Basic Immunology

• The immune system is the body’s natural defense in combating

organisms.

• The immune system can be thought of as having two “lines of

defense”:

1.1. Innate immune systemInnate immune system: Non-specific (no memory)

response to antigen (substance to which the body regards as

foreign or potentially harmful).

2.2. Adaptive immune systemAdaptive immune system: which displays a higher degree

of memory and specificity.

Basic Immunology

Innate immune system:

• It is what we are born with and it represents the first line of defense to

an intruding pathogen.

• The response is rapid, and is unable to “memorize” the same pathogen

in the future.

Adaptive immune system:

• Although cells and molecules of the adaptive system possess slower

dynamics, they possess a high degree of specificity.

• It is genetically based and we pass it on to our offspring.

• It frequently incorporates cells and molecules of the innate system in its fight

against harmful pathogen.

Basic Immunology

Components of the immune system

Innate immune systemAdaptive immune system

Response is non-specificPathogen and antigen specific response

Exposure leads to immediate maximal response

Lag time between exposure and maximal response

Cell-mediated and humoral componentsCell-mediated and humoral components

No immunological memoryExposure leads to immunological memory

Found in nearly all forms of lifeFound only in jawed vertebrates

Basic Immunology

Basic Immunology

• The immune system protects human from infection (bacteria, viruses,

etc..) with layered defenses of increasing specificity.

• Physical barriers prevent pathogens from entering the body.

• If a pathogen breaches these barriers, the innate immune system will

provide an immediate, but non-specific response.

• If pathogens successfully evade the innate response, a third layer of

protection will take an action, which is the adaptive immune system.

• The adaptive immune system will adapt its response during an

infection to improve its recognition of the pathogen.

• This improved response is then retained after the pathogen has been

eliminated, in the form of immunological memory.

Basic Immunology

Surface barriers :Surface barriers :

1. The first most important barrier is the SKIN. The skin cannot be penetrated

by most organisms unless it already has an opening, such as a cut or

scratch.

2. Mechanically, pathogens can be expelled from the lungs by cilliary action of

mobility, also by coughing or sneezing. Also the flushing action of tears,

saliva and urine will force out pathogens as does sloughing off skin.

3. Sticky mucus in respiratory and gastrointestinal tracts traps many

microorganisms.

4. pH acidity (<7.0) of skin secretions inhibits bacterial growth as well as hair

follicles secretions.

5. Saliva, tears and nasal secretion contain lysozome (an enzyme that

destroys bacterial wall causing cell lysis).

6. The stomach is a formidable obstacle as its mucous secrete hydrochloric

acid (pH <3.0) and protein-digesting enzymes that kill many pathogens.

Lymphatic SystemLymphatic System

Lymphatic System

• The lymphatic system is involved in the

immune system, i.e. in phagocytosis and

by maintaining the immune system.

The lymphatic system is a complex

network consisting of:

Lymphoid organs

lymph nodes

lymph ducts

Lymph tissues

lymph capillaries

lymph vessels

Lymphatic System

• Lymphatic system functionsLymphatic system functions:

1. Filtering out organisms that cause diseases.

2. Absorption of fatty acids and subsequent transport of fat to the

circulatory system.

3. Production of immune cells (such as lymphocytes, monocytes, and

plasma cells).

4. Distribution of fluids and nutrients in the body, because it drains

excess fluids and protein.

Lymphatic System

LYMPH:LYMPH: originates as blood plasma that leaks from the capillaries of the circulatory system, becoming interstitial fluid, and filling the spaces between cells.

• plasma is forced out of the capillaries (filtration) and forced back in (absorption) due to interactions of hydrostatic pressure and oncotic pressure.

• while out of the capillaries, the fluid mixes with the interstitial fluid.

• most of the fluid is returned to the capillaries.

• the excess interstitial fluid is collected by the lymphatic system by diffusion into the lymph capillaries and is processed by the lymph nodes then returned to the circulatory system.

• once within the lymphatic system the fluid is called lymph, and has almost the same composition as the original interstitial fluid.

Lymphatic System

Lymph nodes:Lymph nodes:

• Act as filters, with an internal reticular

connective tissue filled with

lymphocytes that collect and destroy

bacteria and viruses.

• when the body is fighting an infection,

lymphocytes multiply rapidly and

produce a characteristic swelling of the

lymph nodes.

Lymphatic System

Lymphatic Circulation:Lymphatic Circulation:

• The lymphatic system acts as a secondary circulatory system, except that it

collaborates with white blood cells in lymph nodes to protect the body from

infection.

• Unlike the circulatory system, the lymphatic system is not closed and has no

central pump.

• Like veins, lymph vessels have one-way, smilunar valves and depend mainly

on the movement of the muscles to squeeze fluid through them to the

lymphatic capillaries.

• The fluid is then transported to a larger lymphatic vessels terminating in the

lymphatic duct; these ducts drain into the circulatory system.

Lymphatic System

Lymphatic vessels:Lymphatic vessels:

• lymph capillaries are thin-walled tubes that carry lymph from the tissue spaces to other large lymphatic vessels.

• lymphatic vessels have valves to prevent the backflow of fluid.

• lymph fluid always flow toward the thoracic cavity, where it empties into veins in the upper thoracic region.

Lymphatic System

Lymphoid organs:Lymphoid organs:

Tonsils:Tonsils: are masses of lymphatic tissues located in the upper portions of the

nose & throat, where they form a protective ring of lymphatic tissue:

Nasopharyngeal tonsils.

Palatine tonsils.

Lingual tonsils.

Lymphatic System

Spleen:Spleen: is the largest of the lymphoid organs, present in the left

upper quadrant of the abdomen, just below the diaphragm and

behind the stomach.

Functions of the spleen:Functions of the spleen:

1. Producing lymphocytes & monocytes.

2. It filters microorganisms & other debris which are not destroyed by

the lymphatic system.

3. Storage of red blood cells.

4. Maintaining balance between cells & plasma in the blood.

5. Removing non-viable red blood cells.

Lymphatic System

Head and Neck lymph nodes:Head and Neck lymph nodes:

Cervical lymph nodes:

Anterior cervical lymph nodes.

Posterior cervical lymph nodes.

Tonsillar lymph nodes.

Submandibular lymph nodes.

Submental lymph nodes.

Supraclavicular lymph nodes.

The SkinThe Skin

The Skin

• The skin is the body’s first line of defense against diseases.

• Sometimes is called the integumentary system.

Functions of the skinFunctions of the skin

It helps to regulate body temperature.

It provides a barrier against bacteria from entering the body.

It excretes liquids and salts.

It provides sensitivity to touch.

It uses ultraviolet rays from the sun to convert chemicals into the vitamin D necessary for absorption of Calcium.

The Skin

Skin structure:Skin structure:• The skin is composed of different layers:

Epidermis.

Dermis.

Subcutaneous fat.

The Skin

The epidermis:The epidermis:

• Is the outer layer of the skin.

• It has NO blood supply of its own, the cells receive their nutrients from vessels underlying tissues.

• As new cells are pushed to the surface, the older cells die and sloughed off.

• Hair and skin color are determined by the melanin produced in the epidermis.

The Skin

The dermis:The dermis:

• Is a thick connective tissue layer that gives bulk to the skin.

• It contains many free nerve endings and receptors, which allow for detection of touch, temperature and pain.

• With age, the connective tissue becomes less elasticized and wrinkles develop.

The Skin

The subcutaneous fat layer:The subcutaneous fat layer:

• Is a layer of loose connective tissues that anchors the skin to the underlying organs.

• It insulates against heat loss and cushions underlying organs.

• The distribution of subcutaneous fat is responsible for the difference in body contours between individuals.

The Skin

Skin appendages:Skin appendages:

• The skin has a number of appendages including:

Hair.

Nails.

Glands.

The Skin

HairHair

• Is found on almost ALL skin surfaces.

• It is enclosed in a follicle and consists of a root and a shaft.

• The bulk of the shaft is made of dead material and protein.

The Skin

NailsNails

• It primarily consists of non-living matter.

• It has a root and body. The body is the visible portion, and the root is covered by skin called the cuticle.

• The extensive blood supply in the underlying dermis gives nails their pink color.

The Skin

Glands Glands

Three types of glands in the skin are:

1. Sebaceous glands.

2. Sweat glands (sudoriferous).

3. Apocrine sweat glands.

The Skin

Sebaceous glands:Sebaceous glands:

• found in all areas of the body except for the pals of the hands and the sole of the feet.

• they are oil glands that keep the hair and skin soft.

• they are also associated with sex hormone and become active during puberty.

• Sebaceous activity decreases with age, which is why hair and skin become dry as aging occurs.

The Skin

Sweat (sudoriferous) glands:Sweat (sudoriferous) glands:

• They are distributed all over the body and provide heat regulation by secreting sweat.

• Sweat is also produced in response to stress.

The Skin

Apocrine sweat glandsApocrine sweat glands

• Are the largest skin glands and are found under the arms, around the nipples and in the genital region.

• Bacterial action causes the secretions to break down, producing body odor.

The Skin