The Kidney
The kidney has many vital roles to play in the excretory system of both mammals and fish, these are:
- Ensuring that the blood pressure stay the same
- Maintaining the water and mineral levels in the body
- To remove nitrogenous waste (products of metabolism) from the body
- Ensuring that the blood pressure stay the same
- Maintaining the water and mineral levels in the body
- To remove nitrogenous waste (products of metabolism) from the body
Blood pressure
The kidney ensures that the blood pressure stays the same by releasing a hormone into the blood, the hormone is called rennin. Rennin works by triggering angiotensin, which is used for narrowing blood vessels, and by narrowing the blood vessels the blood pressure will be higher. At the same time as the angiotensin is narrowing the blood vessels it is also stimulating the adrenal cortex, by producing aldosterone. This hormone makes the kidney keep an excess amount of sodium and water, which will also raise the blood pressure levels.
Maintaining the water and mineral levels
Kidneys is able to detects when there is too much, or not enough minerals or water in the body, this is done by:
Too much water - the hypothalamus is able to detect the excess water, through its osmoreceptors, which then tell the pituitary gland to produce more of the antidiuretic hormone (ADH). This hormone then tells the kidney to excrete a higher amount of water out of the nephron tubules.
Not enough water - the hypothalamus is able to detect the lack of water, through its osmoreceptors, which then tell the pituitary gland to produce more of the antidiuretic hormone (ADH). This hormone then tells the kidney to retain more water, which is done in the nephron tubules.
Mineral levels - the main mineral that must be maintained is sodium, which is maintained by the hormone aldosterone, which is secreted by the adrenal cortex when sodium levels are low, and this tells the kidney to reabsorb the needed amount of sodium.
Too much water - the hypothalamus is able to detect the excess water, through its osmoreceptors, which then tell the pituitary gland to produce more of the antidiuretic hormone (ADH). This hormone then tells the kidney to excrete a higher amount of water out of the nephron tubules.
Not enough water - the hypothalamus is able to detect the lack of water, through its osmoreceptors, which then tell the pituitary gland to produce more of the antidiuretic hormone (ADH). This hormone then tells the kidney to retain more water, which is done in the nephron tubules.
Mineral levels - the main mineral that must be maintained is sodium, which is maintained by the hormone aldosterone, which is secreted by the adrenal cortex when sodium levels are low, and this tells the kidney to reabsorb the needed amount of sodium.
Remove nitrogenous waste
The kidney removes nitrogenous waste by filtering the blood, this is how it it done:
The blood travels into the kidney through the renal artery, and as it enters the blood is split up and goes into the nephrons, which are the filtering units, and there are approximately one million nephrons in each kidney!!
The nephrons then filter out the blood, this is done by the glomerulus, which are located in each of the nephrons, the glomerulus is comprised of a network of capillaries that the blood flows through, it is there that the nitrogenous waste is removed. The waste then travels down a small tubule which effects the levels of the sodium, chloride, potassium, calcium, hydrogen, phosphate and pH. Some of which is restored back into the body, the remaining is set down into the bladder as urine. The filtered blood leaves the kidney through the renal vein, and travels back up to the heart.
The blood travels into the kidney through the renal artery, and as it enters the blood is split up and goes into the nephrons, which are the filtering units, and there are approximately one million nephrons in each kidney!!
The nephrons then filter out the blood, this is done by the glomerulus, which are located in each of the nephrons, the glomerulus is comprised of a network of capillaries that the blood flows through, it is there that the nitrogenous waste is removed. The waste then travels down a small tubule which effects the levels of the sodium, chloride, potassium, calcium, hydrogen, phosphate and pH. Some of which is restored back into the body, the remaining is set down into the bladder as urine. The filtered blood leaves the kidney through the renal vein, and travels back up to the heart.