Lymphatic SystemCh 16

Structures

Lymph Lymphatic vessels Lymphocytes Spleen Thymus Tonsils Peyer’s patches Lymph nodes

Functions

Production, maintenance, and distribution of lymphocytes

Return of fluid and solutes from peripheral tissues to the blood

Distribution of hormones, nutrients, and waste products from their tissues of origin to the general circulation

Lymph

A fluid that resembles blood plasma but contains a much lower concentration of suspended proteins.

Travels through the lymphatic vessels and carries lymphocytes.

Lymph Nodes

Small, oval lymphoid organs that function much like a kitchen water filter.

It filters and purifies lymph before it reaches the venous circulation.

Removes at least 99% of the antigens in lymph

Also provide an early warning system

Location of Nodes

Located where peripheral lymphatics enter the trunk

Groin, axillary, neck

Lymph Nodes

Thymus

Located in the mediastinum, just posterior to the sternum and just above the base of the heart.

Reaches its greatest size (compared to the body)in the 1st year or two after birth but reaches its maximum size just before puberty, after which it begins to decrease in size.

Thymus Location

Thymus Function

Produces the hormone thymosin, which promotes the development and maturation of lymphocytes.

Spleen

The adult spleen contains the largest collection of lymphoid tissue in the body.

Lies along the curving lateral border of the stomach, extending between the 9th and 11th ribs.

Spleen Location

Functions of the Spleen

Removal of abnormal blood cells and other blood components by phagocytosis

Storage of iron from recycled RBCs The initiation of immune responses

by B cells and T cells in response to antigens in circulating blood.

Injuries to the Spleen

An impact to the left side of the abdomen can damage the spleen, which is very delicate.

If the capsule is rupture, severe abdominal bleeding may result, leading to circulatory shock.

Sutures typically tear out so a badly damaged spleen usually is removed.

More susceptible to bacterial infections Enlarges during Mono (restricted from

contact sports)

Fetal Spleen

The spleen in a fetus is a secondary site for the production of red blood cells.

This lasts until about the 5th month of gestation.

After this, the bone marrow takes over.

Pathogens

Viruses, bacteria, fungi, and parasites capable of not only surviving but thriving inside our bodies-and potentially causing us great harm.

Nonspecific Defenses

Also called innate defense Do not distinguish one type of threat

from another. Present at birth Includes physical barriers (skin,

mucous membranes), phagocytic cells, interferons, complement, inflammation, and fever.

Phagocytes

Perform janitorial and police services in peripheral tissues, removing cellular debris and responding to invasion by foreign compounds or pathogens

Microphages/Macrophages

Microphages are neutrophils and eosinophils that circulate through the blood and leave the bloodstream and go to the tissues (diapedesis)

Macrophages are large, actively phagocytic cells that derived from monocytes

They are either fixed (permanent residents of specific tissue) or free (travel throughout the body)

Immunological Surveillance

Natural killer cells are responsible for recognizing and destroying abnormal cells when they appear in peripheral tissues.

Interferons

Small proteins released by activated lymphocytes and macrophages and by tissue cells infected with viruses.

They bind to the membrane of normal cells and trigger the production of antiviral proteins in the cytoplasm.

They do not interfere with the virus entering the cell, but interfere with viral replication inside the cell.

Complement

Your plasma contains 11 special complement proteins which form the complement system. It complements the action of antibodies.

Destruction of target cells Stimulation of inflammation Attraction of phagocytes Enhancement of phagocytosis

Inflammation

A localized tissue response to injury. Produces local sensations of

swelling, redness, heat, and pain1. To perform a temporary repair at

injury site and prevent access to other pathogens

2. To slow the spread of pathogens away from the injury site

3. To mobilize local, regional, and systemic defenses to overcome the pathogens

Fever

The maintenance of a body temperature greater than 99o F.

High body temps can inhibit some viruses and bacteria

Most likely benefit is increased metabolism. For every 1oC rise in temp, your metabolism increases 10%.

Results in quicker mobilization of tissue defenses and accelerated repair process

Specific Defenses

Also known as adaptive defenses Protect against particular threats Many develop after birth as a result

of accidental or deliberate exposure Depend on the activities of

lymphocytes Produce specific resistance or

immunity.

Specific Defenses

T cells are responsible for cell-mediated immunity

B cells are responsible for antibody-mediated immunity

Immunity

Innate-genetically determined and present at birth

Acquired-not present at birth, acquire immunity to a specific antigen only once you have been exposed to that antigen.

Acquired

Active-appears after exposure to an antigen, as a consequence of the immune response.

Naturally-after exposure to antigens in the environment

Induced-after administration of antigen to prevent disease (vaccine)

Passive (borrowed)

Induced-Administration of antibodies to combat infection

Natural-transfer of maternal antibodies across placenta or in breast milk

Herd Immunity

The immune resistance of a population of interest—e.g., military recruits, children in a day-care centre—to invasion and spread by a particular pathogen, based on the resistance of most individual members of the group

Antigens

An antigen is any substance that causes your immune system to produce antibodies against it. An antigen may be a foreign substance from the environment such as chemicals, bacteria, viruses, or pollen. An antigen may also be formed within the body, as with bacterial toxins or tissue cells

Antibodies

any of numerous Y-shaped protein molecules produced by B cells as a primary immune defense, each molecule and its clones having a unique binding site that can combine with the complementary site of a foreign antigen, as on a virus or bacterium, thereby disabling the antigen and signaling other immune defenses.

Autoimmunity

The healthy human body is equipped with a powerful set of tools for resisting the onslaught of invading microorganisms (such as viruses, bacteria, and parasites). Unfortunately, this set of tools, known as the immune system, sometimes goes awry and attacks the body itself. These misdirected immune responses are referred to as autoimmunity, which can be demonstrated by the presence of autoantibodies or T lymphocytes reactive with host antigens.

Allergen

an environmental substance that can produce a hypersensitive reaction in the body but may not be intrinsically harmful. Common allergens include pollen, animal dander, house dust, feathers, and various foods. Studies indicate that one of six Americans is hypersensitive to one or more allergens.

Tissue Rejection

Graft rejection, organ rejection, tissue rejection. The constellation of host immune responses evoked when an allograft tissue is transplanted into a recipient; rejection phenomena may be minimized by optimal matching of MHC antigens and ABO blood groups and ameliorated with immunosuppressants–eg, cyclosporin, tacrolimus, rapamycin Exceptions of TR Corneal transplants, identical twins.

Isograft

Isografts are from genetically identical people; this would be from an identical twin. They are anatomically like allografts, but because they have the same genetics, there isn't an immune response.

Autograft

self transplant that includes skin grafts, taking a vein from the leg to use in heart surgery. There are no immune issues from this.

Allograft

this is the most common type and is transplant of non-identical people. This is what most transplants are (heart, lung, kidney etc transplants from when people donate their bodies); immunosuppressants need to be taken to prevent the body from rejecting this type of transplant.

Xenograft

Xenograft-transplant from another species. Most commonly would be a pig's heart valve used to replace a human valve. This has the immune issues like allografts. Animals can also be harder to control the diseases and this is important since the person would need immunosuppressants.

Diseases We Vaccinate Against

Flu Pertussis (Whooping cough) H1N1 Hepatitis A & B Measles Diptheria Mumps Tetanus Rubella Rabies Chicken Pox HPV Polio Typhoid Fever Small Pox Yellow Fever HiB Meningitis