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8/9/2019 Circulation Lecturer.
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Circulation
1. CIRCULATION IN ANIMALS Every organism must exchange materials with
its environment
This exchange ultimately occurs at the cellular
level
In unicellular organisms, these exchanges occur
directly with the environment
Simple diffusion adequate for exchange ofmaterials between cell and external environment
Diffusion alone is not adequate for internal
transport of material for animals with many cell
layers/multicellular organisms
A specialized circulatory system is required
which interacts with every organ system in the
body
1.1 Types of circulatory system1.1.1 Invertebrate circulatory system The wide range of invertebrate body size and
form is paralleled by a great diversity in
circulatory systems
Most invertebrate have a gastrovascular cavity
or a circulatory system for internal transport
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Circulation
Open circulatory system: (Refer Figure. 42.2,pg. 869)
Vessels have open ends
No distinction between blood and interstitial
fluid, both are referred as body fluid =
hemolymph.
In insects and other arthropods, the heart = an
elongated dorsal tube.
Heart contracts: hemolymph pumps intointerconnected sinuses surrounding the
organs allowing exchange between
hemolymph and body cells
Heart relaxes: hemolymph draws into the
circulatory system through pores/ ostia.
Body movements that squeeze the sinuses
help circulate the hemolymph.
Insects: hemolymph mainly distributesnutrients & hormones. Gases/oxygen is piped
directly to cells by the tracheal system
Mollusks & arthropods: hemolymphpigment = hemocyanin(contains blue colouredcopper which binds to oxygen)
Q : W h a t a re so m e a d va n ta g e s o f o p e nc i rcu la to ry sys tem ? Lower hydrostatic pressure less energy
expenditure
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Circulation
Lack of extensive system of blood vesselless
energy required to build and maintain
Closed circulatory system (Refer Figure 42.3,pg. 869)
Annelids, cephalopods, echinoderms & all
vertebrates
Blood confined to vessels
Blood distinct from interstitial fluid
Heart pumps blood into large vessels that branch
into smaller vessels
Q: S ta te the ad vantages o f c lose c i rcu la to rys y s t e m .
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Heart
Hemolymph insinusessurrounding ograns
Anterior
vessel
Tubularheart
Lateral
vessels
Ostia
(a) An open circulatorysystem
Figure 42.3a
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Circulation
Higher blood pressuremore effective at
transporting fluids to meet the high metabolic
demands of the tissue and cells of larger and
more active animals.
Earthworms:
3 major vessel branch into smaller vessels thatsupply blood to various organ.
The dorsal vessel: The main heart, pumping
blood forward by peristalsis.
anterior: five pairs of vessels loop around the
digestive tract. Function = auxiliary hearts,
propelling blood ventrally
Blood contains hemoglobin dissolved in plasma
(in vertebrates hemoglobin red blood cells)
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Figure 42.342.3b
Interstitialfluid
Hear
t
Small branch vesselsin each organ
Dorsalvessel(main heart)
Ventralvessels
Auxiliaryhearts
(b) A closed circulatorysystem
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Circulation
1.1.2. Vertebrate Circulation/Cardiovascularsystem
The closed circulatory system of human and
other vertebrates is often called the
cardiovascular system.
Components:
(1) Heart
(2) blood vessels
(3) blood
1.1.2 Functions of vertebrate circulatorysystem
Q : L is t o u t th e fu n c t io n o f ve r te b ra tec i rcu la tory system
(1) Transport nutrients, oxygen, waste,
hormones
(2) Helps maintain fluid balance
(3) Defends body against invading
microorganisms
(4) Helps distribute metabolic heat within
body/maintain constant body temperature
for endotherms
(5) Helps maintain appropriate pH
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Circulation
1.2. Blood Vessel (Refe r F igu re . 42 .9 , pg .8 7 5 )
1.2.1 Characteristics and functions of bloodvessels
Structural differences of arteries, vein andcapillary correlate with their differentfunctions.
Wall of arteries & veins have 3 similar
layers:Outside: Connective tissue with elasticfibers & collagen allow the vessel tostretch and recoil.Middle: Smooth muscle & more elastic
fibers
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Circulation
Inner layer/lining lumen: Endothelium/single layer flattened cells thatminimize resistance to blood flow.
Q : A r te r ie s h a ve th ic k e r m i d d le a n d o u te rl aye rs than ve ins .W hy?
T o a c c o m m o d a t e t h e h i g h p r e s s u re o f b l o o dp u m p e d f ro m t h e h e a r t.The i r e l as t ic i t y he lps m a in ta in b loodpressure even w hen the hear t re laxes .
In the thinner-walled veins, blood flowsback to the heart mainly as a result ofskeletal muscle action.Within larger vein, flaps of tissues act asone way valves that allow blood to flowonly toward the heart. (Re fe r F igu re 42 .10pg . 875 )
Capillaries: Has only endothelium &basement membrane, thus enhancingexchange.
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Circulation
1.2.2. Comparison of blood vesselsQ : F il l in t he ta b le t o sh o w th e d if fe re n c e
betw ee n the b lood vesse l s .
Artery Capillaries VeinSmoothmuscle
Thick None Thin
Elastictissue
Abundant None Little
Lumen Small Large Large Bloodpressure
High Low Low
Valves In aorta andpulmonary
artery only
None Semilunar
valves/Ven
ous valves
Function Transportblood away
from heart
Exchange
of material
between
blood and
extra
cellular
fluid
Transport
blood back
to the
heart
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Circulation
Q : O bs erv ed th e in te rre la tio ns hip o f b lo odf lo w v e lo c i ty , t o ta l c r o s s s e c t io n a l a r e ao f b lo o d v e s se ls , a n d b lo o d p r es s u re inF igu re 42 .11 pg . 876
Blood flow highest in aorta (force from
contraction of ventricle), decreases significantly
in arterioles, lowest in capillaries due to
increase in total cross-sectional area. Blood
velocity begins to increase in veins due to
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Circulation
reduction in cross sectional area and
contractionof skeletal muscles squeezing the
veins
Blood pressure highest in aorta, arteries,
decreases as it passes through arterioles,&
capillaries due to peripheral resistance , lowest
in veins (pressure by pumping of heart has
dissipated, contraction of skeletal muscles
squeezing the veins help to create pressure for
blood flow in veins)
Enormous number of capillaries, small diameter
of capillaries makes capillaries have the
greatest cross sectional area than any other
vessel.
1.3 Heart1 . F ig ure 1 w i ll he lp y ou r ev ie w t he f lo w o f
b lo o d t hr ou g h a m a m m a l ia n c ir cu la to rys y st e m . L a b e l t h e in d ic a te d p a rt ,c o lo rth e o x yg e n -r ic h b lo o d c e l l an d th e nt ra c e t h e f lo w o f b l o o d b y n u m b e r in g t h ec ir cle s f r om 1 - 1 1 . S t ar t w ith n u m b er 1in the r ight ven t r ic le .
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Circulation
Figure 42.5The mammalian cardiovascular
system : an overview
2 Id e n t i fy th e la b e le d s t ru c tu re s in th isd i a g ra m o f a h u m a n h e a r t.
Figure 42.6 The mammalian heart: a closer look
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Circulation
1.3.1 Mechanism of heart electricalexcitat ion and contract ion of theheart (Refer Figure 42.8 pg. 874)
Some cardiac muscle cells = self-excitable.
Can contract without any signal from the
nervous system.
The sinoatrial (SA) node, located in the wall of
the right atrium or pacemaker sets the rate and
timing at which all cardiac muscle cells
contract.
Q : D is tin gu is h be tw e e n a m yo ge nic h e artand neurogen ic hear t
Vertebrate heart = myogenic heart(Pacemaker
made up of specialized tissues located withinthe heart itself)
Most arthropod = neurogenic heart(Pacemaker
originate in motor nerves arising from the
outside)
The SA nodes generates electrical impulses that
spread across both atria simultaneously, via the
gap junctions in the intercalated discs between
cells
The AV (atrioventricular) node, located in the
lower right atrium, acts as a delay and relay
node
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Circulation
After a slight delay, transmission continues into
the atrioventricular (AV) bundle
The AV bundle splits, sending branches upward
over both ventricles (Purkinje fibers) resulting in
ventricular contraction
Q : S ta te a nd e x p la in th e fac to rs th a ti n f luenced the pac e o f SA nodes .
The pacemaker is influenced by two set of
nerves with antagonistic signals, hormones,
body temperature, and exercise.
Symphatetic nerve speeds up the SA nodes
Parasympathetic/vagus nerve - slow it down
Hormones Ex. Epinephrine heart rate
Temperature SA nodes. An increase of only 1C
raises the heart rate by about 10 beats perminute
Exercise heart rate
Electrocardiogram (ECG or EKG) Spread of electrical activity through heart
creates currents that can be recorded from
surface of body using electrodes placed on limbs
and chest
Recording = an electrocardiogram
Depolarization contraction of the heart
chambers
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Circulation
Repolarization relaxation of the heart
chambers
First peak P = depolarization of the atria
The second larger peak, QRS= ventricular
depolarization Last peak T= ventricular repolarisation
Sometimes a fourth peak is observed; U =
ventricular diastole
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Circulation
1.3.2 The cardiac cycle (Refer Figure. 42.7,pg. 873)
The heart contracts and relaxes in a rhythmic
cycle called the cardiac cycle
Systole: The contraction, or pumping, phase of
the cycle
Diastole: The relaxation, or filling, phase of the
cycle
For a human at rest with a pulse (heart rate) of
about 75 beats per minute, one complete cycle
takes about 0.8 sec.
Consisting of atrial systole and ventricular
diastole followed by atrial diastole and
ventricular systole
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1: During the relaxation phase (atria and
ventricles in diastole) lasting about 0.4 sec,
blood returning from the large veins flows into
atria and ventricles.
2: A brief period (about 0.1 sec) of atrial systole
forces all the remaining blood out of the atria
and into the ventricles.
3: During the remaining 0.3 sec of the cycle,
ventricular systole pumps blood into the large
arteries.
Q : E x p la in w h a t c a u se s th e f i rs t a n dseconds hear t sound .
The lub heart sounds caused by the closing of
the AV valves and mark the beginning of
ventricular systole, then dup sound marks the
closing of the semilunar valves and the beginning
of ventricular diastole
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Q : D e f in e h e a rt m urm ur a n d e xp la in i tsc a u s e .
A heart murmur is the detectable hissing sound
of blood leaking back through a defective valve/
by valves that do not close properly
Cardiac output(CO):
the volume of blood that the left ventriclepumped into the systemic circulation per minute
CO = Stroke volume x heart rate/min
Stroke volume =volume of blood one ventricle
pumps during one beat/in each contraction
Average stroke volume in human 75 ml
Q : C a lc ula te th e c ard ia c o utp ut in re st in ga d u lt w he re th e s t ro k e vo lu m e is 7 0m l/s t ro k e a n d th e he a rt ra te is 7 5s t roke /m in .
Resting adult = 70ml/stroke x 75 strokes/min
=5250 ml/min (5.25L/min)
Stress/Heavy exercise , CO = 20 to 30 L/min
Blood pressure Force /hydrostatic pressure exerted by blood
against inner wall of blood vessels
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= blood flow x peripheral resistance
CO, blood flow , BP CO, blood flow , BP Blood volume (hemorrhage/chronic bleeding),
blood flow , BP Constriction of blood vessels (vasoconstriction)
reduce the diameter of vessel, friction between
blood and blood vessel , BP. Dilation of blood vessels (Vasodilation), friction
between blood and blood vessel , BP. BP reading = systolic pressure
--------------------------------
diastolic pressure
Q : D ef in e sys to lic p re ssu re a nd d ia sto licp ressure .
Systolic pressure = the pressure in the arteriesduring ventricular systole. The highest pressure
in the arteries
Diastolic pressure = the pressure in the arteries
during diastole
Can be measured using sphygmomanometer.
(Refer Figure 42.12, pg. 877)
Normal BP = 120/80
1.3.3 Control of the heart (Refer Figure42.12, pg. 820 Solomon)
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Circulation
Heart rate is regulated by both nervous and
endocrine system.
Baroreceptors: receptors sensitive to changes
in blood pressure located at the arch of aorta
and carotid arteries.
Baroreceptors activate neurons, relay
information to cardiovascular control center
(CCC) in medulla oblongata.
Negative Feedback mechanism to restorehomeostasis. Blood pressure falls:
CCCsympathethic nerves (autonomic)
norepinephrine heart rate& strength of
contraction neuronsblood vessels of skin and viscera(internal organs)vasconstriction/constrictionof arterioles
Blood pressure high:
CCCparasympathetic
nervesacetylcholineheart rate& strength
of contraction
neuronsblood vessels of skin and viscera
(internal organs)vasodilation/dilation of
arterioles
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Circulation
1.4 The Cardiovascular Disease (Refer pg.883)
Are disorders of the heart and the blood
vessels
Atherosclerosis: (Refer Figure 42.18, pg. 883) Definition: Accumulation of fatty material,
smooth muscle, cholesterol deposits, fibrin
deposits & cellular debris within walls of
arteries
Effect: lumen of artery to reduce/narrow/Blood
flow reduced
Factors that promote: genetic factors, smoking,
hypertension, high blood cholesterol levels
Prevention: diet low in cholesterol/fat, reducehypertension, stop smoking, regular exercise,
high fibre diet.
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Circulation
Arteriosclerosis Definition: hardening of arteries/ thickening &
loss of elasticity to wall of arteries Cause: calcium deposition within arterial walls/
(severe atherosclerosis)
Effect: reduce blood flow/heart has to work
harder to pump blood.
Factors that promote: genetic factors, smoking,
hypertension, high blood cholestrol levels
Prevention: diet low in cholestrol/fat, reduce
hypertension, stop smoking, regular exercise,
high fiber diet
Hypertension (High blood pressure) 120-139/80-89 = Prehypertensive always > 140/90 = Hypertension Promotes atherosclerosis and increases the risk
of heart attack and stroke
Causes of hypertension: heredity, aging,
smoking, high salt intake, stress
Prevention: regular exercise, reduce salt intake,
stop smoking, limit alcohol, heart healthy diet,
reduce stress.
Q : B r ie f ly e x p la in th e d iso rd e r k n o w n a shypotens ion .
Refer to abnormally low blood pressure
Relative term because the blood pressure normally
varies greatly with activity, age and medication.
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Circulation
Q : D is t in g u ish b e tw e e n a m yo c a rd ia li n fa rc t i on and a s t roke .
M yo card ia l i n fa rc t ionThe term myocardial infarction is derived from
myocardium (the heart muscle) and infarction
(tissue death due to oxygen starvation
Commomly known as heart attack
The death of cardiac muscle tissue resulting
from blockage of one or more coronary arteries.
St rokeThe death of nervous tissue in the brain, usually
resulting from rupture or blockage of arteries in
the head
The effects of a stroke and the individualschance depend on the extent and location of the
damaged brain tissue.
Angina pectoris Condition where a person feel occasional chest
pain
Due to partially blocked of coronary artery
A signal that part of the heart is not receiving
enough blood especially when the heart is
laboring because of physical or emotional stress.
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http://en.wikipedia.org/wiki/Myocardiumhttp://en.wikipedia.org/wiki/Infarctionhttp://en.wikipedia.org/wiki/Myocardiumhttp://en.wikipedia.org/wiki/Infarction8/9/2019 Circulation Lecturer.
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1.5 The Lymphatic System1.5.1 Components and function
The lymphatic system consists of lymphatic
vessels and lymph tissue (Refer Figure 43.5, pg.
901)
Lymph tissue: Composed of connective tissue
with many lymphocytes
Lymph nodes and nodules: Small masses of
lymph tissue. Lymph nodes function to filter the
lymph and attack viruses and bacteria.
Larger organ :The spleen, tonsils, and thymus
Tonsils: Masses of lymph tissue in the
pharyngeal region that filter out pathogens
Lymph vessels conduct lymph, derived frominterstitial fluid
Lymph capillaries are one-way vessels, which
join and merge to form larger lymphatics (lymph
veins)
Lymph vessels ultimately empty into the
subclavian veins via the larger thoracic duct and
the right lymphatic duct
Q : S ta te h o w th e ly m ph is m ove d in o n ed i rec t ion i n mam m als .
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Lymph is moved in mammals by differences in
pressure, pulsation of vessel walls, and
contraction of skeletal muscles
Lymph vessels have valves to prevent back flow
of fluid towards capillaries
The lymphatic system plays an important role in
fluid homeostasis
Functions of lymphatic system: return of interstitial fluid to the circulatory
system
immunity
absorption of lipids from the gastrointestinal
tract
1.5.2 The interrelationship between the lymphaticsystem and the circulatory system.
Fluid movement between blood and interstitial
fluid. (Refer Figure 42.14 pg. 870 and Figure
42.20, pg. 827 Solomon)
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Arterial end
of capillary
Blood
pressure
(+40)
Osmotic
pressure
of plasma
(- 28)
At arterial end of capillary, (high)
blood pressure (+40) forces plasma out of
capillary (into interstitial fluid)
Osmotic pressure of blood similar
at arterial & venular ends. Created by thepresence of nonfilterable plasma proteins
Some fluid reenters blood at
venular end due to osmotic pressure of plasma
greater than blood pressure at venular end
Most of interstitial fluid enter
lymph capillarieslymph
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Q : F il l in t he t ab le t o s ho w t he c o m p ar is onb etw e e n th e b lo od c irc u la to ry s ys te mand the l ympha t ic sys tem
Blood Cir. Syst. Lymphatic Syst.Type of
system
Closed Syst Closed Syst.
Pump Heart None Pressure
Depends on heart
pumping action for
arteries, depends
on external
pressures in veins.
Different pressure
in differentvessels
Depends on
external
pressures.
Generally low
pressure
Valvesinvessels
In vessel leading
towards heart,
(veins), pulmonary
artery, & aorta
In most vessels
Fluid invessels
Blood Lymph
Function
Transport of
nutrients, gas,
waste, for defend
Transport of fat,
filter foreign
particles,
lymphocytes
destroy foreign
bodies.
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Three available routes for lateral transport :
(Refer Figure 36.8(b) pg. 743)
1. Transmembrane route : repeated crossings of
plasma membranes /cell wall, solutes exit one
cell, enter next
2. Symplastic route : pathway within the
continuum of cytosol, require minimum of one
crossing of plasma membrane, move from cell
to cell via plasmodesmata
3. Apoplastic route : pathway consisting of cell
wall and extracellular spaces without entering
protoplast/no crossing of plasma membrane
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Presence of Casparian Strip within endodermis
ensures that no minerals reach vascular tissue
without crossing a selectively permeable plasma
membrane.
Those that are not already within the
symplastic route will be excluded from the
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Endodermis
Only minerals already
in simplast or entering
pathway by crossing
plasma membrane of
an endodermal cell
can pass into xylem
VascularcylinderXylem
Water from soil
Root epidermis
Soil solution (water +
minerals) absorbed by root
hair surface
Cortex
Apoplastic/extracellular
route(cell wall &
intercellular space)
Symplastic route(cytoplasmic
continuum with
plasmodesmata)
A belt/layer of waxy
material within
endodermal cell wall-
CASPARIAN STRIP
Passage of water
and minerals
through apoplast is
blocked
Regions
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vascular tissueselective/preferential transportof minerals from soil to xylem
Long distance transport : Bulk flow transport : Movement of fluid
driven by pressure (high to low)
Phloem: loading of sugar createspositive pressure at one end forcing sap to move
to other end
Xylem: tension/negative pressure at
leaves (transpirational pull) creates tension
pulling water from root (high pressure) to top
(low pressure)
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1.6.1 Xylem and ascend of sap
Xylem sap flows upward to veins that branch
throughout each leaf, providing each with water.
Rises against gravity to reach heights of more
than 100 m in the tallest trees.
Pushing xylem sap: Root pressure
At night: transpiration~0, minerals
constantly pumped into cells by active transport
s (solute potential) root alwayshigher than soil
(water potential) root always lowerthan soil
water always diffuse into rootroothair always turgid
Root cells continue pumping mineral
ions into the xylem of the vascular cylinder,
lowering the water potential
Water flows in from the root cortex
generating a positive pressure called root
pressureforces fluid up the xylem.
Guttation (water droplets at tips of
leaf/grass)- when more water enter leaves than
are transpired (at night & dawn)
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Root pressure-is actually a minor
mechanism to force water up. At most able to
push only a few metres up.
After sunrise it is the transpirational pull that
provides the major force that causes upward
flow of water and minerals in xylem
Pulling Xylem Sap :
Transpiration-Cohesion tension
mechanism( Refer Figure 36.12 pg. 747)
90% of water absorbed by root is lost
through transpiration
Transpiration- pull creates -ve pressure/ -ve
water potential at surface of leaves/ top of plant)
Cohesion and adhesion of water (hydrogen
bonding) transmits upward pull along the entirelength of xylem to roots. Producing a continuous
column of water
Water vapor diffuse from air space to
atmosphere through stomata
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Negative
pressure at air-
water interface
Mesophyll cells
Xylem
Direction of
water flow
Root ( high water
potential)
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1 .6 .2 . P hlo em an d T ra ns lo ca tio n
Translocation of organic
nutrients occur within sieve tubes of phloem
Sieve plates allow sap to flow
along sieve tube
Phloem sap-primarily sucrose,
other solutes: minerals, amino acids, hormones
Direction that phloem sap
travel can vary, always from a sugar source to a
sugar sink.
Q: Define sugar source and sugar sink.
Sugar source: plant organ that
is a net producer of sugar (photosynthesis or
starch breakdown) e.g. leaves
Sugar sink: organ that is a net
consumer or store of sugar, e.g. growing roots,
buds, stems, fruits Storage organs(may be eithera source or a sink depending on the season)
Mass Flow/Pressure Flow Hypothesis:The mechanism of translocation inangiosperms
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Phloem loading: Sucrose manufactured in
mesophyll cells either can travel to sieve tube
member via symplast or by active transport via
aploplast (Refer Figure 36.17 a and b, pg. 752)
Active transport :using the proton pump and
cotransport of sucrose and H+ mechanism
Loading of sugar/sucrose into sieve tube
reduces water potential of the sieve tube.
Water enters sieve tube from xylem by osmosis
sieve tube take up water by osmosis (from
xylem)
Positive pressure/hydrostatic pressure
generated
Phloem sap flows along phloem from region of
high pressure to lower pressure (sink)
Unloading of sugar (passive) occurs at sink
followed by water. (hence sink always lowerpressure compared to source)
Unloaded sugar used for respiration/growth
metabolism/converted into insoluble starch at
sink
Some water from phloem at sink diffuses back
to xylem and is recycled back to source. (Refer
Figure 36.18 pg. 753)
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Loading of sucrose into floem
Pressure flows in a sieve tube
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