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Page No 301: - Chapter 19 Excretory Products & Their Elimination class 11 ncert solutions Biology - SaraNextGen [2024]

Question 8:

What is meant by the term osmoregulation?


Osmoregulation is a homeostatic mechanism that regulates the optimum temperature of water and salts in the tissues and body fluids. It maintains the internal environment of the body by water and ionic concentration.

Question 9:

Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why?


Terrestrial animals are either ureotelic or uricotelic, and not ammonotelic. This is because of the following two main reasons:

(a) Ammonia is highly toxic in nature. Therefore, it needs to be converted into a less toxic form such as urea or uric acid.

(b) Terrestrial animals need to conserve water. Since ammonia is soluble in water, it cannot be eliminated continuously. Hence, it is converted into urea or uric acid. These forms are less toxic and also insoluble in water. This helps terrestrial animals conserve water.

Question 10:

What is the significance of juxtaglomerular apparatus (JGA) in kidney function?


Juxtaglomerular apparatus (JGA) is a complex structure made up of a few cells of glomerulus, distal tubule, and afferent and efferent arterioles. It is located in a specialised region of a nephron, wherein the afferent arteriole and the distal convoluted tubule (DLT) come in direct contact with each other.

The juxtaglomerular apparatus contains specialised cells of the afferent arteriole known as juxtaglomerular cells. These cells contain the enzyme renin that can sense blood pressure. When glomerular blood flow (or glomerular blood pressure or glomerular filtration rate) decreases, it activates juxtaglomerular cells to release renin.

Renin converts the angiotensinogen in blood into angiotensin I and further into angiotensin II. Angiotensin II is a powerful vasoconstrictor that increases the glomerular blood pressure and filtration rate. Angiotensin II also stimulates the adrenal cortex of the adrenal gland to produce aldosterone. Aldosterone increases the rate of absorption of sodium ions and water from the distal convoluted tubule and the collecting duct. This also leads to an increase in blood pressure and glomerular filtration rate. This mechanism, known as renin-angiotensin mechanism, ultimately leads to an increased blood pressure.

Question 11:

Name the following:

(a) A chordate animal having flame cells as excretory structures

(b) Cortical portions projecting between the medullary pyramids in the human kidney

(c) A loop of capillary running parallel to the Henle’s loop.


(a) Amphioxus is an example of a chordate that has flame cells as excretory structures. Flame cell is a type of excretory and osmoregulatory system.

(b) The cortical portions projecting between the medullary pyramids in the human kidney are the columns of Bertini. They represent the cortical tissues present within the medulla.

(c) A loop of capillary that runs parallel to Henle’s loop is known as vasa rectae. Vasa rectae, along with Henle’s loop, helps in maintaining a concentration gradient in the medullary interstitium.

Question 12:

Fill in the gaps:

(a) Ascending limb of Henle’s loop is ____________to water whereas the descending limb is___________to it.

(b) Reabsorption of water from distal parts of the tubules is facilitated by hormone____________.

(c) Dialysis fluid contains all the constituents as in plasma except   ________.

(d) A healthy adult human excretes (on an average) _______ gm of urea/day.


(a) Ascending limb of Henle’s loop is  to water, whereas the descending limb is to it.

(b) Reabsorption of water from distal parts of the tubules is facilitated by the hormone .

(c) Dialysis fluid contains all the constituents as in plasma, except .

(d) A healthy adult human excretes (on an average)  gm of urea/day.

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