Human Excretion and Kidney Physiology

The blood leaves the glomerulus through efferent arteriole. They play an important role in maintaining the glomerular filtration rate despite fluctuations in blood pressure.

A glomerulus is a network (as a tuft) of capillaries located at the beginning of a nephron in the kidney. It serves as the first stage in the filtering process of the blood carried out by the nephron in its formation of urine. The glomerulus is surrounded by a cup-like sac known as Bowman's capsule.

It is partly responsible for the regulation of potassium, sodium, calcium and pH. It is the primary site for the kidneys' hormone based regulation of calcium (Ca).

Spironolactone opposes the actions of aldosterone and so, has the opposite effect. It is an aldosterone receptor antagonist that causes the kidneys to remove water and sodium from the body, with reduced losses of potassium.

The process of passing out of urine from the body is known as micturition.

Accumulation of nitrogenous waste products in the blood is an indication that the kidneys are not functioning properly. Kidneys play a critical role not only in excreting waste products, but also in maintaining electrolyte and water balance. As kidney function declines, nitrogenous waste products, i.e. blood urea nitrogen (BUN), and creatinine accumulate.

In crustaceans like prawns, paired green glands are the excretory organs. In insects like cockroaches, malpighian tubules perform the task of excretion.

Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as urine flows along the tubular part of the nephron. So, option 3 is correct.

Kidney contains extraglomerular mesangial cells.

Renin is secreted by juxtaglomerular cells of kidney.

When the body temperature begins to rise, a negative feedback response works to counteract and stop the rise in temperature. Thus, sweating is a suitable example of negative feedback.

The kidney is the primary excretory organ that filters blood and removes water, metabolic wastes, and excess substances including fat breakdown products. While skin does excrete water and salts through sweat, the kidney is responsible for comprehensive filtration and excretion of various catabolic wastes from the body.

 The kidneys remove waste products from the blood and produce urine.

Role of sodium and potassium ions in the body is to maintain the body osmotic pressure. Whenever there is an increase in sodium and potassium concentration in the blood, the kidney releases most of it in order such that there will be enough water for use by the body. But when there is a decrease in their concentration, there is more release of water to store more sodium which the body needs dearly. This process is known as osmoregulation. 

Approx. 95% of the volume of normal urine is due to water. The other 5% consists of solutes (chemicals that are dissolved in the water). Some of these solutes are the result of normal biochemical activity within the cells of the body. Other solutes may be due to chemicals that originated outside of the body, such as pharmaceutical drugs.