Excretion 1 Flashcards
what are the major forms of nitrogenous wastes
Ammonia, urea and uric acid are the major
forms of nitrogenous wastes excreted by the animals. Ammonia is the
most toxic form and requires large amount of water for its elimination,
whereas uric acid, being the least toxic, can be removed with a minimum
loss of water.
what is ammonotelism? what are its features and ammonotelic animals
The process of excreting ammonia is Ammonotelism. Many bony fishes,
aquatic amphibians and aquatic insects are ammonotelic in nature.
Ammonia, as it is readily soluble, is generally excreted by diffusion across
body surfaces or through gill surfaces (in fish) as ammonium ions. Kidneys
do not play any significant role in its removal.
tadpoles are ammonotelic but frogs are ureotelic( the mode of excretion of organism can change in various stages of life cycle)
what is ureotelism? which animals are ureotelic?
Terrestrial adaptation
necessitated the production of lesser toxic nitrogenous wastes like urea
and uric acid for conservation of water. Mammals, many terrestrial
amphibians and marine fishes mainly excrete urea and are called ureotelic
animals. Ammonia produced by metabolism is converted into urea in the
liver of these animals and released into the blood which is filtered and
excreted out by the kidneys. Some amount of urea may be retained in the
kidney matrix of some of these animals to maintain a desired osmolarity
what are uricotelic organisms
Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric
acid in the form of pellet or paste with a minimum loss of water and are
called uricotelic animals. It requires least amount of water and least soluble in water.
Bird pellets are used in the manfucature of fertilisers due high nitrogen content.
why are marine fishes excreting in urea
The osmolarity of sea water is very high, due to very high concentration of dissolved salts.. Hence in order to maintain osmotic balance, they excrete in the form of urea.
explain the excretory organs of some invertebrates
(i)Protonephridia or flame cells are
the excretory structures in Platyhelminthes (Flatworms, e.g., Planaria),
rotifers, some annelids and the cephalochordate – Amphioxus.
Protonephridia are primarily concerned with ionic and fluid volume
regulation, i.e., osmoregulation.
(ii)Nephridia are the tubular excretory
structures of earthworms and other annelids. Nephridia help to remove
nitrogenous wastes and maintain a fluid and ionic balance.
(iii)Malpighian
tubules are the excretory structures of most of the insects including
cockroaches. Malpighian tubules help in the removal of nitrogenous
wastes and osmoregulation.
(iv)Antennal glands or green glands perform
the excretory function in crustaceans like prawns.
what is
i)osmoregulation
ii) osmolarity
the process that regulates the body’s salt and fluid balance is called osmoregulation
osmolarity is total solute concetration expressed as the no of moles of solute present per litre of the soolution
parts of human excertory system
In humans, the excretory system consists
of a pair of kidneys, one pair of ureters, a
urinary bladder and a urethra
describe the kidneys
Kidneys are reddish brown, bean
shaped structures situated between the
levels of last thoracic and third lumbar
vertebra(7th thoracic to 3rd lumbar vertebrae) close to the dorsal inner wall of
the abdominal cavity. Each kidney of an
adult human measures 10-12 cm in
length, 5-7 cm in width, 2-3 cm in
thickness with an average weight of 120-
170 g
which blood vessel eneters the kidneya nd which one exits the kidney
the renal artery is laden with impurities and enters the kidneys. It is removed of impurities in the kidneys.
the renal vein exits the kidney, it is pure without impurities however it is deoxygenated.
explain the internal structure of kidneys
Towards the centre of the inner
concave surface of the kidney is a notch
called hilum through which ureter, blood
vessels and nerves enter. Inner to the hilum
is a broad funnel shaped space called the
renal pelvis with projections called calyces.
The outer layer of kidney is a tough
capsule. Inside the kidney, there are two
zones, an outer cortex and an inner
medulla. The medulla is divided into a few
conical masses (medullary pyramids)
projecting into the calyces (sing.: calyx).
The cortex extends in between the
medullary pyramids as renal columns called
Columns of Bertini
what is a nephron? what are its 2 main parts
A nephron is the basic structural and functional unit of the kidney. There are about a million nephrons in our kidneys.
They consist of 2 main parts which are glomerulus and renal tubules.
describe the 2 main parts of the nephron
Glomerulus is a tuft of capillaries formed by
the afferent arteriole – a fine branch of renal
artery. Blood from the glomerulus is carried
away by an efferent arteriole.
The renal tubule begins with a double
walled cup-like structure called Bowman’s
capsule, which encloses the glomerulus.
Glomerulus alongwith Bowman’s capsule, is
called the malpighian body or renal
corpuscle (Figure 19.4). The tubule
continues further to form a highly coiled
network – proximal convoluted tubule (PCT). A hairpin 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 distal
convoluted tubule (DCT). The DCTs of many
nephrons open into a straight tube called
collecting duct, many of which converge and
open into the renal pelvis through medullary
pyramids in the calyces.
explain the capillary system of nephron
The efferent arteriole emerging from the glomerulus forms a fine
capillary network around the renal tubule called the peritubular
capillaries. A minute vessel of this network runs parallel to the Henle’s
loop forming a ‘U’ shaped vasa recta.
explain the position of the nephrons in the kidney
The Malpighian corpuscle, PCT and DCT
of the nephron are situated in the cortical
region of the kidney whereas the loop of Henle
dips into the medulla
