Monday, 28 April 2014

TEXTBOOK ANSWERS AND SOLUTIONS Chapter-19-Excretory Products & Their Elimination CBSE-CLASS-XI-BIOLOGY

1) Define Glomerular filtration Rate (GFR)

     The amount of the filtrate formed by the kidney per minutes is called Glomerular filtrations

2) Explain the auto regulatory mechanism of GFR.

     The kidneys have built in mechanisms for the regulation of glomerular filtrations rate. One such efficient mechanism is carried out by juxta glomerular apparatus (JGP). It is special sensible region formed by cellular modifications in the distal convoluted tubules & the afferent arterioles cells to release their which was stimulate the Glomerular blood flow & thereby the GFR back to normal.

8) Indicate whereas the following statement is true or false

a) Maturation is carried out by a reflex
b) ADH helps in water elimination making the urine hypotonic
c) Protein free fluids filtered from blood plasma into Bowman’s capsule.
d) Henle’s loop always plays an important role in concentrating the urine
e) Glucose is actively reabsorbed in the proximal convoluted tubule

a) True  b) false   c) true   d) true   e) true

9) Match the column

              Column I                Column II
a) Ammonotelism                   I) Birds
b) Bowman’s capsule               ii) water reabsorption
c) Maturation                iii)  Bony fish
d) Uricotelism                    iv) urinary bladder
e) ADH                       v) Renal tubule

     Ans -         (a) – (iii)
              (b) – (v)
              (c) – (iv)
              (d) – (i)
              (e) – (ii)

5) What is meant by the term osmoregulation?
     It is the maintenance of fixed osmotic concentration inside the body cells & the extracellular fluids by controlling the amount of water and salts.

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

     Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and is called ureotelic animals. Ammonia produced by metabolism is converted into urea in the liver of these animals & release into blood which in filtered & exerted out by the kidneys. Some amount of urea may be retained in the kidney matrix of some of these animals to maintains desired osmolarity reptiles, birds, land snails& insects excrete nitrogenous waste as uric acid in the form of pellet or paste with minimum loss of water & are called uricotelic animals

7) Name the following:

a) A chordate animal having flame cell as execratory structures  Ans. – Amphioxus
b) Cortical portions projecting between the medullar pyramids in human kidney Ans – Columns of bertin
c) Loop of capillary running parallel to henry’s loop Ans – vas rectum
     Fill in the blanks

8)   A) Ascending limb of henle’s loop is ____________to water
     as descending limb is _______________to it

     b) Reabsorption of water from distal parts of tubules facilitated by hormone _________________________.

     C) Dialysis fluid contains all constituents as in plasma except _____________

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

          Ans.      a = Impermeable, permeable
              b = ADH
               c = nitrogenous waste
              d = 20 – 30 gm.

9) Give a brief account of the counter current mechanism.

     The counter current mechanism helps to concentrate the filtrate which occurs in the loop of henls & vasa rectum in the medulary region of kidney

              Fig – ncert book

     The flow of filtrate in the two limbs of loops of henle Is in opposite directions and thus forms a counter current. The flow of blood in the two limb of vasa recta is also in opposite direction & therefore forms a counter current.

10) Describe the role of liver, lungs & shin in excretion.

     Role of liver – urea is formed in the liver which is eliminated through kidneys liver cells also degrade the hemoglobin of worn out red blood corpus ells into bile pigment (bilirubin & biliverdin) liver cells also excrete cholesterol, certain products of steroid hormone some vitamin. Liver secrets these substances in the bile. The bile carries these substances to the urethra & is poured out with penis.

     Role of lungs- human lungs regularly remove about 18 lit of co2/hour & about 400 ml of water/day in normal resting condition. Water loss through the lungs is small in hot humid climate & large in coed dry climate. These Co2 & water (both are metallic wastes reduced during oxidation of food is the cells) are removed in via lungs.

     Role of skin– In aquatic animals’ ammonia is mainly excreted out into the surrounding water by diffusion through the skin. Human skin has two types of glands:

              Sudoriferous (sweat) glands
              Sebaceous (oil) glands

     Sudoriferous glands – Secrete an aqueous fluid called sweat sweat contains water (99.5%) near urea lactic acid, amino acids & glucose. Sweat desert contain uric acid. The volume of sweat varies from negligible to 14L a day depending upon the activity & temperature.

     Sebaceous glands – secrete as oily or wax like secretion called sebum. It helps the spin oily. Sebum removes some lipids like waxes stereos, other hydrocarbons & fatly acids from the body.

11) Explain micturition

     The expulsion of urine from urinary bladder is called micturition. It is a reflex process but in grown up children & adults, it can be controlled voluntarily to some extent –

     Nerve supply to urinary bladder and sphincters–

     The urinary bladder and the internal sphincters supplied by both sympathetic & parasympathetic nervous systems of autonomic nervous system whereas, the external sphincter is supplied by somatic nerve.

     Function of sympathetic nerves – The stimulation of nerve causes relaxation of detrusor muscle of the urinary bladder and constriction of internal sphincters. So it causes filling of the urinary bladder and sympathetic nerve is called nerve of filling

     Function of Para – sympathetic nerve – The stimulation of this nerve causes contraction of detrusor muscle and relaxation of the internal spintcher leading to emptying of the urinary bladder. So the parasympathetic nerve is called the nerve of emptying or serves of micturition.

     Function of somatic nerve – It maintains the tonic concentration of the skeletal muscle fibers forming external sphincter so that, the external sphincter is constricted always.

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

     JGA operates a multi hormonal Renin Angiotensin – Aldosterone system (RAAS) JG cells secrete an enzyme rennin into the blood stream. Renin changes plasma protein called angiotonsinogen to a peptide, called angiotensin II when works as hormone. Angiotensin II increases blood pressure by causing arterioles to constrict. It also increases Blood volume into two ways finally it reduces proximal convoluted tubules to release more nacl & water.

     Secondly it stimulates the adrenal glands to release a hormone called aldosterone that reduce the distal convoluted tubule to absorb more Na+ & H2o. 

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