Excretory Products and their Elimination Test -2

The blood plasma is filtered through the capillaries of the glomerulus into the capsule. The Bowman's capsule empties the filtrate into the proximal tubule that is also part of the duct system of the nephron. A glomerulus receives its blood supply from an afferent arteriole of the renal circulation

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.

Homeostasis is the maintenance of constant body temperature. It is mainly maintained by excretion and osmoregulation, which is the function of kidney.

Urinary bladder is absent in snake and bird because the urine of these is semi-solid consisting mainly of uric acid. The primary function of urinary bladder is to store urine in mammals. The urinary bladder cannot store semi-solid urine.

Ascending limb of Henle’s is not permeable to water. The descending limb is although permeable to water. Counter current exchange takes place between the loop of Henle’s and arteries surrounding it.

Nephrons are the physical unit or functional unit of kidney. Millions of nephrons are present in each kidney but physiological unit of kidney is urinigerous tubule.

adult human kidney is metanephric, the third and final excretory organ that develops in a vertebrate embryo. First embryonic tubules formed in vertebrates during embryonic development are pronephric.

The urinary bladder is a hollow elastic organ that functions as the body's urine storage tank. Urine produced by the kidneys flows through the ureters to the urinary bladder, where is it stored before passing into the urethra and exiting the body.

Each nephron consists Bowman’s cup, tubules and loops of Henle’s. filtration of blood occurs in glomerulus cells present in Bowman’s cup. Some materials are added to initial filtrate in distal convoluted tubule.

Inside the kidney, there are two zones, an outer cortex and an inner medulla. The cortex extends in between the medullary pyramids as renal columns called columns of Bertini.

• The human body loses water by sweating, excretion, and breathing. Sweating, excretion, and breathing are the different excretory mechanisms of the body. 
• The body loses excess electrolytes and ions through sweat. The body loses nitrogenous wastes and excess electrolytes through urine. The body loses carbon dioxide and a little amount of water in the form of vapor through breathing.

A ureotelic organism excretes excess nitrogen as urea. It is one of the three major forms of excretion of nitrogenous waste in organisms, the others being ammonotelism and uricotelism. Urea is less toxic than the ammonia excreted by ammonotelic organisms. It requires 0.05 L of water to excrete 1 g of nitrogen, approximately only 10% of that required in ammonotelic organisms. Ureotelic organisms include cartilaginous fish, some bony fish, adult amphibians and mammals. Humans can be described as being ureotelic organisms. Thus, option B is correct.

The nephrons are the functional unit of excretory organs, i.e., kidneys. Each nephron has two parts the glomerulus and the renal tubule. The renal tubule begins with a double walled cup-like structure, called as Bowman's capsule, which encloses the glomerulus. 

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.

Bowman's capsule is also called as capsula glomeruli, or glomerular capsule. It is a cup-like sac at the beginning of the tubular component of a nephron in the kidney that performs the first step in the filtration of blood to form urine. A glomerulus is enclosed in the sac. Fluids from blood in the glomerulus are collected in the Bowman's capsule (i.e., glomerular filtrate) and further processed along the nephron to form urine. Thus, option A is correct.

Animals accumulate ammonia, urea, uric acid, carbon dioxide, water and ions like $$Na^+$$, $$K^+$$, $$Cl^-$$, phosphate, sulphate, etc., either by metabolic activities or by other means like excess ingestion. These substances have to be removed totally or partially. Ammonia, urea and uric acid are the major forms of nitrogenous wastes excreted by the animals. Thus animals may be ammonotelic, ureotelic or uricotelic respectively depending on the major excretory substance. Ammonia is the most toxic form and requires large amount of water for its elimination, whereas uric acid, being the least toxic, can be removed with a minimum loss of water.

• The organs, tubes, muscles, and nerves that work together to create, store, and carry urine are referred to as the urinary system, which is another name for the renal system. The renal system filters the plasma of blood and regulates blood volume by excreting excess water in the form of urine. Urine transport follows a path through the kidneys, ureters, bladder, and urethra, which are collectively known as the urinary tract.
• Urine is essentially water, ions, and secreted molecules that leave the collecting duct of the many nephrons of the kidney and flow into the ureters. The ureters are two tubes that drain urine from the kidneys to the bladder. Each ureter is a muscular tube that drains into the bladder. Smooth muscle contractions in the walls of the ureters, over time, send the urine in small spurts into the bladder, the organ where urine is stored before it can be eliminated.
• The bladder is a hollow muscular organ shaped like a balloon. It sits in the pelvis and is held in place by ligaments attached to other organs and the pelvic bones. The bladder stores urine until enough of it accumulates for removal from the body. It swells into a round shape when it is full and gets smaller when empty.
• Nerves in the bladder are stimulated as the bladder fills with urine and becomes larger, which in turn stimulates the need to urinate. When you urinate, the brain signals the bladder muscles to tighten, squeezing urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax. As these muscles relax, urine exits the bladder through the urethra and leaves the body through an opening in the genital region that contains the urethra. When all the signals occur in the correct order, normal urination occurs, removing urine from the body.

The urinary system serves in urine production and its conduction outside the body. Lymphatic system  serves in body defense and fluid maintenance. The circulatory system is responsible for transport of respiratory gasses and digested food throughout the body. Respiratory system serves in exchange in respiratory gasses while integument system serves in the protection of body's interior and keeping it separated from surroundings.

Excretion is the removal of metabolic waste products from the body. The major excretory products are carbon dioxide, urea, ammonia, uric acid, guanine, etc. The storage of the excretory products in the body acts toxic for the cell and hampers metabolic activity. The major excretory organ in humans is the kidney. Other organs of excretion are lungs, skin, etc.

The nephron is the structural and functional unit of the kidney. The body of the nephron is composed of Bowman's capsule, proximal convoluted tubule (PCT), Loop of Henle and distal convoluted tubule (DCT). Hence proximal and distal convoluted tubules are parts of Nephron.