoregulation. It is known as the structural and functional unit of the kidney. The glomerulus and renal tubule are the two parts of the nephron. The glomerulus is formed by the afferent arteriole. Efferent arterioles are formed by the glomerular capillaries. The renal tube has a bowman’s capsule and distal convoluted tubule and proximal convoluted tubule. The concentration of salts and water is performed by the nephrons at its distal end. This is the actual osmoregulation meaning. It also helps in the formation of urine. 

Types of Osmoregulation

After having an idea about what is osmoregulation, you should also know that it is divided into two major types – 

1. osmoconformer

2. osmoregulator. 

Those organisms that strictly regulates their body osmolarity, and their overall internal conditions stays same despite the osmotic condition of external environment, are known as osmoregulator. Mostly freshwater and marine organisms fall under this category.

Osmoconformer are those that adapt their body’s osmolarity according to the outside environment. This may be done either actively or passively. Marine organisms are mostly osmoconformer.

Functions of the Tubules

After understanding the kidneys, we will understand what is osmoregulation in biology and the structures that are responsible for its maintenance. 

• Proximal Convoluted Tubule: Cuboidal brush border epithelium cells line this tubule. This helps in increasing their surface area for the reabsorption of salts and water. About 70-80% of the electrolytes are absorbed in this tubule. More than 80% of water is reabsorbed at this segment. The Proximal convoluted tubule is very helpful in maintaining the ionic balance of the body fluids and also the pH balance of the body. This is done by selective secretion of hydrogen ions and ammonia and the absorption of hydrogen carbonate ions from it. 

• Loop of Henle: Minimum reabsorption takes place in this segment. But it plays a major role in maintaining the high osmolarity of the medullary interstitial fluid. The descending loop is permeable to water and impermeable to electrolytes. The ascending loop is permeable to electrolytes and impermeable to water. 

• Distal Convoluted Tubule: A selective reabsorption of sodium and water ions takes place here. Also, it is capable of selectively secreting hydrogen and potassium ions and ammonia so as to maintain the pH and the osmotic balance in the body. 

• Collecting Duct: As the name suggests, this duct helps in collecting all the water and concentrates that have been filtered out by the tubules so far. It plays an important role in maintaining the pH and mineral concentration of the blood. 

Regulation of Kidney Function

After answering the question of what do you mean by osmoregulation, now we will learn about the hormones that are responsible for its maintenance. There is hormonal feedback that is responsible for the maintenance of kidney functions. The hypothalamus, the juxtaglomerular apparatus, and the heart are responsible for the regulation of kidney functions. There are certain osmoreceptors that are activated when there are changes in the volume of the blood. When there is excessive loss of fluid from the body then these receptors are activated. The anti-diuretic hormone is released from the neurohypophysis. It is also known as vasopressin. It then facilitates the reabsorption of water from the distal convoluted tubule. When things are normalized, then the secretion of this hormone is stopped. This helps us to understand osmoregulation meaning and the ways by which it is maintained.