Visualizing Human Bio Ch 9

First line of defense

innate immunity (or non-specific immunity) which includes skin (the cutaneous membrane) and mucous membranes

Second line of defense

antimicrobial proteins (interferon), fever, inflammation, and phagocytes

Third line of defense

specific immunity which includes the interactions of white blood cells, antibodies, and macrophages

Innate vs specific

is it innate or induced?

Skin

Skin is the primary physical barrier to the outside world; prevents the entry of disease-causing microbes (pathogens); composed of a superficial epidermis and a deeper dermis.

Epidermis

The epidermis is composed of stratified squamous epithelium and has no blood supply.

Keratinocytes

The top layer of the epidermis is composed of dead cells (keratinocytes) joined by strong cell-to-cell junctions which are filled with a protein called keratin.

Mucous membranes

Mucous membranes provide nonspecific immunity and line any cavity open to the exterior (mouth, digestive tract, respiratory tract, urinary tract, reproductive tract).

Mucus

Mucus retards pathogens and is secreted by the epithelial cells of the membrane.

Innate chemical barriers

When the physical innate barriers (skin and mucous membranes) fail to stop a pathogen, chemical barriers aid in the first line of defense.

Sebum

Sebum (oily secretion) forms a protective acidic film over the skin surface that is hostile to many bacteria.

Lysozyme

Perspiration, tears, and saliva contain an enzyme called lysozyme, which is an antibacterial chemical.

Gastric juices

Gastric juices have an extremely low pH of the acid produced by the stomach lining (~ pH 2) which creates an unfriendly environment for many pathogens.

Normal flora

Bacteria (normal flora) help create a hostile environment for other microbes.

Complement system

A series of chemical reactions which bring together a group of proteins that are usually floating freely in the plasma, effective against bacteria but not viruses.

Interferon

The chemical answer to viral infection is interferon, a 'local' hormone that is secreted to affect nearby cells.

Fever

Fever is defined as a change in the body's temperature set point, resulting in an elevation in body temperature.

Pyrogens

Proteins called pyrogens reset the body's thermostat to a higher temperature.

Inflammation

Inflammation is a localized method for increasing enzyme function, producing swelling, redness, and heat.

Phagocytes

Phagocytes are 'eating cells' that wander through the tissues, engulfing and removing anything that does not belong there.

Macrophages

Macrophages are large, actively patrolling cells that arise from blood cells and travel through every tissue looking for foreign material.

Lymphatic system

The lymphatic system is composed of lymph, lymphatic vessels, and lymphatic organs and tissues.

Lymph nodes

Lymph nodes function in concert with lymphatic tissue, organs, and vessels to return excess fluid from the tissues to the bloodstream and help defend the body against pathogens.

Lymph filtration

Before lymph returns to the bloodstream, it must be filtered and cleaned, which occurs in the lymphatic organs (lymph nodes, tonsils, spleen, Thymus gland).

Lymphocytes

Lymphocytes have receptors on their cell membranes waiting to detect the exact antigen which fits the receptor like a lock and key.

B cells

B cells mature in the Bone marrow, spend most of their time inside lymph nodes, and produce antibodies that are specific to a particular pathogen.

T cells

T cells mature in the Thymus gland and do not produce antibodies, but kill pathogens directly.

Antibody-mediated immunity

This part of our immune system takes place in the fluids of the body and involves B Cells.

Memory cells

Memory cells contribute to future immune responses.

Vaccinations

Vaccinations are often weakened pathogens, which carry the 'look and feel' of a harmful pathogen, but without the ability to cause disease.

Immune response to vaccinations

The body responds as if the weakened pathogen were still capable of causing illness.

Cell-mediated immunity

The cell-mediated immune system is governed by the T cells (helper T and cytotoxic T).

Helper T cells

Stimulated helper T cells will travel through the blood and lymph to the lymph nodes where they will stimulate the matching B cell.

Cytotoxic T cells

The cytotoxic T cell will seek out and destroy the stimulating pathogen wherever it occurs in the body.

T cell activation

When activated, both kinds of T cells make copies of themselves to fight pathogens, and produce memory cells for fighting future invasions.

Active immunity

Active immunity is immunity from experience; the immune system is exposed to the antigen in the natural course of life and immune cells respond and actively combat the pathogen.

Passive immunity

Passive immunity occurs when antibodies are transferred without stimulating the immune system, like from mother to infant (for example through breast milk).

Advantages of active immunity

The primary advantage of active immunity comes from the creation of memory cells.

Secondary response

The secondary response to a particular antigen happens far faster than the first response because the immune system needs to stimulate and clone only the memory cells.

Energy requirement in secondary response

The secondary response requires less energy from the body.

Immediate resistance in passive immunity

Passive immunity does not expend energy creating antibodies; introduced antibodies provide the recipient with immediate resistance to specific antigens.

Duration of passive immunity

Once the antibodies are used or broken down, however, the body cannot create more, and the immune protection is lost.

Maternal antibodies

The antibodies received by the baby from the maternal blood in utero sustain the infant for approximately two to three months.

Artificial passive immunity

Passive immunity can also be administered artificially by the injection of antibodies designed to match the pathogens the patient may contact, which generally lasts 3-6 months.

Autoimmune diseases

An autoimmune response is an immune response in which the body attacks itself; autoimmune diseases have different effects depending on what tissue is under attack.

Multiple sclerosis

An example of an autoimmune disease where nervous tissue is attacked.

Crohn's disease

An example of an autoimmune disease where a portion of the intestines is attacked.

Type I diabetes mellitus

An example of an autoimmune disease where the pancreas is attacked.

Lupus

An example of an autoimmune disease where the site of the attack may vary (it may affect the skin, joints, kidney, or lungs).

Rheumatoid arthritis

An example of an autoimmune disease that attacks the joints of the body.