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1. TRANSPORTINSIDE THE BODY by two circulating fluids — the blood
and the lymph.
digestive system digests and absorbs nutrients
The respiratory system oxygen is transported to all partsof the body, CO2
collected and carried to the
excretory system to removed extrawater, excess salts, and the
nitrogenouswastes
Hormonesfrom endocrinesystem
circulating to wherever required.
FLUIDS IN OUR BODY
3 principalfluidsin our body
(i) Blood
(ii) Tissue fluid, occupyingspacesbetween cells in
the organs.
(iii) Lymph, which is contained within lymph
vessels and lymphatic organssuch as the spleen
and the tonsils.
closed blood circulatory system body circulates through blood
vessels all the time
open blood circulatory system certain animalssuch as insects, blood mostly
flowsthrough open spaces in the body from the heart without vessels.
Non-circulatingfluids: synovialfluid filled in the cavities of skeletal joints,
vitreoushumour in the eye do not circulate.
PROPERTIESOF BLOOD:
Never Stationary
Colour somewhatthick fluid, bright red when taken from an artery or dark
red when taken from a vein.
Volume— An average adult human has 5 to 6 litres
Taste - saltish
pH slightly alkaline with a pH of 7.3 to 7.45
FUNCTIONS OF BLOOD
A. TRANSPORTBY BLOOD
l. Transportof digested food from the alimentary canal to the tissues.
glucose, amino acids, vitamins, mineralsalts, etc.

2. 2. Transportof oxygen from the lungsto the tissues by meansof red blood
cells in combination with hemoglobin in the form of an unstable compound
oxyhemoglobin, which on reaching the tissues breaks up to deliver
oxygen.
Hb +02 Hb.02 (oxyhemoglobin)
3. Transportof carbon dioxidefrom the tissues to the lungs. It occurs partly
in combination with hemoglobin and partly as solution in blood plasma.
Hb+ C02 Hb.C02 (carbaminohemoglobin)
4. Transportof excretory material from the tissues to the liver, kidney or the
skin for elimination or to render them harmless.
5. Distribution of hormonesfrom endocrineglandsdirectly into the blood
6. Distribution of heat. Maintainingthe temperatureof the body uniform by
distributing heat.
B. PROTECTION BY BLOOD
1)formsa bloodclotwherever thereis a cut in a blood vessel.
(i) preventfurther loss of blood and
(ii) preventthe entry of disease-causinggerms.
2)whiteblood corpusclesprotectthe body from diseases by engulfing
bacteria
3)produces antitoxins and antibodies whichneutralize thepoisonous
substances or kill the germs
COMPOSITION OF BLOOD
(i) Plasma— fluid part, (55-60 %) of blood. The liquid portion of blood ,light-
yellow coloured, alkaline liquid.
Water 90-92%
Proteins 7-8%
Inorganicsalts 1% (sodium chlorideand sodium bicarbonate)
Other substances traces (glucose, amino acids, fibrinogen, hormones, urea,
etc.)
SerumTheplasmafrom which the protein fibrinogen has been removed.
(ii) Cellular elements — red and white cells, and platelets (40-45 %)
(2) White blood cells (leukocytes)
(3) Blood platelets (thrombocytes)
(1) Red Blood Cells (RBCs) erythrocytes
~minutebiconcavedisc-likestructures, Flatin thecenter andthick and
roundedattheperiphery.
~very small: 7 micron(μ) diathesmall size , concavities ,providea large
surfacevery efficient in absorbing oxygen. Enables RBC to travel through
very finecapillaries in the body where they have to travel in a single file.

3. ~Adulthuman malehas 5 Adultfemalehas 4.5 million. / mm3
~ colourless spongy body or stroma which contains pigmenthemoglobin
(Hb).
Hemoglobin
~effectivechemical constituentof RBCs.
~formed of an iron containingpart(haemin) and aprotein(globin).
~combinereadily with O2 to form oxyhemoglobin, an unstablecompound
which readily gives up oxygen to the needy tissues.
~Haemoglobin can carry a very small quantity of CO2 in the form of
carbamino-haemoglobin(HbCO2).
Haemoglobin has for carbonmonoxide formingastable
compound Carboxyhaemoglobin(HbCO). This cutsdowntheoxygen
transportingcapacity of theblood of, sometimes resulting in death.
Veins too carry oxygen but less than the arteries!
~lungs, the haemoglobin (Hb) becomes 97-99per centsaturatedwith
oxygen.
~respiringtissues Hb releases only about23% of itsoxygen
~returningin veinsstill containsabout 75% oxygen.
Life and death of RBCs
~ RBCsare produced
in Adults:themarrow of longbones, ribs,breastboneandiliumof hip girdle.
In an embryo they areproduced in the liverandspleen.
In children, bonemarrow of allbones until 5 years of age.
~The mature RBChaveno nuclei, when produced, they have one.
As they mature, the nucleiare lost, i.e., they becomeenucleated.
~The averagelife of an RBC is about 120days. Theold and weak RBC are
destroyed in the spleen, liver andbonemarrow, their iron partisretainedin
the liverwhilethe rest is excreted as a bilepigment (bilirubin). In anormal
adult, approximately 2 millionRBCs aredestroyed everysecond.In other
words,
about I % of the total erythrocytesin the body are destroyed everyday.
DEFICIENT,BUTMOREEFFICIENT!Mammalianredbloodcells
when mature circulate in the blood system and are devoid of
certain organelles. They have no nucleus,mitochondria ,endoplasmicreticulum.
RBC, thoughdeficientaremoreefficient incarryingout their task of picking up and
delivering oxygen. The factorsmaking them more efficient in this
workare as follows:
1. Lossof nucleus, makestheredcellsbiconcave, thusincreasingtheir surface
areato volumeratio forabsorbingmoreoxygen.

4. 2. Lossof mitochondriameansthat thered cellscannotuseoxygen and
glucose for themselves(cellularrespirationoccursin mitochondria).Thusall
the oxygenglucoseistransportedanddeliveredto thetissuesunconsumed.
3. No endoplasmicreticulummeansincreasedflexibilityof RBCsfortheir
movementthroughnarrowcapillaries.
Number of RBC
Newborn 6-7 million per mm3
duringsleep is lowered by 5%
Higher duringphysical activity
Nearly30% more at height of 4,200 m
Abnormally increased Polycythaemia, abnormally decreased Erythropenia.
2) WhiteBloodCells(WBCs)
~number ismuch usually about4000-8000per mm3 of blood
~areamoebicidal and can produced pseudopodia
~they can squeeze through the walls of the capillaries into tissues
(diapedesis)
~classified into 2 major categories (granularand non-granular)
~spendmostof their time 90% in tissuefluidor in thein thelymph and 10%
time in the blood.
~produced in redbonemarrow, lymphnodes and sometimeseven in liver
and spleen.
~averagelife is about two weeks. Neutrophilslivefor only a few hrs.,
~Destroyedin the samewayasthe RBCs
~ LeukemiamanifoldmoreWBC Leukopenia abnormaldecreasein WBC
Two Major
cat. of WBC
5 Types of
cells
Distinguishing features Functions Site of
productions
-Granular
-Cytoplasm
-contains
Nucleus
-Nucleus
usually
constricted
into lobes
Neutrophils
(62%)
-Nucleus with 3-4 lobes
-Granular cytoplasm
-Stain with neutral dyes
Engulfing bacteria
(Phagocytosis)
Bone Marrow
Eosinophils
(2.3%)
-Nucleus with 2 lobes
- large cytoplasmic
granules
-stains dark red with eosin
(acid dye)
-Engulfing bacteria
-secrete anti-toxin
-and associated with
allergies.
Bone Marrow
Basophiles
(0.4%)
-large and indistinctly
lobed nucleus
-granules stained with
basic dyes (eg: methylene
blue)
-releases chemical
(histamine) for
inflammation which
dilates blood vessels
Bone Marrow
Agranulocytes
-A single large
nucleus
Lymphocytes
(30%)
-smallest WBC
-single large nucleus
- produce anti-bodies Bone Marrow and
lymph glands like
spleen and tonsils
Monocytes
(5.3%)
-nucleus large and kidney
shaped
- ingest germs Bone Marrow

5. -at site of infection,
transformed into
macrophages
FunctionsOf Leukocytes(WBCS)
1 PHAGOCYTOSIS: WBC particularly the neutrophil; engulfs particle-like solid substances, especially
bacteria. Abnormal increase in WBC count up to about 50,000ormore /mm3 indicates some
infectionin the body.
2. INFLAMMATION: Inflammation occurs due to the reaction of tissues to injury and to
localized invasion of germs. The inflamed spot has several characteristics: increased local
heat, redness, swelling, pain, etc. Here the leucocytes (specially the monocytesand
neutrophils) migrate through the walls of the blood vessels by diapedesis(Fig. 8.3), and
fight against disease-causing germs. They also destroy the damaged cells by phagocytosis. Pusis
mainly composed of the deadwhite blood cells together with the tissue cells destroyed by the bacteria.
3. FORMATION OF ANTIBODIES: The WBCs (specially the lymphocytes)produce
antibodies which kill or neutralizethe germs, orthe poisonsfrom them. Introducingweakened
germs or germ substances (vaccines) during vaccinationstimulates formation of particular antibodies
which, at a later period, would destroy the particular disease-causing germs if they enter into the body.
ANTIBODIESand "ANTITOXINS" When disease-causing germs gain entry irno the stream, they
produce poisonous substances called toxins(meaning poisons). In response. lymphocytesof the blood produce
chemical substances called antibodies whch circulate freely in the blood plasma The antibodies are specific to the toxins for
which they are produced. The antibodies act as antitoxins which neutralize(destroys) the poisonous effed of
the toxins. Antibodies may persist longafter the fflsease has been overcome, and the person who has recovered becomes
immuneto the disease. This is the underlying principle of vaccination (a deliberate introduction of weakened disease germ to stimulate
production of the specific antibodies).
(3) BLOOD PLATELETS (Thrombocytes) (Initiators of clotting of blood) Blood platelets are minuteoval
or round structures, non-nucleated, floating in the blood are about 200,000to 400,000per cu mm-
of blood in an adult The platelets are derived from some giant cells called megakaryocytesin the red bone
marrow. These are budded off from the megakaryocytes in a manner that each one is completely surrounded with membrane. Their life
span is 3 to 5 daysand are destroyed mainly in the spleen (a lymphatic organ located in the
abdomen). They are very important in clotting of blood- At the site of injury,the platelets disintegrateto release
a chemical substance thrombokinasewhich initiates the process of clottingof blood.
FUNCTIONS OF PLATELETS -—
CLOTTING OF BLOOD (COAGULATION) If no blood clotting, the injured person would bleed to death- Clotting
(coagulation) occursin a series Of Steps as follows:
1. The injured tissuecells and the platelets which disintegrate at the site of the wound releasea
substance thrombokinase (also called thromboplastin). (More recently it is called “Factor X" or Stuart
factor).

6. 2. The thrombokinase acts as an enzymeand with thehelp of the calcium ionspresent in theplasma,
it converts a substance prothrombin (inactive) of theplasma, into thrombin (active).
3. Thrombin in thepresenceof calcium ions, reacts with the solublefibrinogen of theplasmato convert
it into insoluble fibrin. Fibrin is asubstancethat forms threads. These microscopicthreadsof
fibrin are sticky and form a network (mesh) at thewound.
4. Blood cells are trapped in thenetwork of fibrin; the network then shrinks and squeeze out
therest of the plasma in theform of aclear liquid, theserum. The solid mass left behind is called clot (or
thrombus)
Clotting In A Test-Tube
If blood is taken in a test-tube i.e., when it is stationary for some time, Serum will be
squeezed out and will collect on the surface. ClottingNot dependentonexposureof blood to Air,
clottingcanbecaused by themovement of blood over aroughsurfaceas on cholesterol depositon the
insideof a blood vessel.
Blood Transfusion and Blood Groups
Injection of blood from a healthy person (donor) into the veinsof apatient (recipient). is called
blood-transfusion. for blood-transfusion it is necessarythat typeof blood transfused should
match (or be compatible) with recipient’s blood
Blood Grouping
~KarlLandsteiner
~ RBC havespecific types of proteinson their surfaceAntigen A or Antigen B.
~plasmaof theblood has its complementary antibodies called antigens Dependingon thepresenceor
absenceof theseantigens thereare four typesof blood groupsas in the table.
Blood Groups Antigen on RBC Antibodiesin plasma
A Antigen A anti b
B Antigen B anti a
AB Antigen A & b no Antibody
O No Antigen anti a and anti b
Several systems of blood grouping- ABOsystem and Rhsystem are most important.
Classified into four type - A, B, AB and O.
Blood group
of Donor
Blood group of recipient
A B AB
(universal
recipient)
O
A ✔ ❌ ✔ ❌
B ❌ ✔ ✔ ❌
AB ❌ ❌ ✔ ❌
O Universal donor ✔ ✔ ✔ ✔
RH system

7. Blood of mostpeoplecontains a substance called RH factor. (Rh +ve People D antigens on the
surfaceof RBC),When theblood of such an individual (Rh-positive) istransfused into persons
lacking it (Rh negative), theblood of the recipientdevelops an antibody for Rh substance within
two weeks(gets sensitized). Now a Repeat of transfusion will cause a reaction
This is similar to the developmentof an allergy. [Rh-positivemay bewritten in short as Rh+veor as
Rh+ and similarly, the Rh-negative may written as Rh-ve.
BLOOD CIRCULATORY SYSTEMsystem consists ofheart,arteries, veins andcapillaries.
The Heart
Location(not on the left side,but it is felt so.) rightin the center between the two lungsandabove
the diaphragm. The narrowendofthe roughly triangular heartis pointed totheleft side
Covering: The heart inadulthumans is aboutthe sizeof our closed fist — 12 cm in length and 9
cm in width. It is protectedby a doublewalledmembranous coveringcalledPericardium. Itcontains
lubricating Pericardial fluid which reduces friction during heartbeatand protects itfrom
mechanical injuries.
Chambers of the heart
The heart consists of fourchambers— two atria (sing. atrium) and twolower ventriclesThe atria
(also calledauricles) have thinner walls becausetheir major functionis to receiveblood from the body and
pump it intotheverynext ventricle.
The ventricles have thick muscular wallsbecausethey haveto pump blood to long distancesThe
rightventriclepumps blood only up tothelungs for oxygenation. But theleftventricle pumps it up tothe
farthestpoints in the body, up to thetoes in thefeet or upto the brain againstgravity, andso its walls arethicker.
Blood vessels entering and leaving theheart
A) Entering the heart
~The Right Atriumreceives two largevessels
(l) Anterior venacava(also calledsuperior vena cavaor precaval) brings deoxygenatedblood
the anterior or upper regionsofthe body inducing head, chestand arms
(2) Posterior venacava(or the inferior) brings blood fromtheposterioror the lower regionofthe body
including abdomen and legs.
(3)The left atriumreceives 4 Pulmonary veins(two fromeach lung). The pulmonary veins bring oxygenated
blood.
B) leavingthe heart
Arising from theventricles two largeblood vessels.
1. The Pulmonarv Arteryarises fromthe rightventricleand caries deoxygenatedblood tothe
lungsfor oxygenation.
2. The Aortaarises from theleftventricleand oxygenatedblood tosupply itto allpartsofthe body.

8. Coronary arteries: two coronaryarteries (rightand left) arising fromthebaseof the
aorta. These supply blood to the heart muscles. When thereis a blockagein any coronary
arteryor in any oneor moreoftheir branches, there is a "deadening'ofthe corresponding area oftheheartmuscles
leading to"myocardial infarction"or a heart attack inpopular language. The Coronary veins collectblood
from heart walls and pour itinto theright auricle. "Angina pectoris"is the chestpaindueto insufficientsupplyof
blood to theheartmuscle.
Valves regulate the flowofblood in a singledirection
There are 4 valvesin theheart as follows :
l. Right Atrio-Ventricular valveis locatedattheaperturebetweenthe rightauricleand
the rightventricle. It has 3 thin triangular leaf-likeflaps (cusps)andis thereforealso called
Tricuspidvalve. The ‘apices’(pl. ofapex) of theflapsare heldin positionby tendinous cords
(chordae tendinea)arising fromthe muscular projectionsoftheventriclewallknown as
papillary muscles.
2. Left Atrio-Ventricularvalve is locatedattheaperturebetweenthe leftauricle and the left
ventricle. It has 2 cusps, andis, therefore, calledbicuspid(also Mitral)valve.
3. Pulmonary semilunar valvesarelocated atthe opening ofthe rightventricleinto the
pulmonary artery. Thesearepocket-shaped 3 in number.
4. Aortic semilunar valves are locatedatthepoint of origin of aorta fromthe left ventricle.
These arealso 3innumber and pocket- shaped.
Circulation of bloodin the heart
1)It starts withthe contractionofthetwo atria (auricles). The ventriclesatthis timearerelaxing(or dilating) and
are empty Therefore,the bloodfrom the atriapasses into the ventricleseasily.
2)Next, the ventricles contract, andtheatria relaxThe blood fromthe ventricles under
pressure(enter the pulmonary arteryfrom the rightventricle)andthe(aortafromthe
left ventricle.
- pressuretends to return tothe atria, butthe flaps of the two cuspid (meaning pointed projection)
valves get tightened and puffed up, thus closing thepassageand preventing thereturn ofblood
The chordaetendinea (like cords ofa parachute). hold theflaps of the valves in positionand
prevent their overturning intotheatria
-The mouths of the pocket-likevalvesat the bases ofthese two bloodvessels faceaway fromthe
ventricles. Therefore,the bloodleaving theventricles presses thevalves flatand gets a clear passagein
between.
-Whenthe ventricles dilate, the bloodfrom the pulmonary artery and theaorta tends toreturn, theblood fills the
pockets of the valvesand closes thepassage.
Heart Beat
The whole sequenceofevents in theheart beat is called cardiac cycle. Steps ofa heart-beat(Cardiac cycle)
— Each heart-beatconsists of two main steps:
1)The contraction of atriafirst followedby the the ventricles.The contraction phases (Systole)
2) is followedby a relaxing expansion phase(Diastole)

9. Each full beat ofthehuman heartlasts for about0.85 seconds.
Systoleof atria (auricles) 0.15 sec
Systoleof ventricles 0.30 sec
All chambers in relaxed state 0.40 sec
At the end of ventricular systole,theventricles startrelaxing (ventriculardiastole). Meanwhiletheatria (auricles) have also been relaxing
(atrial diastole) andfor a short period,boththeatria andtheventricles arein a relaxed state (jointdiastole).
The HeartSounds — ' ' LUBB" and "DUP"Ifyou hearyour heartsoundby placing a stethoscopeon your chest,you
will hear twosounds "LUBB" and "DUP" in shortsuccession followed by a gap. The first sound
"LUBB"is produced whentheatrio-ventricular (tricuspidandbicuspid) valves getclosed
sharply at the start of ventricular systole.
sound "DUP" Produced whenatthe beginning of ventricular diastole,thesemilunar valves at
the roots of aorta and pulmonary artery get closed.
Rate of heart-beat varies among different species
Whale 15
Elephant 25
Horse 40
Adult men 64-72
Adult women 72-80
Cat 120
New born infant 140
Rat 250
Sparrow (in vigorous activity) 800 - 900
Smaller the size, faster the heart rate.
This is because smaller the animal, the more it loses its body heat due to higher surface volume ratio, and therefore, the increased heart-rate distributes body heat faster.
Secondly, the young growing stages, such as the human baby, have higher metabolism for body growth and therefore, the faster heart rate keeps the "supply?' and "take off" of the
metabolic substances in right quantities.
8.8.6 Pacemaker
1)The impulse or command which starts theheart- beatarises in"Pacemaker"(sino-atrial
node, "SAN")located inthe walls of theright auriclenear the opening of the superior
vena cava
2)This impulseis relayed to the ventricleswith the helpof specialconducting fibres.
3) from SAN first goes to AVN node (atrio-ventricular node) found nearthe inter-auricular
septumnearthe tricuspid valve.
4)A bundle of muscle fibres called 'Bundle of HIS'begins fromAVNand extends to the
inter ventricular septum. BundleofHIS consists of branches of fibres(((running along the wallof the
ventricle, called 'Purkinjefibres’))).
All thesetogether forma system which creates anImpulseand conducts it toevery partofthe Heart
The blood vessels are branched tubes extending from the heartto allparts ofthe body. They areofthree kinds —
arteries,capillaries and veins.
An ARTERY is a vesselwhichcarries bloodawayfromthe heart towards any organ.
Characteristics ofanartery
• thick muscular walls
• a narrow lumen (the central bore), and
• Blood flowspurtswhichcorrespondto theventricularcontractions of theheart-
Characteristics of aVein.
• thin muscular walls,
• a wider lumen,
• the blood in itflows uniformly, and

10. • it contains thinpocket-shaped valves (Fig. 8.11) whoseopenings facein the direction oftheheart. These valves preventthe
backflow of theblood.
The smallestor the finalbranchofan arteryis calledanArteriole.Arterioles are highly muscular
and can changetheir diameter manifold. The arteriole breaks up intocapillaries
A Capillary
1) is a very narrow tube(about8 micrometersin diameter);
Characteristics ofa capillary
• its wallconsists ofa singlelayer of Squamous Epithelial cells(Endothelium),and
• has no muscles (Fig. S.12B). The totalnumber ofblood capillaries present inthewholebody is
almostinconceivable. endto end ina rowextend toa length of100,000 kilometres total wall surface
would be morethan500 square metres.
2) Functions of capillaries
(i) To allow outward diffusion of oxygen into the intercellular fluid and from thereinto thetissue
(ii) To allow inward diffusion of carbon dioxidefrom the intercellular flui&
(iii) To allow twoway diffusionofsubstances like glucose, amino acids, urea, hormones, etc.
(iv) To allow leukocytes (WBCs) to squeezeout throughthe capillarywalls bymeans of amoeboid
movement.
3) The capillarieshave thepower of dilating (vasodilation) and contracting
(vasoconstriction) which respectively>&< the blood supply to the body parts.Evidence ofthesechanges in
capillaries is seenin the colour ofthe skin.
• Walk in thehotsun (increasedblood flow). — Faceturns pink
• When it is toocold (reducedblood flow). — Faceturns bluish
4) The capillaries gradually reuniteand increasesizeassuming thesame three layers
(connective tissuelayer, muscular layer and endothelium) as in arteries and
veins.The smallest unitedcommon branch is calleda venule. The venules join to form larger veins Comparedwith
arterioles the venules arelarger with much weaker muscular coat.
Differences betweenarteries and veins
ARTERIES VEINS
Definition vessels which carry blood away from the
heart and into an organ.
Blood vessels whichcarryblood flowstowards the heart. (Except
hepaticportal vein)
1 Progressively branched,decreasing in size Progressively unite Increasing In size.
2 Smallestartery breaks into arterioles. Smallestvein arises from venules.
3 Have thick and muscularwalls. Have thin and muscular walls.
4 Walls areelastic. Walls arenon-elastic.
5 Have narrower lumen. Have wider lumen.
6 Have no valves in their innerlirung. Have valves in their inner lining toprevent backwardnow ofblood.
7 Can constrict or dilate to controlflow. Cannot constrict.
8 Usually, deeper placed. Usuallymore superficial(nearer to skinsurface).
9 Do not collapse when empty Collapse when empty.
10 Blood flows withjerksand under pressure flows continuously and under very little pressure

11. 11 Carry fully oxygenated blood (except
pulmonary artery).
Carry partially deoxygenated and CO2 laden blood(except
pulmonary vein).
THETWO BLOOD CIRCULATIONS —
PULMONARY AND SYSTEMIC Blood flows twicein the heartbefore itcompletes one full round;
(l) the shortpulmonary (lung) and
2) the longsystemic (general body) circulation.
For this reasontheblood circulation inthehuman body is also ‘doublecirculation"
(l) The pulmonary circulationpertains to the lungs. Itstarts in the Pulmonary arteryarising fromthe
right ventriclewhich soon divides into two branches thatenter the respective lungs.
Pulmonary veinscollect the oxygenated bloodfrom the lungs and carry it back to the left auricle of the
heart.
(2) The systemic circulationpertains tothemajor circulation in thebody.It starts with the aortathat arises
from the leftventricle(figs. 8.8 & 8.14). The aorta arches back and continues behind as the dorsal aorta. The aorta
sends arteriesto various body parts andtheir tissues. From therethe bloodis collected by veins andpouredback intotheheart
Hepatic Portal System
The veins starting fromthe stomach and intestines do not directlyconvey theblood totheposterior
vena cava. Instead they firstenter the liver as a combined hepatic portal veinThereitbreaksup into
capillariesin contrast tothegeneralcharacteristic ofa veinand a new vein called haptic veinis formed
by their reunionwhich joins theposterior vena cava
By definition, therefore, a portalvein is one which starts with capillaries and also ends in
capillaries.
utility OF HEPATIC PORTAL SYSTEMThe foodabsorbed by the stomach and intestines firstbroughtto the liver which
acts likea store to regulatethequantity of nutrients flowing into blood circulation,for example,excess
sugar is storedas glycogen.Also,certainpoisons if through food aredetoxified(rendered
harmless) in the lever.

13. The pulse
The arteries on account oftheir elastic muscular walls distend every timeblood is forcedthroughthem due tothecontraction oftheheart.
This distensioncan beeasily felt by pressing your finger gently over anarterythathas comeup
superficially, suchas the radial artery of the wrist on thesideofthe thumb. Counting ofthe pulseis
indirectly the counting of the heart beat.The pulserateincreases due tophysical exerciseor even under
certainemotions.
BLOOD PRESSURE
adults is 100 - 140 mm(systolic) and 60-80 mm
(diastolic). A rise in blood pressureabove140/90 is
known as hypertension (high blood pressurein
popular language).
Tissuefluid and lymph
A.TissueFluid (or Intercellular Fluid)As the blood flows in thecapillaries ofthetissues,the plasmaand
the leukocytes "leak out" through their walls. This fluidbathes the cellsandis called the tissue
fluidor the intercellular or extracellular fluid(Fig. 8. I). It is from this fluid thatthecells absorb oxygen and other
requiredsubstances,and inturn, giveoutcarbon dioxideand other wastes back into it.
B. Lymph and Lymphatic SystemSome ofthe tissue fluid may bereabsorbedinto thebloodvessels, but
most of it enters another setof minutechannels named lymphvessels where it is called lymph.
The lymph flowsin thesevessels dueto contractionofthe surrounding muscles. This again is a beneficial
effect of physical exercise. The lymphvessels on the way drainlymph intolymph nodesfrom wherefreshlymph channels
arise and ultimately pourthelymph intothe majoranterior veins closetotheir entryintothe
right auricle, and is again in circulation.
Composition ofLymph
(a) Cellular part•Only leukocytes (mostly lymphocytes) (No blood platelets)
(b) Non-cellularpart :Water — 94%.
Solids (proteins, fats, carbohydrates,enzymes, antibodies, etc.) — 6%.
Functions of Lymph
(i) Nutritive: Supplies nutritionandoxygen tothoseparts whereblood cannotreach.
(ii)Drainage: It drains away excess tissuefluid and metabolites and returns proteins to theblood from
tissuespaces.
(iii) Absorption: Fatsfrom the intestine areabsorbed through lymphatics (lacteals locatedin the
intestinalvilli.)
(iv) Defence : Lymphocytes andmonocytes ofthelymphfunction to defend the body.The lymphatics also remove
bacteria fromthe tissues.
The lymph nodes tend tolocalizethe infection and prevent it from spreading to the body as
a whole. The tonsils on thesides ofthe neck are alsolymph glands. een is a largelymphaticorgan,aboutthesize ofa clenched fist)
reddishbrown in colour andsituated in theabdomenbehind the stomachand abovetheleft kidney.
Functions of Spleen
I. It acts likea blood reservoir. In an emergency such as haemorrhage, physical or emotionalstress, orin carbon
monoxidepoisoning, the spleen releases the stored blood into the blood stream.
2. It produces lymphocytes.
3, It destroys worn-out'red blood cells (sharing this function withtheliver).
4, In an embryo,spleen produces RBCs.