SAMACHEER CLASS 10 UNIT 14 NOTES

 

UNIT 14

   samacheer SCIENCE
CLASS 10

BIOLOGY

TRANSPORTATION IN PLANTS & CIRCULATION IN ANIMALS

 

INTRODUCTION

·        Multicellular organisms – possess millions of cells

·        Every cell – needs essential substances – nutrients & oxygen – to maintain life & survival

·        Food – only source of energy

·        Each cell – get energy by breaking of glucose

·        Cells utilise this energy - & carries out various activities

 

TRANSLOCATION

·        Water & mineral salts – absorbed by roots – reach all parts of the plant – through Xylem

·        Food – synthesized by the leaves – translocated to all parts of the plant – through Phloem

·        Bulk movement of substances – through vascular tissue – called Translocation

·        Transport – means to carry things from one place to another

·        In larger animals – transport of nutrients, salts, oxygen, hormones & waste products – around the body – done by ‘Circulatory system’

·        Circulatory system – consists of circulating fluids (blood, lymph) & the heart & blood vessels – form the collecting & transporting system

 

MEANS OF TRANSPORT

·        Transport of materials – in & out of cells – carried out by – diffusion & active transport in plants

 

DIFFUSION

·        Movement of molecules – in liquid & solid – from region of higher concentration – to region of lower concentration – without using energy – Diffusion

·        This is a passive process

ACTIVE TRANSPORT

·        Uses energy to pump molecules – against concentration gradient

·        Carried out by membrane bound proteins

·        These proteins – use energy to carry substances across the cell membranes – called pumps

·        Pumps – transport substances – from low concentration to high concentration – uphill transport

 

OSMOSIS

·        Movement of solvent or water molecules – from region of higher concentration – to region of lower concentration – through semi-permeable membrane

·        This process – carried out till – an equilibrium is reached

·        Osmosis – passive movement of water / solvent molecules

 

PLASMOLYSIS

·        Occurs when water moves out of the cell – results in shrinkage of – cell membrane – away from cell wall

DEMONSTRATION OF OSMOSIS

·        A thistle funnel – mouth covered with semi-permeable membrane

·        Funnel – filled with sucrose solution

·        Funnel – kept inverted in a beaker – containing water

·        Water – diffuse into funnel – across the membrane – due to osmosis

·        Result – raise in the level of sucrose solution in the funnel

 

IMBIBITION

·        A type of diffusion – in which a solid absorbs water – swells up

·        Example: Absorption of water – by seeds & dry grapes

·        If there is no imbibition – seedlings would not emerge out of the soil

 

ROOT HAIR

·        Millions of root hairs – tips of roots – absorb water & minerals – by diffusion

·        Root hairs – thin walled, slender – extension of epidermal cells – that increase surface area for absorption

 

PATHWAY OF WATER ABSORBED BY ROOTS

·        Once water enters root hairs – concentration of water becomes more – than its cortex

·        So, water from root hairs – moves to cortex (cortical cells) – by osmosis

·        Water – then reaches xylem

·        Xylem – transports water to stem & leaves

 

HOW DO PLANTS ABSORB WATER?

·        Water – absorbed along with minerals – by root hairs – through diffusion

·        Once water is absorbed by root hairs – it moves deeper into root layers – by 2 pathways

·        (i) Apoplast Pathway

·        (ii) Symplast Pathway

 

APOPLAST PATHWAY

·        Apoplastic movement of water – occurs through – intercellular spaces & the cell walls

·        Does not involve – crossing the cell membrane

·        Movement – dependent on the gradient – (Higher concentration to lower concentration)

 

SYMPLAST PATHWAY

·        Symplastic movement – water travels through cells – i.e., through cytoplasm

·        Intercellular movement – through plasmodesmata

·        As water moves through cytoplasm – movement is slower

·        Movement – down a potential gradient (Water potential – tendency of water to move from one place to another – due to osmosis, gravity, etc.,)

 

TRANSPIRATION

·        Transpiration – evaporation of water in plants – through stomata (leaves)

·        Stomata – open (Day); closed (night)

·        Opening & closing of stomata – due to turgidity of guard cells

·        Turgidity (increases) – stoma opens

·        When guard cells lose water (turgidity decrease) – stoma closes

 

TRANSPIRATION PULL

·        Water evaporates from – Mesophyll cells – through stomata

·        Water concentration – lowers in mesophyll cells

·        Result – water from xylem (veins) à drawn into mesophyll cells (through osmosis)

·        As water is lost from leaves – pressure created at top – this pulls more water from xylem to mesophyll cells – process called ‘Transpiration Pull’

·        This pressure – extends upto roots – cause the roots to absorb more water from soil – ensures continuous flow of water – from roots to leaves

 

FACTORS THAT AFFECTS TRANSPIRATION

EXTERNAL FACTORS

·        Temperature

·        Light

·        Humidity

·        Wind speed

 

INTERNAL FACTORS

·        Number of stomata

·        Percentage of open stomata

·        Water status of plant

·        Canopy structure (organisation/spatial arrangement of a plant)

 

IMPORTANCE OF TRANSPIRATION

·        Creates transpirational pull for – transport of water

·        Supplies water for photosynthesis

·        Transports minerals – from soil to all plant parts

·        Cools leaf surface – by evaporation

·        Keeps cells turgid – maintains their shape

 

ROOT PRESSURE

·        As ions from soil – actively transported into xylem of the root – water moves and creates pressure inside xylem – called root pressure

·        Root pressure – responsible for pushing water – to smaller height in the stem

UPTAKE OF MINERALS

·        Plants – depend on minerals in the soil – for its nutrition

·        All minerals – cannot be passively absorbed by roots

·        2 factors for this

·        (i) Minerals in soil – charged particles (ions) – cannot move across cell membrane

·        (ii) Concentration of minerals in soil – lower than their concentration in the root

·        Therefore, most minerals enters root by – active absorption – through cytoplasm of epidermal cells

·        This process – needs energy (ATP)

·        Absorbed minerals – transported to all parts – by transpiration pull

 

TRANSLOCATION OF MINERAL IONS

·        Minerals – remobilised from older dying leaves – to younger leaves

·        This phenomenon – seen in – Deciduous plants

·        Elements – P, S, N & K – easily remobilised

·        Elements – Ca – not remobilised

·        Small amount of material – exchange between xylem & phloem

 

PHLOEM TRANSPORT

·        Food – produced in leaves – transported by phloem – to area of requirement / stored

·        Phloem tissue – composed of sieve tubes – have sieve plates – cytoplasmic strands pass through the pores in sieve plates

·        Phloem – transport food (sucrose) – from source to sink

·        Source – where food is synthesized (leaves)

·        Sink – where is needed / stored

·        Source & sink – may be reversed – depending on season / plant’s need

·        Since, source-sink relationship – variable – direction of movement in phloem – can be upwards / downwards – Bidirectional

·        Movement in xylem – always upwards – Unidirectional

 

TRANSLOCATION OF SUGARS

·        Translocation of sugars – from source to sink – through pressure flow hypothesis

·        Glucose at source (prepared by photosynthesis) – converted to sucrose

·        Sucrose – moves to companion cells – then into living phloem sieve tube cells – by active transport

·        This process creates – hypertonic condition in phloem (water content less)

·        Water from adjacent xylem – moves into phloem – by osmosis

·        Osmotic pressure builds up – makes phloem sap moves to – area of lower pressure

·        By active transport – sucrose moves to places – where its needed / stored

·        As sugars moved – osmotic pressure decreases – water moves out of phloem

 

ASCENT OF SAP & ITS EVENTS – AN OVERVIEW

·        Upward movement of water & minerals – from roots to different plant parts – called ascent of sap

·        Many factors play a role in this

 

STEPS INVOLVED

·        ROOT PRESSURE

·        Water from soil – enters root hairs – by osmosis

·        Root pressure – moves water upwards – up to base of stem

·        CAPILLARY ACTION

·        Water / any liquid – rise in capillary tube – due to physical force – phenomenon called Capillary action

·        Water in stem – rises up to certain height – due to capillary action

·        ADHESION-COHESION OF WATER MOLECULES

·        Water flows continuously in xylem – due to adhesion & cohesion forces among molecules

·        COHESION

·        force of attraction between water molecules

·        ADHESION

·        force of attraction between molecules of different substances

·        Water molecules – stick to xylem – due to adhesion force

·        TRANSPIRATION PULL

·        Transpiration through stomata – creates vacuum – creates suction – called Transpiration pull

·        Transpiration pull – sucks water in xylem tubes – makes water to rise to great heights – even in tall plants

 

MORE TO KNOW

·        Dews – droplets of water – on leaves of grass – seen early morning – climate is humid & excess water in soil

·        This is due to root pressure – phenomenon called Guttation

·        Takes place through – special cells – Hydathodes

 

DEMOSTRATION OF ROOT PRESSURE

·        Choose – small soft stemed plant

·        Cut the stem – horizontally near the base – in the morning

·        Drops of solution – oozes out of the cut stem

·        This is due to root pressure

 

BLOOD

·        Blood – main circulatory medium – in our body

·        Red coloured fluid – connective tissue

 

COMPONENTS OF BLOOD

·        Blood – 2 main components

·        (i) Fluid plasma

·        (ii) Formed elements (blood cells) – suspended in plasma

 

(i) PLASMA

·        Slightly alkaline, non-living, intercellular substance

·        Constitute 55% of blood

·        Organic substances – proteins, glucose, urea, enzymes, hormones, vitamins & minerals – present in plasma

 

(ii) FORMED ELEMENTS OF BLOOD

·        Blood corpuscles – 3 types

·        (1) Red Blood Corpuscles (RBC) or Erythrocytes

·        (2) White Blood Corpuscles (WBC) or Leucocytes

·        (3) Blood Platelets or Thrombocytes

 

(1) RED BLOOD CORPUSCLES (ERYTHROCYTES)

·        Most abundant cells – in human blood

·        Formed in – Bone marrow

·        RBC’s – red colour – due to presence of respiratory pigment – Haemoglobin

·        Matured Mammalian RBC’s – lack cell organelles & nucleus

·        Biconcave & disc shaped

·        Life span – 120 days

·        RBC’s – transport O₂ from lungs to tissues

 

WHY MAMMALIAN RBC LACK CELL ORGANELLES & NUCLEUS?

·        Lack nucleus – makes the cell biconcave – increase surface area – for O₂ binding

·        Loss of Mitochondria – allows RBC to transport all O₂  to tissues

·        Loss of ER – makes RBC more flexible – to move through narrow capillaries

 

(2) WHITE BLOOD CORPUSCLES (LEUCOCYTES)

·        WBC – colourless; Do not have Haemoglobin & nucleated cells

·        Found in – bone marrow, spleen, thymus & lymph nodes

·        Capable of amoeboid movement

·        WBC – grouped into 2 categories

·        (A) Granulocytes   

·        (B) Agranulocytes

 

(A) GRANULOCYTES

·        Contain granules – in cytoplasm

·        Nucleus – irregular / lobed

·        3 types

·        (i) Neutrophils

·        (ii) Eosinophils

·        (iii) Basophils

 

(i) NEUTROPHILS

·        Large in size

·        Have 2 to 7 lobed nucleus

·        These corpuscles form 60 to 65% of total leucocytes

·        Number increases – during infection & inflammation

 

(ii) EOSINOPHILS

·        Bilobed nucleus

·        Constitute 2 to 3% of total leucocytes

·        Number increases – during allergy & parasitic infections

·        Brings about – detoxification of toxins

 

(iii) BASOPHILS

·        Lobed nucleus

·        Form 0.5 to 1.0 % of total leucocytes

·        They release chemicals – during inflammation

 

(B) AGRANULOCYTES

·        Granules – not found in cytoplasm

·        2 types

·        (i) Lymphocytes

·        (ii) Monocytes

 

(i) LYMPHOCYTES

·        Forms 20 to 25% of total leucocytes

·        They produce antibodies – during bacterial & viral infections

 

(ii) MONOCYTES

·        Largest of leucocytes

·        Amoeboid in shape

·        Form 5 to 6% of total leucocytes

·        They are phagocytic & engulf bacteria (Cells uses plasma membrane to engulf large particles)

 

(3) BLOOD PLATELETS OR THROMBOCYTES

·        Small & colourless

·        Do not have nucleus

·        There are 2,50,000 – 4,00,000 platelets / cubic mm of blood

·        Life span – 2 to 3 days

·        Helps in clotting of blood

·        Platelets – form clot at site of injury – prevents blood loss

 

Platelet

MORE TO KNOW

·        ANEMIA – Decrease in number of erythrocytes

·        LEUCOCYTOSIS – Increase in no. of Leucocytes

·        LEUKOPENIA - Decrease in no. of Leucocytes

·   THROMBOCYTOPENIA - Decrease in no. of Thrombocytes

FUNCTIONS OF BLOOD

·        Transport of respiratory gases (O₂ & CO₂)

·        Transport of digested food to different body cells

·        Transport of hormones

·        Transport of nitrogenous wastes – Ammonia, urea & uric acid

·        Involved in protection of body & defence against diseases

·        Acts as buffer & helps in regulation of pH & body temperature

·        Maintains proper water balance in the body

 

BLOOD VESSELS – ARTERIES & VEINS

·        Blood vessels – network of branched tubes – transports blood

·        3 types of blood vessels – Arteries, Veins & Capillaries

 

ARTERIES

·        Thick & elastic vessels

·        Carry blood away from heart to different body parts

·        All arteries carry oxygenated blood, except Pulmonary artery (carry de-oxygenated blood to lungs)

 

VEINS

·        Thin & non-elastic vessels

·        Carry blood to the heart from different body parts

·        All veins carry de-oxygenated blood, except Pulmonary veins (carry oxygenated blood from lungs to heart)

 

CAPILLARIES

·        Narrow tubes – formed by branching of arterioles – unite to form venules & veins

·        8 µm – diameter

·        Formed of single layer of endothelial cells

DIFFERENCES BETWEEN ARTERY & VEIN

 

TYPES OF CIRCULATORY SYSTEM

·        Animals possess – 2 types of Circulatory system

·        (i) Open type

·        (ii) Closed type

 

(i) OPEN TYPE

·        Blood is pumped by heart – into blood vessels

·        Blood vessels – open into blood spaces – called Sinuses

·        Sinuses are body cavities – called Haemocoel

·        Capillary system – absent

·        Example: Arthropods, Molluscs & Ascidians

 

(ii) CLOSED TYPE

·        Blood flows in a complete circuit – around the body – through blood vessels

·        Blood flows – from arteries to veins – through capillaries

·        Example: Vertebrates

MORE TO KNOW

·         Closed circulatory system – discovered by – William Henry (1828) – Father of Physiology

 

STRUCTURE OF HUMAN HEART

·        Heart – muscular pumping organ – pumps blood into blood vessels

·        Human heart – situated between lungs – slightly tilted towards left – above the diaphragm – in thoracic cavity

·        Heart – made of specialized muscle – Cardiac muscle

·        Heart – enclosed in – double walled sac – Pericardium – contains lubricating fluid – Pericardial fluid

·        Pericardial fluid – reduces friction during heart beat – protects from mechanical injury

CHAMBERS OF THE HEART

·        Human heart – 4 chambers

·        2 upper, thin walled chambers – auricle or atria (sing. Atrium)

·        2 lower, thick walled chambers – Ventricles

·        Chambers separated by – partition – Septum

·        Septum between auricle & ventricle – prevents mixing of oxygenated & deoxygenated blood

 

AURICLES

·        2 auricles separated by – interatrial septum

·        Left atrium – smaller than right

·        Right atrium – receives deoxygenated blood – from different body parts – through main veins (Superior vena cava, Inferior vena cava & coronary sinus)

·        Pulmonary Veins – brings oxygenated blood – to left atrium – from lungs

·        Right & left auricles – pump blood to – right & left ventricles respectively

 

VENTRICLES

·        Ventricles – lower part of the heart

·        2 ventricles – separated by – inter ventricular septum

·        Left & right ventricles – thick walled – because they have to pump out blood with force away from heart

·        Right ventricle – arises – Pulmonary trunk – bifurcates to form – right & left Pulmonary arteries

·        Right & left pulmonary arteries – supply deoxygenated blood – to lungs of respective sides

·        Left ventricle – longer & narrower than right ventricle

·        Left ventricle – walls 3 times thicker than right ventricle

·        Left ventricle – arises – Aorta – supplies oxygenated blood to different parts of the body

·        Coronary arteries – supply blood to heart

 

VALVES

·        Valves – muscular flaps – regulate flow of blood – in single direction

·        Prevents back flow of blood

·        3 types of valves

·        (i) Right atrioventricular valve

·        (ii) Left atrioventricular valve

·        (iii) Semilunar valves

 

(i) RIGHT ATRIOVENTRICULAR VALVE

·        Located between – right auricle & right ventricle

·        Has 3 thin triangular leaf like flaps – called Tricuspid valve

·        Apices of flaps – held in position by – Chordae Tendinae – arise from – muscular projection in ventricle wall – called Papillary muscles

 

(ii) LEFT ATRIOVENTRICULAR VALVE

·        Located between – Left auricle & left ventricle

·        Has 2 cusps – called Bicuspid / Mitral valve

 

(iii) SEMILUNAR VALVE

·        Major arteries (Pulmonary artery & Aorta) – which leave the heart – have semilunar valves

·        They present the back flow of blood into ventricles

·        They are Pulmonary & Aortic semilunar valves

 

MORE TO KNOW

·        Heart chambers in Vertebrates

·        Two chambered – Fishes

·        Three chambered – Amphibians

·        Incomplete four chambered – Reptiles

·        Four chambered – Aves, Mammals & crocodiles (reptiles)

TYPES OF BLOOD CIRCULATION

·        Blood circulates – as oxygenated & deoxygenated blood

·        Types of circulation

·        (i) Systematic Circulation

·        (ii) Pulmonary Circulation

·        (iii) Coronary Circulation

 

(i) SYSTEMATIC CIRCULATION

·        Circulation of oxygenated blood – from left ventricle – to various body organs – through Aorta

·        Return of deoxygenated blood – to right Atrium

 

(ii) PULMONARY CIRCULATION

·        Circulation starts in – right ventricle – deoxygenated blood is carried by – pulmonary artery – to lungs

·        Pulmonary veins – collect oxygenated blood from lungs – supplies to left atrium

 

(iii) CORONARY CIRCULATION

·        Supply of blood – to heart muscles (Cardiac muscles)- Coronary circulation

·        Cardiac muscles – gets oxygenated blood from – coronary arteries – originate from Aortic arch

·        Deoxygenated blood from Cardiac muscles – drains into right atrium – by coronary sinuses

CIRCULATION

DOUBLE CIRCULATION

·        When blood circulates through the heart – one complete cycle – called Double Circulation

·        Here oxygenated blood & deoxygenated blood – do not mix

 

SINGLE CIRCULATION

·        In some animals – oxygenated & deoxygenated blood mix – pass through heart only once – called Single Circulation

 

HEART BEAT

·        One complete contraction (systole) & relaxation (diastole) – of atrium & ventricle of heart – Heart beat

·        Normal heart beat – 72 to 75 times per minute

 

MORE TO KNOW

Neurogenic Heart Beat

·        Initiated by – nerve impulse – from a nerve ganglion – near the heart

·        Example: Annelids, most Arthropods

Myogenic Heart Beat

·        Initiated by – specialized group of modified heart muscles

·        Example: Mollusca, Vertebrates

 

CONDUCTION OF HEART BEAT

·        Human heart – myogenic in nature

·        Contraction – initiated by – Sino-atrial (SA) node (special portion of heart muscle)

·        SA node – present in the wall of right atrium – near opening of Superior vena cava

·        SA node – broader at top; tapering below – made of thin fibres

·        SA node – acts as ‘Pacemaker’ of heart – as it is capable of initiating impulse – stimulates heart muscles to contract 

·        Impulse from SA node – spreads as wave of contraction – over right & left atrial wall – pushing blood through Atrioventricular valves – into ventricles

·        Wave of contraction from SA node – reach Atrioventricular (AV) node – stimulated to emit an impulse of contraction – spreads to ventricular muscle – via atrioventricular bundle & Purkinje fibers

DO YOU KNOW?

·        Atrioventricular bundle – discovered by HIS (1893) – called Bundle of HIS

 

PULSE

·        When Heart beats – blood forced into arteries

·        Expansion of artery – every time when blood is forced into – called Pulse

·        Felt by placing fingertip – on artery – near the wrist

·        Normal pulse rate – 70 to 90 /min

 

CARDIAC CYCLE

·        Sequence of events – from beginning to completion of one heart beat – Cardiac cycle

·        During Cardiac cycle – blood flows through heart chambers – in a specific direction

·        One cardiac cycle – lasts 0.8 second

·        Events during cardiac cycle involves

·        (a) Atrial Systole – contraction of auricles (0.1 sec)

·        (b) Ventricular Systole – contraction of ventricles (0.3 sec)

·        (c) Ventricular diastole – relaxation of ventricles (0.4 sec)

HEART SOUND

·        Rhythmic closure & opening of valves – causes sound of the heart

·        First sound – LUBB – longer duration – produced by closure of Tricuspid & Bicuspid valves – Ventricular Systole

·        Second sound – DUPP – shorter duration – produced by closure of semilunar valves – at the end of Ventricular Systole

 

BLOOD PRESSURE

·        Force exerted – during blood flow – against the lateral walls of arteries – Blood Pressure

·        BP – high in arteries &  capillaries; Low in veins

·        BP – expressed in terms of – Systolic pressure & diastolic pressure

 

SYSTOLIC PRESSURE

·        During ventricular systole – left ventricle contracts – forces blood into Aorta

·        Pressure – rises to peak – Systolic Pressure

 

DIASTOLIC PRESSURE

·        During Diastole – ventricles relax – pressure falls to the lowest value – Diastolic Pressure

 

BLOOD PRESSURE

·        Healthy adult – Normal systolic & diastolic pressure – 120 mm/80mm Hg

·        BP varies – during physical exercise, anxiety, emotions, stress & sleep

·        Prolonged or constant elevation of BP – Hypertension (High BP) – increase the risk of heart attack & stroke

·        Decrease in BP – Hypotension (Low BP)

 

STETHOSCOPE

·        Used to detect – sounds produced by internal organs of our body

·        Heart sound – heard by placing stethoscope – on chest

·        Useful diagnostic tool – to identify & locate health problems & diagnose disease

·        Modern Electronic Stethoscope – high precisioned instrument

SPHYGMOMANOMETER

·        Clinical instrument – used to measure BP – when the person is in – relaxed & resting condition

·        Pressure of brachial artery – measured

·        Helps to diagnose – increased/decreased BP

·        Monometric & modern digital types – used to measure BP

BLOOD GROUPS

·        Blood grouping concept – developed by – Karl Landsteiner (1900)

·        He identified blood groups – A, B & O

·        AB blood group – recognised by – Decastello & Steini (1902)

·         Human blood – contains Agglutinogens or Antigens (Ag) & Agglutinins or Antibodies (Ab)

·        Ag – found on the membrane surface of RBC

·        Ab – present in plasma

 

BLOOD GROUPS

·        Based on the presence of antigen & antibodies – human blood group is classified as – A, B, AB & O

·        An individual has one of the 4 blood groups

·        (i) ‘A’ GROUP individuals

·        Antigen A – present on RBC’s surface

·        Antibody b (anti-b) – present in plasma

·        (ii) ‘B’ GROUP individuals

·        Antigen B – present on RBC’s surface

·        Antibody a (anti-a) – present in plasma

·        (iii) ‘AB’GROUP individuals

·        Antigen A & B – present on RBC’s surface

·        Antibody – absent in plasma

·        (iv) ‘O’ GROUP individuals

·        Antigen A or B –  absent on RBC’s surface

·        Antibodies a & b (anti a & b)– present in plasma 

 

BLOOD DONATION

·        In blood transfusion – we must consider – antigen & antibody compatibility (matching) – between donor & recipient

·        When the blood group is mismatched – it leads to agglutination (clumping) – causes death

·        Persons with ‘AB’ blood group – Universal recipient – can receive blood from any blood group

·        Persons with ‘O’ group – Universal Donor – can donate blood to any blood group 

 

RH FACTOR

·        Rh Factor – discovered by Landsteiner & Weiner (1940) – in Rhesus Monkey

·        Antigen Rh – found on the surface of RBC’s

·        Rh⁺ (positive) persons – have Rh antigen on the RBC’s surface

·        Rh^- (negative) persons – donot have Rh antigen on the RBC’s surface

·        Antibodies developed against Rh antigen – Rh antibodies

 

LYMPHATIC SYSTEM

·        Lymphatic system consists of – lymphatic capillaries, lymphatic vessels, lymph nodes & lymphatic ducts

·        Lymph – fluid that flows through lymphatic system

·        Lymphatic capillaries – unite to form large lymphatic vessels

·        Lymph nodes – small oval or pear shaped structures – located along lymphatic vessels

LYMPH

·        Lymph – colourless fluid – formed when plasma, proteins & blood cells – escape into intercellular spaces – through pores present in walls of capillaries

·        Lymph – from intercellular space – drains into lymphatic capillaries

·        Similar to blood plasma – but colourless & contains less proteins

·        Lymph – contains very less – nutrients, oxygen, CO₂, water & WBC

 

FUNCTIONS OF LYMPH

·        Supplies nutrition & O₂ - to parts – where blood cannot reach

·        Drains away – excess tissue fluid & metabolites

·        Returns – proteins to the blood from tissue spaces

·        Carries absorbed fats from small intestine to blood

·        Lymphatic capillaries of intestinal villi (Lacteals) – absorb digested fats

·        Lymphocytes in Lymph – defend body from infections