All questions of Excretory Products and their Elimination for NEET Exam

Nephron functional unit of kidney the structure that actually produces urin in the process of removing waste and excess substance from the blood.there are about 1000,000 nephron in each human kidney. nephron is the minet or microscope the renal cropuscle consists of a tuft of capillaries called a glomerulus and a cup- shaped structure called bowmens there types of nephron can be distinguished superficial ,midcortical and juxtamedullary nephron. A healthy adults has 1 to 1.5 million nephron per kidney. sir William bowmen first baronet discovered nephron .

Effects of removing one kidney from the human body:
Removing one kidney from the human body does not directly lead to death, poisoning, uremia, or stoppage of urination. The person can still survive with only one functioning kidney. Here are the effects of removing one kidney:

1. Compensation by the remaining kidney:
- The remaining kidney will compensate for the loss of the removed kidney by increasing its size and functioning capacity. It will take over the filtration and excretion of waste products from the body.

2. Maintenance of normal kidney function:
- The remaining kidney will continue to filter blood, remove waste products, and regulate electrolyte and fluid balance in the body. It will maintain normal kidney function.

3. Adaptation of the urinary system:
- The urinary system will adapt to the loss of one kidney by adjusting its filtration rate and reabsorption abilities. This ensures that the body can still eliminate waste products adequately.

4. No significant change in overall health:
- As long as the remaining kidney is healthy, the person can lead a normal, healthy life with one kidney. They can still perform regular activities and maintain overall health without any major complications.

5. Potential long-term effects:
- In some cases, individuals with a single kidney may have a slightly higher risk of developing kidney disease or experiencing kidney-related problems later in life. However, the risk is generally low, especially if the remaining kidney is functioning well.

6. Kidney donation:
- It is worth mentioning that kidney donation is a common procedure, where a healthy individual voluntarily donates one kidney to someone in need. These donors live with one kidney and continue to lead normal lives without any major health issues.

Conclusion:
Removing one kidney from the human body does not result in death, poisoning, uremia, or stoppage of urination. The person can survive with one kidney as the remaining kidney compensates for the loss and maintains normal kidney function. However, long-term monitoring of kidney health is recommended for individuals with a single kidney.

The juxtaglomerular apparatus is an important structure located in the kidney. It plays a crucial role in regulating blood pressure and kidney function. It is composed of three main components: juxtaglomerular cells, macula densa, and lacis cells.

1. Juxtaglomerular cells:
- Juxtaglomerular cells, also known as granular cells, are specialized smooth muscle cells found in the afferent arterioles of the kidney.
- These cells contain secretory granules called renin, which plays a central role in the regulation of blood pressure.
- When stimulated, juxtaglomerular cells release renin into the bloodstream, which initiates a cascade of events leading to the production of angiotensin II, a potent vasoconstrictor.
- Renin release is regulated by various factors, including blood pressure, sympathetic nervous system activity, and sodium levels in the kidney.

2. Macula densa:
- The macula densa is a group of specialized epithelial cells located in the distal convoluted tubule of the nephron, near the juxtaglomerular cells.
- These cells are sensitive to changes in sodium chloride concentration in the urine.
- When sodium chloride levels are low, the macula densa sends signals to the juxtaglomerular cells to release renin.
- This mechanism helps maintain appropriate sodium and water balance in the body by regulating blood pressure and kidney function.

3. Lacis cells:
- Lacis cells, also known as extraglomerular mesangial cells, are located between the afferent and efferent arterioles at the vascular pole of the renal corpuscle.
- These cells have contractile properties and contribute to the regulation of blood flow within the glomerulus.
- Lacis cells also provide structural support to the juxtaglomerular apparatus.

In summary, the juxtaglomerular apparatus is made up of juxtaglomerular cells, macula densa, and lacis cells. These components work together to regulate blood pressure and kidney function by sensing changes in sodium chloride concentration and releasing renin when necessary.

Urea is a nitrogenous waste formed as a result of metabolism of various food in the body as excreated in urine.so not taking food or beverages will have less urea in urine .so option B is correct

The Principal Nitrogenous Excretory Compound
The primary nitrogenous waste product in humans is urea. Understanding its synthesis and elimination is crucial for grasping human metabolism and excretion.
Synthesis of Urea
- Urea is synthesized in the liver through the urea cycle.
- This process converts ammonia, a toxic byproduct of protein metabolism, into urea, which is much less toxic.
Elimination of Urea
- Although urea is synthesized in the liver, it is primarily eliminated from the body through the kidneys.
- The kidneys filter the blood, removing urea and other waste products, which are then excreted in urine.
Importance of Urea Cycle
- The urea cycle is essential for detoxifying ammonia, preventing its accumulation in the body.
- By converting ammonia into urea, the liver plays a critical role in maintaining metabolic balance and homeostasis.
Conclusion
- The correct option is "D: in the liver, but eliminated mostly through the kidney."
- This highlights the liver's role in synthesizing urea and the kidneys' role in excreting it, emphasizing the collaborative function of these organs in human waste management.

Explanation of the Incorrect Statement
The correct answer to the question is option 'C', which states that blood enters the glomerulus through efferent arterioles. This statement is incorrect due to the following reasons:
Blood Flow in the Kidney
- Afferent Arterioles: Blood enters the glomerulus through afferent arterioles, not efferent arterioles. The afferent arterioles branch from the renal arteries and lead directly into the glomerulus, where filtration occurs.
- Efferent Arterioles: After blood is filtered in the glomerulus, it exits through the efferent arterioles. These arterioles carry the filtered blood away from the glomerulus to the peritubular capillaries and eventually back into the venous system.
Understanding Kidney Structure
- Cortex and Medulla: The kidney is divided into two main regions. The outer region is called the cortex, and the inner region is referred to as the medulla.
- Malpighian Corpuscles: These structures, which consist of glomeruli and Bowman's capsules, are located primarily in the cortical region of the kidney.
- Hilus of the Kidney: The hilus is the concave part of the kidney where blood vessels, nerves, and the ureter enter and exit the organ.
Conclusion
In summary, option 'C' is incorrect because blood enters the glomerulus through afferent arterioles, and not efferent arterioles. Understanding the correct flow of blood and the structures involved is crucial for comprehending kidney function and anatomy.

Explanation:

Haemoglobin:

Haemoglobin is a protein found in red blood cells that is responsible for carrying oxygen to the tissues and removing carbon dioxide from the body. It is not normally excreted in urine because it is a large protein molecule that is too large to pass through the filtration barrier in the kidneys.

Uric acid:

Uric acid is a waste product that is formed when the body breaks down purines, which are substances found in certain foods and in the body's own cells. It is excreted in urine and is the main component of kidney stones and gouty tophi.

Ketone bodies:

Ketone bodies are produced when the body breaks down fats for energy in the absence of carbohydrates. They are excreted in urine when their concentration in the blood becomes high, such as in uncontrolled diabetes or during fasting.

Hippuric acid:

Hippuric acid is a waste product that is formed when the body breaks down certain substances, such as benzoic acid, which is found in some fruits and vegetables. It is excreted in urine and is used as a biomarker for exposure to certain environmental toxins.

Summary:

Out of the options given, haemoglobin is not normally excreted in urine because it is a large protein molecule that is too large to pass through the filtration barrier in the kidneys. Uric acid, ketone bodies, and hippuric acid are all normally excreted in urine.

The correct option representing the parts of nephron that respectively absorb various substances is option 'C', which includes:

(i) Proximal Convoluted Tubule (PCT) - Absorption of Glucose
(ii) PCT - Absorption of Amino Acids
(iii) PCT - Absorption of Inorganic Ions (Na+, K+, Cl-)
(iv) Ascending Limb of Loop of Henle - Absorption of Urea

Let's discuss each of these parts in detail:

1. Absorption of Glucose:
Glucose is actively reabsorbed in the proximal convoluted tubule (PCT) of the nephron. This process is facilitated by glucose transporters (SGLT proteins) present on the apical membrane of the PCT cells. These transporters help in the co-transport of glucose along with sodium ions into the PCT cells. From there, glucose is transported out of the cells and into the peritubular capillaries via facilitated diffusion through glucose transporters (GLUT proteins) present on the basolateral membrane.

2. Absorption of Amino Acids:
Similar to glucose, amino acids are also actively reabsorbed in the PCT of the nephron. Amino acids are transported into the PCT cells via specific transporters on the apical membrane. Once inside the cells, amino acids are transported out into the peritubular capillaries through specific transporters on the basolateral membrane.

3. Absorption of Inorganic Ions (Na+, K+, Cl-):
Inorganic ions such as sodium (Na+), potassium (K+), and chloride (Cl-) are primarily reabsorbed in the PCT of the nephron. Sodium ions are actively transported out of the tubular lumen into the PCT cells through sodium-potassium ATPase pumps on the basolateral membrane. This creates a concentration gradient for sodium ions, allowing their passive reabsorption from the PCT cells into the peritubular capillaries through sodium channels. Chloride ions follow the movement of sodium ions passively through facilitated diffusion. Potassium ions are also reabsorbed along with sodium ions in the PCT.

4. Absorption of Urea:
Urea is primarily reabsorbed in the ascending limb of the loop of Henle. It is passively reabsorbed through urea transporters present on the apical membrane of the tubular cells. These transporters allow the movement of urea down its concentration gradient from the tubular lumen into the interstitial fluid. From there, urea can be reabsorbed into the bloodstream through the vasa recta capillaries.

In summary, the correct option 'C' represents the parts of the nephron that are involved in the absorption of glucose (PCT), amino acids (PCT), inorganic ions (Na+, K+, Cl-) (PCT), and urea (ascending limb of the loop of Henle).

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Matching Column-I with Column-II:

Column-I | Column-II
-------- | ---------
(A) PCT | (iii) Reabsorption of 70-80% electrolytes
(B) DCT | (iv) Ionic balance
(C) Loop of Henle | (i) Concentrated urine formation
(D) Counter-current mechanism | (v) Maintenance of concentration gradient in medulla
(E) Renal corpuscle | (ii) Filtration of blood

The correct option is (a) A-(iii), B-(iv), C-(i), D-(v), E-(ii).

Explanation:

- PCT (Proximal Convoluted Tubule) is responsible for the reabsorption of 70-80% electrolytes from the filtrate.
- DCT (Distal Convoluted Tubule) is responsible for maintaining the ionic balance of the body by regulating the levels of sodium, potassium, and calcium ions.
- Loop of Henle is responsible for the formation of concentrated urine by creating a concentration gradient in the medulla.
- Counter-current mechanism is the exchange of fluids that occurs in the loop of Henle, which helps in maintaining the concentration gradient in the medulla.
- Renal corpuscle is responsible for the filtration of blood and the formation of the initial filtrate.

Hence, option (a) correctly matches the functions of each structure in the nephron.

Possible Clinical Symptom: Anuria and Haematuria

Anuria refers to the absence of urine production, while haematuria refers to the presence of blood in the urine. In the context of a suspected ureteric calculus (stone), anuria and haematuria are possible clinical symptoms.

1. **Ureteric Calculus:** A ureteric calculus is a stone that forms in the ureter, the tube connecting the kidneys to the bladder. When a calculus obstructs the ureter, it can lead to various symptoms.

2. **Obstruction and Urine Flow:** The presence of a calculus in the ureter can cause partial or complete obstruction, blocking the normal flow of urine from the kidneys to the bladder.

3. **Increased Pressure:** The obstruction caused by the calculus leads to an increase in pressure within the urinary system, particularly in the kidneys and ureters.

4. **Anuria:** The increased pressure within the urinary system can impede the formation and flow of urine. In severe cases, this can result in anuria, where little or no urine is produced.

5. **Haematuria:** The presence of a ureteric calculus can cause irritation, inflammation, and sometimes injury to the lining of the ureter. This can lead to blood being released into the urine, resulting in haematuria.

6. **Other Possible Symptoms:** In addition to anuria and haematuria, other possible symptoms of a ureteric calculus may include severe flank or abdominal pain, referred pain to the groin or genitals, urinary urgency, frequency, or hesitancy, and possible urinary tract infections.

7. **Clinical Evaluation:** A suspected ureteric calculus is typically assessed using various diagnostic tests, including X-rays, ultrasound, CT scans, and urine analysis. An X-ray of the lower abdomen may reveal a shadow in the region of the ureter, indicating the presence of a calculus.

8. **Management:** The management of a ureteric calculus depends on various factors, such as the size, location, and symptoms associated with the stone. Treatment options may include conservative management with pain relief and hydration, medical therapy to facilitate stone passage, or surgical intervention such as extracorporeal shock wave lithotripsy (ESWL) or ureteroscopy.

In conclusion, a shadow in the region of the ureter on an X-ray of the lower abdomen, suspected to be a ureteric calculus, can present with symptoms such as anuria and haematuria due to obstruction and increased pressure within the urinary system. Prompt diagnosis and appropriate management are necessary to alleviate symptoms and prevent complications.