veterinary Muscle & Body Biomechanics (Animal)

Muscle & Body Biomechanics

MUSCLE FIBER ARRANGEMENT

EFFECT ON STRENGTH

The amount of force that a muscle can generate is proportional to the cross-sectional area of muscle fibers (a.k.a. muscle cells) attaching to its tendon, i.e., the number of contractile proteins (actin and myosin) pulling on the tendon and contributing to

muscle force.

•  pennation design increases the number of muscle fibers (cross sectional area) attached to the tendon 

•  since force is a function of cross sectional area - a pennated muscle can generate more force than a comparable muscle with parallel fibers.

EFFECT ON SHORTENING

In this example, again consider two muscles - one with parallel fibers the other pennate

Assume each muscle fiber will contract to 50% of its resting length

Therefore:

•  with parallel-arranged muscle fibers the entire muscle can contract by 50% 

•  with the pennate arrangement each individual muscle fiber is pulling at an angle, resulting in reduced overall shortening of the entire muscle belly.

DEFINITIONS:

LINEAR FORCE:

Force can be broken down into various vectors. 

•  Vertical vectors (e.g. the downward forces due to body weight and the upward forces of the supporting surface)

•  Horizontal vectors (e.g. forces exerted to propel forward and

backward forces to brake forward motion)

With adequate force and friction (traction) the body can propel itself forward.  (practical application dictates a need for good traction to allow this forward motion – whoa to those leading a horse on ice)

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ROTATIONAL FORCE (TORQUE)  

 

Rotational force = force (F) x distance from fulcrum (d)

Limb rotation = muscle force (F) x distance from joint (d)

Torque input (muscle generated) = torque output (limb movement)

Muscles generate forces which when applied to the skeleton will generate rotation about a joint.   

MUSCLE ATTACHMENT EFFECTS 

The location of the muscle attachment (e.g. distance from joint) influences the resultant movement of that joint 

MECHANICAL ADVANTAGE VERSUS VELOCITY ADVANTAGE

Muscles that attach further from the joint have a mechanical advantage over muscles attached closer to the joint In the diagram below if muscles #1 and #2 were of equal strength (i.e., can generate the same force) then muscle #2 could produce a greater rotational force because its attachment is at a greater distance from the joint (rotational force = muscle force X distance from joint). 

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Conversely  muscles  that  attach  close  to  the point  of  rotation  are  able  to  produce  faster movement  of  the  lever  arm  than  muscle  that attach farther from the fulcrum.  In  the  diagram  to  the  right  if muscle  #1  and muscle  #2  both  contract  10% during  an identical time period  - muscle #1’s contraction would result  in a  larger movement of  the  lever arm  during  that  same  frame  of  time  than muscle  #2.    In  other  words,  muscle  #1  will result in a more rapid rotation - it has a velocity

advantage.

  

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Muscles attaching close to the joint with their velocity advantage are termed “high gear” muscles and those with a more distal attachment resulting in a mechanical advantage are termed “low gear” muscles.

It may be helpful to consider a similar gear analogy as in a car or bike.  At low gears the output force is relatively large  – allowing the vehicle to climb up a steep hill.  High gears on the other hand generates a lot of speed  – as would be advantageous in passing a vehicle. 

 

JOINT POSITIONING EFFECTS

THE BODY’S LEVER SYSTEM

Unique skeletal features result from functional adaptations over time.

In the figure below - the upper diagram is an example of an animal that uses it’s front limbs for digging; the muscles attached to the point of the elbow (olecranon) are positioned further from the elbow joint (fulcrum of movement) thereby generating large

forces for digging.  

The lower diagram with muscles attaching closer to the elbow joint is an runner adaptation that can result in a rapid rotation with muscle contraction

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For the same force and velocity input (left arrows), note the

relative magnitude of bolded arrows to the right of the diagrams –       a large downward force (F) is generated in upper diagram and

rapid rotation (V; velocity) of movement is produced in the

lower diagram.

veterinary Male Genitalia (Animal)

 Male Genitalia

Scrotum:    

situated between penis & anus

cutaneous pouch;  scrotal septum formed by dartos = “smooth  

cutaneous muscle” 

 spermatic  fascia: internal = a fibrous membrane (fibrous tunic) bound to parietal vaginal tunic 

         external = areolar connective tissue within dartos

         

 cremaster  muscle—   from internal abdominal oblique   m.; attaches to     internal spermatic fascia

 (not  developed  in the cat — where a levator scroti m. attaches to   the scrotal     septum )

 Testis:    pl.=  testes

         

produces spermatozoa and testosterone; coated by tunica albuginea (thick, white, c.t. capsule) & enveloped by visceral vaginal tunic 

  blood vessels are tortuous & highly branched for counter-current heat exchange;

  histologically, seminiferous tubules connect to a rete testis which connects to efferent ductules. which converge at the cranial pole of the testis to form epididymis.

Epididymis: 

spermatozoa storage & maturation occurs within the epididymis;  single coiled duct: head  —>  body  —>  tail  —>  ductus  deferens

proper ligament of the testis  —  homologous with proper ligament of ovary

ligament of the tail of epididymis —  (embryonic gubernaculum) homologous with round ligament of uterus

Ductus Deferens:   pl.= ducti deferentes

enveloped by visceral vaginal tunic connected to mesoductus deferens; traverses inguinal canal, penetrates prostate, & empties into urethra at the colliculus seminalis; terminal end of the ductus deferens features an ampulla (except in cat & pig) that has glands in its wall.

Spermatic  cord = ductus deferens + testicular vessels + vaginal tunics & spermatic fascia.

Accessory Genital Glands:  contribute seminal fluid to

                                                            the ejaculate  prostate (body + disseminated components) — all males. 

 bulbourethral glands (paired,  at ischial arch)  — not dog.

         

(vesicular glands [seminal vesicles] — neither dog nor cat )

 glands in wall of terminal segment of ductus deferens — all males

Penis:

three regions: root (contains bulb of penis & crus of penis),  body,  

                         and free part

 the penis is composed of: 1) penile urethra, 2) erectile tissue & 3)

                                              extrinsic muscles

Three bodies of erectile tissue:

corpus spongiosum penis: unpaired;  surrounds urethra;  begins as bulb of penis at root of penis

corpus cavernosum penis: paired; main erectile organ     (fibroelastic tunica albuginea)

crus of penis at the root of the penis — attaches to ischial arch;  covered by the ischiocavernosus m.;  replaced by os penis within free portion (carnivores)

glans (corpus spongiosum glandis)

dog : pars longa glandis & pars bulbus glandis (covers whole free portion)

cat : glans thin and distal [note: proximal skin has penil spines (cornified  papillae)]

Extrinsic penile muscles:    

bulbospongiosus m. (unpaired)— covers the bulb of the penis;

           

ischiocavernosus mm.(paired)—  covers the crus of the penis;

           

ischiourethralis mm. (paired)— small, inserts on ring around dorsal vein of penis;

retractor penis mm.(paired but together at midline) —smooth muscle;

 Prepuce:

cutaneous sheath which contains free part of penis (domestic mammals) 

 fascicles of cutaneous trunci m. encircling preputial orifice (dog)      = (retractor) preputial m.

Process of Erection: dog

parasympathetic effect — arterial vasodilation and venous constriction;

 

inflow to penis exceeds outflow and blood accumulates in penis;

pressure increases within fibroelastic capsules of erectile bodies;  

pressure mechanically compresses internal veins to further impede outflow;

contraction of extrinsic penile mm. pumps blood in against the increasing pressure; ischiourethralis m. occludes dorsal vein of penis to expand pressure within glans;

           

following intromission, the   superficially located dorsal veins   of penis, which drain

           

 the glans, are mechanically constricted. In the dog, the bulbus glandis expandsfollowing  intromission and this explains the  “tie” during copulation.

Ejaculation: 

          sympathetic pathway — contraction of ductus deferens, smooth m. in prostate & other glands, and internal urethral  sphincter (to prevent reflux   into bladder)

           also, contraction of urethralis m.& extrinsic penile mm.       

          propels ejaculate along urethra.

Veterinary IMMUNOLOGY (Animal)

IMMUNOLOGY

(Animal)

All living organisms are continuously exposed to substances that are capable of causing them harm. Most organisms protect themselves against such substances in more than one way with physical barriers, for example, or with chemicals that repel or kill invaders. Animals with backbones, called vertebrates, have these types of general protective mechanisms, but they also have a more advanced protective system called the immune system. The immune system is a complex network of organs containing cells that recognize foreign substances in the body and destroy them. It protects vertebrates against pathogens, or infectious agents, such as viruses, bacteria, fungi, and other parasites.

 Lymphocytes - Heart of the Immune System

Lymphocytes  - a class of white blood cells- are theprincipal active components of the adaptive immune system.

The other components are antigen-presenting cells, which trap antigens and bring them to the attention of lymphocytes so that thev can mount their attack.

When an antigen invades the body, normally only those lymphocytes with receptors that fit the contours of that particular antigen take part in the immune response. When they do, so-called daughter cells are generated that have receptors identical to those found on the original lymphocytes. The result is a family of lymphocytes, called a lymphocyte clone. with identical antigen-specific receptors. lymphocytes are made from stem cells in the bone marrow lymphocytes then undergo a second stage of development, or processing, in which they acquire their antigen-specific receptors.

 By chance, some lymphocytes are created with receptors that happen to be specific to normal, healthy components of the body. Fortunately, a healthy immune system purges itself of these lymphocytes, leaving only lymphocytes that ignore normal body components but react to foreign intruders. If this purging process is not completely successful, the result is an autoimmune disease in which the immune system attacks normal components of the body as though they were foreign antigens, destroying healthy molecules, cells, or tissues. Antibodies attack antigens by binding to them. Some antibodies attach themselves to invading microorganisms and render them immobile or prevent them from penetrating body cells. In other cases, the antibodies act together with a group of blood proteins, collectively called the complement system, that consists of at least 30 different components. In such cases, antibodies coat the antigen and make it subject to a chemical chain reaction with the complement proteins. The complement reaction either can cause the invader to burst or can attract scavenger cells that eat the invader.

Cytotoxic T cells destroy cells infected with viruses and other pathogens and may also destroy cancerous cells. Cytotoxic T cells are also called suppressor lymphocytes because they regulate immune responses by suppressing the function of helper cells so that the immune system is active only when necessary.

The receptors of T cells are different from those of B cells because they are trained to recognize fragments of antigens that have been combined with a set  of molecules found on the surfaces of all the body's cells. These molecules are called MHC molecules. As T cells circulate through the body, they scan the surfaces of body cells for the presence of foreign antigens that have been picked up by the MHC molecules. This function is sometimes called immune surveillance.

  

Immune Response

When an antigen enters the body, it may be partly neutralized by components of the innate immune system. It may be attacked by phagocytes or by preformed antibodies that act together with the complement system. Often, however, the lymphocytes of the adaptive immune system are brought into play. If lymphocytes encounter an antigen trapped by the antigen-presenting cells of the lymphoid organs, lymphocytes with receptors specific to that antigen stop their migration and settle to mount an immune response locally. As these

lymphocytes accumulate in the affected lymphoid tissue, the tissue often becomes enlarged for example, the lymph nodes in the groin become enlarged if there is an infection in the thigh area.

Antigen-presenting cells degrade antigens and ofteneliminate them without the help of lymphocytes. If there are too many antigens for them to handle alone, however, the antigen-presenting cells secrete IL- 1 and display fragments of the antigens to alert thehelper T cells. The IL-1 facilitates the responsiveness of T and B cells to antigens and, if released in large amounts, can also cause fever and drowsiness. Helper T cells that encounter IL-  1 and fragments of antigens transform into cells  called lymphoblasts, which then secrete a variety of interleukins that are essential to the success of the immune response. TheIL-2 produced by helper T cells promotes the growth of cytotoxic T cells, which may be necessary to destroy tumorous cells or cells infected with viruses. The IL-3 increases the production of blood cells in the bone marrow and thus helps to maintain  an adequate supply of the lymphocytes and lymphocyte products necessary to fight infections. Helper T cells also secrete interleukins that act on B cells, stimulating them to divide and to transform intoantibody-secreting plasma cells. The antibodies thenperform their part of the immune function.

The process of inducing an immune response is called immunization. It may be either natural through infection by a pathogen or artificial through the use of serums or vaccines. The heightened resistance acquired when the body responds to infection is called active immunity. Passive immunity results when the antibodies from an actively immunized individual are transferred to a second, nonimmune subject. Active immunization, whether natural or artificial, is longer-lasting than is passive immunization because it takes advantage of immunologic memory

Veterinary COMPLIMENT,OPSONISATION and PHAGOCYTOSIS (Animal)

COMPLIMENT,OPSONISATION                 

and 

PHAGOCYTOSIS

Opsonisation is the process of coating micro-organisms with plasma proteins to increase their adherence to phagocytic cells in preparation for phagocytosis. The two main opsonins are IgG antibody and the third component of complement

(C3) which bind to the surfaces of micro-organisms.

Phagocytic cells have membrane receptors for IgG (Fc piece) and activated C3 (which is called C3b). IgG antibody binds to micro-organisms because the Fab portion recognises bacterial epitopes. C3b binds because during activation of C3 a thiol bond is exposed which permits the formation of ester or amide bonds (covalent binding) with the bacterial surface structures. C3 is activated by limited proteolysis by enzymes called C3 convertases. There are two C3 convertases, one produced by activation of the classical pathway which is antibody dependent (IgM or IgG), while the alternative pathway can be activated in the absence of antibody. The classical pathway is inactivated when the C1q subcomponent of first component of complement binds to two adjacent IgG molecules or a single IgM molecule. The C1s subcomponent of C1 becomes an active protease and activates C4 and C2 to form the classical pathway C3 convertase which is a complex of activated C4 (C4b) and C2 (C2a) it is designated C4b2a. The alternative pathway is activated when micro-organisms come into contact with body fluids. The pathway is always being activated slowly to generate small amounts of activated C3 (C3b). When C3b binds to a micro-organism activation of the alternative pathway is amplified so that a large amount of the alternative pathway C3 convertase is

formed on the surface, followed by deposition of activated C3 (C3b). Complement can also kill micro-organisms directly. Once C3b has been formed, same binds to the C3 convertase to change it to a C5 convertase which activates C5 to form C5b. Subsequently C6, C7, C8 and C9 bind together with C5b to form a hollow cylinder which is inserted into cell membranes to produce lysis. Thus complement kills micro-organisms in two ways:

1. Opsonisation followed by phagocytosis and intracellular killing (indirect).

2. Assembly of the cytolytic C5b-9 membrane attack complex (direct).

Neutrophils and monocytes/macrophages are the two important phagocytic cells. Neutrophils and monocytes circulate in the blood and migrate into the tissues at the post-capillary venule. Initially they adhere to endothelium and then migrate through intercellular junctions. In the tissues they migrate  towards bacteria by means of a process called chemotaxis, which is defined as direct movement along a concentration gradients of chemotactic agents (e.g. C5a leukotriene B4, IL-8, bacterial peptides). Phagocytes recognise their targets by specific sugar residues (e.g. mannose or LPS) but binding is greatly enhanced if the organism is opsonised with IgG and/or C3b. Phagocytes possess Fc and C3b receptors and there is co-operation between these receptors. Thus an organism opsonised with IgG and C3b is more effectively phagocytosed. Ingestion (phagocytosis) is a localised endocytosis process requiring energy. The plasma membrane envelopes the particle and buds off to form an intracellular vesicle, the phagosome. Following fusion of the phagosome with lysosomal  granules the phagolysosome is formed and the bacteria are killed by oxygen-dependent and oxygen independent process.

Veterinary PHAGOCYTOSIS (Animal)

 PHAGOCYTOSIS

 Phagocytosis is a nonspecific defense mechanism in which

various phagocytes engulf and destroy the microorganisms

of disease.

Phagocytes.

Among the important phagocytes are the circulating white

blood cells called neutrophils and monocytes. In the tissues,

the monocytes are transformed into phagocytic cells called macrophages. The macrophages move through the tissues of the body performing phagocytosis and destroying parasites. They are part of the reticuloendothelial system. Phagocytes also initiate the processes of the immune system.

The process of phagocytosis begins with attachment and ingestion of microbial particles into a bubblelike organelle called a phagosome. Once inside the phagocyte, the phagosome containing the microorganism joins with a lysosome, which contributes enzymes. The fusion of phagosome and lysosome results in a phagolysosome. Microorganism    are destroyed within minutes, and the microbial debris is eliminated from the cell in the process of egestion. In the immune process, chemical portions of the microorganism called antigenic determinants are displayed on the surface of the phagocyte to stimulate the immune process.  

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Phagocytosis is enhanced by products of the immune system called antibodies.These protein molecules bind to microorganisms and encourage engulfing by phagocytosis.

The complement system. 

The complement system is a series of proteins that circulate

in the blood and encourage phagocytosis or otherwise complete the defensive process. Many immune reactions stimulate the complement system. The complement system operates in a cascade of reactions. In the pathway, certain complement components react with one another and produce new substances that induce other components to react. The results of the myriad reactions are substances that induce other complement components into action. The overall result is a number of substances toxic to microorganisms. The substances encourage phagocytosis or bring about destruction of microbial membranes.

Two general pathways for complement activity exist. The classical pathway  operates with the highly specific immune system and is initiated when certain antibodies unite with antigens and stimulate the complement system into action. The alternative  pathway is nonspecific and is initiated by tumors, cell wall components of bacteria, and various microorganisms. It is sometimes called the properdin pathway because properdin is one of the proteins

operating in it. The alternative pathway invokes a slower and less specific method for ridding the body of parasites, particularly Gram-negative bacteria and viruses.

Veterinary LYMPHOID (Animal)

 LYMPHOID

The lymphatic system performs three important tasks in the mammalian body.

1.      It is closely tied to the cardiovascular system and helps maintain the fluid balance between the blood vessels and the tissues.

2.      The lymphatic system plays a large role in immunity.

3.      This important system also absorbed digested fats from the small intestine.

The components of the lymphatic system are divided in to two groups

1.     Primary organs :- The thymus gland and the bone marrow are primary organs. They regulate the production and differentiation of lymphocytes- the cells that make up the immune system.

2.     Secondary organs :- The secondary organs include the lymphatic vessels, lymph nodes, aggregated lymphoid tissue, and spleen. These secondary organs are involved , to some extent, in all three lymphatic functions.

Primary organs

Thymus

The mammalian thymus has two lobes and is situated slightly above the heart and ventral to the trachea. It is relatively large at birth, but after sexual maturity, it begins to degenerate and is quit small animals.

The main function of the thymus is to “educate” certain white blood cells of the immune system called T- lymphocytes, or T- cells identify foreign cells in the  body, such as invading bacteria, and mark them for destruction by other immune cells. The T- cells mature in the thymus gland and are taught to distinguish between self and non-self cells. If they develop correctly, they are able to recognize the difference between those cells that are supposed to be in the body and those that are foreign T- cells  that fail to recognize this difference are destroyed by the thymus so they cannot harm the body. After maturing in the thymus, the T- cells move to the secondary organs, where most of them will remain.

Bone marrow

Bone marrow is the soft material in the cavities of bones. It is a network of connective tissue fibers, fat cells, blood vessels, and blood producing cells. Bone marrow produces both red and white blood cells, including the lymphocytes. Both T- lymphocytes and B-lymphocytes are produced in the bone marrow. The young T-cells move to the thymus for final development, but the B-cells remain in the bone marrow during maturation. Once the B-cells are fully developed in the bone marrow, they are also released into circulation and most of them take up residence in the secondary lymphatic organs.

 The B-cells are white blood cells that are sensitive to          

 antigens and produce antibodies against them.Antigens          are any chemicals that produce a immune response in the body, such as toxins, foreign proteins, particulate matter, or  bacterial cells. When an antigen is present, the B-cell becomes active and begins to produce antibodies against that antigen. Antibodies are special proteins that bind to antigens and mark them for destruction. Antibodies are antigen specific, and the immune system is able to remember each antigen it fights. Once a B-cell makes antibodies against a certain antigen, e.g., a bacteria, it keeps a memory of that antigen. If the antigen appears again, the B-cell can produce a large number of antibodies very rapidly. In this way, a second infection with that bacteria is often prevented.

Secondary organs

As mentioned, the secondary organs include the lymphatic vessels, lymph nodes, aggregated lymphoid tissue, and spleen. While the primary organs are only involved in the immune function of the lymphatic system, the secondary organs are collectively involved in all three functions:

1.  Immunity

2. Fat absorption

3. Fluid regulation

Lymphatic vessels

The lymphatic vessels link together all of the secondary organs and also connect to the cardiovascular system. They provide a route for the one-way flow of lymph from the tissues of the body to the heart. Lymph is the clear, yellowish fluid that is collected from the intestinal spaces into lymphatic capillaries.Lymphatic capillaries are interwoven with the blood capillaries. Fluid and proteins are forced out of the arterial end of the blood capillary and into the interstitial space.

About 90% of the fluid is reabsorbed in the venous end of the blood capillary, but none of the proteins are able to reenter the blood vessels because they cannot fit through the tight junctions of the cells. The lymph capillaries have extremely loose cell junctions, however, and they are able to absorb the remaining 10% of the fluid along with the plasma proteins. Once inside of the lymph vessels, the fluid is then termed lymph.

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The lymphatic vessels are structured similar to veins, with thin walls and valves to prevent backflow. They are not muscular vessels, and external forces such as limb movement regulate the flow of lymph. Once in the capillaries, the lymph moves into progressively larger vessels, passes through the lymph nodes and or spleen, reaches the large ducts, and enters the blood circulation near

the junctions of the jugular and subclavian veins in the upper chest. Thus, the fluid and proteins are eventually returned to the blood, which helps maintain the proper balance of fluid between the blood vessels and the tissues

.

All of the lymph from the lower body, left arm, and left thorax are drained through the thoracic duct into the junction of the left jugular and subclavian veins. The fluids from the neck, right arm, and right thorax empty into the right lymphatic duct which joins the venous system at the junction of the right jugular and subclavian veins. Near the small intestine, where fats are digested and absorbed, the lymphatic vessels have a special function and, therefore, a special name. They are involved in the absorption of digested fat from the small intestine, and are called lacteals. After a meal the fluid within the lacteals generally has a fat content of 1-2%, and it appears cloudy.  This cloudy lymph in the lacteals is called chyle.

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Lymph nodes

Lymph nodes are round or bean-shaped structures that are widely distributed throughout the body. Imbedded in connective tissue or fat, they are concentrated in the cervical, axillary, and inguinal regions – the neck, armpits, and groin, respectively. They are typically less than ½ inch in length,                                                            

depending on the size of the animal. The lymph nodes filter the lymph before returning it to the veins. They are arranged so that all lymph has to pass through at least one node before returning to the veins.

Lymph nodes are enclosed by a capsule of connective tissue and comprised of several compartments called lymph nodules. The nodules are masses of T-cells, B-cells, and macrophages. Macrophages are specialized cells that ingest and destroy foreign material. The nodules are separated by spaces called lymph sinuses. The vessels that deliver unfiltered lymph are called afferent vessels, and there are several per node. The lymph is then filtered for antigens and particulate matter, and an immune response is generated, if necessary. The filtered lymph leaves the node through one or two efferent vessels near an indentation called the hilum. Blood vessels also enter and exit the node at the hilum.

Aggregated lymphoid tissue

Aggregated lymphoid tissues are collections of lymphoid tissue that are not encapsulated. They have varying degrees of size and organization. The most highly organized and widely known examples are tonsils and Peyer's patches. The tonsils are found at the back of the oral cavity. Peyer's patches are found in the lining of the small intestine. Tonsils and Peyer's patches have specialized epithelial cells that are capable of transporting antigens, and though they do not filter lymph, they are generally surrounded by capillaries. The main purpose of the aggregated lymphoid tissue is defense from invasion at the mucosal surfaces. These are sites where large numbers of bacteria and other microorganisms are present and can easily enter the body. These specialized lymphatic cells help to prevent infections from developing at these sites.

Spleen

The spleen is a spongy organ located in the upper left portion of the abdominal cavity along the outside curve of the stomach. It is composed of two types of tissue -:

1. The red pulp is mostly used to store blood and break down old red blood cells.

2. The white pulp has the lymphatic function of filtering the blood for antigens.

The spleen traps antigens and is another site for initiation of the immune response. In a sense, it is like a large lymph node. A swollen spleen can be a sign of serious infection and is easily palpated.

Veterinary ANTIGENS and ANTIBODIES (Animal)

   ANTIGENS and ANTIBODIES

Antibodies, or Y-shaped immunoglobulins, are proteins found in the blood that help to fight against foreign substances called antigens. Antigens, which are usually proteins or polysaccharides, stimulate the immune system to produce antibodies. The antibodies inactivate the antigen and help to remove it from the body. While antigens can be the source of infections from  pathogenic bacteria and viruses, organic molecules detrimental to the body from internal or environmental sources also act as antigens. Genetic engineering and the use of various mutational mechanisms allow the construction of a vast array of antibodies (each with a unique genetic sequence).

Specific genes for antibodies direct the construction of antigen specific regions of the antibody molecule. Such antigen-specific regions are located at the extremes of the Y-shaped immunglobulin-molecule.

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Once the immune system has created an antibody for an antigen whose attack it has survived, it continues to produce antibodies for subsequent attacks from that antigen. This long-term memory of the immune system provides the basis for the practice of vaccination against disease.The immune system, with its production of antibodies, has the ability to recognize, remember, and destroy well over a million different antigens.

There are several types of simple proteins known as globulins in the blood: alpha, beta, and gamma.

Antibodies are gamma globulins produced by B lymphocytes when antigens enter the body. The gamma globulins are referred to as immunoglobulins. In medical literature they appear in the abbreviated form as Ig. Each antigen stimulates the production of a specific antibody (Ig). Antibodies are all in a Y-shape with differences in the upper branch of the Y. These structural differences of amino acids in each of the antibodies enable the individual antibody to recognize an antigen. An antigen has on its  surface a combining site that the antibody recognizes from the

combining sites on the arms of its Y-shaped structure. In response to the antigen that has called it forth, the antibody wraps its two combining sites like a lock around the key  of the antigen combining sites to destroy it.

An antibody's mode of action varies with different types of antigens. With its two-armed Y-shaped structure, the antibody can attack two antigens at the same time with each arm. If the antigen is a toxin produced by pathogenic bacteria that cause an infection like diphtheria or tetanus, the binding process of the antibody will nullify the antigen's toxin. When an antibody surrounds a virus, such as one that causes influenza, it prevents it from entering other body cells. Another mode of action by the antibodies is to call forth the assistance of a group of immune agents that operate in what is known as the plasma complement system. First, the antibodies will coat infectious bacteria and then white blood cells will complete the job by engulfing the bacteria, destroying them, and then removing them from the body. There are five different antibody types, each one having a different Y-shaped configuration and function. They are the Ig G, A, M, D, and E antibodies. IgG is the most common type of antibody. It is the chief Ig against microbes. It acts by coating the microbe to hasten its removal by other immune system cells. It gives lifetime or long-standing immunity against infectious diseases. It is highly mobile, passing out of the blood stream and between cells, going from organs to the skin where it neutralizes surface bacteria and other invading microorganisms. This mobility allows the antibody to pass through the placenta of the mother to her fetus, thus conferring a temporary defense to the unborn child.

After birth, IgG is passed along to the child through the mother's milk, assuming that she nurses the baby. But some of the Ig will still be retained in the baby from the placental transmission until it has time to develop its own antibodies. Placental transfer of antibodies does not occur in horses, pigs, cows, and sheep. They pass their antibodies to their offspring only through their milk.This antibody is found in body fluids such as tears, saliva, and other bodily secretions. It is an antibody that provides a first line of defense against invading pathogens and allergens, and is the body's major defense against viruses. It is found in large quantities in the bloodstream and protects other wet surfaces of the body.  While they have basic similarities, each IgA is further differentiated to deal with the specific types of invaders that are present at different openings of the body.  Since this is the largest of the antibodies, it is effective against larger microorganisms. Because of its large size (it combines five Y-shaped units), it remains in the bloodstream where it provides an early and diffuse protection against invading antigens, while the more specific and effective IgG antibodies are being produced by the plasma cells.

The ratio of IgM and IgG cells can indicate the various stages of a disease. In an early stage of a disease there are more IgM antibodies. The presence of a greater number of IgG antibodies would indicate a later stage of the disease. IgM antibodies usually form clusters that are in the shape of a star.

This antibody appears to act in conjunction with B and T-cells to help them in location of antigens. Research continues on establishing more precise functions of this antibody. 

The antibody responsible for allergic reactions, IgE acts by attaching to cells in the skin called mast cells and basophil cells In the presence of environmental antigens like pollens, foods, chemicals, and drugs, IgE releases histamines from the mast cells. The histamines cause the nasal inflammation and the other discomforts of hay fever or other types of allergic responses, such as hives, asthma, and in rare cases, anaphylactic shock. An explanation for the role of IgE in allergy is that it was an antibody that was useful to early man to prepare the immune system to fight parasites. This function is presently overextended in reacting to environmental antigens. The presence of antibodies can be detected whenever antigens such as bacteria or red blood cells are found to agglutinate (clump together), or where they precipitate out of solution, or where there has been a stimulation of the plasma complement system. Antibodies are also used in laboratory tests for blood typing when transfusions are needed and in a number of different types of clinical tests, such as the Wassermann test for syphilis and tests for typhoid fever and infectious mononucleosis.