Chapter 14- Transport

Transport - XI Zoology

Transport - Circulatory System

HUMAN HEART

INTRODUCTION

Heart, the most powerful organ in the circulatory system is conical, hollow & muscular organ, situated in middle mediastinum.

POSITION OF HEART

Heart lies in the thoracic cavity between the lungs slightly towards left, enclosed with in ribcage with the sternum in front & vertebral column behind.

SIZE & WEIGHT

The heart measures about 3 ½ Inches & weighs about 300 gm in males & 250 gm in females.

MAIN FUNCTION OF HEART

Heart works continuously like a muscular pump & pumps the blood to various parts of the body to meet their nutritive requirements.

COVERING OF HEART PERICARDIUM

Heart is surrounded by a double layered pericarcdium. The outer layer is called Fibrous pericardium & inner layer is called as serous pericardium.

PERICARDIAL FLUID

Fluid is secreted in b/w the two layers of pericardium which is known as pericardial fluid.

FUNCTION

Pericardial fluid acts as LUBRICANT & reduces friction b/w heart walls & surrounding tissues during beating of heart.

STRUCTURE OF HEART

Human heart consists of four chambers.

CHAMBERS OF HEART

1. RIGHT ATRIUM

Right Atrium is the right upper chamber of heart & acts as thin walled low pressure pump.

OPENINGS (INLETS) OF RIGHT ATRIUM

1. Superior Vena Cava

2. Anfenior Vena Cava

3. Coronary Sinus

FUNCTION

It receives venous blood from the whole body & pump it to the right ventricle through the right atrioventricular (tricuspid opening) valve.

2. LEFT ATRIUM

Left atrium is upper triangular chamber which is present posteriorly. It also acts as low pressure pump.

OPENINGS (INLETS) OF LEFT ATRIUM

Two pairs of pulmonary veins.

FUNCTION

It receives oxygenated blood from the lungs through 4 pulmonary veins and pumps it to the left ventricle through the left atrioventricular orifice (mitral or bicuspid).

3. RIGHT VENTRICLE

Right ventricle is the right lower chamber of heart, which is triangular in shape.

OPENINGS OF RIGHT VENTRICLE

• Tricuspids valve

• Pulmonary Aorta through pulmonary valve.

THICKNESS OF WALL

• The wall of right ventricle is thinner than that of left ventricle in a ratio of 1:3

SIZE OF CAVITY

Cavity of right ventricle is broader than left because of thin muscular walls, and both of these features are due to the fact that right ventricle has to pump the blood into lungs only against low pressure system (i.e. pulmonary circulation).

FUNCTION

Right ventricle receives deoxygenated blood from right Atrium and pumps it to the lungs through pulmonary aorta for oxygenation.

4. LEFT VENTRICLE

Left ventricle is the most thick walled chamber and forms the apex of heart.

OPENING OF LEFT VENTRICLE

• Bicuspid or Mitral valve

• Systemic Aorta through aortic valve.

THICKNESS OF WALL

The walls of left ventricle are 3 times thicker than those of right ventricle. Blood pressure is 6 times high.

SIZE OF CAVITY

The cavity of left ventricle is narrower than the right ventricle because of more muscular walls. It is due to the fact that left ventricle has to pump the blood to the entire body against high pressure system (Systemic Circulation).

FUNCTION

It receives oxygenated blood from left atrium & pumps it into the aorta.

INTERNAL STRUCTURE OF VENTRLES

Interior of ventricles show two parts

1. Rough in flowing part

2. Smooth out flowing part

1. ROUGH PART

TRABECULAE CARNEAE

Inflowing part of each ventricle is rough due to presence of muscular ridges called as Trabeculae carneae.

2. SMOOTH PART

Out flowing part of each ventricle is smooth which gives origin to pulmonary trunk in right ventricle & Ascending Aorta in left ventricle.

PAPILLARY MUSCLES

Papillary muscles are the type of Trabeculae carneae being attached by their bases to ventricular walls, & their apices are connected to, the cusps of valves through chorda tendinae.

CHORDA TENDINAE:

These are delicate fibrous chords, which connect the papillary muscles to the cusps of Atriovertritcular valves.

FUNCTION

Chorda Tendinae don’t left the valves open back into the atria when the ventricles contract.

SEPTUM OF HEART

1. INTERATRIAL SEPTUM

Internally, the right & left atria are separated by a vertical membranous septum called as Interatrial septum.

2. INTERVENTRICULAR SEPTUM:

The right & left verticals are also separated by a thick muscular septum called as Interventricular septum.

3. ATRIOVENTRICULAR SEPTUM

Atria lie above & behind the ventricles & are separated from ventricles by Atrioven-tricular septum.

HEART VALVES

Heart possesses two types of valves, which regulate the flow of blood with in the heart.

TYPES OF HEART VALVES

1. Atrioventricular valves -> Bicuspid, Tricuspid

2. Semilunar vlaves -> Aortic valve, Pulmonary valve

1. ATRIOVENTRICULAR VALVES

INTRODUCTION

Valves, which are present in b/w the Atria & ventricles are called Atrioventricular valves.

TYPES OF ATRIOVENTRICULAR VALVES

They are of two types.

1. Bicuspid or Mitral

2. Tricuspid.

1. BICUSPID OR MITRAL VALVE

Blood flows from left Atrium to the left ventricle through left atrioventricular on orifice, which is guarded by bicuspid or Mitral valves.

CUSPS

It has tow (2) cusps so it is called as bicuspid.

2.TRICUSPID VALVE

Blood flows from right Atrium to the Right ventricle through right Atrioventricular orifice, which is guarded by Tricuspid.

CUSPS

It has 3 cusps so it is called as TRICUSPID.

2. SEMILUNAR VALVES

This is the second category of heart valves, which guard the emergence of pulmonary & systemic Aorta.

TYPES OF SEMILUNAR VALVES

It has Two Types:

1. Aortic Valve

2. Pulmonary Valve

1. AORTIC VALVE==

This valve guards the Aortic orifice in left ventricle

CUSPS

It consists of 3 Semilunar cusps.

2. PULMONARY VALVE

This valve guards the pulmonary orifice in right ventricle.

CUSPS

It also consists of 3 semi lunar cusps.

FUNCTIONS OF VALVES

Heart valves maintain unidirectional flow of the blood & prevents its regurgitation in the opposite direction.

Transport - Circulation of Blood

CARDIAC CYCLE

Sequence of events which take pace during completion of one heart beat is called “Cardiac Cycle”

PHASES

(I) DIASTOLE

It is resting period of heart chambers.

II) SYSTOLE

During which heart’s chambers contract. In cardiac cycle, blood is circulated in whole body.

TYPES OF CIRCULATION

PULMONARY CIRCULATION

In pulmonary circulation following events take place.

RT. ATRIAL SYSTOL

First the blood from whole systems of body, except lungs enter in right Atrium through superior and Inferior vena cavae into the right atrium by atiral systole, blood comes into right ventricle from right atrium via Tricuspid valve.

RT. VENTRICLE SYSTOLE

After coming of blood into the Rt. Ventricle, it goes to the lungs via pulmonary trunk by ventricular systole, for oxygenation of blood by passing through pulmonary valve.

SYSTEMIC CIRCULATION

In systemic circulation, following events take place.

LEFT ATRIAL SYSTOLE

When oxygenated blood comes into left atrium, then left atrial sytole causes blood to enter left ventricle through bicuspid valve

LEFT VENTRICULAR SYSTOLE

When blood reaches here it sends into aorta through aortic valve to provide blood to body systems.

CARDIAC OUTPUT

The blood volume pump per minute by left ventricle into the systemic circulation

HEART BEAT

The contraction of heart chambers are known heart beat which are regular, rhythmic.

Ventricular systole is LUB

Ventricular diastole is DUB

TIME FOR HEART BEAT

0.8 sec is time for one heart beat.

CONDUCTING SYSTEM OF HEART

It consists of

1.AV-NODE

2.SA-NODE

3)AV-BUNDLE

4) PURKINJI FIBERS.

1. SA-NODE

SA NODE found near upper end of superior vena cava in RT. atrium

PARTS

1. Specialized cardiac Muscles.

2. Autonomic Nerve endings.

FUNCTIONS

It Initiates the contraction of heart chambers through impulses & also transmit to AV node.

2. AV- NODE

It is found in lower end of RT. Atrium. Structurally it is smilar to SA-NODE

FUNCTION

It transmit nerve impulses to ventricles for contraction rhythmically.

3. AV-BUNDLE

AV BUNDLE are the fibers originate from AV node. The bundle divided into Right AV bundle, Left AV bundle

FUNCTION

It transmit nerve impulses to ventricles.

4. PURKINJI FIBERS

AV bundles red divided into small fibres which penetrate the ventricle wall also known as purkinji fibers / Bundle of His small thin fibers.

LEUKEMIA

DEFINATION

“The malignant disorder of increase number of abnormal leucocytes in blood.”

CAUSE

The cause of leukemia is unknown.

FACTORS

Factors associated with leukemia are

• Ionizing Radiation

• Cytotoxic drugs.

• Retroviruses.

• Genetic

EFFECTS OF DISEASE

• In result of leukemia, normal leucocytes counts become less.

• This is progressive, and fatal condition which leads to heamorrhage or infection

THALASSEMIA

DEFINITION

“Genetically impaired globin chains formation leads to impaired or defected formation of hemoglobin.”

GENETIC DISEASE

Thalassemia is a genetic disorder, it may be

1. Hetrozygous /Mild thalassemia:

2. Homozygous.

TYPE

• BETA - Thalassemia

• α - Thalassemia

BETA-THALASSEMIA

When globin chain is impaired or defected. It is most common one.

ALPHA-THALASSEMIA

when α-thalassemia globin chain of (HB) hemoglobin is defected.

KINDS OF THALASSEMIA

THALASSEMIA MINOR

When thalassemia is of heterozygous type with mild anemia.

THALASSEMIA MAJOR

When thalassemia is of homozygous type with profound hypochromic anemia. It is more common in children & results with enlargement of kidney.

REMEDY

The only remedy is transfusion of blood at regular intervals.

CVD CARDIOVASCULAR DISEASE

Diseases of heart, blood vessels and blood circulation are generally term as CVD.

ATHEROSCLEROSIS

The disease of arterial wall with lose of elasticity, thickness of inner wall causing narrowing of lumen, results in impairing of blood flow.

ATHEROMATOUS PLAQUES

The narrowing is due to formation of fatty lesions called atheromatous plaque in inner lining of arteries.

COMPONENTS OF PLAQUE

These plaques consist of

• LDL-LOW DENSITY LIPO PROTEINS

• DECAYING MUSCLES CELLS

• FIBROUS TISSUE

• PLATELETES

• CLUMP OF BLOOD

CAUSES

Smoking, Hypertension, Obesity, Diabetes (Severe), family history of arterial disease

EFFECTS

Atherosclerosis produces no symptoms until the damage to artery is so severe that it restricts blood flow.

ANGINA PECTORIS

If blood flow to heart muscles is restricted causes (cell damage) necrosis called angina pectoris. Pain in chest, arm, or jaws usually during exercise.

THROMBUS FORMATION

The formation of blood clot with in the intact blood vessel initiated by atheromatous plaque.

REASON FOR THROMBUS FORMATION

Due to formation athromatous plaque loss of elasticity, intact blood vessel get destroyed, blood from vessel wall comes out & later change to blood clot and blocks the lumen of small arteries.

RESULT OF THROMBUS FORMATION

Initially thrombus block the lumen partially result in decrease blood flow to organs & leading to impairment of physiology of organs. Later on, thrombus blocks the lumen completely so due to complete loss of blood supply, cells damage occur.

CORONARY THROMBOSIS

Type of thrombosis when narrowing of lumen occurs in coronary blood vessels due to formation of clot.

EFFECT

Occulsion of coronary atery causes myocardial infarction and heart attack.

HEAMORRHAGE

The escaping of blood from intact blood vessels.

==STROKE Most dangerous type of heamorrhage is that of brain which results in paralysis or strokes.

HAEMATOMA

The accumalation of blood in interstitial spaces known as haematoma.

This will lead to edema.

STROKE

DEFINITION

The damage to the part of brain caused by, restriction in blood supply or leakage of blood outside the vessels.

CHARACTERISTICS

Impairment of sensation, movement & function controlled by damage part of brain.

CAUSES

• Hypertension

• Atherosclerosis

HEMIPLEGIA

Damage to any, one cerebral hemisphere can cause weakness or paralyses of one side of body called hemiplegia

PRECAUTIONARY MEASURES

Blood pressure should be with in normal range through proper diet. Salt should be used in less quantities exercise should be the regular habit. Smoking must be avoided. Person life should be free of worries.

BLOOD VESSELS

DEFINITION

"The closed vessels or tubes through which transporting medium or blood circulate with in body called “blood vessels”.

TYPES OF BLOOD VESSELS

1. Arteries.

2. Capillaries.

3. Veins.

ARTERIES

DEFINITION

Thick walled blood vessels which carry blood from heart to the organs of body.

LAYERS

It consists of three layers.

1. Tunica Externa/ Adventitia

2. Tunica Media

3. Tunica Intima

1-TUNICA EXTERNA

It is thin but tough layer, having abundant amount of collagen fibers. It is outer most layer.

2-TUNICA MEDIA

The middle layer has smooth muscle fibers & elastin fibers. It is the thickest layer.

3-TUNICA INTIMA

It consists of squamous endothelium.

LUMEN

Thick walled vessels & having smaller lumen than that of veins except arteries of brain & related to cranium having large lumen.

SEMILUNAR VALVES

They are not present in arteries.

BRANCHES - DIVISIONS

Aorta divides into large arteries, large arteries into smaller arteries, smaller arteries into arterioles, then they give rise to capillary.

At arteriole level, small sphincters are present which are known as PRE-CAPILLARY SPHINCTER.

SPHINCTER

FUNCTION

They are for regulating the diastolic pressure.

CHARACTERSTICS

• Arteries are elastic so during systolic pressure, they do not rupture and dilate.

• During ceasement/ stopage of systolic pressure of heart, arteries contract & supply even flow of blood.

• The arteries carry oxygenated blood except pulmonary arteries.

VEINS

DEFINITION

The thin walled blood vessels that drian blood from body parts/organs into heart called veins.

LAYERS

• Tunica Externa

• Tunica Media

• Tunica Intima

1. TUNICA EXTERNA

Thickest layer in veins. It contains collagen, elastin and smooth muscles cells.

2. TUNICA MEDIA

Not thicker as that of arteries. Elastic tissues and small smooth muscle.

3. TUNICA INTIMA

Contains endothelial cells layer.

LUMEN

It has large lumen and thin wall.

SEMILUNAR VALVES

They are present in veins to prevent back flow of blood in the influence of gravity.

TRIBUTARIES

Veninules -> small veins -> large veins -> vena cava.

BLOOD PRESSURE

In veins blood pressure is low and are non pulsatile.

CHARACTERISTICS

The blood flows slowly and smoothly in veins. Veins are superficial and collapse when empty.

CAPILARIES

The intimate microscopic closed channels of both arterial & veinous interconnected network is called capillaries.

DIAMETER

Capillaries are extremely narrow in diameter of about 7-10 μ.

LAYERS

Capillaries are thin walled vessels & contains single layer of endothelium which offers small resistance in transport of material across the capillary wall.

FUNCTION

Through diffusion and active transport of oxygen is transported to tissues & CO2 to capillaries. Nitrogenous waste is filtered through the capillaries into excretory tubules.

BLUE BABIES (CYANOSIS)

Blue baby is a layman terminology. In medical science it is known as cyanosis.

DEFINITION

The term cyanosis” means the blueish discolouration of the skin & mucous membrane due to excessive cone of reduced (deoxygenated haemoglobin) in the blood & it appears when reduced Hb conc in capillaries is more than 5 gm/dl of blood. The reduced Hb has an intense dark blue purple colour that is transmitted through the skin.

MOST COMMON CAUSE OF CYANOSIS

Although there are various other causes of cyanosis but the most common cause is CONGENITAL CYANOTIC HEART DISEASE.

BASIC CAUSE OF CYANOSIS

In congenital heart diseases, there is an abnormal connection b/w right and left side of heart, which permits the large amount of unoxygenated venous blood to bypass the pulmonary capillaries & dilute the oxygenated blood in systemic arteries i.e RIGHT TO LEFT SHUNT, which results in cyanosis.

SOME EXAPLES OF CONGENITAL HEART DISEASES

• Some congenital heart diseases which are responsible for the abnormal connection between right and left sides of heart are as follows.

• ATRIAL SEPTUM DEFECT (ASD)

• VENTRICULAR SETPUM DEFECT (VSD)

• PERSISTANT DUCTUS ARTEROSUS

• In all these conditions, blood begins to flow from the aorta (left side) into pulmonary arteries (right side) & the people donot show cyanosis until late in life when heart fails or lungs become congested.

TETRALOGY OF FALLOT (RIGHT –TO-LEFT SHUNT)

It is the most common cause of cyanosis or blue baby in which aorta originates from right ventricles rather than left & receives deoxygenated blood.

Transport - Lymphatic System

DEFINITION

A System of blind vessels (lymphatic) that drains lymph from all over the body back into blood stream is called lymphatic system OR Lymphatic System is essentially a drainage system, which reinforces the venous drainage. There is no circulation i.e it is a unidirectional flow towards heart.

MAIN FUNCTION OF LYMPHATIC SYSTEM

All body tissues are bathed in a watery fluid derived from the blood stream. This intercellular or tissue fluid is formed when blood passes trough the capillaries. The capillary walls are permeable to all components of blood except the R.B.C’s & blood proteins. The fluid passes from the capillary into the intercellular spaces as the inter-cellular or tissue fluid. About 85% of the tissue fluid returns into the blood at the venous end of capillary. The rest 15 % of tissue fluid drains into lymphatic capillaries as lymph along with W.B.C’s, cell debris & micro organism like Bacteria , are transported back to the heart through lymphatic system.

COMPONENTS OF LYMPHATIC SYSTEM

Lymphatic System Consists of

1. Lymph

2. Lymphatic tissues

3. Lymphatic vessels or Lymphatics

4. Lymph nodes (type of lymphatic tissue)

DETAILS OF COMPONENTS

1. LYMPH

DEFINITION

“Lymph is the name given to the tissue fluid once it has entered a lymphatic vessel. OR It can be defined as “Colour less body fluid that contains lymphocytes (agranular WBC’S), small proteins & fats”.

EXPLANATION

Lymph is a medium of exchange between blood & body cells. It takes the fluid substances from cell of tissues & intercellular spaces, which cannot penetrate the blood capillaries.

2.LYMPHATIC TISSUES

DEFINITION

“Lymphatic tissues are a type of connective tissues that contain large no. of lymphocytes”

ORGANS THAT CONTAIN LYMPHATIC TISSUES

Lymphatic tissue is organized into following structures (organs).

• Lymph nodes

• Thymus

• Spleen

• Tonsils

• Some of the patches of tissues in vermiform appendix & in small intestine.

FUNCTION

Lymphatic tissue is essential for immunologic defenses of the body against viruses & bacteria

3. LYMPHATICS

DEFINITION

Lymphatic vessels or lymphatics are blind tubes that assist the cardiovascular system in removal of tissue fluid from tissues spaces of the body, the vessels then return the fluid to the blood.

AREAS WHERE LYMPHATIC ARE NOT PRESENT:

Lymphatics are present in all tissues & organs of the body except.

• Central Nervous System

• The eye ball

• Internal Ear

• Epidermis of Skin

• Cartilage & bone

TYPES

Two Types of Lymphatics are there:-

SMALL - LYMPH CAPILLARIES

LARGE - LYMPH VESSELS.

1. LYMPH CAPILLARIES

DEFINITION

“Lymph capillaries are a network of thin walled, anastomosing, microscopic vessels which are closed towards the tissue sinuses & drain the Lymph from tissues."

2. LYMPH VESSELS

DEFINATION

The capillaries are in turn drained by lymph tubes having larger diameters & beaded appearance, called the Lymph vessels.

These vessels contain smooth muscles in them as well as Internal valves to prevent the back flow of Lymph. The Lymph circulates through the Lymph vessels by the contraction of surrounding skeletal muscles in one direction (towards the heart). These vessels converge into collecting ducts i.e right

Lymphatic duct & thoracic duct that drain into large veins at the root of neck.

4. LYMPH NODES

DEFINITION

“Lymph nodes are lymphoid tissue which are present through out the course of Lymphatics, through which the lymph must passes”

INTERNAL STRUCTURE

Each node consists of a thin, fibrous, outer capsule & an inner mass of lymphoid tissue.

AFFERENT VESSELS

Several small Lymphatics which carry the lymph into the lymph node are referred to as “Afferent vessels.”

EFFERENT VESSEL

A single large vessel which carry the lymph away from the node is called “Efferent vessel”

FUNCTION

Lymph nodes act as filters that trap the microorganisms & other foreign bodies in the lymph. The Lymphocytes & macro-phages present here, neutralize & engulf the microorganisms, respectively.

MAJOR FUNCTIONS OF LYMPHATIC SYSTEM.

From Text Book Pg. 379.

EDEMA

DEFINITION

“Whenever the tissue fluid accumulates rather than being drained into the blood by the lymphatic system, tissue & body cavities become swollen. This condition is known as “Edema”.

TYPES OF EDEMA

There are two types of Edema.

1. INTRACELLULAR

2. EXTRACELLULAR

1. INTRACELLULAR EDEMA

“Accumulation of excess of fluid within the cells causing cellular swelling is called “Intra cellular Edema. It usually occurs after severe extracellular Edema.

2. EXTRACELLULAR EDEMA

"Excess fluid accumulation in extra cellular spaces is called Extracellular Edema. "

It is the most commonly occurring form of Edema.

FACTORS CAUSING EDEMA

Any factor that increases the tissue fluid high enough than normal value can cause excess tissue fluid volume causing edema. Some of these factor are as follows.

• High blood pressure

• Kidney failure

• Hart failure & etc.

CAUSES OF EDEMA

Following are three main causes of Edema.

1. HYPOPROTEINEMIA (SEVERE DIETARY PROTEIN DEFICIENCY)

When body is starving for Amino acids, it consumes its own blood proteins. This reduces the osmotic potential of the blood causing tissue fluid to accumulate in body tissues rather than being drawn back into capillaries, resulting in Edema.

2. LYMPHATIC OBSTRUCITON (COMMONEST CAUSE –FILARIASIS )

Another cause of edema is lymphatic obstruction, which results in more & more protein collection in the local tissue fluid hence, the increased volume. Commonest cause of lymphatic obstruction is FILARIASIS (infection by NEMOTODES) such condition is also called as “Elephantiasis” (because of swollen legs).

3. INCREASED PERMEABILITY OF CAPILLARIES (CAUSES-BURNS & ALLERGIC REACTIONS)

Sometimes the permeability of capillaries increase due to burns or allergic reactions, so blood proteins & plasma come out of capillaries & enter the tissue fluid thus causing Edema.

Transport - Immune System

IMMUNITY

DEFINITION

“The ability of human body to resist almost all types of micro-organisms, their toxins if any, foreign cells & abnormal cells of the body is termed as “Immunity”

IMMUNOLOGY

DEFINITION

“The study of functioning & disorders of Immune system is termed as “Immunology”.

IMMUNE SYSTEM

Immunity is conferred to animals through the activities of the Immune System, which combats infectious agents.

DEFINITION

“Immune System is a collection of cells & proteins that work to protect the body from potentially harmful, infectious micro-organisms”

MAIN FUNCTIONS OF IMMUNE SYSTEM

Protection of body from all types of micro organisms & toxins that tend to damage the tissues and organs of body.

ADDITIONAL FUNCTIONS

Immune system also play important role in:

• Control of cancer

• Allergy

• Hypersensitivity

• Rejection problems when organs or tissues are transplanted.

DIVISIONS OF IMMUNE SYSTEM

• Immune system can be divided into two functional divisions:

1. Innate Immunity System

2. Acquired Immunity System

INNATE IMMUNITY

DEFINITION

“The NON SPECIFIC type of immunity which result from general processes , rather than from processes directed at specific disease organism (Such as antigen –antibody reaction) is called. INNATE OR NATURAL IMMUNITY & the system which is responsible for this type of immunity is called Innate IMMUNITY System.

TYPES OF BARRIERS PROVIDED BY INNATE IMMUNITY SYSTEM

• This system provides two types of barriers:

• Physical Barrier

• Chemical Barrier

PHYSICAL BARRIERS

• SKIN

• MUCOUS MEMBRANE & etc.

CHEMICAL BARRIERS

• Lysozyme

• Gastric juice (Acidic secretion of stomach) & etc.

FIRST LINE OF DEFENCE

Skin, Mucous membrane & their secretions act as “First line of Defence”

1. SKIN

The intact skin provides an impenetrable barrier to the vast majority of infectious agents.

2. MUCOUS MEMBRANES

Most of the micro-organisms can enter only through the mucous membranes that lines the digestive, respiratory & urogenital tracts. However these areas are protected by movements of mucous & secretions (e.g Lysozyme in tears) to destroy many microbs.

3. ACIDIC SECRETIONS

Most of he microorganisms present in food or trapped in swallowed mucus from the upper respiratory tracts are destroyed by highly acidic gastric juice of stomach.

SECOND LINE OF DEFENSE

If some how micro-organisms are able to penetrate the outer layer of the skin or mucous membrance, they encounter a second line of Defence offered by Innate Immunity system.

It is non specific & comprises of

1. PHAGOCYTES

2. ANTIMICROBIAL PROTEINS

3. INFLAMMATORY RESPONSE

1. PHAGOCYTES

Phagocytes are certain type of WBC’S which can injest internalize & destroy the particles including infectious agents.

EXAMPLES OF PHAGOCYTIC CELLS

• NEUTROPHILS

• MACROPHAGES

NEUTROPHILS

Neutrophils (Polymorphonuclear Neutrophiles are short lived phagocytic cells which can ingest the bacteria or any foreign matter very actively.

MACROPHAGES (BIG EATERS)

The other phagocytic cells, the MONOCYTE can develop into large LONG-LIVED MACRO PHAGES when they reside in various tissues of body. ALSO CALLED AS ANTIGEN PRESENTING CELLS.

• Macrophages not only destroy individual micro organisms but also play a crucial rule in further immune response by “Presenting” parts of that microorganisms to other cells of immune system. For this reason, they are termed as “ANTIGEN PRESENTING CELLS.

NATURAL KILLER (NK ) CELLS

Natural killer cells (NK Cells ) are the large lymphocytes, which destroy the

• Virally infected own cells of the body

• Foreign cells

• Abnormal cells (cancerous cells)

MECHANISM OF ACTION (CYTOTOXICITY)

NK cells do not phagocytize the target cells, instead, they bind to their target cells, release some PORE FORMING PROTEINS (PERFORINS), that literally punch large round holes in the membrane of attacked cells & eventually cause lysis of the target cells. This kind of destroying the target cells is called “CYTOTOXICITY”

2. ANTIMICROBIAL PROTEINS

EXAMPLES

• Important antimicrobial proteins are:

• Lysozyme

• Compliment proteins

• Interferon

LYSOZYMES

Lysozyme, is a mucolytic polysaccharide that causes the LYSIS OF BACTERIA it is present in TEARS, SALIVA, & MUCUS SECRETION.

COMPLEMENT PROTEINS

Complement is a collective terms that describes a system of about 20 PROTEINS, many of which are INACTIVE ENZYME PRECURSORS. The principal actors in this system are 11 Proteins. All these proteins are present among the Plasma Proteins.

ACTIVATION OF COMPLIMENT PROTEINS

These proteins can be activated by two ways.

• CLASSICAL PATH WAY-Act in Adaptive Immunity system.

• ALTERNATIVE PATH WAY- Act in Innate Immunity System.

FUNCTIONS

Main functions of compliment proteins are as follows:

1. DIRECT LYSIS OF BACTERIA

2. PROMOTE THE PHAGOCYTOSIS OF BACTERIA

3. NEUTRILIZATION OF VIRUSES

4. CHEMOATTRACTANTS FOR MACROPHAGES.

INTERFERONS (ANTIVIRAL AGENTS)

Interferon are secreted by virally infected cells or some lymphocytes to induce a state of ANTI VIRAL RESISTANCE in unaffected tissues of the body.

3. INFLAMMATION

Inflammation is the body’s reaction to an injury or by entry of micro organisms.

EFFECTS OF INFLAMMATION

A cascade of chemical reactions take place during inflammatory response.

1. When injured, BASOPHILS and MAST CELLS release a substance called HISTAMINE which causes.

• Increased permeability of adjacent capillaries.

• Local vasodilatation

• Increased leakage of capillaries.

2. Due to CHEMOTAXIS, Phagocytes & macrophages are attracted at the injured site. Thus Phagocytes literally eat up microorganisms, dirt, cell debris & etc forming pus.

SYMPTOMS

Redness, heat, swelling, pain in injured tissue.

FEVER -(ALSO CONTRIBUTES TO DEFENSE OF BODY)

In case of warm blooded animals, a no. of micro organisms who escape away from inflammatory response to infect some large part of the body, trigger FEVER. It is usually caused by WBC’S, that release the substance called as PYROGEN.

FUNCTIONS

• High fever is dangerous but moderate fever contributes to the defense of the body.

• It inhibits the growth of micro-organisms.

• May speed up the repair of damaged tissues.

• Facilitates the phagocytosis, increase the production of interferons.

ADAPTIVE IMMUNE SYSTEM

DEFINITION

“The specific type of Immunity which does not develop until after the body is first attacked by a bacterial disease or a toxin, is called “Adaptive or Acquired Immunity”. The system which provides this type of immunity is called “ADAPTIVE or ACQUIRED IMMUNE SYSTEM”

OR

“Acquired Immunity is provided by special Immune System that form Antibodies & activated lymphocytes that attack & destroy the specific organisms or toxins. This is the THIRD LINE OF DEFENCE.

DEVELOPMENT OF IMMUNE SYSTEM (LYMPHOCYTES ARE THE BASIS OF ADAPTIVE IMMUNE SYSTEM)

Acquired Immune system is actually the product of body’s Lymphocytic system. The responses of adaptive Immune system is provided by Lymphocytes.

TYPES OF LYMPHOCYTES

During fetal development, all lymphocytes come from Bone Marrow. But depending upon their migration & maturity, they can be divided into two populations.

1. “T” - Cells or “T” LYMPHOCYTES

2. “B” - Cells or “B” LYMPHOCYTES.

1. “T” LYMPHOCYTES

DEFINITION

“The lymphocytes that are destined to eventually form ACTIVATED “T” LYMPOCYTES first migrate to & then mature in THYMUS GLAND, that is why, they are called as “T” LYMPHOCYTES”

FUNCTIONS

These are responsible for “CELL-MEDIATED IMMUNITY

2. “B” LYMPHOCYTES

DEFINITION

“The lymphocytes that are destined to form ANTIBODIES are processed first in the LIVER (before birth) & then in BONE MARROW (after the birth). This population of cells was first discovered in birds where processing occurs in BURSA OF FABRICIUS (not found in mammals), hence they are called as “B” LYMPHOCYTES.”

FUNCTIONS

These are responsible for HUMORAL IMMUNITY

ADAPTIVE IMMUNE SYSTEM IS INITIATED BY ANTIGENS

In order to develop a specific immune response, the immune system must recognize the invading organisms and / or foreign proteins from its self tissues & proteins.

ANTIGEN

Any foreign substance, that elicit the immune response is called antigen. In general Antigens are proteins or large polysaccharides.

RESPONSE OF IMMUNE SYSTEM TO ANTIGEN

The immune system responds to an antigen by ACTIVATING LYMPHOCYTES & PRODUCING ANTIBODIES (Soluble Proteins). The antibody combines with antigen & helps to eliminate it from the body.

BASIC TYPES OF ADAPTIVE IMMUNITY

The adaptive immune system mounts two types of attacks on invading micro-organisms.

1. HUMORAL IMMUNITY

2. CELL MEDIATED IMMUNITY (CMI)

1. HUMORAL IMMUNITY

DEFINITION

“The immunity which is mediated by circulating antibodies produced by B-lymphocytes is called “ HUMORAL IMMUNITY”.

MAJOR FUCTIONS OF HUMORAL IMMUNITY

Humoral Immunity provides major defence against “BACTERIAL INFECTIONS

MECHANISM OF ACTION OF B CELLS

“B” CELL RECEPTORS

Each B-cell has specific type of antibodies on its cell surface. This antibody serves as ANTIGENIC RECEPTOR.

ACTIVATION OF SPECIFIC “B” CELLS

On entry of foreign antigen, those B cells specific for that antigen enlarge immediately, becomes activated & form two types of cells:

1. PLASMA CELLS

2. MEMORY CELLS

1. PLASMA CELLS

The activated B-cells proliferate rapidly & transform into enlarged effectors cells called plasma cells.

FUNCTION

Plasma cells secrete ANTIBODIES into the circulation that help to eliminate that particular antigen.

ACTIONS OF ANTIBODIES.

After the formation of antigen-antibody complex antibody can inactivate the invading agent in one of the several ways.

• By activation of complement system that cause the Lysis.

• Direct Phagocytosis.

• Neutralization of the toxins released by bacteria.

• Agglutination of microorganism.

2. MEMORY CELLS

DEFINITION

Some of the activated B-cells don’t go on to form the plasma cells but instead, form moderate number of new B-cells, which don’t secrete antibodies such cells are called as Memory cells.

FUNCTIONS

The memory cells play important role in future immunity to this specific organism in case of re-infection.

2. CELL MEDIATED IMMUNITY (CMI)

DEFINITION

The second type of acquired immunity is achieved through the formation of large number of Activated LYMPHOCYTES. This is called cell mediated or T-cell immunity.

FUNCTIONS OF CMI

• CMI is responsible for delayed allergic reactions & rejection of transplantation of foreign tissue.

• It provides major defence against infections due to VIRUSES, FUNGI, TUBERCLE BACILLI & some parasites.

• It also provides defence against TUMOUR CELLS.

MECHANISM OF ACTION OF “T”-CELLS.

T-CELL RECEPTORS (TCRS)

Antigens bind with specific RECEPTOR MOLECULES on the surface of T-Cells, in the same way that they bind the antibodies.

ACTIVATION OF SPECIFIC “T” CELLS.

On exposure to proper antigen, the “T” cells of specific type proliferate & release large no. of activated T-Cells.

SEVERAL TYPES OF “T” CELLS

Different types of T cells are classified into four major groups.

• HELPER “T” CELLS

• CYTOTOXIC “T” CELLS

• SUPRESSER “T” CELLS

• MEMORY “T” CELLS

1. HELPER “T” CELLS

Helper T cells are the MAJOR REGULATOR of all the immune functions.

RECEPTORS

Helper T cell receptors actually recognize a combination of antigen fragment & one of the body’s own self marker called. “MAJOR HISTO-COMPATIBILITY” (MHC) CLASS II molecules on the surface of macrophages or B cells.

FUNCTIONS

Helper T-cells secrete the LYMPHOKINES which stimulate the production of both CYTOTOXIC & SUPRESSER TOXINS.

2. CYTOTOXIC “T” CELLS (KILLER CELLS)

RECEPTORS

Receptors on the surface of cytotoxic ‘T” cells recognize a combination of antigen fragment & self surface marker molecules called MHC CLASS I , found on every nucleated cells of its own body.

FUNCTIONS

They are especially lethal to virally infected cells. They also destroy the cancer cells, heart transplant cells & other foreign cells.

3. SUPRESSOR “T” CELLS

Along with helper cells, In supressor, T-cells are classified as Regulatory T-Cells

FUNCTIONS

After the conquerence of infection, they seems to shut off the immune response in both B-cells & cytotoxic T-cells.

4. MEMORY “T” CELLS

During CMI response, some T-cells turn into MEMORY CELLS

FUNCTION

Memory cells protect the body in case of reaction in future.

TYPES OF IMMUNE RESPONSE

The immune system has also the ability to memorize the antigen it has encountered. Thus upon subsequent exposure to the same pathogen responds in two different ways.

1. Primary Immune Response

2. Secondary Immune Response

1. PRIMARY IMMUNE RESPONSE

DEFINITION

The first exposure to an antigen to the immune system elicits formation of clones of effectors cells to develop specific immunity with in 5 to 10 days. This response of immune system is termed as Primary Immune response.

CHARACTERISTICS

• DELAYED APPEARANCE

• WEAK POTENCY

• SHORT LIFE

2. SECONDARY IMMUNE RESPONSE

DEFINITION

Subsequent exposure of same antigen causes a much more rapid & much more potent antibody response. This is called Secondary Immune response. It develops to it max. with in 3-5 days.

CHARACTERISTICS

• Rapid & quicker appearance

• Far more potent

• Longer duration (form antibodies for many months rather than for only a few weeks.)

BASIS OF SECONDARY RESPONSE (IMMUNOLOGICAL MEMORY)

The quicker secondary response is made possible due to ability called “Immunological Memory” of the immune system. It is based upon the long lasting memory cells produced with short lived effectors cells of pri immune response. The development of memory cells may provide life long protection against some diseases like chicken pox.

ACTIVE & PASSIVE IMMUNITY

ACTIVE IMMUNITY

DEFINITION

The immunity which is acquired by own immune response is called active immunity

FUNCTION OF ACTIVE IMMUNITY

Active immunity due to development of immunological memory provide LONG TERM PROTECTION, even in some diseases (e.g in chicken Pox ) life long protection is provided.

TYPES OF ACTIVE IMMUNITY

There are two types.

1. Natural active immunity

2. Artificial active Immunity

1. NATURAL ACTIVE IMMUNITY

DEFINITION

When the active immunity is acquired as a consequence of natural infection then it is called Natural active immunity”

2. ARTIFICIAL ACTIVE IMMUNITY

DEFINITION

Active immunity can be acquired artificially by vaccination. In this case it is said to be “ARTIFICIAL ACTIVE IMMUNITY”

PASSIVE IMMUNITY

DEFINITION

Temporary immunity which is achieved in a person without injecting an antigen, by transferring the antibodies, activated T-cells or both obtain from another person or even an animal, is called passive immunity.

FUNCTIONS OF PASSIVE IMMUNITY

Although, acquired passive immunity is short lived (last for 2-3 weeks), it boosts the immune response of the victim several folds.

TYPES OF PASSIVE IMMUNITY

There are 2 Types:

1. Natural passive Immunity

2. Artificial passive Immunity

1. NATURAL PASSIVE IMMUNITY

DEFINITION

When antibodies are transferred from one person to another of the same species during natural processes, then such immunity is called Natural passive immunity.

EXAMPLE

A pregnant woman passes some of the antibodies to her fetus through placenta. The first breast feeding, the colostrum, of mother pass certain antibodies to her newly born infant.

2. ARTIFICIAL PASSIVE IMMUNITY

DEFINITION

PASSIVE IMMUNITY can also be transferred artificially by introducing antibodies derived from animals or human being who are already actively immunized to that disease. This is called artificial passive immunity.

EXAMPLE

RABIES is treated in man by injecting antibodies derided from persons who have been already vaccinated against rabies. This confers the rapid immunity to combat the rapidly progressing rabies in new victim.

IMMUNIZATION

The process of inducing immunity as a preventive measure against certain infectious diseases is called immunization.

ADVANTAGES OF IMMUNIZATION

The incidence of number of diseases (e.g Diptheria, Measles) has declined dramatically since the introduction of effective immunization programmes. Some dread full diseases (e.g. Tuberclosis) is now under control.

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