Chapter 1 Homeostasis

Chapter 1
Homeostasis
BY─ Prof Mansoor Abro SUM ACADEMY LARKANA

What is homeostasis
• ─ The maintenance of a constant environment in the
body is called Homeostasis.
• ─ Homeostasis a term coined by the English
Physiologist Walter Cannon (means standing same).
• ─ Greek Homo = same + Stasis = standing
Important aspects of homeostasis
• ─ Homeostasis - stable internal environment
maintained.
• ─ Done in three ways.
• ─ 1 Thermoregulation - maintenance of
specific body temperature.
• ─ 2 Excretion - get rid of wastes.
• ─ 3 Osmoregulation - maintenance of water
and solute balance.
BY─ Prof Mansoor Abro

How is homeostasis generally maintained in a
multicellular organism?
• ─ Chemically via hormones

• ─ Electrically via the nervous system

Homeostasis is based on feed back
mechanism
• ─ The check and balance mechanism is termed as feed
back mechanism.
• ─ Negative feed back: helps restore conditions back to
their original state (i.e. move back to their normal).
• ─ In other words any further change away from set point
is counteracted.
• ─ Positive feed back: helps amplify conditions away
from original state (i.e. move away from normal) .
• ─ In other words any further change away from the set
point is amplified.

Feed back mechanism in homeostasis needs
• ─ Receptors or Sensors to detect changes (Stimuli)
in the internal or external environment. ( e.g. skin has
hot receptors and cold receptors)
• ─ A Regulator which receive message from receptor

and process information for maintaining the set point
of the system (e.g. Hypothalamus has
thermoregulatory centre).
• ─ The set point is range of normal functional values

of an organ or structure.
• ─ Effectors which receive message from regulator

and bring the system back to the set point. ( e.g.
muscles and glands)
Three basic components of control
system

Example of negative feed back
• ─ Thermoregulation: example of nervous system
negative feedback loop (response is opposite of
stimulus).
Positive feed back
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Positive feedback
Positive feed back
• Oxytocin is released from the posterior
pituitary during childbirth to stimulate
uterine contractions.
• In this situation positive feedback occurs.
• The uterus contracts and more oxytocin is
released which stimulates more uterine
contractions and more oxytocin is released
and so on.
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Fever is a positive feedback mechanism
• ─ Fever is positive feedback because it's very
presence causes it's increase.
• ─ Medical term for fever is Pyrexia is from the Greek
pyro meaning fire.
• ─ A fever is body temperature elevation over 98.6 °F or
37 °C.
• ─ Substances which induce fever are called pyrogens.
• ─ A state of elevated body temperature, (fever) is part of
the body's defense against invading microbes.
• ─ Fever is often dangerous.
• ─ Heat stroke, also known as sun stroke, is a severe
heat illness, defined as hyperthermia with a body
temperature greater than 40.6 °C (105.1 °F).
• ─ Heat stroke can kill or cause damage to the brain and
other internal organs.
─ Fever included in 2nd line of defense,
characterized by high body temperature above
set point.
─ Pyrogen: A substance that produces fever.
Interleukin 1, called a pyrogen –secreted by macrophages.
Osmoregulation
• ─ The general process by which organisms
control solute concentrations and balance their
water gain and loss.
• ─ Osmotic pressure and water potential
• ─ Osmotic pressure is capacity of a living
system to gain water.
• ─ Osmotic pressure is the opposite of water
potential.
• ─ Water potential is capacity of a living
system to lose water.
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Osmosis
• ─ The movement of
water molecules across
semipermeable
membrane from an area
of high concentration to
an area of low
concentration.
• OR
• ─ The movement of
water molecules across
semipermeable
membrane from
hypotonic solution to
hypertonic solution.
Animation
Tonicity
• ─ Tonicity refers to the relative
concentration of solute on either side of a
membrane.
• ─ According to tonicity solutions may be
• ─ Isotonic
• ─ Hypotonic
• ─ Hypertonic

Isotonic solution
• ─ In an isotonic solution, the
concentration of solute is the same on both
sides of the membrane (inside the cell and
outside).
• ─ Water diffuses into and out of the cell at
equal rates in isotonic solution.
• ─ Most cells in the body are in an isotonic
solution.
Hypotonic solution
• ─ A hypotonic solution is one that has less solute
(more water).
• ─ Cells in hypotonic solution tend to gain water.
• ─ Animal cells can lyse (rupture) in a hypotonic
solution due to the osmotic pressure.
• ─ The cell wall of plant cells prevents the cell
from rupturing.
• ─ The osmotic pressure, called turgor
pressure, helps support the cell.
• ─ A cell in which the contents are under
pressure is turgid.
Hypertonic solution
• ─ A hypertonic solution is one that has a high
solute concentration.
• ─ Cells in a hypertonic solution will lose water.
• ─ Animal cells placed in a hypertonic solution
will undergo crenation, a condition where the
cell loses water and undergo shrinkage .
• ─ Plant cells placed in a hypertonic solution will
undergo plasmolysis, a condition where the
plasma membrane pulls away from the cell wall
as the cell shrinks.
• ─ The cell wall is rigid and does not shrink.
• ─ Cells gain water when placed in hypotonic
solution.
• ─ Cells lose water when placed in hypertonic
solution.
• ─ Water diffuses into and out of the cell at equal
rates in isotonic solution.
• ─ Solute potential Symbol Ψ s .
• ─ Definition: The component of water potential that is
due to the presence of solute molecules.
• ─ Definition in text book: “In case of plant cell water
potential of cell sap is called solute potential ”.
• ─ Cell sap is aqueous solution inside large vacuole.
• ─ Water potential Symbol Ψ.
• ─ Water potential has two components.
• ─ Solute potential Symbol Ψ s and pressure
potential Symbol Ψ p.
• ─ Pressure potential (Ψ p): The component of water
potential due to the hydrostatic pressure in a cell.
• ─ Equation : Ψ = Ψs + Ψp , there fore water potential of
a solution is generated by a combination of both Solute
potential and Pressure potential.
• ─ Plasmolysis is shrinkage of protoplasm due to ex-
osmosis when a plant cell is placed in concentrated or
hypertonic solution.
Osmoregulation in plants
• ─ Plants are grouped into four groups on

the basis of availability of water.
• ─ Hydrophytes
• ─ Halophytes
• ─ Mesophytes
• ─ Xerophytes
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Hydrophytes
• ─ These plants (such as water lily) are
found in fresh water habitat either partially
or completely submerged.
Water lily
Hydrophytes adaptations for Osmoregulation
• ─ Lack cuticle
• ─ Stomata open most of time (as water is
abundant )
• ─ Increased number of stomata
• ─ Large flat leaves on surface plants for
flotation.

Halophytes
Glass wort
• ─ Halophytes are
plants adapted to
living in a saline
environment.
• ─ Halophytes are
found on coastlines
and also on the
drier lands where
salt is present in the
soil.
• ─ E.g. glass wort Cord grass
and cord grass.
Halophytes adaptations for osmoregulation
• ─ These plants have special physiological
adaptations that enable them to absorb water
from salty soil.
• ─ They actively absorb salts into their roots so
that the roots develop lower water potential
which brings in water by osmosis.
• ─ Excreting salt glands occur in numerous
halophytes.
• ─ The salt gland is an organ for excreting
excess salts.
• ─ In Halophytes the salt crystals trap water
vapors from the surrounding air, which are
absorbed by leaves in liquid form.
Mesophytes
• ─ Mesophytes are
terrestrial plants which are
adapted to neither a
particularly dry nor Rose
particularly wet
environment.
• ─ Any plant that doesn't
live in a pond or in a hot
place is a mesophyte.
• ─ Mesophytes are plants
with average water corn
requirements e.g. rose,
corn.
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Mesophytes adaptations for Osmoregulation
• ─ They can easily compensate water lost by

transpiration.
• ─ To prevent excessive transpiration they have
cuticle.
• ─ Mesophytes growing in high rainfall and
humid conditions have problem of losing
excess water by transpiration, they lose water
by a process called guttation.

Xerophytes
• ─ Xerophytes are plants which are able to
live in very dry places.
Cactus
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Xerophyte adaptations summary:
Osmoregulation in terrestrial
animals
• ─ Water proof external covering
• ─ To prevent water loss through external
surfaces, vertebrates like reptiles, birds
and mammals have water proof
keratinized epidermis.
• ─ Insects have developed an external
water proof layer called cuticle.

Storing and excretion of solid wastes
• ─ Reptiles, birds and insects excrete uric
acid which is insoluble in water.
• ─ It is in semi-fluid form.
• ─ Less amount of water is required to
remove uric acid from the body.
• ─ Only 10 ml of water is required to
remove one gram of uric acid.
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Use of metabolic water
• ─ Some mammals like
camel, kangaroo rat etc.
make use of water
produced during break
down of body fats.
• ─ Kangaroo rats derives
their name from bipedal
hopping.
• ─ They hop in a manner
similar to the much larger
kangaroo, although they kangaroo rat
are not related.
Storing the wastes
• ─ Mammals do retain some urea in their tissues
where it helps in reabsorption of water.
• ─ When water is not available camel will not
produce urine but will store the urea in the
tissues and exclusively depends up on
metabolic water.
• ─ When water is available they rehydrate
themselves by drinking up to 80 liters of water in
10 minutes.
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Osmoregulation in aquatic habitat
• ─ Osmoregulation by contractile vacuole
• ─ Fresh water protozoans constantly take in
water because hypertonic body fluids cause
water from the surroundings to enter the cell.
• ─ Osmoregulation in freshwater protozoans is
accomplished by contractile vacuoles that
pump a hypotonic urine from the cytoplasm
back into the environment.
• ─ This counters the osmotic influx of water
across the plasma membrane.
• ─ In many protozoans the contractile vacuole is
a conspicuous feature of the cell.
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Osmoregulation by contractile vacuole
Osmoregulation in fresh water fish
• ─ Freshwater fish have (hypertonic) higher body
fluid ion and osmotic concentrations than does
their freshwater medium (hypotonic).
• ─ Water is gained by osmosis, by drinking and in
food, and ions are lost by diffusion and in urine.
• ─ Water is excreted by producing a copious
amount of dilute urine.
• ─ Ions are actively absorbed by gill salt pumps,
and are obtained in food.
Osmoregulation in
fresh water fish
Osmotic water gain through gills
and other parts of body surface
Uptake of
some ions
in food
Uptake of Excretion of
salt by large amounts of
gills water in dilute
urine from kidneys
Osmoregulation in marine fish
• ─ A marine fish is an iono-regulator and
osmoregulator and its body is (hypotonic) in
relation to sea water (hypertonic).
• ─ Consequently, there is a constant influx of
ions by diffusion and a loss of water by osmosis.
• ─ Water is replaced by drinking and from food,
and excess salts are removed by active gill
pumps.
• ─ There is some loss of water and ions by the
production of small amounts of urine.

Gain of water and Osmoregulation in marine fish
salt from food
and by drinking
seawater Osmotic water loss
through gills and other
parts of body surface
Excretion of excess
ions and small
Excretion of salt
amounts of water
from gills
in scanty urine
from kidneys
Osmoconformers and Osmoregulators
• ─ Osmoconformers: isotonic to environment.
• ─ Osmoregulators: maintain internal osmolarity
different from environment.
• ─ Osmoconformers : no net movement of water or salt.
• ─ No mechanisms for control of balance.
• ─ E.g. marine invertebrates.
• ─ Evolved in ocean (remain isotonic)
• ─ Osmoregulators: Actively control salt and water
balance.
• ─ Hypotonic or hypertonic or terrestrial.
• ─ Ancestors evolved osmolarity in different environment.
• ─ Hydra, Earthworm, grasshopper, fish and mammals
• ─ Evolved mechanisms for control of salt and water
balance.
Osmoregulation in sharks
• ─ The blood composition of cartilaginous fishes, such as
sharks and rays, is similar to that of bony fishes.
• ─ However, the blood of sharks contains urea and
trimethylamine oxide (TMAO).
• ─ The shark's blood electrolyte composition is not similar
to that of seawater, but maintains isotonicity with
seawater by storing urea at high concentrations.
• ─ Sharks are "ureotelic" animals that secrete urea to
maintain osmotic balance.
• ─ Urea damages living tissues so, to cope with this
problem, some fish retain trimethylamine oxide (TMAO).
• ─ This provides a better solution to urea's toxicity.

Osmoregulation in shark
• ─ Salt glands: The salt gland is an organ for excreting

excess salts.
• ─In sharks salt glands are found in rectum called rectal
glands.
• ─ Salt glands maintain salt balance and allow marine
vertebrates to drink sea water.
• EXCRETION- is the
process of removing Excretion
metabolic wastes
(metabolic means it
has entered the body
cells)
• The metabolic
activities of living
organisms result in
the production of
waste materials.
• Excretion:
maintains
homeostasis by
regulating the
chemistry of body
fluids and
maintaining body
temperature.
Excretion in plants
• ─ Plants do not excrete nitrogenous
wastes as they recycle breakdown
products of nitrogen metabolism.
• ─ Plants produce a variety of organic and
inorganic substance as byproducts during
metabolism which are excreted in variety
of ways.

Excretion in plants
• ─ Oxygen and Carbon dioxide are produced as
waste products during photosynthesis and
respiration respectively.
• ─ Oxygen is excreted in photosynthesis.
• ─ Carbon dioxide is excreted in respiration.
• ─ Water is produced as waste product during
photosynthesis and respiration. It is excreted by
transpiration.

Excretion in plants
• ─ Plants produced various organic and inorganic
waste products during metabolism.
• ─ These waste substances are stored in the
vacuoles of leaf cells and their increasing
concentration may result in their crystal
formation in the vacuoles.
• ─ Leaves also store heavy-metals which toxic.
• These leaves become yellow and fall of in
autumn thus removing the waste substances.
• ─ Such leaves are also called excretophores.

Excretion in plants
• ─ Tropical trees deposit chemicals like gums,
resins, tannin in the old xylem cells of stem
which become darker in color and called ebony
or hard black wood called heartwood.
• ─ Ebony is no longer involved in conduction of
water and minerals and thus serves as storage
region of some wastes.
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Excretion in animals
• ─ Different animals expel different
nitrogenous compounds. On the basis of
the type of nitrogenous end product.
• ─ There are 3 modes of excretion. They
are
• ─ Ammonotelism
• ─ Ureotelism
• ─ Uricotelism
Proteins Amino acids Nitrogenous bases Nucleic acids
—NH2
Amino groups
Most aquatic animals, Mammals, amphibians, Birds and many other

including most fishes sharks, some bony reptiles, insects, land
fishes snails
Ammonia Urea Uric acid

Ammonotelism
• ─ Animals that excrete excess nitrogen in the form of
ammonia (NH3) (the end product of protein metabolism)
are called ammonotelic.
• ─ Ammonia diffuses through the cell membrane
extremely fast because of its high water solubility and
small molecular size.
• ─ Therefore, prompt excretion of ammonia occurs in
aquatic animals (aquatic invertebrates, fishes, larvae,
permanently aquatic amphibians (permanently
aquatic gilled salamanders, lung less salamanders).
• ─ Some salamanders that are terrestrial have lungs that
are used in respiration .
• ─ The route of ammonia diffusion in these animals is
through skin, gills or kidneys.
Ureotelism
• ─ Animals that excrete excess nitrogen in the
form of urea are ureotelic.
• ─ Terrestrial animals cannot use water freely for
excretion (because of less availability in the
environment), so ammonia is converted into a
less toxic and easily soluble product, urea.
• ─ 2NH3 + Co2 → CO(NH2)2 + H20
• ─ In mammals and semi-terrestrial adult
amphibians, urea is a major nitrogenous
excretory product, therefore these animals are
called ureotelic.
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Uricotelism
• ─ Animals that excrete a major portion of nitrogenous waste in
the form of semi-solid or solid uric acid are called uricotelic
animals (e.g. birds, lizards, snakes, terrestrial insects, snails.)
• ─ Uric acid is less toxic, and relatively insoluble in water, can
be excreted with a relatively small amount of water.
• ─ Arachnids (e.g. spiders, scorpions, etc.) excreted mostly
guanine and hence are said to be guanotelic.
• ─ The above terms apply to the predominant form of excretory
product, but do not exclude the excretion of other forms in
minor quantities.
• ─ Man also excretes a small amount of uric acid in his urine
formed by the catabolism of nucleic acids.
Excretion in Hydra
• ─ Hydra is
ammonotelic.
• ─ Almost all the cells
of Hydra are in direct
contact with water.
• ─ Ammonia is
removed by simple
diffusion from the
external surface as
well as internal
surface into external
and internal water of
gastro-vascular cavity.
Excretion in Planaria
• ─ Planaria is ammonotelic flat worm.
• ─ Planaria use a Nephridium as their
excretory organ.
• ─ Excretory organs of Planaria are
protonephridia.
• ─ Protonehridium: is a tubular excretory
system lacking internal openings caped by
a number of cells called flame cells.
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Excretion in Planaria
Excretion in Earthworm
• ─ Earthworms are normally ammonotelic but become
ureotelic when starved, the ornithine cycle detoxifying
excess ammonia liberated by increased protein
catabolism.
• ─ Excretory organs of earthworm are metanephridia.
• ─ Metanephridium: a tubular excretory system having
internal openings that collect nitrogenous wastes from
coelomic fluid.
• ─ Metanephridia occur in all the segments of the body
starting from the third segment downwards.
• ─ Based on their location three kinds of nephridia can be
distinguished.
• ─ Integumentary Nephridia
• ─ Septal Nephridia
• ─ Pharyngeal Nephridia
• ─ Integumentary Nephridia: These lie
attached to the inner side of the body wall
in all segments except the first two.
• ─ Septal Nephridia: These lie attached to
both sides of the septa behind the 15th
segment.
• ─ Pharyngeal Nephridia: These are
located only in the 4th, 5th and 6th
segment.
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Parts of a Metanephridium
• ─ Structure of septal
nephridia:
• ─ A typical nephridium
consists of
• ─ A ciliated funnel or
nephridiostome which
opens into the coelomic
cavity.
• ─ The main body of the
nephridium consists of a
short straight region called
the straight lobe and a long
spirally twisted loop.
• ─ The coiled tubular part
dilates to form bladder
before opening to outside
by nephridiopore.
• ─ Physiology of Excretion
• ─ The rhythmic beating of the cilia of the
nephridiostomes and tubules of the septal
nephridia drives a steady stream of coelomic fluid
containing metabolic waste materials, such as
urea, ammonia and remains of dead cells, into
nephridial tube.
• ─ Some excretory substances are also secreted
by cells of the tubule.
• ─ Selective reabsorption of useful substances
also occurs.
• ─ The excretory wastes are then finally
discharged into the nephridiopore.
Excretion in Cockroach
• ─ The excretory organ of
cockroach are malpighian
tubules.
• ─ They are found at the
junction of the mid gut
and hind gut and are
about 150 in number.
• ─ They are fine, yellow
colored and branched
threads present in
bundles. They lie freely in
the haemolymph.
Physiology of excretion in Cockroach
• ─ The distal parts of the tubules
extract inorganic ions, uric acid and
amino acids by active transport and
water by diffusion from the
surrounding haemolymph.
• ─ The filtrate moves towards the
ileum.
• ─ In the proximal parts of the
malpighian tubules water and other
useful substances are reabsorbed.
• ─ The remaining materials passes
into the gut.
• ─ More water and inorganic ions are
reabsorbed in the rectum.
• ─ Almost solid uric acid, is finally
eliminated with the faeces.
Excretion in Man
• ─ Excretory organs in man are
• ─ Kidneys eliminate nitrogenous wastes
• ─ Liver excrete nitrogenous wastes, bile
pigments
• ─ Skin excrete salts along with sweat
• ─ Lungs excrete carbon dioxide.

Liver- an important homeostatic organ
• ─ The liver is the second largest (after skin)
organ in the body, weighing 2 kg in the average
adult.
• ─ As adult humans can be of different size, so
can the liver.
• ─ It is approximately 21-22.5 cm across its
widest point, 15-17.5 cm at its greatest vertical
height, and 10-12.5 cm from front to back.
• ─ The liver plays a major role in homeostasis
and has a number of functions in the body.

FUNCTIONS OF LIVER
• AS A METABOLIC FACTORY : It maintains the
appropriate level of nutrients in blood and body. It is
performed in 3 ways.
• (A) GLUCOSE METABOLISM:
• 1) Additional (Surplus) Glucose is converted into
Glycogen by action of INSULIN after every meal. This is
called Glycogenesis.
• 2) Glycogen is broken into Glucose for body needs. This
is called Glycogenolysis.
• 3) New glucose for body requirement is formed by non-
carbohydrate compounds. This is called
Gluconeogenesis.

FUNCTIONS OF LIVER
• (B) Amino acid metabolism:
Body can not store excess
amino acids.
• Excess amino acids are
broken down.
• First deamination (removal of
amino group takes place).
• Amino group (-NH2) is
converted to ammonia while
rest of the residual
of amino group is supplied to
carbohydrate metabolism for
respiration.

• ─ Urea is formed in the liver
by a cyclic process called as Liver- Urea cycle
urea cycle or Ornithine cycle. (Ornithine cycle)
• ─ Three amino acids
participate in the process.
• ─ Ornithine combines with
ammonia and carbon dioxide
to form citrulline
• ─ Citruline combines with
more ammonia to form water
and arginine.
• ─ Arginine is then
decomposed to form urea and
Ornithine in the presence of
enzyme arginase and water.
• ─ Ornithine is set free for
reuse in the urea cycle.
2NH3 + Co2 → CO(NH2)2 + H20

FUNCTIONS OF LIVER
• (C): Fatty acid metabolism: Ketone bodies are
produced from fatty acids in liver to low availability of
carbohydrate fuel (in the blood plus stored as glycogen)
• Two of the three are used as a source of energy in the

heart and brain while the third (acetone) is a degradation
breakdown product of acetoacetic acid.

Liver- Production of bile
• ─ Bile is a alkaline
yellow, and green
fluid secreted by
hepatocytes from the
liver.
• ─ Bile is stored in the
gall bladder and
discharged into the
duodenum where the
bile salts process the
digestion of lipids by
emulsification.
• ─ pH of bile juice is
7.5
Liver- Production of bile
• ─ Constituents of bile juice
• ─ Water
• ─ Cholesterol
• ─ Bile pigments: Bilirubin “red” and Biliverdin
“Green” excretory products of haeme part of the
broken haemoglobin.
• ─ Bile pigments serve no digestive function.
• ─ Bile salts: Such as sodium glycocholate,
sodium taurocholate, involved in emulsification
of fats.
SUM ACADEMY LARKANA

How bile salts emulsify fats?
• ─ Lipids are hydrophobic and hence insoluble within the aqueous
environment of the body
• ─ They will group together (coalesce) to form large droplets of fat (fat
globules).
• ─ Bile salt molecules have both a hydrophobic and hydrophilic end.
• ─ The hydrophobic end attaches to the lipid while the hydrophilic end
interacts with water – preventing lipids from attaching there.
• ─ This divides the fat globule into smaller droplets (emulsification),
increasing the total surface area available for enzyme activity.
Liver- Detoxification of hydrogen peroxide
• ─ The role of these various enzyme activities in the
liver is to convert fat soluble toxins into water
soluble substances that can be excreted in the urine
or the bile.
• ─ Hydrogen peroxide a by product of many
chemical pathways is a highly toxic substance.
• ─ It is broken down into hydrogen and oxygen by an
enzyme catalase which is present in high
concentration in liver cells.
Break down of hydrogen peroxide

Liver- Formation of cholesterol
• ─ Cholesterol is chiefly synthesized in liver.

• ─ Excess amount of cholesterol is removed in bile.
• ─ Excess amount of cholesterol can precipitate to form
gall bladder stones which may lead to jaundice.
• ─ Thermoregulation : Due to efficient supply of blood,
large size and high metabolic rate liver plays important
role in maintaining body temperature.
• ─ Storage of vitamins : Liver stores a number of
vitamins such as A,B, D.
SUM ACADEMY LARKANA

Urinary system of man
• Components of urinary
system
• ─ A) Kidneys- paired organs
that form the urine.
• ─ B) Ureters - carry urine to
bladder, one from each
kidney.
• ─ C) Bladder - site where
urine is collected and stored
until urination
• ─ D) Urethra - carries urine
from bladder to external
environment .
Urethral sphincter
• ─ The term urethral
sphincter refers to one of
two muscles used to control
the exit of urine in the urinary
bladder through the urethra.
• ─ There are two urethral
sphincters: the internal and
external urinary sphincters.
• ─ Internal sphincter : smooth
muscle. (Involuntary control)
• ─ External sphincter :
Skeletal muscles (voluntary
control)
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Position of kidneys
• ─ In humans, the kidneys are located in the
abdominal cavity being attached with dorsal
body wall on either side of vertebral column.
• ─ The left kidney lies a little higher than the
right kidney.
• ─ The asymmetry within the abdominal cavity
caused by the liver results in the right kidney
being slightly lower than the left one while the
left kidney is located slightly more medial.
• ─ The kidneys are approximately at the
vertebral level T12 to L3.
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Relation ship of kidneys to vertebrae
• ─ Kidneys: The kidneys are
kidney bean-shaped organs Urinary system of man
located on either side of the
vertebral column.
• ─ Size : 4 inches (10
centimeters) long, 2.5 inches
(6 centimeters) wide.
• ─ The right kidney usually is
slightly lower than the left
because the liver displaces it
downward.
• ─ Each kidney is enclosed
by thin membranous
covering called peritoneum.
(Visceral Peritoneum)
• ─ The concave side of each
kidney called the hilus.
• Through the hilus the renal
artery enters and the renal
vein and ureter exit.
• ─ Each kidney is covered
by tough capsule.
• ─ Renal capsule: The
renal capsule is a smooth,
transparent, fibrous
membrane that surrounds,
encloses, and protects the
kidney.
• ─ Each kidney has it's
own renal capsule (outer
layer), which helps to
maintain the shape of the
kidney as well as
protecting it from damage.
SUM ACADEMY LARKANA

Structure of the Kidney (Gross Anatomy of the Kidney)
• ─ Renal cortex: The

renal cortex is the outer
part of the kidney and
has a reddish colour.
• ─ Renal medulla: The
renal medulla is the
inner part of the kidney.
"Medulla" means "inner
portion". It is inner
lighter region.
SUM ACADEMY LARKANA

• ─ Renal
pyramids: There are
approx. 5 - 18 striated
triangular structures
called "Renal Pyramids"
within the renal medulla
of each kidney.
• ─ Renal pelvis: The
renal pelvis is the
funnel-shaped dilated
part of ureter.
• ─The major function of
the renal pelvis is to act
as a funnel for urine
flowing to the ureter.
SUM ACADEMY LARKANA

The Structure of a Kidney Nephron
• ─ Kidney nephrons are the

functional units of the
kidneys.
• ─ There are about 1
million kidney nephrons in
each of the two kidneys in
the body.
• ─ There are two parts of a
kidney nephron: the renal
corpuscle, and the renal
tubule.
SUM ACADEMY LARKANA

Bowman’s
capsule
PCT
Glomerulus Renal cortex
DCT
Renal artery
Renal vein
Ascending limb
Descending limb Collecting

duct
Renal medulla
Loop of Henle
Structure of nephron To renal pelvis

• ─ 1) Renal Corpuscle The Structure of a
• consists of two
structures: a glomerulus Kidney Nephron
and a Bowman's
capsule.
• ─ Glomerulus: a cluster
of capillaries where
waste products are
filtered from the blood.
• ─ Bowman's capsule: a
capsule-shaped
membranous structure
surrounding the
glomerulus of each
nephron.
• ─ First part of nephron
where filtrate is collected.
• ─ (2) Renal Tubule The Structure of a
• ─ The renal tubule is the Kidney Nephron
part of the kidney nephron
into which the glomerular
filtrate passes after it has
reached the Bowman's
capsule.
• ─ Proximal Convoluted
Tubule: Where selective
reabsorption occurs.
• ─ Loop of Henle: U-
shaped part, important for
establishing a salt gradient
in the medulla.
The Structure of a
• ─ Distal Convoluted
Kidney Nephron
Tubule: Final site of
selective reabsorption.
• ─ Collecting
Duct: Feeds into ureter
and is where
osmoregulation occurs.
• ─ Vasa Recta: Blood
network that reabsorbs
components from the
filtrate.
SUM ACADEMY LARKANA

Urine Production
• Steps in Urine Production
• 1.(Ultra)Filtration
• 2. Tubular Reabsorption
• 3. Tubular Secretion
• 4. Counter-current exchange
SUM ACADEMY LARKANA

• ─ The process in which
hydrostatic pressure causes 1. ULTRA-FILTERATION
water and small dissolved
molecules from blood into
Bowman’s capsule
• ─ The glomerulus has a
capillary bed that is highly
pressurized
• ─ Therefore, dissolved
solutes pass through the
walls of the glomerulus
into the Bowman’s
capsule.
• ─ The fluid that passes
from the blood through the
capillary walls of the
glomeruli into nehron is • ─ The daily volume of
called filterate isotonic to glomerular filtrate; 150-180
liters/day.
plasma with exception of • ─ 99% returns to the
proteins. bloodstream via reabsorption, so
1-2 liters are excreted as urine.
1. Filtration
What is the kidney ‘selectively permeable’ for?
However, urea is the MOST ABUNDANT of the waste products the kidney must excrete!
2. SELECTIVE REABSORPTION
• ─ Substances that are needed by the body
are reabsorbed into the blood capillaries
surrounding the nephron
• ─ e.g. water, glucose and amino acids,
salts
SUM ACADEMY LARKANA

Selective reabsorption
PCT
DCT
Ascending
Limb
Descending
limb Collecting duct
3. Tubular Secretion
• ─ Tubular secretion is the transfer of materials from
peritubular capillaries to lumen of nephron.
• ─ Tubular secretion is caused mainly by active
transport.
• ─ Tubular secretion and involves substances being
added to the tubular fluid (nephron lumen).
• ─ This removes excessive quantities of certain dissolved
substances from the body.
• ─ Tubular secretion maintains the blood at a normal
healthy pH (which is typically in the range pH 7.3 to pH
7.4).
SUM ACADEMY LARKANA

Tubular secretion
In distal convoluted tubules, potassium ions or hydrogen
ions may be passively secreted in response to active
reabsorption of sodium ions
Counter current exchange
• ─ Countercurrent exchange : The exchange of
chemicals between two fluids flowing in opposite
directions is called counter current exchange.
Loop of Henle
Vasa recta Vasa recta

Nephric filterate Nephric filterate
Na+ Na+
interstitium interstitium
H2O
Na+ Na+
Two counter current mechanisms in
kidney
• ─ There are two counter current
mechanisms operating in kidney.
• ─ Vasa rectae
• ─ Henle’s loop
• ─ Loop of Henle is known as counter
current multiplier.
SUM ACADEMY LARKANA

• ─ The ascending limb of the
loop of Henle transports
solutes (Na+) out of the tubule
lumen with little or no water.
• ─ This generates
hyperosmotic medullary
interstitium. Ascending limb
• ─ Countercurrent exchange of
solutes between ascending
and descending vasa recta Na+
minimizes solute washout from
the medullary interstitium. Interstitium
• ─ The countercurrent system
permits forming a
concentrated urine.
Loop of Henle
• ─ The vasa recta serve as countercurrent exchangers,
minimizing washout of solutes from the medullary
interstitium.
• ─ As blood descends into the medulla it becomes
progressively more concentrated, partly by solute entry
from the interstitium.
• ─ As blood ascends back toward the cortex, it becomes
progressively less concentrated as solutes diffuse back
out into the medullary interstitium and as water moves
into the vasa recta.
• ─ U shape of the vasa recta capillaries, which act as
countercurrent exchangers.
• ─ Thus, the vasa recta do not create the medullary
hyperosmolarity, but they do prevent it from being
scattered.
Loop of Henle
Vasa recta Vasa recta

Nephric filterate Nephric filterate
Na+ Na+
interstitium interstitium
H2O
Na+ Na+
URINE
Analysis of urine in diagnosis of disorders
• ─ Urine normally has no sugars, proteins
or blood cells but in pathological conditions
urine may have such compounds
• ─ Urine with sugar called glycosuria, in
diabetes mellitus.
• ─ Urine with albumen protein called
albuminuria,
• ─ Urine with ketone bodies in ketonuria,
• ─ Urine with blood cells in haematuria.
Kidney as osmoregulatory organ
• ─ The hypothalamus detects
changes in the amount of
water present in the blood.
• ─ If there is too little water
(the blood is too
concentrated) it tells the
pituitary gland to secrete
ADH.
• ─ The ADH makes the
kidney re-absorb water from
the ultra-filtrate.
• ─ The result of reabsorbing
water is to reduce the
concentration of the blood.
• ─ By negative feed back the
pituitary makes less ADH.
Kidney as Excretory organ
• ─ 1) Excretion of metabolic wastes:

• ─ Urea ( By product of amino acid metabolism)
• ─ Ammonia (Renal ammonia excretion)
• ─ Ammonia produced in the kidney cells
(ammoniagenesis) excreted into the urine.
• ─ Creatinine ( By product of creatine phosphate break
down in muscle cells)
• ─ Creatinine (C4H7N3O )
• ─ Uric acid ( By product of break down of nucleotides)
( whose build up causes gouty arthritis)
Two types of nephron
• Cortical nephrons
– ~85% of all nephrons
– Located in the cortex
• Juxtamedullary nephrons
– Closer to renal medulla
– Loops of Henle extend deep into renal pyramids
SUM ACADEMY LARKANA

Cortical and Juxtamedullary Nephrons
Juxtamedullary
nephrons have
longer Loop of
Henle deeply
extended into
Cortical nephrons
renal medulla.
have shorter Loop
of Henle slightly
extended into renal
medulla.
Cortical nephrons have
shorter Loop of Henle
slightly extended into
renal medulla.
Juxtamedullary
nephrons have longer
Loop of Henle deeply
extended into renal
medulla.
Cortical and
Juxtamedullary Nephrons
Effects of hormones on the working of
kidney
• ─ The posterior lobe of the pituitary releases Antidiuretic
Hormone (ADH), It is also known as vasopressin.
• ─ Function : acts on the collecting ducts of the kidney to
facilitate the reabsorption of water into the blood.
• This reduces the volume of urine formed (giving it its
name of antidiuretic hormone).
• ─ A deficiency of ADH leads to excessive loss of urine, a
condition known as diabetes insipidus also called
diuresis.
• ─ In many species, high concentrations of antidiuretic
hormone cause widespread constriction of arterioles,
which leads to increased arterial pressure. It was for this
effect that the name vasopressin was coined.
Effects of hormones on the working
of kidney
• ─ Aldosterone secreted by adrenal gland acts on
the kidney promoting the reabsorption of Na+
into the blood and the maintenance of normal
blood pressure.
• ─ The parathyroid glands are 4 tiny structures
embedded in the rear surface of the thyroid
gland.
• ─ They secrete parathyroid hormone (PTH).
PTH promotes reabsorption of Ca2+ from the
fluid in the tubules in the kidney.
SUM ACADEMY LARKANA

Kidney stones (Renal calculi)
• ─ Kidney stones (calculi) are hardened

mineral deposits that form in the kidney.
• ─ They originate as microscopic particles
and develop into stones over time.
• ─ The medical term for this condition is
nephrolithiasis, or renal stone disease.

Causes of kidney stones
• ─ Kidney stones form when there is a high level
of calcium (hypercalciuria), oxalate
(hyperoxaluria), or uric acid (hyperuricosuria) in
the urine; or insufficient water in the kidneys to
dissolve waste products.
• ─ The kidneys must maintain an adequate
amount of water in the body to remove waste
products.
• ─ If dehydration occurs, high levels of
substances that do not dissolve completely (e.g.,
calcium, oxalate, uric acid) may form crystals
that slowly build up into kidney stones.
Kidney stones
• ─ 70% kidney stones are composed of calcium oxalate
or phosphate.
• ─ 5% calculi are formed by combination of calcium,
magnesium and ammonium phosphate.
• ─ 5% calculi are formed by uric acid.
• ─ 20% Infective kidney stones (Struvite stones)
• ─ First described by Christian Von struve.
• ─ These stones are formed in urinary tract infected with
ammonia-producing bacteria.
• ─ These stones are made up of magnesium ammonium
phosphate.
Lithotripsy
• ─ Lithotripsy is a
medical procedure that
uses shock waves to
break up stones in the
kidney, bladder, or
ureter (tube that
carries urine from your
kidneys to your
bladder).
• ─ After the procedure,
the tiny pieces of
stones pass out of
your body in your
urine.
• ─ Video

Renal failure
• ─ Renal failure or kidney failure is a situation in
which the kidneys fail to function adequately.
• ─ It is divided in acute and chronic forms.
• ─ Symptoms of kidney failure include
• ─ High levels of urea in the blood
• ─ Vomiting
• ─ Nausea
• ─ Weight loss
• ─ High blood pressure etc

Dialysis
• ─ Dialysis is a procedure to remove waste
products and excess fluid from the blood when
the kidneys stop working properly.
• ─ When is dialysis needed?
• ─ You need dialysis when you develop end
stage kidney failure --usually by the time you
lose about 85 to 90 percent of your kidney
function.

Hemodialysis
• ─ Hemodialysis
uses a man-made
membrane
(dialyzer) to remove
wastes and extra
fluid from the blood.
• ─ The fluid used to
filter or clean the
blood is called
dialysate.
• ─ Video
Peritoneal dialysis
• ─ A form of dialysis
in which the blood is
cleaned inside the
patient's body, using
the peritoneum (a
natural membrane
that lines the wall of
the abdomen) as a
filter.
Peritoneal dialysis
Kidney transplant
• ─ A kidney
transplant is a
surgical procedure to
place a kidney from
a live or dead donor
into a person whose
kidneys no longer
function properly.
What are the two types of kidney
transplant?
• ─ 1.Those that come from a living donor.
• ─ Living-donor renal transplants are further
characterized as genetically related (living-
related) or non-related (living-unrelated)
transplants, depending on the biological
relationship between the donor and recipient.
• ─ 2.Those that come from those donor who
have died (cadaveric donor).
• ─ CADAVER = a dead body
What is rejection
• ─ The most important complication that may
occur after a transplant is rejection of the kidney.
• ─ The body’s immune system guards against
attacks by all foreign matter such as bacteria.
• ─ This defense system may recognize tissue
transplanted from someone else as "foreign" and
act to fight this foreign invader.

Marker proteins
• ─ Marker proteins extend across the
cell membrane and serve to identify
the cell.
• ─ The immune system uses these
proteins to tell friendly cells from
foreign invaders.
• ─ They are as unique as
fingerprints.
• ─ They play an important role in
organ transplants.
• ─ If the marker proteins on a
transplanted organ are different
from those of the original organ the
body will reject it as a foreign
invader.

Thermoregulation
• ─ Thermoregulation is maintenance of
body temperature that enables the body to
function efficiently.
• ─ The normal temperature range for active
life is 10 °C to 35 °C for most of the
organisms.

Thermoregulation in plants
• ─ Adaptations to low temperature
• ─ Damages of low temperatures
• ─ In low temperature the fluidity of the cell
membrane alters because lipids of the
membrane become locked into crystalline
structure which effect the transport of
solute.
Adaptations
• ─ Plants respond to cold stress by
increasing proportion of unsaturated fatty
acid, which help membrane to maintain
structure at low temperature by preventing
crystal formation.
• ─ Adaptations to freezing temperature
• ─ Freezing temperature causes ice crystal formation.
• ─ The formation of ice formation around cell wall does
not effect as badly and plant survive, however, formation
of ice crystals with in protoplasm perforates membranes
and organelle hence killing the cells.
• ─ Fructans are fructose-based polymers synthesized
from sucrose.
• ─ Plants store them to thrive at low temperatures since
fructans confer tolerance to freezing.
• ─ They bind to membranes, thereby helping to keep
cells intact (not damaged).

• ─ Damages of high temperature
• ─ High temperature denatures the enzymes and
damages the metabolism therefore harms or kills the
plants.
• ─ Adaptations
Plants use evaporative cooling to manage with high
temperature.
• ─ Most plants have adaptive to survive in heat stress as
plants of temperate regions face the stress of 40 degree
centigrade.
• ─ Heat shock proteins
• ─ These proteins protect enzymes and other proteins
thus help prevent denaturizing.
Thermoregulation in animals
• ─ Organisms obtain heat energy from two

basic sources i.e. externally or internally.
• ─ Animals can be divided into two
categories on the basis of gaining heat.
• These are
• ─ Ectotherms
• ─ Endotherms
Ectothermy and Endothermy
• ─ Ectotherms: Ectotherms are animals
that produce metabolic heat at low rates
and rely primarily on thermal conditions
of their surroundings.
• ─ Ectotherms have low metabolic-rate.
• ─ Poikilotherms: animals whose body
temperature varies with the environment
• ─ Ectotherms attempt to regulate their
temperatures within broad limits by
behavioural means.
─ Endotherms: Endotherms are animals that generate
their own body heat and are able to maintain internal
temperatures.
─ This is achieved through elevated basal metabolism.
Homoiotherms: animals whose body temperature
remains the same, e.g. birds & mammals
Endothermic birds & mammals are successful

lives in polar regions
Examples of Endotherms and
Ectotherms
• Endotherms
– mammals, birds
• Ectotherms
– fish, amphibians, reptiles, invertebrates

Ectothermy and Endothermy
• ─ Ectotherms and Endotherms differ in the
way of gaining heat but they lose heat by
same mechanisms, these are
• ─ Evaporation
• ─ Radiation
• ─ Convection
• ─ Conduction
Evaporation: the process of a liquid changing into a gas.
Evaporation of water from body surface cools the body.
Radiation: Transfer of heat by electromagnetic waves is

called radiation.
Convection: Transfer of heat as gas or liquid particles move
around the body surface.
Conduction: is direct transfer of heat when objects

of different temperature come in contact.
Heterotherms
• ─ Heterotherms are animals that exhibit characteristics
of both poikilothermy and homeothermy.
• ─ Heterotherms are endotherms that can switch
between ectothermic and endothermic strategies.
• ─ These changes in strategies typically occur on a daily
basis.
• ─ Heterothermic creatures are homeothermic for one
portion of the day and poikilothermic for second portion
of day (daily cycle).
• ─ (e.g. bats & hummingbirds)
• ─ In bats and hummingbirds body
temperature and metabolic rate,
are elevated only during activity.
• ─ When at rest, these animals Heterothermy
reduce their metabolism
drastically, which results in their
body temperature dropping to
that of the surrounding
environment.
• ─ This makes them
homeothermic when active, and
poikilothermic when at rest.
• ─ Torpor is a state of decreased
physiological activity in an
animal, usually by a reduced
body temperature and metabolic.
• ─ Bats and hummingbirds reduce
their set point every day while
they are inactive.
Hummingbird Torpor
• ─ BODY TEMPERATURE: Normally at about 40.5
degrees C (105-108 degrees F).
• ─ On cold nights, a hummingbird can lower its body
temperature by about 20 degrees C , thus conserving
energy that is used to maintain its normal temperature.
• ─ The next morning, the hummingbird speeds up its
metabolism and get its body temperature back up to
normal within a few minutes.
• ─ Video : Sleeping Torpor Hummingbird.
• ─ Hummingbirds enter torpor at night to slowdown their
metabolism.
• ─ They will even hang upside down. It takes them as
much as an hour to fully awaken.

Means of thermoregulation
• ─ Behavioural regulation: This regulation
involves some behaviuoral means
exhibited by an animal.
• ─ Behavioral responses
– Used by endotherms and ectotherms
– Examples
– Moving to the sun or shade
– Migrating
– Bathing
All ectotherms employ behavioral means of
thermoregulation
• Animals which have
no metabolic
method of
regulating their
body temperature
are known as
ectotherms.
• How can ectotherms • Ectotherms use behaviour to control
regulate there body their body temperature by altering
temperature if not the amount of heat they are gaining
by an internal or losing by convection, conduction
metabolic means? and radiation.
Means of thermoregulation
• Physiological means: It involves the regulation of
body temperature by some physiological means.
• ─ It is exhibited by
• ─ Change in blood circulation
• ─ Cooling by evaporation
• ─ Shivering
• ─ Hormonal changes boost metabolic rate in
birds and mammals
• ─ It is one of the characteristics of endotherms.

Thermoregulation in mammals
• ─ The basal-metabolic rate generate heat in
endotherms including birds and mammals.
• ─ Mammals maintain their body temperature
within range of 36 °C to 38 °C.
• ─ Birds maintain their body temperature within
range of 41°C to 43 °C.

Thermogenesis
• ─ Thermogenesis means the creation of
heat.
• ─ There are two types of thermogenesis.
• ─ shivering thermogenesis
• ─ Non-shivering thermogenesis.

Shivering thermogenesis
• ─ Creation of heat by means of increase
contraction of skeletal muscles is called
shivering thermogenesis.
• ─ The hypothalamus triggers the skeletal
muscles to contract and causes shivering,
which produces heat.
• ─ The shivering heats up the body.

Non-shivering thermogenesis
• ─ Non-shivering thermogenesis occur due to
action of certain hormones.
• ─ Newborn babies contain brown fat in their
neck and upper back that serves the function of
nonshivering thermogenesis.
• ─ Brown adipose tissue gets its color from the
high density of mitochondria in the individual
adipose cells.
• ─ Mitochondria-packed brown-fat cells burn
energy and produce heat.

Brown fat
• ─ Brown adipose tissue (BAT) : Brown fat is type of
adipose tissue composed of several small lipid (fat)
droplets and a large number of iron-containing
mitochondria (the cell’s heat-burning engine).
• ─ The iron, along with lots of blood tiny blood vessels,
gives this fat its brownish appearance.
• ─ It is located mainly around the neck and large blood
vessels of the thorax.
• Function : The purpose of brown fat is to burn calories
in order to generate heat.

Mechanism of thermoregulation in cold
temperature
• 1. Physiological
means
• A) Non-shivering
thermogenesis
• Erection of hairs
• Reduction in blood
flow towards skin
• Sub-cutaneous fat
accumulation
• Erection of hair: This traps a layer of warm air which
acts like an insulator.
• ─ The Erector pili muscles attached to each body hair
contract, causing the hair to stand up, called
piloerection. This reduces the airflow over the skin, and
the amount of heat lost.
• ─ Reduction in blood flow towards skin: by
vasoconstriction.
• ─ When the environment is very cold these blood
vessels can constrict, greatly reducing to conserve
heat for important organs.
• ─ Subcutaneous fats: found just beneath the
skin aids in process of homeostasis by forming
a layer of insulation there fore stopping heat
loss.
temperature
Shivering thermogenesis
• ─ Creation of heat by means of increase
contraction of skeletal muscles is called
shivering thermogenesis.
• ─ The skeletal muscles create the
shivering.
• ─ The shivering heats up the body.

An other way of gaining heat
• ─ Chemical thermogenesis
• ─ Glands secrete adrenaline and thyroxine
respectively, which increase the metabolic
rate in different tissues, especially the
liver, so generating heat.

temperature
• ─ Behavioural means:
• ─ Moving to a warmer location
• ─ Huddling close together with other
individuals
• ─ In humans putting on additional clothes.

Mechanism of thermoregulation in hot
temperature
• ─ Physiological means:
• ─ Lowering hairs which reduces the
insulating effect.
• ─ Reduction in subcutaneous fats which
reduces the insulating effect
• ─ Increase sweating
• ─ vasodilatation

• ─ Vasodilation: blood vessels connected to arteries
carrying this heat dilate, or widen.
• ─ This allows more blood flow into the capillaries in the
skin, and results in heat loss from the body through the
skin.
• ─ Some mammals do not have sweat
glands in skin or scanty glands in skin,
perform panting.
• ─ It is efficient method of losing heat from
the mouth, tongue and respiratory
passage.
temperature
temperature
• ─ Behavioural means:
• ─ Moving to a cooler location
• ─ Use of thin clothes
• ─ Bathing
Fever (Pyrexia)
• ─ Hypothalamus is body's thermostat,
usually set at 37oC.
• ─ Fever or pyrexia displaces
hypothalamus set point.
─ Fever included in 2nd line of defense,
characterized by high body temperature above
set point.
─ Pyrogen: A substance that produces fever.
Interleukin 1, called a pyrogen –secreted by macrophages.

Non-infectious Fever
• ─ Infection may be absent in fever.
• ─ This is called non-infectious fever.
• ─ Causes:
• ─ Drug fever (drug allergy)
• ─ Hyperthyroidism can produce fever
through excess thyroid hormone altering
thermoregulation.

Chapter 1 Homeostasis

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Chapter 1 Homeostasis

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Chapter 1

BY─ Prof Mansoor Abro SUM ACADEMY LARKANA

BY─ Prof Mansoor Abro

• ─ Chemically via hormones

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

• ─ A Regulator which receive message from receptor

• ─ The set point is range of normal functional values

• ─ Effectors which receive message from regulator

BY─ Prof Mansoor Abro

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

BY─ Prof Mansoor Abro

• ─ Plants are grouped into four groups on

SUM ACADEMY LARKANA

BY─ Prof Mansoor Abro

SUM ACADEMY LARKANA

• ─ They can easily compensate water lost by

BY─ Prof Mansoor Abro

SUM ACADEMY LARKANA

BY─ Prof Mansoor Abro

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

• ─ Salt glands: The salt gland is an organ for excreting

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

SUM ACADEMY LARKANA

Most aquatic animals, Mammals, amphibians, Birds and many other

Ammonia Urea Uric acid

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

BY─ Prof Mansoor Abro

2NH3 + Co2 → CO(NH2)2 + H20

• Two of the three are used as a source of energy in the

BY─ Prof Mansoor Abro

SUM ACADEMY LARKANA

Break down of hydrogen peroxide

• ─ Cholesterol is chiefly synthesized in liver.

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

• ─ Renal cortex: The

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA

• ─ Kidney nephrons are the

SUM ACADEMY LARKANA

Descending limb Collecting

Structure of nephron To renal pelvis

SUM ACADEMY LARKANA

SUM ACADEMY LARKANA