The kidneys are the most important organs in the human body as they constantly attempt to filter blood, eliminate waste substances harmful to the human body, control the volume of water in the body and ensure a normal level of internal environment. They are small but their contributions to the general health are immense. These organs make sure that the fluids that are flowing in the body are in balance and the elimination of toxins is done effectively. The absence of proper functioning of the kidneys would make the body unable to support the normal chemistry within a short time.
Kidneys are very precise in their work. All the blood that flows through them is thoroughly filtered, checked and adjusted. They regulate electrolytes like sodium, potassium and calcium that are critical to nerve activity, muscle contraction and cell stability. They also control the amount of water in the body such that the level of hydration is maintained at a given level despite changes in diet or even environmental factors.
The knowledge of how the kidneys filter blood gives an extra understanding of the internal systems of the human body. To get to know more about the functioning of these organs, you may have a look at the following resource:
Get to know more on how the kidneys filter blood here.
The Structure of the Kidneys and Their Functional Units
Kidneys are bean-shaped structures, which are positioned on both sides of the spine and just below the rib cage. The average kidney has about one million nephrons, or microscopic units that wear out blood and generate urine. What enables the kidneys to effectively carry out their complex physiological functions is their complex architecture.
The Components of a Nephron
The nephrons have two main components of each:
- The Renal Corpuscle: this is the glomerulus and the Bowman capsule.
- The Renal Tubule: that contains the proximal tubule, the loop of Henle, the distal tubule and the collecting duct.
The blood flow and blood vessels reach the kidneys via the renal artery to the glomerulus where the filtration process starts in the form of a network of capillaries. The force within the glomerular capillaries drives the plasma and thin solutes out of the blood and into the Bowman’s capsule. There, the fluid moves through the various parts of the renal tubule where crucial elements are reabsorbed and waste is concentrated.
How the Kidneys Filter Blood
The filtration process consists of a mixture of mechanical pressure, selective permeability as well as active transport. Every step will make sure that useful materials are retained and the waste and surplus are eliminated.
Glomerular Filtration
The initial urine formation process is glomerular filtration. In this case, the pressure of blood forces water and solutes including the electrolytes, glucose and amino acids out of the blood and into Bowman capsule. Smaller molecules such as proteins and blood cells cannot enter and hence their presence in the urine is an indication of kidney damage.
The result of this filtration process is the filtrate, which is a fluid one resembbling plasma but minus huge proteins. Approximately 150-180 liters of filtrate are filtered by the kidneys each day, although not all of this is to be retained in urine (only 1-2 liters). This is because of the reabsorption that is meticulously followed in the renal tubules.
Tubular Reabsorption
Water, glucose and the electrolytes are reabsorbed as the filtrate passes the proximal tubule. The body absorbs exactly what it requires and such a process of reabsorption is exquisitely adapted to give attention to moment-to-moment requirements.
- At normal conditions, glucose is completely reabsorbed.
- One of the key electrolytes, sodium, is actively carried and provides the impetus to the further water flow.
- Sodium is followed by water through osmosis.
The loop of Henele creates a concentration gradient within the medulla, which enables the kidneys to generate either watered down or concentrated urine based on the level of hydration. Renin reabsorption persists in the distal tubule and collecting duct, which is under hormone control, e.g., aldosterone and antidiuretic hormone (ADH).
Tubular Secretion
Besides reabsorption, the renal tubules also actively secrete things to the filtrate. These are hydrogen ions, potassium ions, ammonium and some drugs. This refines the blood pH and eliminates foreign chemicals in the body.
Urine Formation and Excretion
When the filtrate gets into the collecting duct it is filled with pure waste products, extraneous ions and the unwanted water that is not required by the body. The urine is then passed to the renal pelvis which is passed on to the ureters and the bladder where it is kept until excreted.
Electrolyte Balance and Its Importance
Electrolytes needed to maintain normal functioning include sodium, potassium, calcium, chloride and bicarbonate. Kidneys preserve the correct balance between these ions by altering the processes of reabsorption and secretion.
- Sodium balances the fluid and blood pressure.
- The potassium maintains adequate nerve conductive and muscular activity.
- Phosphate and calcium maintain metabolic processes and bone.
- The use of bicarbonate assists in maintaining the acid-base level of the body.
The kidneys constantly equate the ion concentrations of these elements in the blood and readjust themselves. Any slight disruptions have the potential to disrupt the heart rhythm, nerve transmission, and muscle contractions.
Water Balance: How the Kidneys Prevent Dehydration
Water balance is important in ensuring the blood volume, temperature regulation and metabolic reactions. Kidneys are at the center of stage in the regulation of volume of water excreted in urine.
The urine generated by the kidneys is dilute when the body is well-hydrated. The water levels falter and they save on water by manufacturing concentrated water. This is a skill to survive, and it is important in these situations when the amount of water is scarce.
The Role of Hormones in Fluid Homeostasis
Antidiuretic hormone (ADH) and aldosterone are two hormones that are particularly significant in controlling the functioning of the kidneys as well as fluid balance.
Antidiuretic Hormones (ADH)
The hypothalamus produces the ADH which is released by the posterior pituitary gland to control the level of water stored by the kidneys. ADH levels get elevated when the body gets dehydrated or the osmolarity of blood increases.
ADH increases the permeability of the walls of the collecting ducts to water. This makes water to be reabsorbed into the blood thus decreasing the amount of urine produced and aids the body in retaining water. In the case of sufficient hydration, ADH is reduced, and this leads to increased dilute urine.
Aldosterone
Aldosterone is made by adrenal cortex and it regulates sodium and potassium level. It enhances sodium reabsorption and secretion of potassium in the distal tubule and the collecting duct.
Sodium comes after water hence water is retained indirectly by aldosterone. This hormone is very important in the regulation of blood pressure. The renin-angiotensin-aldosterone system (RAAS) works when blood pressure decreases to elevate it and this is done by stimulating sodium and water reabsorption.
How Hormones Work Together to Maintain Stability
The ADH and aldosterone act as a concerted mechanism. ADH regulates the levels of water whereas aldosterone regulates the levels of sodium. Together, they:
- Prevent dehydration
- Keep electrolyte homeostasis.
- Regulate blood pressure
- Normalize metabolic functions.
In case of any disruption in either of the hormones, severe effects may arise. For example:
- ADH deficiency causes diabetes insipidus which involves excessive urination and life threatening dehydration.
- High levels of aldosterone cause hypertension as there is too much sodium retention.
The Impact of Kidney Function on Blood Pressure
Close to the work of kidneys is blood pressure. Kidneys control the quantity of circulated as well as the amount of water that is shed off or saved. Increase in fluid volume leads to an increase in blood pressure. On the other hand, as the kidneys pump more water, the blood pressure becomes low.
The RAAS system also makes the blood pressure stay the same. When the level of blood flow or sodium is detected to be low by the kidneys, renin is released, which causes a chain reaction that eventually results in the high blood pressure.
Such a complicated interaction demonstrates the reason why people with kidney diseases develop hypertension frequently, and why kidney health matters to cardiovascular stability.
The Kidneys and Metabolic Function
In addition to the blood filtering and maintaining fluid balance, kidneys have a wide range of metabolic activity:
- They stimulate vitamin D that is vital in the absorption of calcium.
- They also secrete erythropoietin which is a hormone that helps in the production of red blood cells.
- They control the pH of the blood through balancing of the levels of hydrogen and bicarbonate.
In case of kidney dysfunction, such processes are not coordinated, which leads to such complications as anemia, bone disorders, and metabolic acidosis.
Kidney Failure and Its Consequences
As soon as the kidneys fail to filter the blood effectively, waste and fluid are built up. This is referred to as renal failure and may either be acute or chronic. Kidney disease is a long term illness that may later result to end stage kidney disease which necessitates dialysis or transplantation.
Signs of decreased renal functions are:
- Pitting edema of the legs and ankles.
- Fatigue
- Nausea
- Shortness of breath
- Changes in urine output
All these impacts emphasize the interdependence between kidney functions and the general health.
Supporting Kidney Health
Healthy kidneys depend on:
- Adequate hydration
- Balanced diet
- Controlled blood pressure
- Limited salt intake
- Evade generous/ too many NSAIDs.
- Management of diabetes
Early diagnosis and frequent medical examination may play a significant role in averting the development of kidney related illnesses.
Conclusion
Internal balance is controlled by the kidneys as their masters. They help sustain hydration, waste, and other vital processes like blood pressure management and metabolic balance through filtration, reabsorption, secretion as well as hormone-regulated changes. The fact that kidneys play a crucial role in ensuring that the body is in its best state should be considered through the prism of the fact that they help to filter blood and ensure that the body stays in a fluid homeostasis state.
Their capacity to observe and readjust so many critical parameters is that the internal environment of the body will stay constant despite the external ones. Long-term health and well-being should thus be taken care of by having a proper kidney care.
