biology mcqs
Excretory Products & Their Elimination: MCQs
Test your understanding of excretory products, human excretory system, and kidney function with these multiple-choice questions.
Test Your Knowledge
Showing questions 81 - 100 of 169
81. In the kidney of the rabbit, the Loop of Henle is the part of –
The nephron, also called the uriniferous tubule, is the structural and functional unit of the kidney. It is composed of several distinct parts, including the Glomerulus, Bowman's capsule, Proximal Convoluted Tubule (PCT), Loop of Henle, and Distal Convoluted Tubule (DCT). Therefore, the Loop of Henle is an integral part of the uriniferous tubule.
82. In the kidney, the formation of urine involve the following processes arranged as –
Urine formation in the kidney is a complex process that occurs in three main steps, in a specific sequence: 1. Glomerular Filtration (Ultrafiltration): Blood is filtered in the glomerulus, producing a protein-free fluid called glomerular filtrate. 2. Tubular Reabsorption: Useful substances (like glucose, amino acids, most water and electrolytes) are selectively reabsorbed from the filtrate back into the blood. 3. Tubular Secretion: Waste products and excess ions that were not filtered are actively secreted from the blood into the filtrate. This sequential process ensures the efficient removal of wastes while conserving essential body components.
83. A severe fall in blood pressure disturbs the function of kidneys and reduces –
Blood flow through the glomerular capillaries occurs under significant pressure, known as glomerular hydrostatic pressure (GHP). This pressure is the primary driving force for glomerular filtration. A severe fall in systemic blood pressure directly translates to a decrease in GHP, which would then reduce the net filtration pressure (GFP) and consequently, the Glomerular Filtration Rate (GFR).
84. In a glomerulus –
The glomerulus is a tuft of capillaries supplied by an afferent arteriole and drained by an efferent arteriole. A crucial anatomical feature is that the afferent arteriole (which brings blood to the glomerulus) has a wider diameter than the efferent arteriole (which carries blood away). This difference in lumen diameter helps to maintain the high blood pressure necessary for efficient ultrafiltration within the glomerulus.
85. High blood pressure is maintained in glomeruli than in other capillaries because –
High blood pressure is essential within the glomerulus for effective ultrafiltration. This high pressure is maintained primarily because the efferent arteriole, which drains blood from the glomerulus, has a narrower diameter than the afferent arteriole that supplies blood to it. This creates a higher resistance to blood flow out of the glomerulus, leading to increased hydrostatic pressure within the glomerular capillaries, facilitating filtration.
86. Ultrafilatration occurs in a glomerulus when-
Ultrafiltration in the glomerulus occurs when the net filtration pressure is positive. This net pressure is calculated as Glomerular Hydrostatic Pressure (GHP) minus the sum of Blood Colloidal Osmotic Pressure (BCOP) and Capsular Hydrostatic Pressure (CHP). For filtration to proceed, the driving force (GHP) must be greater than the sum of the opposing forces (BCOP + CHP). Therefore, ultrafiltration occurs when colloidal osmotic pressure plus capsular pressure remain less than glomerular hydrostatic pressure.
87. Workers in deep mines usually suffer from dehydration because –
Deep mine environments are often hot and humid, leading to significant physiological stress. Workers in such conditions would experience extensive sweating as a thermoregulatory response. The skin contains numerous sweat glands that excrete sweat, which is composed of a large amount of water and some metabolic wastes including salts. This continuous and substantial loss of water and electrolytes through sweating leads to dehydration if not adequately replenished. *This explanation draws on general biological knowledge regarding sweating and dehydration, which is consistent with the source's description of skin as an excretory organ.*
88. Aquatic animals are mostly ammonotelic because –
Ammonotelism is a mode of excretion where the main excretory product is ammonia. Ammonia is highly toxic and necessitates a large amount of water for its excretion to dilute it to safe levels. Aquatic animals, living in an environment with an abundant supply of water, can readily excrete ammonia by diffusing it out across their body surface or gill epithelium, making this an energetically efficient excretory strategy for them.
89. Aldosterone stimulates the reabsorption of–
Aldosterone is a hormone released by the adrenal gland that plays a crucial role in regulating electrolyte balance and blood volume. Its primary action in the kidney is to induce the distal convoluted tubule (DCT) to reabsorb more sodium ions (Na+) and, consequently, water. This reabsorption helps to increase blood volume and pressure.
90. Glomerular filtration rate would be decreased by –
The Glomerular Filtration Rate (GFR) is directly influenced by the net filtration pressure. * An increase in renal blood flow or afferent arteriolar pressure would increase GHP, thus increasing GFR. * Constriction of the efferent arteriole would increase the pressure within the glomerulus (GHP), also increasing GFR. * Compression of the renal capsule would increase the capsular hydrostatic pressure (CHP), which is an opposing force to filtration. An increase in CHP would reduce the net filtration pressure, thereby decreasing the GFR.
91. In which part of excretory system of mammals can you first use the term ‘urine’ for contained fluid
The fluid in Bowman's capsule is initially a glomerular filtrate, which then passes through the PCT, Loop of Henle, and DCT, undergoing significant modifications (reabsorption and secretion). By the time the filtrate reaches the collecting tubules and collecting ducts, its composition has been fine-tuned and it is considered final urine. Therefore, the term 'urine' can first be appropriately applied to the fluid within the collecting tubule.
92. In public urinals, the urine on standing gives a pungent smell, due to –
The unpleasant or ammonical smell often associated with urine on standing is explicitly stated in the source to be due to the conversion of urea into ammonia by microbial action. Bacteria present in the environment or residual in the urinal break down urea, releasing volatile ammonia gas.
93. A person who is starving, that is not having food, water and beverages will have –
During prolonged starvation without food intake, the body initially utilizes stored carbohydrates, then fats, and eventually begins to break down proteins for energy. While protein breakdown produces ammonia (which is converted to urea), a person in a long hunger strike with only water intake would primarily focus on conserving water. This involves maximizing water reabsorption by the kidneys, leading to a highly concentrated but reduced volume of urine. Over a long period, if protein catabolism slows down or if the body goes into a state of protein conservation, the overall production and excretion of urea might decrease, leading to less urea in his urine (in terms of total output, not necessarily concentration per unit volume). *This explanation involves inferences and general physiological knowledge beyond the direct statements in the sources regarding starvation and urine composition.*
94. What is “renal threshold” –
The concept of 'tubular maxima' is closely related to renal threshold. The source defines 'tubular maxima' as the maximum amount of substance that can be retained in blood (meaning maximally reabsorbed by the tubules) and beyond which it will be excreted in urine. Therefore, the renal threshold represents the highest concentration of a substance in the blood (and thus in the filtrate) up to which it can be completely reabsorbed by the renal tubules, preventing its appearance in the urine.
95. The glomerular filtrate contains –
The process of ultrafiltration in the glomerulus separates small molecules from larger ones. The resulting nephric (glomerular) filtrate consists of water, electrolytes, glucose, amino acids, hormones, vitamins, urea, creatinine, and uric acid. Crucially, it excludes large-sized particles and structures like fats, proteins, platelets, leucocytes, and erythrocytes (blood cells). Therefore, the glomerular filtrate is essentially blood without its cells and proteins.
96. Which of the following terms refer to painful urination –
Dysuria is the medical term used to describe painful or difficult urination. *This term and its definition are not explicitly provided in the disorders list within the given sources, thus this explanation relies on general medical knowledge.*
97. In diabetes mellitus, the patient drinks more water as there is urinary loss of –
In diabetes mellitus, there is a characteristic condition called glycosuria, which means the presence of glucose in the urine. Due to high blood glucose levels exceeding the renal threshold, glucose remains in the filtrate. This excess glucose acts as an osmotic diuretic, drawing more water into the renal tubules and preventing its reabsorption. This leads to increased urine volume (polyuria), which in turn causes dehydration and increased thirst, prompting the patient to drink more water.
98. A patient who excretes large quantity of sodium in urine has –
The reabsorption of sodium ions (Na+) in the distal tubules and collecting ducts is primarily regulated by the hormone aldosterone. Aldosterone is produced and released by the adrenal cortex. If the adrenal cortex is diseased and its function is impaired (e.g., leading to insufficient aldosterone production), less sodium would be reabsorbed by the kidneys, resulting in the excretion of a large quantity of sodium in the urine.
99. A kidney stone is –
A kidney stone, medically termed Renal Calculi, is defined as an insoluble mass of crystallized salts formed within the kidney. These stones are often composed of substances like calcium oxalate, uric acid, or calcium phosphate, and they typically form in the broad funnel-shaped space of the renal pelvis.
100. Glycosuria is the terms used for –
Glycosuria is a medical term explicitly defined as the presence of glucose in urine. This indicates that glucose, which is normally completely reabsorbed in the PCT, is being lost from the body via the urine.