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Regulating kidney function is very crucial as the prime function of this organ is to remove waste and extra water from blood in the form of urine. Apart from waste removal, the kidney also plays a role in some important functions for the body.
- It maintains the balance of chemicals like sodium, potassium and calcium.
- Kidney makes the hormones that control the blood pressure in the body.
- The two 2 kidneys, together filter out almost 200 liters of fluid everyday.
- The extra water from blood is turned into urine which is collected into the bladder.
- Kidney is protected by ribs and the function of the kidney is regulated by some hormones and organ systems in the body.
| Table of Content |
Key terms: Kidney, Hypothalamus, Juxtaglomerular, Urine, Renin-Angiotensin system.
Structure of Kidney
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Kidneys are a pair of bean-shaped organs protected by ribs. Each kidney is approximately 3 cm thick, 6 cm wide, and 12 cm long. Male have a kidney of about 129 grams for right and 137 for left one whereas a female kidney is about 108 grams in right and 116 grams for left side kidney.
- A fibrous renal capsule surrounds both kidneys and gives support to them.
- The adrenal gland is situated on the top of each kidney.
- Inside area of each kidney has numerous pyramid shaped lobes.
- These lobes contain the outer renal cortex and inner renal medulla.
- There is a nephron that contains a filter, called glomerulus and also includes tubules.
- The filtered blood enters the kidney by renal arteries and it leaves by renal veins.
- Glomerulus filters the blood while tubule returns the necessary substance to blood.
- With the help of all these mechanisms, the kidney plays the role of waste removal by excreting urine through the ureter.
- The ureter is the tube that opens into the bladder.
- Excreted urine will be collected into the bladder and will be excreted outside the body.
Structure of kidney and its parts
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Functions of Kidney
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The main role of the kidney is to filter the blood and remove toxins or unnecessary substances from it. It converts the waste into urine. Kidneys perform many functions to clean our blood and maintain it chemically balanced. The important functions of the kidney are as listed below.
- Filtering the blood to remove toxins and waste products of metabolism.
- Balancing the electrolytes (Sodium and Potassium, the most important electrolyte) and controlling the acid-base balance.
- Secretions of many essential hormones that are necessary for normal body functions..
- Kidneys give site to the adrenal gland that secretes ALD hormone (regulating blood volume and pressure).
- Another hormone kidney secretes is the renin which also helps keep blood pressure normal.
- Erythropoietin is also secreted by the kidney that acts on bone marrow to increase the red blood cells’ production.
- Kidney also activates Vitamin D.
Regulation of Kidney Function
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To regulate the main kidney function i.e. filtering the blood and ionic balance are regulated by osmoreceptors. Hypothalamus is involved in this regulation by osmoreceptors.
Regulation Through Hypothalamus
If any change in blood volume, pressure or iconic balance is recognized in the body, osmoreceptors get activated. This triggers the hormone vasopressin and antidiuretic (ADH) from the neurohypophysis. In order to prevent the water loss and diuresis, ADH stimulates the reabsorption of water from the tubules. When the body fluid is sufficient enough, the receptors get inactivated or switched off thereby ADH gets suppressed and maintains the normal filtration.
Hormone ADH also constricts the blood vessel to increase the blood pressure and thus raises the blood flow in glomerulus and glomerular filtration rate is increased.
Regulation by Juxtaglomerular Apparatus
Increasing the blood flow in glomerulus is also caused by juxtaglomerular cells.
- When there is a decreased blood flow in glomerulus, juxtaglomerular cells release renin.
- The renin-angiotensin mechanism is the other term for regulation by juxtaglomerular apparatus.
- Renin converts the angiotensin in angiotensin I and angiotensin II.
- The later factor is a strong vasoconstrictor causing the increased blood flow and glomerular filtration rate.
- Like ADH, ALD secreted by adrenal cortex, causes the reabsorption of water and sodium from the distal tubules and maintains the blood pressure as well as filtration rate.
- ALD is stimulated to do so by activated angiotensin II.
- One more factor involved in this regulation mechanism is Atrial Natriuretic Factor (ANF).
- It acts on the kidney to increase the sodium excretion and filtration rate in order to antagonize the renal vasoconstriction and to prevent the renin secretion.
ANF gets activated when the blood flow is increased in the atria of the heart, causing the vasodilation to decrease the flow in blood vessels.
Things to Remember
- Kidney is a bean-shaped organ, present in a pair in the abdomen.
- The structure of the kidney includes nephrons, glomerular, tubules, renal arteries and veins, capsule and the ureter.
- Glomerular is responsible for the blood filtration and tubules return the necessary substance to the blood.
- It works mainly for cleansing the blood and balancing the electrolytes.
- Kidney secrets essential hormones for normal body function
- Regulation of kidney function is controlled by hypothalamus and juxtaglomerular apparatus which is nothing but osmoreceptors and renin-angiotensin system.
- All together, maintains the blood flow by constricting the vessel, reabsorption of water and sodium and preventing the water loss.
- Hormones like ADH and ALD, ANF and angiotensin II are involved to increase the blood pressure and filtration rate in the glomerular.
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Sample Questions
Ques. What are the main functions of the kidney? (3 marks)
Ans. The kidney plays an important role in the human body as it functions in blood filtration, waste and toxins removal, hormone secretion and balancing the electrolytes in the blood.
- It filters almost 200 liters of fluid every 24 hours.
- Kidney gives site to adrenal gland that secretes aldosterone for regulation of blood pressure and volume.
- Hormones like renin and angiotensin are secreted by the kidney that helps regulate blood flow.
- It also secretes erythropoietin for red blood cells’ production. Furthermore, vitamin D is activated by the kidney.
Ques. Write a note on the structure of the kidney. (4 marks)
Ans. Kidney is a bean-shaped organ that works in pairs. Both the kidneys are situated at the abdomen and have an adrenal gland on the top of each. The kidney has a fibrous capsule to support the inside tissues.
Along with this, the kidney includes nephrons, tubules, glomerular, renal arteries and veins, and ureter.
The glomerular filters the blood and the tubule is responsible to return the substances which are necessary to blood.
Blood enters the kidney from renal arteries and it exists by renal veins.
The ureter is the tube that opens into the bladder. Urine is collected in the bladder via the ureter.
Ques. What is the role of the renin-angiotensin system? (2 marks)
Ans. The renin-angiotensin system functions in maintaining the blood volume,flow and glomerular filtration rate. Renin is released and converts angiotensin in blood to angiotensin I and angiotensin II.
Angiotensin II is a strong vasoconstrictor that increases blood flow. It also stimulates the ALD and helps to maintain the blood volume by reabsorption of water and the glomerular filtration rate.
Ques. List down the name of hormones secreted by the kidney and their functions. (2 marks)
Ans. Kidney secretes some important hormones which are necessary for normal body functions.
- Aldosterone released from the adrenal gland, situated on top of the kidney. It helps to regulate blood volume and electrolyte balancing.
- Erythropoietin- For the production of red blood cells.
- Renin- Activation of angiotensin I and II.
Ques. How is the hypothalamus involved in the regulation of kidney function? (3 marks)
Ans. Regulation by Hypothalamus:
When any change in blood volume, ion concentration or pressure is recognised, it is sensed by osmoreceptors and it triggers activation of vasopressin and antidiuretic from neurohypophysis. ADH causes the reabsorption of water from the distal part of the tubule and increases the blood volume. If the fluid volume is sufficient enough, the receptors get inactivated and it suppresses the ADH. ADH also constricts the vessels to increase the blood flow and pressure in the glomerulus, consequently increasing the filtration rate in glomerulus.
Ques. The blood flow is increased in the arteries of the heart, which of the following will get activated to regulate the flow? (1 mark)
(a) ANF
(b) ALD
(c) ADH
(d) renin
Ans. a. ANF
Explanation: The ANF stands for atrial natriuretic factor which gets activated when there is increased blood flow in the artery of the heart. It causes vasodilation and decreases the flow in the vessel. Other given options are hormones that regulate the blood volume, pressure and filtration rate. Therefore, the correct answer is option a.
Ques. Write about the location and role of adrenal gland in the regulation of kidney function. (2 marks)
Ans. Location: The adrenal gland is located on the top of each kidney.
Function: It releases the aldosterone that regulates the blood flow, volume and pressure. ALD is stimulated to cause the reabsorption of water from tubules to increase the blood volume. ALd also balances the electrolytes in the blood.
Ques. Which ions are balanced by the kidney? (1 mark)
Ans. Kidney balances the ions like calcium, sodium and potassium, the most important electrolytes in the blood.
Ques. How is the juxtaglomerular apparatus involved in the regulation of kidney function? (5 marks)
Ans. Regulation by juxtaglomerular apparatus:
Apart from hypothalamus, blood flow and filtration rate is also regulated by juxtaglomerular apparatus. Juxtaglomerular apparatus is also called the renin-angiotensin system. Renin converts angiotensin in angiotensin I and II. The angiotensin II is a strong vasoconstrictor that increases the blood flow and pressure, it also stimulates the aldosterone to reabsorb the water from the tubule.
When the blood flow is increased in the arteries of heart, atrial natriuretic factor is activated and causes vasodilation to decrease the blood flow in the blood vessel. This factor also acts on the kidney to increase the sodium excretion to antagonize the renin secretion when required and maintains the blood flow and filtration rate.
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