Excretory Products and their Elimination Test - 15

Urea is formed in the liver by a cyclic process called a urea cycle of ornithine cycle or Knely Henseleit cycle. The amino acids that are not needed in the body are deaminated by an enzyme oxidase, producing ammonia NH₃. Ammonia is toxic and quickly changes to urea.

The Malpighian corpuscle (i.e., glomerulus and Bowman's capsule), PCT (proximal convoluted tubule) and DCT (distal convoluted tubule) of the nephron are situated in the cortical region of the kidney, whereas the loop of Henle dips into the medulla. 
The DCTs of many nephrons open into a straight tube, called as collecting duct, many of which converge and open into the renal pelvis through medullary pyramids in the calyces. Thus, collecting ducts are not found in the cortex of the kidney.
So, the correct answer is option C.

Eliminate options B ,C and D
as they are incorrect - saliva helps in mixing of food,sebum are secreted by oil glands on skin and is not related to sexual attraction and humerus are forelimbs.
Hence, option A is correct.  
Sweating helps in cooling the body temperature, and therefore in summer we sweat more.

Malpighian corpuscles are a number of small, round, deep-red bodies in the cortex of the kidney, each communicating with a renal tubule. Malpighian corpuscles average about 0.2 mm in diameter. Each capsule is composed of two parts: a central glomerulus and a glomerular capsule or Bowman's capsule. The corpuscles are part of a filtering system through which nonprotein components of blood plasma enter the tubules for urinary excretion

So, the correct answer is 'Cortex'.

Nephrons are the cells of kidney which are composed of a renal corpuscle and a renal tubule.  The renal corpuscle is also known Malpighian body. It consists of cup like double walled structure known as Bowman’s capsule and the bunch of capillaries present in the Bowman’s capsule is known as glomerulus. The blood enters the glomerulus under high pressure from the afferent arteriole and leaves through efferent arteriole.
So, the correct answer is 'Afferent arteriole'.

The metanephric kidneys are a paired compact organ whose functional units are nephrons. The nephrons filter initial urine from the blood, reabsorbing water and nutrients, and secrete wastes, producing the final urine, which is expelled. In rabbit and humans, the kidney is metanephric.

Proximal convoluted tubule (PCT) is lined by simple cuboidal brush border epithelium. The brush border epithelium increases the surface area for reabsorption. Nearly all of the essential nutrients, and 70-80 percent of electrolytes. Hence brush border is characteristic of the proximal convoluted tubule.
So, the correct answer is 'Proximal convoluted tubule'.

In the blood supply of the kidney, the vasa recta are a series of straight capillaries in the medulla. They lie parallel to the loop of Henle. These vessels branch off the efferent arterioles of juxta-medullary nephrons (those nephrons closest to the medulla), enter the medulla, and surround the loop of Henle. They participate in a mechanism, called as countercurrent exchange, which is needed for the production of concentrated urine.

The afferent arteriole is of larger diameter than the efferent, due to which blood pressure in the efferent arteriole is higher than the blood pressure in the afferent arteriole. As the blood is forced from a wider vessel to a narrower high resistance is created, producing the back-up of blood in the glomerulus and promoting ultrafiltration.

The afferent vessel and efferent arteriole is arterial in nature. The renal artery enters the kidney and breaks into several arteriole. The arteriole enters the glomerulus as afferent arteriole and supplies oxygenated, urea loaded blood to the glomerulus. The blood is filtered out by ultrafiltration and the deoxygenated blood leaves the glomerulus as efferent arteriole. The efferent arteriole further breaks into capillaries and forms vasa recta which further joins to form the renal vein.

The correct answer is option 'A'.

The Bowman's capsule has an outer parietal layer composed of simple squamous epithelium. The visceral layer, composed of modified simple squamous epithelium.

Amphibians have mesonephric type of kidneys which are primitive compared to metanephric kidneys.
Mesonephric kidneys do not have nephrons but their nephrons do not contain a loop of Henle.
So, the correct option is B.

A loop of Henle is long, a U-shaped portion of the tubule that conducts urine within each nephron of the kidney of reptiles, birds and mammals. The principal function of the loop of Henle appears to be the recovery of water and sodium chloride from the urine. This function allows production of urine that is far more concentrated than blood, limiting the amount of water needed as intake for survival. Many species that live in arid environments such as deserts have highly efficient loops of Henle. So, the loop of Henle is highly developed in animals who lives in the desert than salamanders, freshwater fishes, and lizards.

Therefore, the correct answer is option D.

Mammals are known to be the most advanced creatures with well-developed body systems. The mammals are composed of the metanephric form of the kidney which contains the nephrons. The structure of nephrons is comprised of glomerular apparatus, PCT, Henle's loop and DCT. The Henle's loop is responsible for the reabsorption of water and salts.
Thus, the correct answer is option A.

Mesonephros develops by the formation of mesonephric tubules from the intermediate mesoderm, it is the principal excretory organ during early embryonic life (4—8 weeks). Metanephros arises caudal to the mesonephros at five weeks of development; it is the permanent and functional kidney in higher vertebrates.

The mammalian kidney, the metanephros, is a mesodermal organ classically regarded as arising from the intermediate mesoderm (IM). Indeed, both the ureteric bud (UB), which gives rise to the ureter and the collecting ducts, and the metanephric mesenchyme (MM), which forms the rest of the kidney, derive from the IM.

There are two kidneys in the frog. The kidneys are nearly identical in position. The kidney is trilobulated and there is no cortex or medullary region represented in the case of frogs. The loop of Henle are absent and the malphigian tubules are scattered in the kidney. The excretory wastes are drained form the coelomic fluid into the coelom by an opening of the kidney called nephrostomes. 

Thus, the correct answer is option C.

On the basis of development, kidneys are of 3 types.

(1) Pronephric kidney: Develop from anterior part (pronephros) of nephrotome plate. Its nephrons are simple tubular in shape. Nephrons are not differentiated. For example, cyclostomes and tadpole of the frog.

(2) Mesonephric kidney: Develop from middle part (mesonephros) of nephrotome plate and remaining part of nephrotome is destroyed. Only Bowman's capsule is found in nephrons while remaining part is simple tubular. For example, most of the fishes and adult Amphibians.

(3) Metanephric Kidney: Develops from posterior part (metanephros) of nephrotome while remaining part is destroyed. Nephrons are well differentiated into Bowman's capsule,  PCT, DCT and loop of Henle's eg. Reptile, Aves, Mammals.

Therefore, the correct answer is option B.

Blood plasma contains red and white blood cells, blood proteins, glucose, water, nitrogenous wastes, salt. Glomerular filtrate contains glucose, salt, water, nitrogenous wastes. Blood cells and plasma proteins are not filtered through the glomerular capillaries because they are relatively larger in size.

So, the correct answer is 'Proteins'

Through umbilical cord and placenta excretory products of embryo reach mothers blood. Then as usual, mothers blood is filtered in kidneys.

Anuria means non passage of urine, in practice is defined as passage of less than 100 milliliters of urine in a day. Anuria is caused by failure in the function of kidneys. It may also occur because of some severe obstruction like kidney stones or tumours. It may occur with end stage renal disease.

Diuresis is a condition of production of excessive urine. It is a condition when kidney filters more excess of liquids. It is caused due to reduced reabsorption of fluids in the kidney. It can be caused due to excess of blood glucose level during diabetics. The excess glucose can accumulate and block the reabsorption of water. It is also caused during hypercalcaemia where excess of calcium accumulates in the blood. The kidneys may increase urine output in order to balance calcium levels. So, the correct answer is “The excretion of volume of urine increases”.

Modification of ultrafiltrate, by reabsorption and secretion, transforms it into urine. Glomerular pressure is about 75 millimeters of mercury (10 kPa). It is opposed by osmotic pressure (30 mmHg, 4.0 kPa) and hydrostatic pressure (20 mmHg, 2.7 kPa) of solutes present in capsular space.

The glomerular filtrate contains a large amount of water and other dissolved substances such. as urea, uric acid, creatinine, amino acids, glucose; sodium, potassium, vitamins, etc. The blood after filtration flows into efferent renal arterioles.

Animals that excrete excess nitrogen in the form of ammonia are called ammonotelic. Excretion of ammonia occurs in aquatic animals (aquatic invertebrates, fishes, larvae, permanently aquatic amphibia). The route of ammonia diffusion in these animals is through skin, gills or kidneys. In mammals and semi terrestrial adult amphibians, urea is a major nitrogenous excretory product, therefore these animals are called ureotelic.

Hepatic vein is the vein which carries the blood from the liver. 
Hepatic portal vein supplies blood from liver to intestine. 
Dorsal aorta is the renal artery which supplies blood to the kidney. 
The blood in the renal vein will contain less urea than the renal artery, because having passed through the kidney, urea leaves the blood through pressure filtration at the glomerulus with only a small amount being passively reabsorbed at the proximal convoluted tubule.
Thus, the correct answer is option B

The process of excreting ammonia is ammonotelism. Many bony fishes, aquatic amphibians, frog larva i.e., tadpole and aquatic insects are ammonotelic in nature. Ammonia, as it is readily soluble, is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions. Kidneys do not play any significant role in its removal.

The medical name for blood in the urine is haematuria. If blood in the urine can be observed with the naked eye, it is called "macroscopic", or "visible haematuria". If the blood can only be detected with laboratory testing, it is called "microscopic", or "non-visible". Haematuria is usually painless and not accompanied by other symptoms. When microscopic, it may be found on routine urinalysis when red blood cells have passed from the damaged glomeruli into the filtrate.