All questions of Excretion in Animals & Plants for JAMB Exam

The ans is D).PCT.
Acc. to NCERT nearly all the essential nutrients and 70-80% of the electrolytes and water are reabsorbed by this segment.i.e. PCT

The enzyme 'Renin' is secreted by the cells of juxtaglomerular apparatus (JG apparatus)..in response to decrease in GFR..option D

The least toxic form among the excretory products in animals is uric acid.

Explanation:
• Animals excrete waste products that are formed during metabolic processes.
• The excretory products are mainly classified into three types: ammonia, urea, and uric acid.
• Ammonia is highly toxic and water-soluble. It is excreted by aquatic animals, but not by terrestrial animals because of its toxicity.
• Urea is less toxic than ammonia and water-soluble. It is excreted by most terrestrial animals, including humans.
• Uric acid is the least toxic form among the three. It is insoluble in water and is excreted in the form of a paste or a solid.
• Uric acid is the excretory product of birds, reptiles, and insects. It is also excreted by some other animals, such as snails and spiders.
• Uric acid is less toxic than ammonia and urea because it requires less water for its excretion.
• The excretion of uric acid conserves water, which is essential for survival in arid environments.
• In humans, excess uric acid can lead to gout, a painful condition caused by the deposition of uric acid crystals in the joints.

Therefore, uric acid is the least toxic form among the excretory products in animals.

Erythropoietin is a peptide hormone that is released in response to low oxygen levels in kidney tissues. EPO stimulates the bone marrow to produce red blood cells.

Renal corpuscle, also called malpighian body, filtration unit of vertebrate nephrons, functional units of the kidney. It consists of a knot of capillaries (glomerulus) surrounded by a double-walled capsule (Bowman's capsule) that opens into a tubule.

The renal vein takes blood away from the kidney. The process starts with renal artery which enters the kidney as afferent arteriole. It carries the urea loaded blood into the glomerulus of the kidney. The blood is filtered by the glomerulus into the Bowman's capsule and runs parallel to the loop of Henle. The urea is absorbed into the nephric filtrate by the process of tubular secretion in the loop of Henle, distal convulated tubule and collecting duct. The process of tubular secretion helps to secrete the urea from the blood to the collecting duct which is finally excreted in form of urine. The purified blood comes from the kidney through the renal vein and drained into vena cava outside kidney.
So, the correct answer is 'Renal vein'.

The nephron is the microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and an encompassing Bowman's capsule.

Toxicity Ammonia > Urea > Uric acid

Angiotensin  is produced by the action of renin (an enzyme produced by the kidneys) on a protein called angiotensinogen, which is formed by the liver.

Hypertonic becz. its conc. is 1200 m.osml

Loop of helne part or excretory system... so relative the option..

The function of heart is different from the rest options in a way that heart is an organ that pumps blood throughout the body tissues and removing carbon dioxide and other wastes. And hence does not helps in excretion.

Micturition is the process of voiding urine from the body. During this process, the muscles of the urinary bladder and urethral sphincters play a crucial role in controlling the flow of urine. The correct answer to the given question is option 'A', i.e., the muscles of the urinary bladder will contract, and the urethral sphincters will relax.

Explanation:

The process of micturition involves the following steps:

1. Filling of the urinary bladder: The urinary bladder is a muscular sac that stores urine until it is eliminated from the body. As the bladder fills with urine, its walls stretch, and the pressure inside the bladder increases.

2. Sensory input to the spinal cord: The stretch receptors in the bladder walls send signals to the spinal cord, indicating that the bladder is full.

3. Activation of the micturition reflex: The spinal cord processes the sensory input and generates a reflex response that activates the muscles of the bladder and urethral sphincters.

4. Contraction of the bladder muscles: The muscles of the bladder wall contract, forcing urine out of the bladder and into the urethra.

5. Relaxation of the urethral sphincters: The urethral sphincters, which are circular muscles that control the flow of urine through the urethra, relax, allowing urine to pass out of the body.

Therefore, during micturition, the muscles of the urinary bladder will contract, and the urethral sphincters will relax to allow the flow of urine out of the body.

The ascending limb of Henle is a segment of the nephron in the kidney that is responsible for reabsorbing certain ions from the filtrate. It is located in the loop of Henle, which is a U-shaped structure that dips into the medulla of the kidney.

The ascending limb is divided into two parts: the thin ascending limb and the thick ascending limb.

The thin ascending limb is permeable to water but not to ions. As the filtrate moves up this segment, water is reabsorbed into the surrounding interstitial fluid through osmosis, leading to an increase in the concentration of the filtrate.

The thick ascending limb, on the other hand, is impermeable to water but actively reabsorbs ions, such as sodium (Na+), potassium (K+), and chloride (Cl-), through a process called active transport. This results in the further dilution of the filtrate and the establishment of a concentration gradient in the medulla of the kidney.

Overall, the ascending limb of Henle plays a crucial role in the formation of concentrated urine by reabsorbing ions and establishing a concentration gradient in the medulla.

Introduction:
The opening of the duct of Bellini is an anatomical feature that is relevant to the field of nephrology. It is important to understand the location and function of this opening to comprehend its significance in the renal system.

Explanation:
The duct of Bellini opens on the renal papilla. This opening allows urine to flow from the collecting ducts into the renal pelvis, which is a large funnel-shaped structure in the kidney. The renal papilla is located at the apex of each renal pyramid, which is a conical structure in the medulla of the kidney.

Renal Papilla:
The renal papilla is the terminal portion of the collecting duct system in the kidney. It is responsible for draining urine from the collecting ducts into the renal pelvis. The renal papilla contains multiple openings called the ducts of Bellini. These ducts are small tubules that transport urine from the collecting ducts to the renal pelvis.

Function of Duct of Bellini:
The duct of Bellini plays a crucial role in the process of urine formation and excretion. It serves as a conduit for the transport of urine from the collecting ducts, which are responsible for reabsorbing water and solutes, to the renal pelvis. This allows for the elimination of waste products and excess fluids from the body.

Importance of Knowing the Opening Location:
Understanding the location of the opening of the duct of Bellini on the renal papilla is vital for several reasons:

1. Surgical Procedures: Surgeons need to be aware of the location of the duct of Bellini to avoid damage during surgical interventions involving the kidney.

2. Urinary Tract Disorders: Knowledge of the opening location helps in diagnosing and treating various urinary tract disorders, such as kidney stones or urinary obstructions.

3. Nephrology Research: Researchers studying the renal system need to be familiar with the structure and function of the duct of Bellini to investigate kidney diseases and develop potential treatments.

Conclusion:
In conclusion, the duct of Bellini opens on the renal papilla. This opening allows for the transport of urine from the collecting ducts to the renal pelvis. Understanding the location and function of the duct of Bellini is crucial in the fields of nephrology, surgical interventions, and urinary tract disorders.

The parietal layer of Bowman's capsule consists of squamous epithelial cells resting on a basement membrane. The cells are of polygonal shape and contain prominent bundles of actin filaments running in all directions.

Regulation of Blood Pressure by Hormonal Feedback Mechanisms involving the Hypothalamus, JGA, and Heart

The main function of the hormonal feedback mechanisms involving the hypothalamus, JGA (juxtaglomerular apparatus), and heart is to regulate blood pressure. This involves a complex interplay between various hormones, organs, and feedback loops that work together to maintain blood pressure within a normal range.

1. Role of the Hypothalamus:
The hypothalamus plays a crucial role in regulating blood pressure through the release of hormones. It senses changes in blood pressure and activates the sympathetic nervous system to initiate appropriate responses.

2. Role of the Juxtaglomerular Apparatus (JGA):
The JGA is a specialized structure located in the kidneys that plays a key role in blood pressure regulation. It consists of juxtaglomerular cells and macula densa cells. The juxtaglomerular cells secrete the enzyme renin in response to decreased blood pressure or decreased sodium levels. Renin initiates a cascade of events leading to the production of angiotensin II.

3. Role of the Heart:
The heart also contributes to blood pressure regulation through the release of hormones. When blood pressure decreases, specialized cells in the atria of the heart called atrial natriuretic peptide (ANP) are released. ANP acts to relax blood vessels, reduce sodium reabsorption in the kidneys, and increase urine output, all of which help to lower blood pressure.

4. Renin-Angiotensin-Aldosterone System (RAAS):
The renin-angiotensin-aldosterone system is a hormonal pathway that plays a critical role in blood pressure regulation. When renin is released from the JGA, it converts angiotensinogen into angiotensin I. Angiotensin-converting enzyme (ACE) then converts angiotensin I into angiotensin II, a potent vasoconstrictor. Angiotensin II increases blood pressure by constricting blood vessels and stimulating the release of aldosterone from the adrenal glands. Aldosterone acts on the kidneys to increase sodium reabsorption and water retention, thereby increasing blood volume and blood pressure.

5. Negative Feedback Loop:
The hormonal feedback mechanisms involving the hypothalamus, JGA, and heart operate through a negative feedback loop. When blood pressure is too low, the hypothalamus stimulates the release of hormones to increase blood pressure. Once blood pressure returns to a normal range, the release of these hormones is inhibited, and blood pressure is maintained within a homeostatic range.

In conclusion, the main function of the hormonal feedback mechanisms involving the hypothalamus, JGA, and heart is to regulate blood pressure. This is achieved through the release of hormones such as renin, angiotensin, aldosterone, and atrial natriuretic peptide, which act on various organs and systems to increase or decrease blood pressure as needed.

Primary Function of the Proximal Convoluted Tubule (PCT)
The Proximal Convoluted Tubule (PCT) plays a crucial role in the nephron, primarily focusing on the reabsorption of essential nutrients.
Overview of the PCT
- The PCT is the first segment of the renal tubule after the Bowman's capsule.
- It is lined with epithelial cells that have microvilli, increasing the surface area for absorption.
Reabsorption of Essential Nutrients
- The PCT reabsorbs approximately 65-70% of the filtrate produced in the glomerulus.
- Key nutrients reabsorbed include:
- Glucose: Almost all filtered glucose is reabsorbed through specific transporters.
- Amino Acids: The PCT reabsorbs nearly all amino acids via active transport.
- Bicarbonate: Important for maintaining acid-base balance in the body.
- Electrolytes: Sodium and potassium ions are also reabsorbed, which is crucial for maintaining fluid balance.
Mechanisms of Reabsorption
- Active Transport: Utilizes energy to move molecules against their concentration gradient.
- Passive Diffusion: Some substances move along their concentration gradient without energy expenditure.
- Co-Transport: Nutrients like glucose and amino acids are often reabsorbed alongside sodium ions.
Importance of PCT Function
- Efficient nutrient reabsorption prevents the loss of vital substances in urine.
- It plays a significant role in regulating body fluid composition and ensuring homeostasis.
In summary, the primary function of the Proximal Convoluted Tubule is the reabsorption of essential nutrients, making it vital for maintaining overall health and metabolic balance.

Descending limb is the first part of the loop of Henle. It helps to maintain the concentration of urine. It is highly permeable to water thus water is readily reabsorbed from the descending limb by osmosis. It is impermeable to sodium and chloride ions. Thus the correct answer is option A.

Both the statements are correct
kidney and ureter are paired structure whereas urinary bladder is a single structure
and kidneys typically extend from T12 to L3, although the right kidney is often situated slightly lower due to the presence of the liver. Each kidney is approximately three vertebrae in length.

Yep,because our urine is composed of all the waste and liquid which gets filtered out from our impure blood in the nephron....where it goes from three parts mainly PCT - HENLEY'S LOOP - DCT and then to collecting tubule.

Role of the Distal Convoluted Tubule (DCT) in the Nephron
The Distal Convoluted Tubule (DCT) is a crucial segment of the nephron, playing a significant role in the reabsorption and secretion processes that regulate electrolyte balance, acid-base homeostasis, and overall fluid balance in the body.
Key Functions of the DCT:
- Selective Reabsorption:
- The DCT is primarily responsible for the reabsorption of important ions such as sodium (Na+) and chloride (Cl-).
- It also reabsorbs bicarbonate (HCO3-), which is essential for maintaining acid-base balance.
- Reabsorption of HCO3-:
- The correct answer, option 'C', highlights the DCT's role in the reabsorption of bicarbonate.
- This process is vital as bicarbonate acts as a buffer, neutralizing acids in the blood and helping to maintain a stable pH level.
- Active Secretion:
- The DCT is involved in the active secretion of various substances, including potassium (K+) and hydrogen ions (H+).
- This helps regulate potassium levels and plays a role in acid-base balance.
- Fluid and Electrolyte Balance:
- The reabsorption and secretion processes in the DCT are influenced by hormones such as aldosterone, which promotes sodium reabsorption and potassium secretion.
Conclusion:
In summary, the Distal Convoluted Tubule is primarily responsible for the reabsorption of bicarbonate (HCO3-), along with sodium and chloride, while also playing a role in electrolyte and acid-base balance. This function is critical for maintaining homeostasis in the body.