THE FILTRATE CONCENTRATION MECHANISM

The average person should drink eight to ten glasses of water every day. Water, which includes both internal and extracellular fluid, makes up a large portion of the human body. Excretion is the process through which waste material is expelled from the body.The kidneys create urine, which is concentrated and excreted from the body so that the maximum amount of water is absorbed. The Henle’s loop and the vasa recta are vital in the production of concentrated urine in mammals. The mechanism of concentration is the process of producing concentrated urine.

The mechanism of concentration of the filtrate refers to the process of creating concentrated urine. Learn more about the excretion process, the structure of a nephron, the countercurrent mechanism, and the filtrate concentration mechanism by reading this article.

Mechanism of Concentration of the Filtrate

• Excretion
• Passage of Urine
• Concentration of Urine
• Urine Formation
• Countercurrent Mechanism
• Countercurrent Multiplier
• Countercurrent Exchanger

Excretion

The process by which undesirable chemicals and metabolic wastes are removed from the body is known as excretion. Large volumes of waste products and carbon dioxide are created in the tissues throughout the metabolic process. In addition, the body contains the residue of undigested food, heavy metals, medicines, poisonous compounds, and pathogenic germs. All of these chemicals have to be removed from the body in order to maintain it healthy.

Passage of Urine

The medullary pyramid in the inner zone of the medulla contains straight collecting channels that join to produce papillary ducts of Bellini ducts. They open into a papilla, which is a V-shaped region. The papilla collects urine and empties it into a small calyx. A major calyx is formed when three or four small calyces join together. There are 8 minor calyces and 2 to 3 major calyces in each kidney.

Urine travels through large calyces after passing through minor calyces. This then opens into the ureter’s pelvis. Urine travels from the renal pelvis to the urinary bladder via the remaining segment of the ureter.

Concentration of urine

The kidney excretes dilute urine when the body’s water level is higher. This is accomplished by preventing ADH secretion from the posterior pituitary gland. As a result, water reabsorption from renal tubules is not possible. The urine becomes diluted as a result of this.

The kidney holds water and excretes concentrated urine when the body’s water content drops. It consists of two steps:

1. A countercurrent system is used to create a medullary gradient.
2. ADH secretion.

Urine Formation

The following processes are involved in the production of urine:

• Tubular reabsorption or selective reabsorption
• Glomerular filtration or ultrafiltration of blood plasma by the glomeruli
• Secretion from the tubules

Glomerular filtration :- Glomerular filtration is accomplished by the use of glomerular capillaries, which filter blood through three layers: the endothelium of glomerular blood vessels, the epithelium of Bowman’s capsule, and the basement membrane between these two layers.

  Tubular  reabsorption:- Tubular reabsorption occurs when most of the filtrate passes through   and             into the bloodstream via peritubular capillaries. PCT epithelial cells have a lot of microvilli, which enhances the reabsorption surface area.Active or passive transport happens depending on the sort of molecules being reabsorbed. Water and urea, for example, are reabsorbed through passive transit from a high concentration to a low concentration location. Active transport resorbs glucose and amino acids, while both active and passive transport absorb sodium ions.

Tubular secretion:- This procedure removes substances from the glomerular capillaries that aren’t eliminated by filtration. Both active and passive transport are used to remove these pollutants. These compounds are combined with glomerular filtrate and excreted by urine. These include ions like potassium, hydrogen, and ammonium, as well as medications like penicillin and dangerous substances like cocaine and marijuana.

Countercurrent Mechanism

A countercurrent system is a ‘U Shaped tubular system in which the fluid flows in two limbs of the ‘U Shaped tubules in the opposing direction.

Countercurrent System Divisions

The countercurrent system is divided into two parts:

• A Henle loop is used to create a countercurrent multiplier.
• The vasa recta serves as a countercurrent exchanger.

Countercurrent Multiplier

Henle’s loop acts as a countercurrent multiplier. Hyperosmolarity is caused by active reabsorption of sodium chloride and other solutes from the ascending limb of the Henle loop into the medullary interstitium. The osmolarity rises as these solutes accumulate.

Furthermore, the constant influx of sodium and chloride ions raises the fluid’s osmolarity. As a result, it’s known as a countercurrent mechanism.

Countercurrent Exchanger

Vasa recta has a countercurrent exchanger function. Because of its location, it functions as a countercurrent exchanger. It’s a tubule with a descending limb, a hairpin bend, and an ascending limb.The Vasa recta is parallel to Henle’s loop. Its ascending limb and descending limb are both parallel to the ascending limb of the Henle loop.

Conclusion

The process of excretion is the removal of waste from the body. After producing and modifying a urinary filtrate consisting of a large volume of hypotonic blood filtrate, the excretory system makes, stores, and removes urine. Each nephron is made up of a filtering component called the renal corpuscle and a reabsorption and secretion tubule called the renal tubule. Glomerular filtration, tubular reabsorption, and tubular secretion are all involved in the production of urine. The distal convoluted tubule and collecting duct become permeable to water in the presence of ADH, resulting in water reabsorption and a higher final concentration of urine.