TRANSPORT - THEORY & QUESTION ANSWERS Chapter # 14

 BIOLOGY XI NOTES

TRANSPORT - THEORY & QUESTION ANSWERS
Chapter # 14

Theory & Question Answers
Section IV - Functional Biology

➔ TRANSPORT

INTRODUCTION: (NEED FOR TRANSPORTATION OF MATERIALS) Every cell must obtain the necessary raw materials to support its metabolism. It must obtain nutrients and if it uses aerobic respiration, it must obtain oxygen. At the same time, it must get rid of metabolic wastes such as carbon dioxide and in animals nitrogenous compounds. In short, every cell must be exposed to a medium from which it can extract raw materials and into which it can dump wastes.

TRANSPORT IN PLANTS: (MATERIALS TO BE TRANSPORTED IN PLANTS) Plants are in contact with both soil and atmosphere. Various materials from atmosphere and soil are transported in and out of plant body. At the same time certain materials are transported through out the plant. Transport in plants occurs on three levels:

• Water, gases and solutes move in and out across cell membrane.
• Loading of food from photosynthetic cells into sieve tubes (short distance transport).
• Conduction of water with dissolved minerals and food along the whole plant through xylem and phloem, respectively (long distance transport).

UPTAKE AND TRANSPORT OF WATER AND MINERALS: Soil is the source of water and minerals for plants. They are taken up by roots. Various processes are involved in uptake of these minerals. These are diffusion, facilitated diffusion, osmosis, imbibitions and active transport.

PROCESSES INVOLVED IN THE UPTAKE:

• Diffusion: Movement of molecules from region of higher concentration to lower concentration is called diffusion.

• Facilitated diffusion: Charged particles and large molecules do not pass through cell membrane. Certain meprocess of phloem loading and unloading a force is developed which helps in the flow of food substances in the phloem. Thus source to sink movement is useful in the accumulation of food in the storage regions of cereal grains and other parts, therefore it has a great importance in agriculture.

MECHANISM OF PHLOEM TRANSLOCATION:

(Diagram illustrating pressure flow hypothesis showing loading of sugar at source and unloading at sink tissues)

Pressure Flow Or Mass Flow Hypothesis: (Munch Hypothesis)
To describe the mechanism of translocation many theories have been put forward, but the most important theory is known as Ernst Munch theory which is also called mass-flow or pressure flow. This theory was proposed by Munch in 1930. According to this theory the food migrates from source (leaves) to the sink (growing and storage organ) in a flow, called mass flow. This flow of solution in the sieve tubes is due to the osmotic pressure gradient between source (leaves) and sink (storage region). When leaves manufacture food material by photosynthesis, their osmotic pressure increases, so these mesophyll cells of leaves get water from neighboring cells, as a result of this process a high turgor pressure is developed in mesophyll cells.

The mesophyll cells are connected with each other through small pores, called plasmodesmata. These connections are reached up to the sieve tubes of phloem. The food substances are diffused through plasmodesmata to the sieve tubes due to turgor pressure. The movement is from a region of high turgor pressure (source, leaf cells) to the region of low turgor pressure sink tissues (storage tissues). In this way a mass flow of water and dissolved organic solutes occurs in phloem from upper region to lower region, so it is called mass flow or bulk flow.

Munch’s Hypothesis:
Munch hypothesis can very well be explained with the help of following experiment. Two chambers A and B with semipermeable wall are connected by a tube C. There is present

• mbrane transport proteins such as channel proteins and carrier proteins help them to cross the barrier. This movement of ions and molecules is called facilitated diffusion.

• Osmosis: The word osmosis is derived from a Greek word “osmosis” which means “to push”. “It is a physical process in which solvent molecule (water) move from their higher concentration to lower concentration by the help of semi permeable membrane”.

Osmotic pressure:
"It is the pressure of solvent molecules which is applied on semi-permeable membrane it also helps in the termination of osmosis".

Types Of Osmosis:
There are two main types of osmosis:

• Exosmosis:
  It is a process in which solvent molecules move outside the cell when a cell is put in a hypertonic solution.
• Endosmosis:
  The entrance of water in a cell when a cell is put in a hypotonic solution is called endosmosis.

SIGNIFICANCE OF OSMOSIS:

• The root hairs absorb water by the help of osmosis.
• It also helps in the transportation of water from one cell to another cell in plants.
• It also helps in the transportation of water in living cells of plants from non-living xylem vessels.
• It also provides turgidity to the cell which helps in the stability of immature stems and leaves.
• It also helps in the sleep movement of leaves and flowers.

Active Transport:
Certain molecules or ions move across the cell membrane against the concentration gradient i.e., from lower concentration to higher concentration. The transport takes place at the expense of the cell’s metabolic energy. ATP and is called active transport.

Example:
Phloem loading in plants.

PLASMOLYSIS:
The shrinkage of protoplasm due to exosmosis when a cell is placed in a hypertonic solution is called as plasmolysis. The point when cytoplasm just starts to separate from cell wall is called incipient plasmolysis.

Explanation
When the cell is in turgid states then turgor pressure and wall pressure are always equal to each other but when it (cell) is placed in hypertonic solution then it shows exosmosis and sleaze water molecules due to high concentration of water in cell to lower concentration i.e., Environment. There are turgor pressure of a cell is decreased as well as concentration of cell sap on ceased and finally protoplasm deposits in the center of cell leaving cell wall. This process conditions required:

• The cell must be a living cell.
• The cell should be a place in a hypertonic solution.

Turgidity:
The state in which the cell wall is fully stretched and pressure potential reaches at it maximum.

Turgor Pressure:
Hydrostatic pressure of protoplasm applied on the cell wall due to the turgidity is known as turgor pressure.

Wall Pressure:
An equal and opposite pressure of cell wall exerted on protoplasm called wall pressure.

Deplasmolysis:
The recovery of a plasmolysed cell by the insulation of its protoplasm due to endosmosis, to exert turgor pressure on the cell wall is called deplasmolysis. When a plasmolysed cell is placed in hypotonic solution, endosmosis takes place, the protoplasm retain its original position. It is known as deplasmolysis.

Conditions Required:

• The cell must be a living cell.
• The cell should be placed in a hypotonic solution.

Imbibition:
Adsorption of water and swelling up hydrophilic (water loving) substances known as imbibition. Starch, gum, protoplasm, cellulose and proteins are hydrophilic substances.

WATER STATUS IN PLANTS:
Water is important in the life of plant, because it makes up the matrix and medium in which biochemical processes essential for life occur. The movement of water depends upon the chemical potential of water or water potential, osmotic potential and pressure potential.

Water Potential:
The chemical potential of water is a quantitative expression of the free energy associated with the water. Thermodynamically, free energy represents a potential for performing work. All living things including plants, require a continuous input of free energy. In the case of water movements this free energy is involved in water flow. The unit of chemical potential is energy per mole of a substance (joules per mole).

For practical reason, it turns out that the unit of chemical potential is inconvenient for most work in plant physiology. Therefore, plant physiologists have defined another parameter called water potential as the difference between the free energy of water molecules in pure water and energy of water in any other system (e.g water in solution or in a cell sap of plant). Now, the free energy of water is expressed in pressure unit such as megapascals and symbolized by Greek letter ψ psi (MPa; 1MPa = 9.87 atmosphere). Pure water has been assigned the value of water potential 0 MPa. Addition of solute particles lowers the mole of substance divided by total number of all substances in the system/ solution of water hence; there is a decrease in water potential. Therefore, values of water potential remains less than zero or in negative value.

Osmotic Pressure:
The pressure exerted upon a solution to keep it in the equilibrium with pure water when the two are separated by a semipermeable membrane in known as osmotic pressure. Therefore, the osmotic pressure of a solution is a measure of the tendency of water to move by osmosis into it. In other words we can say that the osmotic pressure is the pressure that must be exerted on a solution to prevent the passage of solvent molecule into when the solvent and solution are separated by a differentially permeable membrane. Thus, it prevents the process of osmosis proceeding.

Osmotic Potential Or Solute Potential:
Osmotic Potential is the tendency of a solution to attract water molecules when the solutions of two different concentrations are separated by a differentially permeable membrane. Pure water is assigned the osmotic potential zero as the highest value. Since the osmotic potential decreases as the osmotic concentration (the no. of osmotically active particles per unit volume) increases, all solutions have value of less than zero. Under constant temperature and pressure, water moves from the solution of lower osmotic potential to the solution of higher osmotic potential when the two solution are separated by a differentially permeable membrane. It is represented by ψs or solute potential. Another term used in relation to water potential is pressure potential, which is defined as the hydrostatic pressure in excess of atmosphere pressure.

WATER RELATIONS OF PLANT CELL:
For practical purposes a plant cell can be divided into three parts:

• Cell Wall: this is non-living, permeable, outer most boundary of cell made up of cellulose.
• Cytoplasm: along with nucleus forms protoplasm - the living material bounded by cell membrane.
• In the centre, there is a vacuole enclosed by tonoplast, central vacuole is filled with cell sap - an aqueous solution of salts, organic acids and sugar. The presence of solute particles lowers the water potential ψ of cell sap. Greater the number of solute particles, the more negative will be the water potential of cell sap. The concentration of solute particles in a solution is known as solute potential ψs. (This has been previously referred as osmotic potential). The value of solute potential is always negative. When a cell is placed in pure water or in an aqueous solution with higher water potential (less negative) than the cell sap, water flows into the vacuole by osmosis through plasma membrane and tonoplast. As more water flows into the vacuole, the tension developed by cell wall causes an internal hydrostatic pressure to develop. This is called pressure potential ψp and it opposes the continued uptake of water into the cell by osmosis. When the cell wall id fully stretched and pressure potential reaches at its maximum, the cell cannot take any more water, and is said to be fully turgid. The relationship between water potential ψ, solute potential ψs and pressure potential Pp is represented by following equation

$$\psi =\psi s+\psi p$$

In a turgid cell ψp is equal and opposite to ψs, so ψ = 0

WATER AND MINERALS UPTAKE BY ROOT:
Absorption of water and minerals by plants:

Absorption:
Water is essential in the body of plant It brings about a number of plant activities. The cytoplasm contains about 90 - 95% of water, it is used in photosynthesis, and it helps to maintain the turgidity of cells. This water is absorbed from the soil and only a very small amount of water is utilized by the plant for its various functions and rest of his amount is lost in transpiration. The intake of water from the soil is known as absorption.

Root:
The root is an underground part of plant which arises from the radical of seed. It helps in the absorption of water and minerals from soil due to the presence of root hairs. Root hairs possess sticky walls and adhere tightly to soil particles which are usually coated with water and dissolved minerals salts. From root hairs and epidermal cells water flows through cortex endodermis, Pericycle and enters xylem. Since transport of water takes place in radial direction it is also termed as lateral transport.

PATHWAYS FOR WATER:
Three pathways are available for water to enter xylem.

• Cellular pathway
• Symplast
• Apoplast

Cellular Pathway:
The first route is from cell to cell. Water enters the root hair or epidermal cell down a gradient of water potential. It flows out of one cell across the cell wall, cell membrane vacuole and enters the adjacent cell which may again pass the substance along the next cell in the pathway. This is known as cellular path way.

Symplast:
The second pathway is symplast through the pores in the cell walls, cytoplasm of cortical cells remain connected with cytoplasm of adjoining cortical cells. These cytoplasmic connections through pores are known as plasmodesmata. These plasmodesmata provide another pathway for transport of water and solutes known as symplastic pathway. This requires only one crossing of plasma membrane at root hair.

Apoplast:
The third pathway is apoplast. The cell walls of epidermal cells and that of cortical cells form a continuous matrix. These walls are hydrophilic. Soil solution flows freely through hydrophilic walls of epidermal and cortical cells. This movement of soil solution through extracellular pathway provided by continuous matrix of cell walls is known as apoplastic pathway. As solutes move along extracellular pathway some of the water and solutes are taken up by the cells of cortex thus changing the route from apoplast to symplast. The inner limiting layer of cortex is endodermis which serves as a barrier or checkpoint because of casparian strip a waxy belt that

extends through the walls of endodermal cells. Thus, water and minerals cannot cross the endodermis and enter xylem via apoplast (extracellular pathway). Symplast is the only way to cross the barrier. Endodermal cells actively transport salts to pericycle resulting in high concentration of salts. This cause a low water potential and water moves into them by osmosis. From pericycle water flows into xylem both via symplast and apoplast.

(Diagram of pathways for water uptake by the root up to xylem)

TRANSPORTATION:
The process in which organic (food) and inorganic (H2O, salts) substances are transferred to all parts of the body is known as transportation.

Types Of Transportation:
In plants, there are two types of transportation.

• Ascent of sap
• Translocation

ASCENT OF SAP:
The upward movement of water from absorptive surface (roots) to the transpiring surface (leaves) against the force of gravity is called “Ascent of sap”. The process of ascent of sap has two aspects.

• Path of ascending sap.
• Forces responsible for ascent of sap.

Path Of Ascending Sap:
In the light of little experimental verification it is observed that the xylem vessels and tracheids are responsible for the path of ascending sap.

Experiment # 1:
Cut branch of plant under water and put it in colored water. The water moves upward through branch, veins and vein lets of leaves. After an hour cut the transverse section of branch and examine under microscope, it will be observed that only xylem vessels and tracheids are colored. It proves that water moves upward through xylem only.

Vessels:
Vessels are dead cells which lack transverse walls. Their walls are thick and lignified. There are some depressions in the walls which are known as pits. Vessels cells are connected one above the vessel. In vessel water moves 10 times faster than tracheids. Vessels are mostly found in angiosperms. The diameter of vessel is about 20-70 µm and the length is about several centimeter.

Tracheids:
Tracheids are also dead cells with thick, lignified angular walls. There transverse walls are perforated. Through these pores water moves from cell to cell. The diameter is 30 µm and it length is several millimeter. Tracheids are only found in ferns gymnosperm and other primitive vascular plants.

Mechanism Of Ascent Of Step:
The mechanism of ascent of sap is described by the following theories.

• Root pressure theory
• Transpiration pulls theory or Adhesion, cohesion and tension theory or Dixon theory.

Root Pressure Theory:
This theory was presented by Stephen Hales in 1727. According to him this force could be responsible for rising of water to the height of 6.4 meter.

Explanation:
If the stem of potted plant dip in water is cut little above the soil, the cut ends exudes water for some time. He suggested that there is a force pushing water up to the stem from roots. This force is known as root pressure.

Objection:

• This is an insufficient force.
• Many tall trees do not generate enough root pressure for upward movement of water.

Transpiration Pulls Theory:
This theory was presented by Dixon and Jolly. According to them to transport water over a long distance plants do not use their metabolic energy. Forces like adhesion, cohesion and evaporating effect of sunlight are mainly responsible for upward conduction of water. Thus ascent of sap is solar produced.

Explanation:
Sunlight raises temperature of leaves so the water begins to evaporate from moist walls of mesophyll cells. The evaporated water is immediately replaced from water inside the cell, which is replaced with water from neighboring cell deeper in the leaf. Ultimately water is pulled from xylem to meet the loss of water. Thus water in xylum is placed under tension which is transmitted to root through vessels. This downward transmission of tension is because of cohesive property of water columns in vessels and tracheids. Water column moves upward by mass flow due to transpiration pull.

Important Factors Of Ascent Of Sap:

• Transpiration:
  It generates a pulling force

• Physical Force:
  Two types of physical forces.

  • Adhesion:
    Adhesion is the sticking together of molecules of different kinds. Water molecules tend to adhere to cellulose molecules of the walls of xylem vessels.

  • Cohesion:
    Cohesion is the joining together of molecules of same kind. Extensive hydrogen bonding in water gives rise to property of cohesion. The cohesing water molecules in xylem vessels form a continuous column.

Transpiration:
In can be defined as, “a process in which excess water is released form the aerial parts of plants in the form of vapours”.

Explanation:
The root hairs absorb water in bulk amount which is utilized in photosynthesis and other metabolic functions. That water which is not involved in these reactions is called excess water. If water is stood in the cells of plant may burst the plant. Therefore, excess amount of water is released from the plant in the form of vapours by the help of aerial parts. Thin process is known as transpiration.

Types Of Transpiration:
The three types of transpiration are given as follows:

• Lenticular transpiration

• Cuticular transpiration

• Stomatal transpiration

• Lenticular Transpiration:
  It’s a type of transpiration in which loss of water occurs by the help of lenticels.

  Lenticels:
  The lenticels are small pores present in stem of higher plants. It’s formed due to secondary growth of plant due to rupturing of epidermal cells.

• Cuticular Transpiration:
  It is type of transpiration which occurs by the help of cuticle.

  Cuticle:
  It is a waxy layer of epidermal cells which are composed by cutin (carbohydrates) it inhibits the excretion of water by epidermal cells. The ratio of lenticular and cuticular transpiration is almost 3% of the total transpiration while 97% of transpiration is through stomata.

• Stomatal Transpiration:
  It is a type of transpiration which occurs by the help of stomata, which are present on epidermal cells of aerial parts of plants.

• Stomata:
  Stomata are the microscopic pores which are found on the surface of leaves and some stems.

No Of Stomata On Sq. mm Of Leaf:
Mostly 50-300 stomata are found on a square millimeter of leaf surface, But according to Eckerson in 1908, 14 stomata/mm² are found on the leaf of wheat. According to Yoccum 1935, 1038 stomata/mm² are present on the leaf of scarlet plant.

Structure Of Stomata:
The stomata are externally covered by two kidney-shaped cells which are known as guard cells. These guard cells differ from other epidermal cells. These guard cells differ from other epidermal cells on the basis of two reasons.

• Presence of chlorophyll
• Specific structure

The outer layer of guard cells is thin and elastic as compared to inner thick wall. This helps in the stomatal movement. The guard cells perform following three functions:

• Exchange of gases
• Transpiration
• Manufacturing of food

Stomatal Movement:
The stomatal movement depends upon the turgidity. Outer wall of guard cells stretches a biconcave opening is formed between two guard cells which is known as stomata. The reverse process of guard cells helps in the closing of stomata.

Opening And Closing of Stomata:
The opening of stomata is normally seen during day time while stomata are closed in night due to following reasons. The CO₂ consume in photosynthesis during day time therefore guard cells suffer in deficiency of CO₂ and also decreases the turgidity of guards cells. Therefore enzyme phosphorylase is active by help of light and it converts starch into glucose 6 phosphate.

$$\text{Starch phosphorylase}\stackrel{\text{Light}}{\to }\text{glucose 6 phosphate}$$

As we know that starch is insoluble in water therefore it cannot produce any effect on the concentration of guard cells while glucose 6 phosphate as soluble in water and increase the concentration of cell sap in guard cells so water is transferred in guard cells from adjoining cells and guard cells become turgid which help in the stomatal movement and stomata becomes close. Light is absent in night therefore no change occurs in the concentration of cell sap guard cells.

Factors Effecting Rate Of Transpiration:
The factors effecting rate of transpiration are classified into two groups:

• External factors
• Internal factors

External Factors:
The following external factors affect on the rate of transpiration.

• Humidity

• Temperature

• Velocity of wind

• Atmospheric pressure

• Water contents in soil

• Light

• Humidity:
  The dry wind increases the rate of transpiration therefore rate of transpiration depends upon humidity. Deficiency of humidity increases the rate of transpiration.

• Temperature:
  The high temperature increases the rate of transpiration because high temperature decreases the humidity in air hence increasing the rate of transpiration.

• Velocity Of Wind:
  The maximum velocity of wind increases the rate of transpiration because high velocity of wind removes water molecules which are present on surroundings of stomata.

• Atmospheric Pressure:
  The low atmospheric pressure decreases the density of air therefore low atmospheric pressure increases the rate of transpiration.

• Water Contents In Soil:
  Due to increase in water contents of soil mesophyll cells will have more water contents resulting in opening of stomata and vice versa hence water contents of soil has direct relation with rate of transpiration.

• Light:
  Light causes dual effect on rate of transpiration light stimulates enzyme phosphorylase which converts starch into glucose 6 phosphate and increases the concentration of guard cells so that most of the plants stomata opens in day time while closes during night. The intensity of light also increases the temperature so light increases the rate of transpiration.

TRANSPIRATION AS NECESSARY EVIL:
Transpiration has its advantage and thus it is necessary the other hand it has grave disadvantages and thus it is an evil.

Advantages:

• Transpiration produces a force in plants which helps in ascent of sap.
• Transpiration increases concentration of salts and minerals on cells therefore more absorption of water occurs in cells.
• Transpiration also helps in transpiration of water in whole.
• It has cooling effect in plant.

Disadvantages:

• It may cause the death of plant due to dehydration.
• In certain plants leaves are modified into scales or spines or shed leaves in order to reduce the transpiration.

Translocation Of Organic Solute: (Phloem Translocation)
The movement of photoassimilates and other organic material from leaves to the growing and straight organs of plants is called translocation. This movement takes place via the phloem and is therefore called phloem translocation. The organic materials are prepared in the form of simple carbohydrates as food in the green leaves of plants. Other parts also require these carbohydrates, so they are transferred to those parts which use them or store them in their tissues.

Path Of Translocation:
In small plants like Bryophyta the body is small and the food material is cover a small distance, so they do not have proper vascular tissues which help in the translocation of important substances. In higher plants the body is large. They contain vascular tissues. In such plant phloem (a part of vascular tissues) is responsible in the translocation of food.

Mechanism Of Phloem Conduction:
In plants the food substances move through the phloem. According to Curtis the movement in phloem occurs in both directions i.e. from up to downward or from down to upward. Phloem is a complicated tissue, composed of many cells. The main vessels are called sieve-tubes, through which movement of food substances takes place.

Source - Sink Movement:
The transport of food substances takes place from the region of supply (source) to the region of metabolism or storage (sink), therefore the phloem transport is also called source-to-sink movement. There are different steps in the movement of food substances from mesophyll cells of leaves to the sieve tubes of phloem in a mature leaf. Initially the synthesized sucrose is transferred from the mesophyll cells to the vicinity of sieve tubes in the smallest veins of the leaf. This process is called short-distance transport pathway. In this transport the solute covers a small distance only two or three cells diameters. After that sucrose is actively transported into sieve tubes of phloem, this process is called phloem loading. The sucrose is transported to other part; it covers a long distance, so it is called long-distance transport.

After covering a long distance when the sucrose is reached to the areas of metabolism or storage i.e. at the sink region, the sucrose is unloaded at the sink it is called phloem unloading. By the

process of phloem loading and unloading a force is developed which helps in the flow of food substances in the phloem. Thus source to sink movement is useful in the accumulation of food in the storage regions of cereal grains and other parts, therefore it has a great importance in agriculture.

MECHANISM OF PHLOEM TRANSLOCATION:

(Diagram illustrating pressure flow hypothesis showing loading of sugar at source and unloading at sink tissues)

Pressure Flow Or Mass Flow Hypothesis: (Munch Hypothesis)
To describe the mechanism of translocation many theories have been put forward, but the most important theory is known as Ernst Munch theory which is also called mass-flow or pressure flow. This theory was proposed by Munch in 1930. According to this theory the food migrates from source (leaves) to the sink (growing and storage organ) in a flow, called mass flow. This flow of solution in the sieve tubes is due to the osmotic pressure gradient between source (leaves) and sink (storage region). When leaves manufacture food material by photosynthesis, their osmotic pressure increases, so these mesophyll cells of leaves get water from neighboring cells, as a result of this process a high turgor pressure is developed in mesophyll cells.

The mesophyll cells are connected with each other through small pores, called plasmodesmata. These connections are reached up to the sieve tubes of phloem. The food substances are diffused through plasmodesmata to the sieve tubes due to turgor pressure. The movement is from a region of high turgor pressure (source, leaf cells) to the region of low turgor pressure sink tissues (storage tissues). In this way a mass flow of water and dissolved organic solutes occurs in phloem from upper region to lower region, so it is called mass flow or bulk flow.

Munch’s Hypothesis:
Munch hypothesis can very well be explained with the help of following experiment. Two chambers A and B with semipermeable wall are connected by a tube C. There is present

concentrated sugar solution in A and water in B. the two chambers are placed in a water-filled vessel. A represents to mesophyll cell in leaf which is the supply end and B to the root which is the receiving end. Water will diffuse rapidly into A under osmosis. Since A is connected to B, the pressure will be transmitted to B and water will be forced out through B. There will be mass flow of solution from A to B through C which represents the phloem. This flow will be continue till the concentration in the two chambers in equal and equilibrium is established. This process can be prolonged if a continuous supply of sugar solution to chamber A is maintained. The same can easily be applied in plants.

TRANSPORT IN ANIMAL:
Animals have efficient means of transportation which are according to their complexity.

Means Of Transportation:
There are three means of transportation found in animals.

• Diffusion

• Active Transport

• Circulatory System

• Diffusion:
  "The movement or molecule from higher concentration to lower concentration called diffusion". In lower and higher class animals diffusion plays important role for transportation of molecules.

• Active Transport:
  "The movement of molecules from lower concentration to higher concentration called active transport". In simple and complex multicellular animals active transport also plays important role in transportation of materials.

• Circulatory System:
  "The rapid flow of mass of material (blood) from one place of body to another place of body to cover the distance called circulatory system”. In high class animals most of the transportation is take place through circulatory system but diffusion and active transport also help in transportation of materials.

Types Of Circulatory System:
There are two types of circulatory system found in animals.

• Open type circulatory system

• Close type circulatory system

• Open Type Circulatory System:
  "The circulatory system in which blood is circulating in sinuses or Haemocoel cavity called open type circulatory system”. In this type of circulatory system interstitial fluid and blood are not distinguishable and its collectively known as Haemolymph. Hemoglobin is absent in open type blood circulatory system, so it does not help in gases transportation. In open type circulatory system blood is also pumped by tubular hearts. This type of circulatory system found in arthropods and molluscas.

Close Type Circulatory System:
"Circulatory system in which blood circulates inside blood vessel by pumping action of heart called close type circulatory system”. In this type of circulatory system Hemoglobin is present in blood so it helps in gases transportation. In close type circulatory system blood is circulate in three types of blood vessels which is found in animals.

• Artery
• Capillary
• Vein

This type of circulatory system found in animals of Phylum Chordata and Annelida.

Single Circuit Circulation:
The circulation in which blood is circulating in one direction called single circuit circulation. This type of circulation found in fishes. The heart of fishes is consists of two chambers.

• Atrium
• Ventricle

Inside atrium blood vessel is open called sinus venosus. Another blood vessel arises from ventricles called conusarterious. Sinus venosus collect deoxygenated blood from body and pour it into the heart. When heart is contract deoxygenated blood supplied to the gills where oxygenation takes place. Then oxygenated blood is supplied to the all parts of body. So in this way blood is circulating in one direction.

Double Circuit Circulation:
The circulation in which blood circulates in two different circuits called double circuit circulation. Double circuit circulation further divided into two types.

• Incomplete Double Circuit Circulation

• Complete Double Circuit Circulation

• Incomplete Double Circuit Circulation:
  Incomplete Double Circuit Circulation found in reptiles and amphibians. Heart of reptiles consists of three chambers except crocodile (four chambers).

  • Right Atrium
  • Left Atrium
  • Ventricle

  Right atrium receives deoxygenated blood from body while left atrium receive oxygenated blood from lungs through pulmonary vein. Between left and right atrium a septum is present which prevent mixing of both types of blood. When both atrium are contract both types of blood are come into ventricle where mixing of blood takes place. After contraction of ventricle mix blood is supply to different parts of body. So this type of circulation is known as incomplete double circuit circulation.

• Complete Double Circuit Circulation:
  Circulation in which blood completely circulates in two different circuits called complete double circulation. This type of circulation found in birds and mammals because their hearts are consists of four chambers.

  • Left Atrium
  • Right Atrium
  • Left Ventricle
  • Right Ventricle

  Left atrium receive oxygenated blood through pulmonary vein while right atrium receive deoxygenated blood of body through vena cava. Both types of blood are not mixed because a septum is present between left and right atrium. Due to contraction of both atria both type of blood is goes into left and right ventricle. Due to contraction of left ventricle oxygenated blood supply to body parts through systemic aorta. While due to contraction of right ventricle deoxygenated blood supply to lungs through pulmonary aorta.

• Systemic Circulation
  The circulation in which blood is circulates between heart and body called systemic circulation.

• Pulmonary Circulation:
  The circulation in which blood is circulates between heart and lungs called pulmonary circulation.

• Red Blood Cells:
  They are also called erythrocytes. They are rounded shape, biconcave, non-nucleated cells. They contain respiratory pigment called hemoglobin. Hemoglobin helps in gasses transportation in body. They are iron-containing protein and due to presence in blood color becomes red. The formation of red blood cells takes place inside the bone marrow of ribs and sternum. The life of red blood cells is 120 days. Due to metabolism of R.B.C two types of bile pigments are produced.

  • Bilirubin
  • Biliverdin

  Red blood cells also contain carbonic anhydrase enzymes which help in transportation of CO₂.

• White Blood Cells:
  They are also called leucocytes. They are spherical or irregular shape cells. They are nucleated. They are produced inside the bone marrow.

  Classification Of White Blood Cells:
  White blood cells are broadly classified into two types.

  • Granulocytes

  • Agranulocytes

  • Granulocytes:
    Those white blood cells which have various shaped nucleus and grains of food called granulocytes. They are further divided in three types.

    • Eosinophills (Acidic)
    • Basophills (Basic)
    • Neutrophills (Neutral)

  • Agranulocytes:
    Those white blood cells in which food grain are absent called Agranulocytes. They are further divided in two types.

    • Monocytes
    • Lymphocytes

  Function Of White Blood Cells:

  • White blood cells produce immunity in the body.
  • Neutrophils and monocytes kill bacteria and viruses by the process of Phagocytosis.
  • Eosinophils, basophils, and lymphocytes produce histamine, antitoxin, and heparin.

• Platelets:
  They are cell fragments which are produced by metabolism of cells. They help in the clotting of blood.

Function Of Blood:
Blood performs the following important functions:

• Transport Of Hormones:
  Blood transports the hormones from endocrine glands to the target organs.

• Transport Of Nutrition:
  Blood transports digested food, water, and other substances from the alimentary canal to the various parts of the body for storage, oxidation, or assimilation.

• Distribution Of Body Heat:
  Blood distributes the body heat throughout the body parts in order to maintain the body temperature.

• Transport Of Waste Product:
  Blood transports waste products from tissues to the excretory organs for their discharge.

• Transport Of Metabolic By-Products:
  Blood transports metabolic by-products from the area of production to other parts of the body.

• Transport Of O₂ And CO₂:
  Oxygen is transported from the lungs to all parts of the body, and carbon dioxide from cells to the lungs for removal.

• Defence Against Diseases:
  The W.B.C of blood protects the body against diseases by phagocytosis through neutrophils and monocytes, which engulf and digest the germs that enter the bloodstream, or by antibodies or antitoxins produced by lymphocytes.

• Protection Against Its Own Loss:
  Blood protects against its own loss by clotting, making a clot over the injured part.

BLOOD DISORDERS:

• Leukaemia:
  Leukaemia is also known as blood cancer. It is the malignant disorder of blood (haemopoietic) tissues which is characterized by an increase of W.B.C (leucocytes) in blood. It obstructs the blood formation in bone marrow. It may be fatal and cause death or haemorrhage or infection. The actual cause of leukaemia is still unknown, but it is thought that leukaemia is developed by ionizing radiation, cytotoxic drug, retrovirus, and genetic etc.

• Thalassemia:
  It is also blood cancer. Thalassemia is an inherited impairment of hemoglobin production. The abnormality may be heterozygous or homozygous.

  Heterozygous Thalassemia:
  It is also known as Thalassemia minor in which the synthesis of hemoglobin is only mildly affected and little disability occurs.

• Homozygous Thalassemia:
  It is also known as Thalassemia major in which patient unable to synthesize hemoglobin or produce very little and after four months of life develop a profound hypochronic anaemia. It is more common in children. It results to the enlargement of kidney. The regular blood transfusion is only remedy.

EVOLUTION OF HEART:
Evolution means gradual. In evolution of heart many changes have taken place.

• In Fishes:
  The heart is shaped two chambered with one atrium and one ventricle. The atrium receives blood of body through sinus venosus and transfers it to ventricle. The ventricle pumps blood to gills (for oxygenation) through conus arteriosus.

• In Amphibians:
  Heart is three chambered (two atria and one ventricle). The right atrium receives deoxygenated blood from body and left atrium receives oxygenated from lungs. These two types of blood are mixed in ventricle.

• In Reptiles:
  Heart is gains three chambered but beginning of partition in ventricle (inter ventricular septum) found in crocodile.

• In Birds And Mammals:
  Both have four chambered heart. Two atria and two ventricles. The two types of blood remain separate. The oxygenated blood circulates through the left side deoxygenated through the right side. Man has complex and developed circulatory system. He has complete double circulation. Circulatory system of man consists of two organs.

  • Heart
  • Blood vessels

HUMAN HEART:
Heart is a vital organ. It is muscular in structure. Heart acts as pumping station. It pumps the blood to the body. Due to the pumping action of heart, blood circulates throughout the body.

• Size:
  The size of heart equal to the man fist.

• Shape:
  Heart has conical shape. Upper end is broad while lower end is pointed. Upper part called Apex of heart and a lower part is known as base of heart.

• Colour:
  Heart is reddish brown in colour. This colour of heart appears due to presence of blood.

• Position:
  Heart is located inside chest cavity between both lungs. Heart is slightly present towards left hand.

• Covering:
  Heart is covered by strong double membranous layer called pericardium. Between membranes a fluid is present called as pericardial fluid.

  • Pericardium and pericardial fluid both protect the heart from jerks.
  • Pericardial fluid keeps moisture to the heart.
  • It also helps in contraction and relaxation of heart.

• Morphology:
  Externally heart has smooth surface. Wall of heart is very strong and it is composed of cardiac muscles or striated involuntary muscles. Cardiac muscles are branched in nature and they are arranged in overlapping pattern. The outer surface of heart has an artery called coronary artery. It supplies blood to the wall of heart.

• Anatomy:
  If we take L.S of heart, internally heart of man is divided into four chambers.

• Right atrium

• Left Atrium

• Right Ventricle

• Left Ventricle

• Right Atrium:
  It is upper chamber of heart and produces apex of heart. It has comparatively thin walls as compared to ventricles.

  There are two large vena cavas open into right atrium.

  • Superior Vena Cava

  • Inferior Vena Cava

  • Superior Vena Cava:
    Superior vena cava collects blood from upper parts of body.

  • Inferior Vena Cava:
    Inferior vena cava collects blood from lower body parts. Both vena cava collect deoxygenated blood so right atrium contains deoxygenated blood. These two vena cava open through an opening called opening of vena cava.

• Atrioventricular Opening:
  Right atrium opens into right ventricle through an opening called Atrioventricular opening.

• Tricuspid Valve:
  The atrioventricular opening of right atrium and right ventricle is guarded by three flapped valve called tricuspid.

• Left Atrium:
  It is also upper chamber of heart and produces apex of heart. It has also thin walls. Two pairs of pulmonary vein open into the left atrium. They carry oxygenated blood from lungs, so the left atrium contains oxygenated blood. Pulmonary veins are open through an opening in left atrium called opening of pulmonary vein.

• Bicuspid Valve:
  The atrioventricular opening of left atrium and left ventricle is guarded by two flapped valve called bicuspid valve.

• Inter Atrial Septum:
  A muscular septum is present between right and left atrium known as inter atrial septum. It prevents the mixing of oxygenated and deoxygenated blood in both atria.

• Right Ventricle:
  It is the lower chamber of heart and forms the base of heart. It has thick walls and conical shape. Right ventricle contains deoxygenated blood which is received from the contraction of right atrium.

• Pulmonary Aorta:
  The large artery arises from right ventricle called pulmonary aorta. Out of heart it is divided into left and right pulmonary artery. It supplies deoxygenated blood to lungs. Pulmonary aorta has a valve at its origin called semilunar valve. It prevents backward flow of blood into right ventricle.

• Left Ventricle:
  It is also a lower chamber of heart that forms the base of heart. It has also thick walls and conical in shape. It is slightly larger than the right ventricle. Left ventricle contains oxygenated blood which comes from left atrium.

• Systemic Aorta:
  A large artery is also arising from left ventricle called systemic aorta. Out of heart it divides into branches and produces arterial system of body. It supplies oxygenated blood throughout body parts. Semilunar valve is also present in systemic aorta which prevents backward flow of blood.

• Inter Ventricular Septum:
  A muscular septum is present between right and left ventricles called inter ventricular septum. It prevents mixing of oxygenated blood with deoxygenated blood.

• Papillary Muscles:
  Muscular threads are present between walls of ventricle and inter ventricular septum called papillary muscles. The muscle fibers help in the contraction of ventricles.

• Cardiac Cycle:

  • During the contraction of heart first both atria are contract and then both ventricles are contract.
  • During relaxation first both atria are relax and then both ventricles are relax.
  • The contraction of atria and ventricles is known as Systole of heart.
  • The relaxation of atria and ventricles is known as Diastole of heart.
  • The events which are take place during systole and diastole of heart called Cardiac Cycle.

• Heart Beat:
  Rhythmic movements of heart are called heart beats. Heart beat consists of seventy two times systole and seventy two times diastole of heart per minute. So, normal heart beat is 72 times/minute. During heart beat heart is produced two types of sounds.

  • LUB

  • DUP

  • LUB:
    LUB sound produced when ventricles contract and blood exerts pressure on bicuspid and tricuspid valves.

  • DUP:
    DUP sound produced when both aorta contract and blood exerts pressure to the semi lunar valve.

• S-A Node: (Sino - Atrial Node)
  Right atrium has known as sino-atrial node. It receives impulses from C.N.S. These impulses stimulate S - A node which arise waves. The waves affect the wall of atrium due to which atria are contract.

• A-V Node: (Atrio - Ventricular Node)
  Another node is present beneath the S - A node at the right ventricle which is known as A - V node. It stimulated by the waves of S - A node and also generates waves. These waves effect on the papillary muscles which result these muscles are contract and systole of ventricle takes place. So the first both atria are contract then both ventricles are contract. The time difference between transfers of signals from S-A node to A-V node is 0.15 second.

• Pace Maker:
  S-A node is also known as pace maker because it provides acceleration to the contraction of heart wall.

• Artificial Pace Maker:
  When the S-A node cannot perform its function properly then artificial pace maker is used. It is an instrument which provides electric signals to walls of heart for contraction. Artificial pace maker implant beneath the skin in chest cavity and two wires are also connecting with heart. The artificial pace maker has battery which produces electric signals and transfers it to heart. It stimulates the contraction of heart.

• Blue Babies: (Cyanosis)
  The bluish discoloration of skin and mucous membrane called blue babies. It is cyanotic, congenital disease which is caused by defect on inter articular and inter ventricular septum. Due to defect or undevelopment of inter articular and inter ventricular septum oxygenated and deoxygenated blood are mixed and caused bluish appearance of skin and mucous membrane.

BLOOD VESSELS:
Those vessels which help in the circulation of blood in the body called blood vessels. There are three types of blood vessels found in man.

• Artery

• Capillaries

• Vein

• Artery:
  Those blood vessels which arise from the heart and run away from the heart are called arteries. Most of arteries contain oxygenated blood except pulmonary artery. Arteries are present deep in tissues. These are responsible for the supply of blood to the whole body.

  Structure:
  Arteries are thick-walled blood vessels. Walls of arteries consist of three layers.

  • Tunica External

  • Tunica Media

  • Tunica Internal

  • Tunica External:
    It is the outermost layer. Tunica External is composed of connective tissues and collagen fibers.

  • Tunica Media:
    It is the middle layer. Tunica Media is composed of two layers of smooth muscles.

  • Tunica Internal:
    It is the inner layer. Tunica interna is composed of the endothelial cell layer.

  Lumen:
  The lumen of the artery is larger than capillary while smaller than vein. Inside the artery, valves are absent.

  Blood flow:
  Inside the artery, blood flows in jerks because the heart pumps blood to the artery.

  Function:
  The prime function of the artery is the supply of blood to the whole body parts. It also helps the transportation of material in the body.

Grading:
Heart → Aorta → Arch → Artery → Arteriole → Capillary

CAPILLARIES:
At the level of tissue or cell, artery is divided into fine branches called capillaries.

• Structure:
  Capillaries are very small, microscopic, and fine blood vessels. Wall of capillaries is composed of a single layer of endothelial cells. It has a permeable wall.

• Lumen:
  The diameter of capillary lumen is 7-10µ.

• Blood Flow:
  Inside capillary blood flow is very slow and blood cells pass through capillary in the form of a row. Capillaries contain both oxygenated and deoxygenated blood at the same time.

• Function:
  Capillaries are present near cells and tissues, so transportation of gases and other substances between blood and cells takes place through capillaries by diffusion.

VEINS:
Veins are those blood vessels which run towards the heart. Most veins contain deoxygenated blood except the pulmonary vein. Veins are present at the superficial layer of the body. They are responsible for collecting blood from whole body parts.

• Structure:
  Veins are thin-walled blood vessels. The wall of a vein consists of three layers.

• Tunica Externa

• Tunica Media

• Tunica Interna

• Tunica Externa:
  It is the outermost layer and is composed of connective tissues and collagen fibers.

• Tunica Media:
  It is the middle layer and is composed of smooth muscles.

• Tunica Interna:
  It is the inner layer and is composed of the endothelial cell layer.

• Lumen:
  Some veins contain internal valves, which help in active transport. The lumen of veins is greater than artery and capillaries.

• Blood Flow:
  Inside the vein, blood flows slowly because blood is coming into the vein through the capillaries.

• Function:
  Veins collect deoxygenated and oxygenated blood from all body parts and pour it into the heart.

Grading:
Capillary → Venoele → Vein → Vena Cava → Heart

CARDIOVASCULAR DISORDERS: (CVD)
Disease of heart, blood vessels, and blood circulation are generally termed as cardiovascular disorders. Some important CVD are discussed as follows:

• Atherosclerosis:
  It is a disease of the arterial wall (intimae) which loses its elasticity. Gradually its inner layer thickness causing narrowing of the artery and consequently impairing the blood flow. The narrowing is due to the formation of fatty lesions called atheromatous plaques (raised patches) in the inner lining of the arteries. These plaques consist of low density lipoproteins or LDL (cholesterol and proteins), decaying muscle cells, fibrous tissue, clumps of blood platelets and sometimes calcium. The arteries become extremely hard and the disease is called arteriosclerosis or simply hardening of the arteries.

  • Causes:
    The possible causes of atherosclerosis are smoking, hypertension, male gender, obesity, physical inactivity, a high serum cholesterol level, severe diabetes, family history of arterial diseases and possibly an anxious or aggressive personality. The risk of atherosclerosis increases with age.

  • Effects:
    Unfortunately, atherosclerosis produces no symptoms until the damage to the arteries is severe enough to restrict blood flow. Restriction of the blood flow to the heart muscles due to atherosclerosis can cause angina pectoris (pain in the chest and arms or jaws usually during exercise or stress).

• Hypertension:
  When the mean arterial pressure is greater than the upper range, accepted normally, the person is said to be hypertensive having hypertension. Usually a mean arterial pressure of greater than 110 mm Hg under resting conditions is considered to be hypertensive. This level normally occurs when the diastolic blood pressure is greater than 90 mm Hg and the systolic pressure greater than 135 - 140 mm Hg. Hypertension is called as “Silent Killer”, because the affected individuals may show no outward symptoms until a stroke or heart attack occurs. It promotes atherosclerosis. As a prolonged consequence, the heart may enlarge and fail to pump the blood effectively. Several factors such as heredity, higher intake of salts in diet, smoking, obesity, and disorders of kidney or adrenal gland are responsible for hypertension.

• Thrombus Formation:
  The formation of blood clot (thrombus) within an intact blood vessel is initiated by atherosclerotic plaques. The plaques, when they destroy the endothelium of the blood vessel, platelets gather at the damaged site to initiate the process of clot. As the growth of the plaque and clot progresses, the lumen of the artery narrows or completely blocks. Ultimately, the blood supply to the concerned organ is either reduced or prevented. Thus due to the lack of oxygen and nutrients, the function of the target organ is impaired. Thrombus of the coronary artery or carotid artery may cause the death of the victim due to heart attack (myocardial infarction) and stroke. If a clot dislodges and travels in the bloodstream, it is termed as embolus. It can obstruct any small artery such as coronary artery; the outcome ranges from angina to heart attack.

• Coronary Thrombosis:
  Narrowing or blockage of one of the coronary arteries (which supply blood to the heart muscle) by a thrombus is called coronary thrombosis. This causes a section of the heart muscles to die because it has been deprived of oxygen. It is one of the main processes involved in coronary heart disease. Sudden blockage of a coronary artery can cause acute myocardial infarction.

• Myocardial Infarction: (Heart Attack)
  It refers to the death of the part of heart muscles characterized in most cases by severe continuous chest pain. This is commonly known as heart attack. Due to the blockage of any of the coronary artery either by thrombus or embolus, the blood supply to some cardiac muscles stops. The area of heart muscle which has zero or little flow of blood that it cannot sustain cardiac muscle function is said to be infracted and the process is called myocardial infarction. As a consequence the affected cardiac muscles die due to lack of nutrients and oxygen. If the damaged area is small, the victim may recover from the heart attack but death of the large area of cardiac muscles is fatal.

• Stroke And Prevention:
  Stroke implies to damage to part of the brain caused by interruption to its blood supply (either by a thrombus or embolus) or leakage of blood outside of vessel walls. It is characterized by the impairment of the sensation, movement, or function controlled by the damaged part of the brain. Damage to any one cerebral hemisphere can cause weakness or paralysis of one side of the body called hemiplegia. Hypertension and atherosclerosis are among the most common causes. The stroke can be prevented by keeping the blood pressure at a normal range, through a proper diet. Salts should be used in less quantity as they increase blood pressure. Fats should also be reduced especially those which are rich in cholesterol. They cause thrombus formation resulting in atherosclerosis of the arteries particularly the coronary arteries. Exercise should be regular habit of life. At least 30 minutes brisk walk per day. Smoking should be avoided. Tension is the major cause of hypertension. The life should be made easy and free of extra worries.

• Hemorrhage:
  The hemorrhage is defined as the escape of blood from the vessels. Small hemorrhages are classified according to their size. The massive accumulation of blood within a tissue is called hematoma. The hemorrhage may occur anywhere in the body. But the most dangerous is the brain hemorrhage causing stroke.

LYMPHATIC SYSTEM:
“A system of blind vessels that drains lymph from all over the body back into the bloodstream is called lymphatic system”. The lymphatic system consists not only of lymph and lymphatic vessels but also of spleen, thymus, tonsils, appendix, and small intestine.

Components Of Lymphatic System:
Lymphatic system consists of the following components:

• Lymph Vessel

• Lymph

• Lymph Node

• Lymph Vessel:
  The vessel of the lymphatic system is known as the lymph vessel. It is divided into lymph, capillary, lymphatic vessel, and collecting duct. Lymph capillaries are fine and microscopic branches of lymph vessels. It is present at the blood capillaries bed. It absorbs the releasing fluid from blood capillaries. Lymph capillaries combine and produce comparatively thick-walled vessels called lymphatic vessels. Its wall is composed of smooth muscles, and internally it contains valves. Lymphatic vessels open into a large vessel known as the collecting duct. It opens into a large vein near the neck region.

• Lymph:
  Lymph is a colorless fluid produced by the secretion of blood capillaries. At the level of blood capillaries, except Red Blood Cells and plasma protein, water, White Blood Cells, Bacteria, virus, nitrogenous waste, and useful substances come out and store in the sinuses found between the cells. 85% of tissue fluid is reabsorbed in the blood at the level of veins, but the remaining 15% of tissue fluid is absorbed through lymph capillaries and back into blood.

• Lymph Node:
  Various lymph vessels open into the circular structure called lymph node. They are microscopic, 1 inch in diameter. Lymph nodes consist of lymphatic tissues. It contains lymphocytes, antibiotics, and macrophages. They kill the viruses and bacteria of tissue fluid and send the clean tissue fluid to the blood.

Functions Of Lymphatic System:
The lymphatic system performs three important functions:

• Drainage of body fluid
• Defense of body
• Absorption and delivery of fats

• Drainage Of Body Fluid:
  Lymphatic vessels act as drainage channels for water and plasma proteins that have leaked away from blood at capillary bed and that must be delivered back to blood circulation. Without which death can occur into 24 hours.

• Defense Of Body:
  Microorganisms, foreign cells, cellular debris in the lymph are removed by macrophages residing in the lymph nodes. These are also the site for differentiation of the B cells into antibody-secreting cells.

• Absorption And Delivery Of Fats:
  Lymph capillaries called lacteals penetrate the villi of the small intestine where fats are absorbed and delivered to the blood circulatory system.

IMMUNE SYSTEM:
The ability of the body to resist microorganisms, their toxins (if any), foreign cells and abnormal cells of body is called as immunity and the system is termed as immune system.

Immunology:
The study of the functioning and disorders of the immune system is called as immunology.

TYPES OF IMMUNE SYSTEM:
They are of two types:

• Innate immune system (non-specific immune system)
• Adaptive immune system (specific immune system)

INNATE IMMUNE SYSTEM: (NON-SPECIFIC IMMUNE SYSTEM)
It is a natural immune system and is nonspecific i.e. prevents infection of all microorganisms. It controls the activity of microorganisms and includes physical body organs like skin and mucous and also chemical substances like gastric juices and lysozyme, etc.

• Physical Body Organ: (First Line Defence)
  Skin and mucous membrane act as the first line of defense. Skin doesn’t allow the infection agents to enter. Some areas are protected by movement of mucous and secretions (lysozyme in tears) which destroy microbes. Microbes present in food or mucus from the upper respiratory tract are destroyed by highly acidic gastric juice in stomach.

Internal Body System: (Second Line Defense)
If a microorganism gains entry in the body, the second line of defense protects the body from microorganisms. These are:

• Phagocytes

• Antimicrobial proteins

• Inflammatory response

• Phagocytes:
  These are the type of W.B.C’s. They destroy microorganisms and other particles. They are of the following types.

  • Neutrophils:
    Ingest bacteria very actively and their lifespan is short.

  • Monocytes:
    Live for a long time and act as presenting cells for antigens, so termed antigen-presenting cells.

  • Natural Killer Cell:
    They destroy infected cells and abnormal cancerous cells. They produce proteins which form pores in infected cells and destroy them. The phenomenon is called cytotoxicity.

• Antimicrobial Proteins:
  In the body, certain proteins are produced which destroy infectious microorganisms and are termed as antimicrobial proteins. These are as follows:

  • Lysozymes:
    It is an enzyme present in tears, saliva, and mucous secretion. It kills bacteria.

  • Complement Proteins:
    These are secreted by macrophages and kill bacteria directly.

  • Interferons:
    These are produced by virally infected cells or some lymphocytes. They resist against viral infection.

• Inflammatory Response:
  It is a condition of fire in any part of the body due to injury or infection by microorganisms. The infected part becomes swollen, reddish, and feels heat and pain. When injury occurs, basophiles and most cells release chemical substances called histamine. It attracts phagocytes and macrophages toward the injured place where they destroy microorganisms and remove dirt and cell-broken parts. In warm-blooded animals, infection and inflammation cause fever. It’s because pyrogen released from W.B.C’s increases the body temperature. Moderate fever is useful as it prevents the growth of micro-organisms and increases production of phagocytes and interferon so damaged tissues are repaired rapidly. Light fever is dangerous for the internal tissues of the body.

ADAPTIVE IMMUNE SYSTEM: (SPECIFIC IMMUNE SYSTEM)
It is the specific immune response against specific microorganisms which is developed in the body especially against many organisms, tumor cells, transplanted tissues and toxins. It is considered as the third line of defense and works with the second line defense system. In adaptive immune system, special types of lymphocytes play an important role called B-Cells and T-Cells. They are produced in bone marrow or thymus.

• Antigen:
  Any organism or foreign particle, which enters the body and disturbs the immune system, is called an antigen.

• Antibody:
  It is a specific soluble protein formed by lymphocytes in response to antigen. The antibody combines with antigen and removes it from the body.

• Memory Cell:
  The immune system has memory cells for antigens. When there is another attack by the same organism, there is a very quick and effective response against it.

Types Of Adaptive Immune System:

• Humoral immunity

• Cell-Mediated immunity

• Humoral Immunity:
  When B-Cells produce antibodies in the circulatory system and these antibodies develop immunity. It is called humoral immunity. This immunity is effective against bacteria. It depends on the appearance of antibodies in the blood. This antibody serves as an antigenic receptor. When infection is caused, antibodies are borne by a few B-Cells and bind with the surface of microorganisms. This antigen and antibodies complex causes the rapid division of B-Cell which results in effector cells called plasma cells. These cells secrete antibodies in the blood circulation that help eliminate the particular antigen.

  • Memory Cells:
    Some of the effector cells do not secrete antibodies; they become memory cells. The memory cells play an important role in future immunity to this specific organism in case of reinfections.

• Cell-Mediated Immunity (CMI):
  This type of immunity is contributed by the second family of lymphocytes called “T” cells. They do not secrete antibodies. The cell-mediated immunity is caused by the killing of infected cells and aiding in inflammation. This type of immunity is particularly against the defense of viruses and endoparasites that they hide within the host cell, tumor cells, and fungi.

Types Of “T” Cells:
Several types of T cells contribute to cell-mediated immunity.

• Helper T cells (TH)
• Cytotoxic Cells (Tc)
• Suppressor Cells (Ta)

Active And Passive Immunity:

• Active Immunity:
  The immunity which is developed by one's own immune response is called active immunity.

  • Natural Active Immunity:
    The immunity which is a consequence of natural infection is called natural active immunity.

  • Artificial Active Immunity:
    The immunity which is developed artificially through vaccination is called artificial active immunity.

• Passive Immunity:
  The immunity which is developed through transported antibodies to a person from another person or even an animal is called passive immunity.

  • Natural Passive Immunity:
    The immunity which is developed through the transformation of antibodies from one person to another person of the same species is called natural passive immunity. E.g., a pregnant female passes some of her antibodies to her fetus through the placenta.

  • Artificial Passive Immunity:
    The immunity which is developed by the transfer of antibodies from one person to another person artificially, in which the first person is already immune to that disease, is called artificial passive immunity. E.g., rabies is treated in humans by inflicting antibodies delivered from persons who have already been vaccinated against rabies.