Excretion NCERT Flashcards
Animals accumulate ammonia, urea, uric acid, carbon dioxide, water and ions like Na +, K+, Cl– ,phosphate, sulphate, etc., either by —— or by other means like ——.
metabolic activities, excess ingestion
These accumulated substances have
to be removed —– or —-.
totally or partially
—-,—- and —- are the major forms of nitrogenous wastes excreted by the animals.
Ammonia, urea and uric acid
—– is the most toxic form and requires large amount of water for its elimination, whereas —–, being the least toxic, can be removed with a minimum loss of water.
Ammonia, uric acid
The process of excreting ammonia is —- , seen in:
——, aquatic amphibians and aquatic insects are
Ammonotelism, Many bony fishes
Ammonia, as it is —–, is generally excreted by —- across body surfaces or through gill surfaces (in fish) as ammonium ions. —– do not play any significant role in its removal.
readily soluble, diffusion
Kidneys
———— necessitated the production of lesser toxic nitrogenous wastes like urea and uric acid for —–.
Terrestrial adaptation
conservation of water
Mammals, many terrestrial amphibians and —– mainly excrete urea and are called ureotelic animals.
—-produced by metabolism is converted into urea in the —- of these animals and released into the blood which is filtered and
excreted out by the kidneys.
marine fishes
Ammonia
liver
Some amount of urea may be retained in the
—– of some of the ureotelic animals to maintain a desired osmolarity.
kidney matrix
Reptiles, birds,—— and —excrete nitrogenous wastes as uric acid in the form of —- or —- with a minimum loss of water and are called uricotelic animals.
land snails, insects
pellet or paste
In most of the —– , excretory structures are simple —- forms
whereas —- have complex tubular —-.
invertebrates, tubular
vertebrates, organs called kidneys
—- or —- are the excretory structures in Platyhelminthes (Flatworms, e.g., Planaria) —-, some annelids and the cephalochordate(—).
Protonephridia or flame cells
Rotifers, Amphioxus
Protonephridia are primarily concerned with —– volume regulation, i.e., osmoregulation.
ionic and fluid
—– are the tubular excretory structures of earthworms and other annelids.
Nephridia
Annelids- excretory structure:
Some: Protonephridia,
Many: Nephridia
Nephridia help to remove —– wastes and maintain a fluid and ionic balance.
nitrogenous
—– are the excretory structures of most of the insects including cockroaches.
Malpighian tubules
Malpighian tubules help in the removal of nitrogenous wastes and —-.
osmoregulation
—– or green glands perform the excretory function in —- like prawns
Antennal glands, crustaceans
In humans, the excretory system consists
of a pair of —-, one pair of ureters, a —- and a urethra
kidneys, urinary bladder
Kidneys are —-colour, bean shaped structures situated between the levels of —– and —- vertebra close to the —- wall of the abdominal cavity.
reddish brown
last thoracic and third lumbar
dorsal inner
Each kidney of an adult human measures —-in length, —- in width, — in thickness with an average weight of —-.
10-12 cm, 5-7 cm, 2-3 cm
120-170 g
Towards the centre of the —– surface of the kidney is a notch called —-through which ureter, blood vessels and nerves enter.
inner concave, hilum
Inner to the hilum is a —– shaped space called the
renal pelvis with projections called —–.
broad funnel
calyces
The outer layer of kidney is a —–.
tough capsule
Inside the kidney, there are two zones, an —– and an ——-.
outer cortex, inner
medulla
The medulla is divided into a few —- masses (medullary pyramids)
projecting into the —-
conical, calyces
The cortex extends in between the medullary pyramids as renal columns called—-
Columns of Bertini
Each kidney has nearly —- complex tubular structures called —–
which are the functional units.
one million
nephrons
Each nephron has two parts – the
—– and the ——.
glomerulus, renal tubule
Glomerulus is a —– formed by the —- arteriole – a fine branch of renal —. Blood from the glomerulus is carried away by an efferent arteriole.
tuft of capillaries, afferent
artery
The renal tubule begins with a ——like structure called Bowman’s
capsule, which encloses the glomerulus.
double walled cup
Glomerulus along with Bowman’s capsule, is
called the —- or —
malpighian body or renal
corpuscle
The tubule continues further to form a highly coiled network – ——
proximal convoluted tubule
A —- shaped Henle’s loop is the next part of the tubule which has a descending and an ascending limb. The ascending limb continues as another highly coiled tubular region called ——–.
hairpin
distal
convoluted tubule (DCT)
The DCTs of many
nephrons open into a —-tube called
—–, many of which converge and
open into the —- through medullary pyramids in the —
straight , collecting duct
renal pelvis, calyces.
The Malpighian corpuscle, PCT and DCT
of the nephron are situated in the —-
region of the kidney whereas the loop of Henle
dips into the —-.
cortical, medulla
In majority of nephrons, the loop of Henle is —-and extends —- into the medulla. Such nephrons are called —- nephrons.
too short, only very little
cortical
In some of the nephrons, the loop of Henle is
very long and —- into the medulla.
These nephrons are called —– nephrons.
runs deep
juxta medullary
The —– emerging from the glomerulus forms a fine capillary network around the renal tubule called the —-.
efferent arteriole
peritubular
capillaries
A minute vessel of the peritubular runs —- to the Henle’s loop forming a —- shaped vasa recta. Vasa recta is absent or —- in cortical nephrons.
parallel , ‘U’,
highly reduced
Urine formation involves three main processes namely,—-, —-,—-, that takes place in different parts of the nephron.
glomerular
filtration, reabsorption and secretion
The first step in urine formation is the —- of blood, which is carried out by the —– and is called glomerular filtration.
filtration , glomerulus
On an average, —- of blood is filtered by the kidneys per minute which constitute roughly — of the blood pumped out by —- of the heart in a minute.
1100-1200 ml
1/5th, each ventricle
The glomerular capillary blood pressure causes filtration of blood
through 3 layers, i.e., the —– of glomerular blood vessels, the —- of Bowman’s capsule and a —- between these
two layers.
endothelium , epithelium, basement membrane
The epithelial cells of Bowman’s capsule called —- are arranged in an —manner so as to leave some minute spaces called —- or —
podocytes, intricate
filtration slits or slit pore
Blood is filtered so finely through these membranes, that almost all the constituents of the plasma except the
—- pass onto the lumen of the Bowman’s capsule. Therefore, it is considered as a process of —–.
proteins
ultra filtration
The amt of filtrate formed by the kidney per minute is called—-
glomerular filtration rate (GFR).
GFR in a healthy individual is
approximately ——, i.e., 180 litres per day !
125 ml/minute
The kidneys have built-in mechanisms for the regulation of —–. One such efficient mechanism is carried out by —— a special sensitive region formed by cellular modifications in the —– and —- at the location of their contact.
glomerular filtration rate
juxta
glomerular apparatus (JGA)
dct and afferent arteriole
A fall in GFR can activate the JG cells to release — which can stimulate the — and thereby the GFR back to normal.
renin, glomerular blood flow
A comparison of the volume of the filtrate formed per day (180 litres
per day) with that of the urine released (—), suggest that nearly —
per cent of the filtrate has to be reabsorbed by the —. This process is called reabsorption.
1.5 litres, 99
renal tubules
The tubular epithelial cells in different segments of nephron perform reabsorption either by — or —mechanisms.
active or passive
For example, substances like —,— and —, etc., in the filtrate are reabsorbed actively whereas the —- are absorbed by
passive transport.
glucose, amino acids, Na+
nitrogenous wastes
Reabsorption of water also occurs passively in the —- of the nephron
initial segments
During urine formation, the tubular cells secrete substances like H+, K+, and ammonia into the —.
filtrate
Tubular secretion is also an important step in urine formation as it helps in the maintenance of —- and — balance of body fluids.
ionic and acid base balance
PCT is lined by —— which increases the surface area for reabsorption.
Nearly all of the essential nutrients, and —- per cent of electrolytes and water are reabsorbed by this segment.
simple cuboidal brush border epithelium
70-80
PCT also helps to maintain the — and — balance of the body fluids by selective secretion of
—, — and — into the filtrate and by
absorption of HCO3 from it.
pH and ionic balance
hydrogen ions, ammonia and potassium ions
Henle’s Loop: Reabsorption is minimum in its —–. However, this region plays a significant role in the maintenance of ——–.
ascending limb
high osmolarity of medullary interstitial fluid
The descending limb of loop of Henle is permeable to water but almost impermeable to –. This — the filtrate as it moves down.
electrolytes
concentrates
The ascending limb is
impermeable to water but allows transport of electrolytes —–. Therefore, as the concentrated filtrate pass —, it gets diluted due to the passage of —– to the medullary fluid.
actively or passively
upward, electrolytes
DCT- —- of Na+ and water takes place in this segment. DCT is also capable of reabsorption
of HCO3– and selective secretion of —-,—- and —
to maintain the — and —balance in blood.
Conditional reabsorption
hydrogen and potassium ions and NH3
pH and sodium-potassium
Collecting Duct: This long duct extends from the —-of the kidney to the—–.
cortex, inner parts of the medulla
Large amounts of water could be reabsorbed from this region to produce a —- urine. This segment
allows passage of small amounts of —- into the medullary interstitium
to keep up the —-.
concentrated
urea , osmolarity
CD also plays a role in the maintenance of —- and —- balance of blood by the selective secretion of H+
and K+ ions
pH and ionic balance
Mammals have the ability to produce a — urine. The Henle’s loop and —- play a significant role in this.
concentrated
vasa recta
The flow of —- in
the two limbs of Henle’s loop is in opposite directions and thus forms a —–. The flow of —-through the two limbs of vasa recta is also in counter current pattern
filtrate, counter current
blood
The —- between the Henle’s loop and vasa recta, as well as the counter current in them help in maintaining
an —– towards the inner medullary interstitium, i.e., from — mOsmolL–1 in the cortex to about —mOsmolL–1 in the inner
medulla.
proximity
increasing osmolarity
300, 1200
This gradient is osmolarity is mainly caused by – and urea.
NaCl
NaCl is transported by the —- limb of Henle’s loop which is exchanged with the —- limb of vasa recta. NaCl is returned to the interstitium by the —–portion of vasa recta.
ascending, descending
ascending
Similarly, small amounts of urea enter the —-segment of the ascending limb of Henle’s loop which is transported back to the interstitium by the —-.
thin , collecting tubule
The above described transport of substances facilitated by the special arrangement of Henle’s loop and vasa recta is called the —- mechanism
This mechanism helps to maintain a —– in the medullary interstitium.
counter current
concentration gradient
Presence of such interstitial gradient helps
in an easy passage of water from the —- thereby concentrating the filtrate (urine).
collecting tubule
Human kidneys can produce urine nearly
— times concentrated than the initial filtrate formed.
four
The functioning of the kidneys is efficiently monitored and regulated by —- mechanisms involving the hypothalamus, JGA and
to a certain extent, the —.
hormonal feedback
heart
Osmoreceptors in the body are activated by changes in —- volume,
—- volume and —-concentration.
blood, body fluid, ionic
An excessive loss of fluid from the body can activate —-receptors which stimulate the —-to release antidiuretic hormone (ADH) or vasopressin from the
—-.
osmo, hypothalamus
neurohypophysis
ADH facilitates water reabsorption from —- parts of the tubule, thereby preventing —.
latter, diuresis
An —- in body fluid volume can switch off the osmoreceptors and suppress the —- release to complete the feedback.
increase , ADH
ADH can also affect the kidney function by its —
effects on blood vessels. This causes an increase in —-.
An increase in blood pressure can increase the —- blood flow and thereby the —-.
constrictory,
blood pressure
glomerular, GFR
The JGA plays a —– role. A fall in glomerular blood
—-/—-/—- can activate the JG cells to release renin which converts in blood to —- angiotensin I and
further to angiotensin II.
complex regulatory
flow, pressure, GFR
angiotensinogen
Angiotensin II, being a powerful —, increases the glomerular blood pressure and thereby
GFR.
vasoconstrictor
Angiotensin II also activates the —- to release Aldosterone.
adrenal cortex
Aldosterone causes reabsorption of —- and — from the distal parts of the tubule. This also leads to an increase in blood
pressure and GFR.
This complex mechanism is generally known as
the —– mechanism.
Na+ and water
Renin-Angiotensin
An increase in blood flow to the — of the heart can cause the release
of —-.
atria, Atrial Natriuretic Factor (ANF)
ANF can cause — and thereby —- the blood pressure.
vasodilation , decrease
ANF mechanism, therefore, acts as a —- on the renin-angiotensin mechanism.
check
Urine formed by the nephrons is ultimately carried to the —- where it is stored till a voluntary signal is given by the —.
urinary bladder, central nervous system (CNS)
The voluntary signal is initiated by the — of the urinary bladder as it gets filled with urine. In response, the —- receptors on the —
of the bladder send signals to the CNS.
stretching
stretch, walls
The CNS passes on —messages to initiate the –of smooth muscles of the bladder and simultaneous — of the urethral sphincter causing the release of urine
motor, contraction
relaxation
The process of release of urine is called micturition and the neural mechanisms causing it is called the —- .
micturition reflex
An adult human excretes, on an average, —- litres of urine per day.
1 to 1.5
The urine formed
is a —- coloured watery fluid which is slightly acidic (pH—)
and has a characterestic –
light yellow , 6.0
odour
On an average, —- of urea is excreted out per day.
25-30 gm
Various conditions can affect the characteristics of urine. Analysis of urine helps in clinical diagnosis of many —- as well as —-.
metabolic disorders, malfunctioning of the kidney
Presence of glucose (Glycosuria) and ketone bodies (Ketonuria) in urine are indicative of —.
diabetes mellitus
Other than the kidneys, —-,—- and — , also help in the elimination
of excretory wastes.
lungs, liver and skin
Our lungs remove large amounts of CO2
(approximately —) and also significant quantities of — every day.
200mL/min, water
—, the largest gland in our body, secretes bile-containing substances like bilirubin, —, cholesterol, degraded — hormones, vitamins and —.
Most of these substances ultimately pass out along with — wastes
Liver,
biliverdin, steroid, drugs
digestive
The — and — glands in the skin can eliminate certain substances through their secretions.
sweat and sebacious
Sweat produced by the sweat glands is a — fluid containing —, small amounts of —-, —-, etc. Though the primary function of sweat is to facilitate a —-
effect on the body surface, it also helps in the removal of some of the wastes mentioned above.
watery,
NaCl, urea, lactic acid
cooling
Sebaceous glands eliminate certain
substances like —, — and —- through sebum.
sterols, hydrocarbons and waxes
Sebum provides a protective — covering for the skin.
oily
Small amounts of nitrogenous wastes could be eliminated through
—- too.
saliva
Malfunctioning of kidneys can lead to accumulation of urea in blood, a condition called —, which is highly harmful and may lead to —.
uremia, kidney failure
called hemodialysis.
In hemodialysis, Blood drained from a convenient —- is
pumped into a dialysing unit after adding an —-
artery,
anticoagulant like heparin.
The dialysing unit contains a —- tube surrounded by a fluid
(dialysing fluid) having the same composition as that of plasma except the —-.
coiled cellophane, nitrogenous wastes
The — cellophane membrane of the tube allows the passage of molecules based on —-gradient.
porous, concentration
As —- are absent in the dialysing fluid, these substances freely move out, thereby clearing the blood.
The cleared blood is
pumped back to the body through a — after adding — to it.
nitrogenous wastes
vein, antiheparin
—- is a boon for thousands of uremic patients all over the
world
Dialysis
Kidney transplantation is the — method in the correction of — renal failures (kidney failure).
ultimate, acute
A functioning kidney is used in transplantation from a donor, preferably a — , to minimise its chances of rejection by the immune system of the host.
Modern clinical procedures have increased the — of such a complicated technique.
close relative
success rate
Renal —: Stone or insoluble mass of crystallised salts (—,
etc.) formed within the kidney.
calculi, oxalates
—-:
Inflammation of glomeruli of kidney.
Glomerulonephritis
