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

Define Glomerular filtration Rate (GFR)
     The amount of the filtrate formed by the kidney
per minutes is called Glomerular filtrations
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.

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
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.
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
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
  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
= nitrogenous waste
              d = 20 – 30 gm.
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.
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.
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
     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.
What is the significance of juxtraglomerulor apparatus (JGA) in kidney
     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.