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CLASS – XII (AKUEB)
BIOLOGY
(ZOOLOGY)

TEACHER
MS. MISBAH ASHFAQ
3
CONTENTS:ZOOLOGY (XII)
Chapter # 15: HOMEOSTASIS
Chapter # 16: SUPPORT &
MOVEMENT
Chapter#17: COORDINATION
AND CONTROL

Chapter # 18: REPRODUCTION

﹡.
Chapter #19: GROWTH AND
DEVELOPMENT
Chapter #23: BIOTECHNOLOGY

Chapter # 24: EVOLUTION

Chapter # 27: MAN AND HIS

ENVIRONMENT 4
﹡.

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 ZOOLOGY PRACTICAL (15 Marks)
CONTENTS
Portfolio (3 Marks)
 Stage 1------------- Spotting (4 Marks)
Task 1 and 2
Identify the given slides/specimens
 Stage 2------------- Slide Prep. (3 Marks)
Task 3 and 4
Stage 3---------- (5 Marks)
Task 5,6,7 and 8

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﹡.

7
﹡.

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9
﹡.

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 SLO # 15.1.1
Define homeostasis
SLO # 15.1.2
.
Significance of
homeostasis
 HOMEOSTASIS
◍ HOMEOSTASIS is the maintenance of a
constant internal environment.

◍ INTERNAL ENVIRONMENT means the

surroundings of the cells of the body
(i.e tissue fluid and blood) or the
conditions within the body of the
organism.
13
HOMEOSTASIS is a set of
regulatory mechanisms,
which are involved in
maintaining an organisms
internal environment
within suitable limits.
14
 Internal environment that must be
kept constant:
OSMOREGULATION: Regulation of osmotic pressure of
cell determined by the relative concentration of solutes
and water.

EXCRETION: Removal of excess substances,

unwanted or toxic metabolic by-products.

THERMOREGULATION: Regulation of temperature

up to a tolerable limit.
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 SLO # 15.2
FEEDBACK SYSTEM
SLO # 15.2.1
.
Define Feedback
system
 15.1.1: FEEDBACK SYSTEMS
A feedback system involves a stimulus
from one part of the body creating a
response from another part that acts to
alter the original stimulus.

There are two types of feedback

mechanisms that counter act upon each
other called Positive and Negative
feedback. 18
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 SLO # 15.2.2
Components of
feedback. system
.
.
 SLO # 15.2.3
Positive and Negative
.
feedback with
examples
NEGATIVE FEED BACK is the opposite effect
produced in relation to any change in the
body fluids. It suppresses the normal
physiological activities to bring body back to
normal state.
For example, as a consequence of eating
sweets or candies the level of glucose is
raised in the blood. It triggers the
mechanism, which decreases the blood
glucose back to normal limit.
Thermoregulation also occurs through
negative feedback. 24
25
26
POSITIVE FEED BACK is
concerned with the increase or
initiates the change of output
for any biological process.
For example if the body is
injured and bleeds positive
feedback begins with the
action of platelets.
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29
Negative feedback is more common
in living organisms than positive
feedback because it shifts the
system toward homeostasis and a
balanced state.
Positive feedback does not maintain
a stable, homeostatic condition
rather it intensifies the change that
is happening to the body.
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Positive and negative
feedback mechanisms
counteract each other
to maintain balance and
stability in a system
31
 SLO # 15.3
.
Osmoregulation
in animals
OSMOREGULATION
(It involves maintaining a
balance between water and
solute contents of cells)

33
Q:Which of these correct statements
describes control by negative feedback?
A-An injury to body tissue activates platelets in the blood
and these activated platelets release.

B-During the menstrual cycle, luteinising hormone

stimulates the release of oestrogen which in turn stimulates
the release of more luteinising hormone.

C-The onset of contractions during childbirth causes the

release of a hormone which stimulates further contractions

D-When blood pressure is high, nerve impulses from the

brain cause the blood vessels to dilate and blood pressure is
reduced. 34
 SLO # 15.3.1
Define Osmosis,
Water potential,
.
Pressure potential,
Solute potential
OSMOSIS : osmosis is the net
movement or diffusion of water
molecules from a solution with a high
concentration of water molecules
(high water potential) to a solution
.
with a lower concentration of water
molecules (low water potential),
through a cell's partially permeable
membrane.
WATER POTENTIAL (potential energy
of water molecule) is the capacity of a
living system to lose water.
The concentration of a solution is
biologically expressed either as
.
water/solute potential (in case of
plants) or
OSMOTIC PRESSURE (in case of
animals) which shows relative amount
of water and solutes in a cell.
 SLO # 15.3.3
Differentiate among
Hypertonic,
.
Hypotonic and
Isotonic solutions
 A solution with a lower solute
concentration as compared to a solvent
is called a hypotonic solution. In
contrast, a solution with a high solute
concentration as compared to a solvent
is called a hypertonic solution.
An isotonic solution
refers to a solution that
has the same osmotic
pressure as the
surrounding tissue.
42
 SLO # 15.3.4
Osmoregulation in
aquatic (fresh
. water
and marine)and
terrestrial animals
 OSMOREGULATORS AND
OSMOCONFORMERS

OSMOREGULATORS are those animals

that can MAINTAIN INTERNAL OSMOTIC
CONCENTRATIONS different from
surrounding medium. Such animals are
hypotonic or hypertonic to their
environment.
E.g. Almost all of the fresh water animals
and most of the marine 44
vertebrates.
OSMOCONFORMERS are those
animals that can CHANGE INTERNAL
OSMOTIC CONCENTRATIONS according
to that of surrounding medium. Such
animals are isotonic to their
environment.
E.g. All marine invertebrates and some
marine vertebrates (hag fishes and
elasmobranches e.g. sharks and rays.)
Some freshwater invertebrates.
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 OSMOCONFORMERS OSMOREGULATORS
1- Organisms that have Organisms maintain a
internal body solute constant internal osmotic
composition equals or environment in spite of
isotonic to the external changes in their external
environment. environment.
2- These are marine They live in marine, fresh
organisms. water and terrestrial
environments.

3- They can survive in wide They can survive in a

range of salinities. narrow range of salinities.

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OSMOCONFORMERS contain urea and
trimethylamine oxide (TMAO) in their
blood to adjust osmotic balance.
TMAO accumulates in the tissues and
protects against the protein-
destabilizing effects of urea.

For example shark and most of the

marine invertebrates like
echinoderms (e.g star fish), mussels,
marine crabs, lobsters, jelly fish,
ascidians are osmoconformers.
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OSMOREGULATION IN AQUATIC (FRESH-
WATER) ANIMALS:
A) OSMOREGULATION BY CONTRACTILE
VACUOLE:

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 B) OSMOREGULATION BY PRODUCING
DILUTE URINE:
Fresh water animals like fishes have a
hypertonic body fluids than the
surrounding water. Thus they remove
excess water by passing large quantities
of very dilute urine. During the excretion
process, they lose some essential ions as
well. However this is overcome by actively
absorbing selected ions from outside,
through gills. E.g. Trout
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OSMOREGULATORY ADAPTATIONS IN FRESH
WATER ANIMALAS

Large
Kidney
volume
reabsorbs the
of diluted
salts that are
urine
required
Actively transport Salts are also
salts from the obtained
outside with the from the
help of special salt food
cells (ionocytes)
51
 15.2.3: OSMOREGULATION IN AQUATIC
(MARINE) ANIMALS:
Marine bony fishes have hypotonic internal
environment so they are liable to lose water.
So in order to conserve water, they constantly
drink water. The salts taken in along with
water are actively excreted by special
excretory cells in the gills. Moreover, the
filtration rate in their kidneys is very low so
small quantity of concentrated urine is
excreted. E.g. Mackerel
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OSMOREGULATORY ADAPTATIONS IN MARINE
ANIMALAS
Small
Excess salts are
amount of
removed across
water in
the gill epithelium
scanty
(Na+,Cl- and K+)
urine
and by the kidney
Some fishes also (Mg++ and Ca++)
have special salt
secreting glands in
the wall of rectum
(rectal glands)
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To combat this, freshwater fish have very efficient
kidneys that excrete water quickly. They also
reabsorb salt from their urine before it is ejected
to minimize losses and actively take salt from
their environment using special cells in the gills.

To combat this, marine fishes drink vast amounts

of water and urinate little. Salt is a more
complicated problem: special cells in the gills
actively eliminate salt at the cost of extra energy
and these fishes do not absorb any salt from the
water they drink.
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OSMOREGULATION IN TERRESTRIAL
ANIMALS:

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a) WATER PROOF EXTERNAL COVERINGS:
To prevent water loss through external surfaces,
vertebrate like reptiles, birds and mammals have
water proof keratinized epidermis. Similarly the
insects have developed an external water-proof
layer called CUTICLE.

59
b) STORING AND EXCRETION OF SOLID WASTES:
Reptiles, birds and insects excrete uric acid as nitrogenous
waste, which is insoluble in water. It is stored temporarily
in cloaca where water is reabsorbed from it before its
removal from the body in semi-fluid form.

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c) USE OF METABOLIC
WATER:
Some mammals like
camel, kangaroo-rat etc.
make use of water
produced during the
breakdown of body fats.

d) STORING THE WASTES:

Mammals do retain some
urea in their kidneys
where it helps in
reabsorption of water. 61
SLO # 15.5
Excretion
.

in animals
 EXCRETION
“Excretion is a process by which
metabolic waste products and toxic
substances are eliminated from the
body of an organism.”
In vertebrates this is primarily
carried out by the lungs, kidneys
and skin.
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 SLO # 15.5.1

EXCRETORY . PRODUCTS
IN RELATION TO
HABITAT
EXCRETORY PRODUCTS IN RELATION TO
HABITAT

AMMONIA CREATINIE OR
TRIMETHYLAMINE
OXIDE (TMAO)
UREA

URIC HYPOXANTHINE
ACID
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TYPES OF EXCRETORY WASTES IN DIFFERENT ANIMALS

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 AMMONIA
(NH3)
1- Ammonia is a small gaseous molecule and is
highly soluble in water.
2- It diffuses very rapidly across the plasma
membrane.
3- It is highly toxic because it tends to raise the
pH of body fluids and interferes with membrane
transport functions.
4- Excreting ammonia by an animal is
advantageous because it does not require energy.
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5- Its toxicity is reduced when diluted with large
quantities of water (1 gm of nitrogen, in the form of
ammonia requires 500 ml of water to dissolve it to
nontoxic level). Such plenty of water can only be
afforded by many aquatic organisms (ammonotelic),
particularly those in freshwater.

6- In soft bodied invertebrates, the entire body

surface is involved in the removal of ammonia from
the body.

7- In fish, most of the ammonia is excreted through

gills as ammonium ions with kidneys playing a minor
role in the excretion of nitrogenous wastes.
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 UREA (CO(NH2)2)

1- Urea is relatively less soluble in water and

about 100,000 times less toxic than ammonia.

2- Some marine organisms and terrestrial

organisms (Ureotelic) remove their most of the
nitrogenous waste in the form of urea, because
they cannot afford to lose a lot of water during
the excretion of nitrogenous wastes ( 1 gm of
nitrogen, in the form of urea, requires 50 ml of
water to dilute it to non toxic level.)
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3- Those animals switched over from
ammonia to urea. This conversion requires
ATP.

4- Urea is produced in the liver by a

metabolic cycle that combines NH3 to CO2.

5- Mammals , most amphibians,

sharks and some bony fishes excrete
urea.
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71
 URIC ACID (C5 O3 N4 H4)

1- Uric acid is relatively larger molecule with

extremely low solubility in water. It is even less
toxic than urea.
2- It is produced as colloidal substance. Thus
further absorption of water results in its
crystallization of urates. ( 1 gm of nitrogen, in the
form of uric acid , requires just 1 ml of water for
its excretion)
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3- Formation of Uric acid requires ATP.
4- The suspension of uric acid is
discharged either in the form of thick
paste or as solid pellets.
5- Terrestrial animals e.g. birds,
many reptiles, insects, gastropods
who need to minimize loss of water
and have eggs enclosed in shells
excrete uric acid. These animals are
called Uricotelics. 73
The given animal excretes:
1- Urea
2- Water
3- Ammonia 1
4- Uric acid
74
 SLO # 15.5.2
Excretory process in
Hydra, Planaria,
.
Earthworm and
Cockroach
 SLO # 15.6
EXCRETORY
.

SYSTEM IN MAN
 EXCRETION

“Excretion is a process
by which metabolic
waste products and
toxic substances are
eliminated from the ﹡.
body of an organism.”
In vertebrates this is
primarily carried out by
the lungs, kidneys and
skin.

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 HUMAN
EXCRETORY
SYSTEM consists of:
1- a pair of kidneys
2- a pair of ureters
3- a urinary bladder
4- the urethra
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The KIDNEYS are a
pair of bean-shaped
organs on either side of
your spine, below your
ribs and behind your
belly. Each kidney is
about 4 or 5 inches
long, roughly the size
of a large fist.
The kidneys' job is to
filter your blood. 79
The URETERS are 25 to 30
cm long tubes connected anteriorly
with kidneys by wide opening
called RENAL PELVIS. Posteriorly
they become narrow and extended
downward to join urinary bladder.
The URINARY BLADDER
is an elastic muscular bag located
in front of the rectum. It stores
urine.
The URETHRA is the duct
through which urine passes from
the bladder to outside of the body.
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15.4.1:STRUCTURE
AND FUNCTION OF
KIDNEY

81
STRUCTURE: kidneys are symmetrical,
bean shaped reddish brown structures.
LOCATION: They located just below
the rib cage, one on each side of the
vertebral column between the 12th
thoracic and 3rd lumber vertebrae.
Kidneys positioned retroperitoneal in
the abdominal cavity. The right kidney
is located slightly below the left kidney
providing space to adjust liver. Left
kidney is slightly larger and closer to
the heart.
SIZE: These are 4-5 inches long almost
size of the fist.
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OUTER LAYERS OF KIDNEY

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 15.4.2:
STRUCTURE
OF
NEPHRON

88
 Both kidneys are
consisted of
millions of
functional units
called NEPHRONS.
These nephrons
are about one
million in each
kidney and mainly
perform filtration
of blood.
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 NEPHRON
is composed of:
1- The RENAL
CORPUSCLE consists
of a tuft
of capillaries called
a GLOMERULUS and
BOWMAN'S
CAPSULE.
2- The RENAL TUBULE
extends from the
capsule. 93
The tubule has 4 anatomically
and functionally different
parts:
(i)The proximal
convoluted tubule followed
by a straight section
(ii)The loop of Henle, which
has two parts, the descending
loop of Henle ("descending
loop") and the ascending loop
of Henle ("ascending loop");
(iii)The distal convoluted
tubule and
(iv)the last part of nephron
the collecting ducts. 94
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 The efferent
arteriole extended
down and forming a
network of
capillaries called
PERITUBULAR
CAPILLARIES that
surrounds the both
PCT and DCT. It
provides nutrients
and oxygen to the
renal cortex. 105
 Peritubular capillaries
moves downward
along with loop of
henle give branches
which are laterally
connected with the
capillaries of renal vein
or venule in the region
of medulla. This
complex network of
capillaries over the
loop of henle called
VASA RECTA. 106
 15.3.3: FUNCTIONS OF THE KIDNEY

1- Kidneys are very important homeostatic

organs.

2- it filters our blood and excretes waste and

extra fluid from our body by urine.

3- Kidney produces an active form of vitamin D3

which helps to absorb calcium and phosphorus in
our bones. These important minerals keep bones
strong.
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4- Kidney also work
as an endocrine
organ and secrete
some vital
hormones like
RENIN and
ERYTHROPOIETIN.
Renin maintains the
blood pressure
while erythropoietin
is involved in red
blood cells
production. 108
5- Kidneys balance the pH of our body by making
changing and adjusting amount of bicarbonate
HCO3- from the urine back to the blood and by
secretion of H+ ions into the urine.

6- Kidney regulates the water balance by

producing dilute and concentrated urine
according to the external environmental
changes.
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89,526,124
Whoa! That’s a big number, aren’t you proud?

113
 REGULATING BLOOD
WATER POTENTIAL
◍ The water potential of the blood has to be kept
relatively constant. Drastic changes of water
potential can cause serious problems. For
example, if blood plasma becomes too dilute,
the blood cells and tissue cells will swell
(because of endosmosis) and burst.
◍ If the blood plasma becomes too concentrated,
exosmosis will cause the blood cells and tissue
cells to become dehydrated and shrink.
114
 OSMOREGULATION
The key point for understanding osmoregulation is that all along the length of the nephron tubule, fluid
and solutes are exchanged between the filtrate in the tubule and the blood in the capillaries. This allows
the kidneys to fine-tune the composition of the blood. The solutes and fluids that aren’t reabsorbed into
the blood are excreted as urine.
Body maintain water and electrolytes concentration at a relatively constant level by the mechanism
of osmoregulation.

Keeping your body fluids isotonic to body tissues is known as osmoregulation, and the key regulator of
your blood’s homeostatic set point for osmoregulation is the hypothalamus,
The hypothalamus is located just above the pituitary gland. When sensors in the hypothalamus detect that
the blood has become too concentrated (hypertonic), they signal the pituitary to release the
hormone ADH into the bloodstream. Antidiuretic hormone (ADH) has the
primary role in osmoregulation by controlling the amount of urine formation.

Anti-diuretic hormone (ADH) regulates the level of water reabsorption in the collecting duct.
Because it’s the antidiuretic hormone, ADH has the opposite effect that a diuretic has. ADH acts on the
lower part of the tubule, a part of the nephron tubule called the collecting duct
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124
DISORDERS OF
URINARY TRACT

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128
 RENAL
STONES
OR
RENAL
CALCULI

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132
1- KIDNEY STONES OR CALCULI are mainly (about
70%) composed of calcium oxalate or phosphate.
Oxalate is an end product of body metabolism and
is present naturally in the urine . The salt it forms
with calcium has a low solubility. An abnormally
high level of oxalate in urine promotes stone
formation and may be related to a diet containing
food or drinks with a high content of oxalic acid,
for example tomato, spinach, leafy vegetables etc.
About 20% of calculi are termed as infective
stones. Such calculi consist of combination of
calcium, magnesium and ammonium phosphate.
Some stones (about 5%)133are formed by uric acid.
LITHOTRIPSY is a recent method for removing
kidney and ureteral stones. In this procedure
shock waves or ultrasonic waves are used to
break up calculi for removal. Ultrasonic
lithotripsy involves the use of an ultrasonic
probe through a telescopic tube to help break
up the stones.
Shock waves lithotripsy is more advance
method in which shock waves are being
focused on stones from outside the body. After
being broken, the smaller fragments are
passed in urine. 134
 LITHONEPHRITIS
The word lithonephritis refers a
condition in which the kidneys
become inflamed due to the
presence of calculi (i.e., kidney
stones). Calculi can irritate the
cells and tissues of the kidneys,
and this irritation can lead to pain
and inflammation.135
136
LITHOTRIPSY

137
138
EXTRACORPO-
REAL
(OUTSIDE THE
BODY) SHOCK
WAVE
LITHOTRIPSY
(ESWL)

139
PERCUTANEOUS NEPHROLITHOTOMY
(PCNL)

140
LAPAROSCOPIC PYELOLITHOTOMY

141
142
 2- KIDNEY/RENAL FAILURE
Kidney failure, also known as end-stage kidney
disease, is a medical condition in which the kidneys are
functioning at less than 15% of normal. There is a
reduction in the ability of the kidneys to filter waste
products from the blood and excrete them in urine, for
osmoregulation and to regulate the blood pressure.
As a consequence the nitrogenous wastes start
accumulating in the blood which leads to the
symptoms such as nausea, vomiting, loss of appetite,
weakness, breathlessness etc.
In severe cases, it leads to coma and death.
Associated complications may include pneumonia,
bleeding in the stomach, high blood pressure etc.
143
 CAUSES OF KIDNEY FAILURE
The most common causes are:
• High blood pressure.
• Chronic glomerulonephritis (kidney damage)
• High blood sugar (diabetes)
• Polycystic kidney disease.
• Blocked urinary tract.
• kidney infection.
• Alcohol abuse(constant heavy drinking)
• Severe accidents that physically damage the kidney
• Complications from undergoing major surgery
144
 DIALYSIS
In medicine, dialysis is the procedure of removing excess water,
solutes, and toxins from the blood in people whose kidneys can no
longer perform these functions naturally. This is referred to as
renal replacement therapy.

Dialysis is used as a temporary measure in either acute kidney

injury or in those awaiting kidney transplant and as a permanent
measure in those for whom a transplant is not indicated or not
possible.

(Normally, the kidneys filter the blood, removing harmful waste

products and excess fluid and turning these into urine to
be passed out of the body.)
145
 TYPES OF DIALYSIS
Dialysis works by filtering toxins, waste and fluid
from the blood through a semipermeable
membrane or by artificial means.
There are different types of dialysis,

(i) HEMODIALYSIS
(ii) CONTINUOUS RENAL REPLACEMENT
THERAPY (CRRT)and
(iii)PERITONEAL DIALYSIS
147
 PRINCIPLE
Dialysis works on the principles of the diffusion of solutes
and ultrafiltration of fluid across a semi-permeable membrane.
Diffusion is a property of substances in water; substances in water
tend to move from an area of high concentration to an area of low
concentration. Blood flows by one side of a semi-permeable
membrane, and a dialysate, or special dialysis fluid, flows by the
opposite side. A semipermeable membrane is a thin layer of
material that contains holes of various sizes, or pores. Smaller
solutes and fluid pass through the membrane, but the membrane
blocks the passage of larger substances (for example, red blood
cells and large proteins). This replicates the filtering process that
takes place in the kidneys when the blood enters the kidneys and
the larger substances are separated from the smaller ones in
the glomerulus. 148
149
 FEATURES OF A DIALYSIS MACHINE
◍ * The dialysis fluid contains
the same concentration of
essential substances as
healthy blood
◍ *The dialysis fluid
(dialysate)does not contain
metabolic waste products
◍ *The tubing in the machine
is narrow, long and coiled
◍ *The direction of the blood
flow is opposite to the flow
of the dialysis fluid
150
151
 AV FISTULA
An AV FISTULA is a connection that's made
between an artery and a vein
for dialysis access. A surgical procedure,
created by a vascular specialist. With an AV
fistula, blood flows from the artery directly
into the vein, increasing the blood pressure
and amount of blood flow through the
vein. The increased flow and pressure
causes the veins to enlarge. The enlarged
veins will be capable of delivering
the amount of blood flow necessary to
provide an adequate hemodialysis
treatment. The fistula usually requires from
8 to 12 weeks for the veins to dilate prior to
initial use. 152
153
154
155
 PERITONEAL DIALYSIS

PRINCIPLE: Installation of dialysis

fluid into the peritoneal cavity creates
trans- membrane osmotic and
diffusive gradients that facilitate
water removal (ultrafiltration [UF]),
convection, and diffusion of solutes
across the membrane.
156
Peritoneal dialysis requires an abdominal incision
which is done in the hospital. Through the incision
a catheter is inserted into the peritoneal cavity.
Dialysate from a bag attached to the catheter
passes into the peritoneal cavity where it is left
for several hours.
As a consequence, wastes from the blood vessels
lining the peritoneal cavity seep through the
peritoneal membrane into the cavity and mixes
with dialysate. The fluid is then allowed to drain
out through the catheter and into the empty
dialysate bag. The process takes about an hour
and is repeated during the157
day or over night.
158
 KIDNEY TRANSPLANT

A kidney transplant is a surgery done to

replace a diseased kidney with a healthy
kidney from a donor. The kidney may
come from a deceased organ donor or
from a living donor. Family members or
others who are a good match may be
able to donate one of their kidneys. This
type of transplant is called a living
transplant. 159
160
THERMOREGULATION

161
POIKILOTHERMS (COLD BLOODED)
are those animals whose body
temperature changes in
accordance with the fluctuations
of the environmental
temperature.
Examples: All invertebrates,
fishes, amphibian and most
reptiles 162
HOMOIOTHERMS (WARM BLOODED)
are those animals who have
constant body temperature which
is independent of the
environmental temperature.
Examples: Few reptiles, Birds
and Mammals
163
ECTOTHERM are those animals
who absorb heat energy from
their environment. They have
behavioural means of
thermoregulation.
Example: Lizards basking in
the sun
164
ENDOTHERMS are those animals
who generate their own heat
energy from their
environment. They have
physiological as well as
behavioural means of
thermoregulation.
Example: Mammals
165
HETEROTHERMS are those
animals who generate heat of
varying degrees so their body
temperature is kept in a
wider range.
Example: Bats, Humming
birds etc.
166
THERMOREGULATION IN
MAMMALS (MAN)

167
There are two ways to increase heat
production:
1- SHIVERING THERMOGENESIS
( Heat production by increasing
contraction of muscles
﹡. through
shivering)
2- NON-SHIVERING THERMOGENESIS
(Heat production due to the action of
certain hormones)
168
In some mammals,
thermogenesis
occurs due to a
specialized tissue
called BROWN FAT,
which is found in the﹡ .
neck and between
the shoulders. This is
specialized for rapid
heat production.
169
 TEMPERATURE REGULATION
HEAT PRODUCTION AND HEAT LOSS

Heat is produced ◍ Heat is lost

within the body as a result ◍ through the skin by
of metabolic activities. convection, radiation and
◍ The body can gain extra to a limited extent, by
heat through vigorous conduction.
muscular exercise, the ◍ by evaporation of water
consumption of hot food in sweat.
and being in warm
environment or from the ◍ in the faeces and urine;
sun’s radiation. and
Excess heat needs to be ◍ in the air that is exhaled
removed from the body. 170
﹡.

171
 TEMPERATURE REGULATION
The HYPOTHALAMUS in the brain monitors
and regulates the body temperature.
The hypothalamus receives information
about temperature changes from two
sources.
(i) Thermoreceptors in the skin which
detects temperature from the environment.
(ii) Thermoreceptors in the hypothalamus
which detect temperature
172 of the blood.
 MECHANISMS OF THERMOREGULATION IN COLD
TEMPERATURE

1- 2-
PHYSIOLOGICAL BEHAVIOURAL
MECHANISMS MECHANISMS
﹡.

(a) Non shivering thermogenesis

(b) Shivering thermogenesis

173
 (a) Non shivering thermogenesis

(i) Erection of hair

(ii) Reduction in blood flow through skin

(Vasoconstriction) ﹡.

(iii) Subcutaneous fat accumulation

(iv) Metabolic rate increased

174
 (b) Shivering thermogenesis
In cold condition, the muscle tone,
initially under nervous control, tend to
rise. If the cold continues shivering
begins which generate ﹡.
heat in muscles.
Under persistant cooler conditions, the
basal metabolic rate is raised in short
term by the secretion of hormone
adrenaline and in longer term by the
secretion of another hormone, thyroxine.
175
 2-
BEHAVIOURAL
MECHANISMS

Behavioural mechanisms
include moving to a warmer
location, huddling close
together with other
individuals; in humans putting
on additional clothes.

176
177
178
MECHANISMS OF THERMOREGULATION IN HOT
TEMPERATURE

1- 2-
PHYSIOLOGICAL BEHAVIOURAL
MECHANISMS MECHANISMS
﹡.

Non shivering thermogenesis

179
 (a) Non shivering thermogenesis
(i) Lowering of hair

(ii) More blood flows through skin

(Vasodilation) ﹡.

(iii) Subcutaneous fat reduction

(iv) Sweat production

(v) Metabolic rate decreased

180
 2-
BEHAVIOURAL
MECHANISMS

Behavioural mechanisms
include moving to a cooler
location, in humans putting on
thin clothes.

181
182
183
ROLE OF BRAIN In
TEMPERATURE
﹡.

REGULATION

184
﹡.

185
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 👍
Thanks!
Any questions?

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