Ch 20--Lymphatic System and Lymphoid Organs

what is the lymphatic system?

it is part of the circulatory system and immune system

returns interstitial fluid and plasma proteins that leaked from capillaries back to the venous system

maintains blood volume, routes for spreading cancer, transportation for digested fat

what is lymph

clear fluid made from blood

lymph nodes

structures that filter lymph

lymphoid organs/tissues

structural basis of the immune system

spleen, thymus, tonsils, lymph nodes, and other tissues

lacteal

lymphatic capillary only found in the small intestines

districution and structure of lymphatic vessels

one way system that merges and becomes larger as they approach the heart

run parallel to blood capillaries and soak up interstitial fluid

lymphatic capillaries

vessels that weave between tissue cells and blood capillaries

3 layers, like blood vessels

increased permeability because of overlapping endothelial cells

what can lymphatic capillaries transport

can take up large molecules and particles

allows uptake and transport of pathogens to lymph nodes and tonsils

what is lymph made from

protein (antibodies) and white blood cells

how does lymph flow

from the capilaries

to the vessels

to the trunk

to the ducts

nodes filter the lymph between vessels

where are lymph ducts and where do they drain

2 lymph ducts near the neck

the right duct drains to the right upper body

the left duct drains to the left upper body and left and right lower body

how does lymph move

it is low pressure

lymph is propelled upward by valves and the contraction of muscles to prevent back flow

immune system cells

lymphocytes: T cell and B cell

antigen presenting cells (APCs): macrophages and dendritic cells

what are the different kinds of T cells

cytotoxic T cells—kill other cells in the body

helper T cells—help T cells become active

suppressor T cells—shuts down the immune system to avoid allergies/autoimmune disease

what is clonal expansion

when lymphocytes make copies of themselves to grow the group

what is the fate of B cells

primary response—the first time you encounter the antigen

memory cells—wait and hang out

plasma cells—form clones and secrete antibodies to fight immediate infection

which cells play a part during T cell activation

cytotoxic T cells, memory T cells, suppressor T cells, and helper T cells

what are the primary lymphoid organs

organs where T and B cells are educated/matured

Thymus (T cells) and bone marrow (B cells)

what are secondary lymphoid organs

organs where mature lymphocyte cells first encounter an antigen

tonsils, spleen, appendix, Peyer’s patches (on the intestines), and lymph nodes

what are lymph nodes

hundreds of nodes found throughout the body that form clusters

not found on the CNS because there is no immune system in the brain or cord

they filter and surveillance of activation

what are the superficial lymph nodes

inguinal, axillary, and cervical clusters are superficial, so we can fell them

what cleans lymph

APCs

what are the two parts of lymph nodes

the cortex and the medulla

how do the nodes stay together

trabeculae extensions cluster things together

what is a sentinel node biopsy

used to determine if cancer has spread from the primary tumor to the lymph system

the sentinel nodes are the first lymph nodes into which a tumor drains

injecting a tracer material

what is the spleen

about the size of a fist, located int eh upper left abdominal quadrant

largest lymph structure

filters blood of old blood cells and platelets

what is the spleen’s lymphatic function

the site of lymphocyte proliferation and immune response

stores and releases some immune cells

what are the different parts of the spleen

the white pulp and the red pulp

white pulp

lymphatic tissue (25%)

immune cells proliferate

contains mostly lymphocytes on reticular fibers (T and B cells)

found around the central splenic artery

red pulp

blood is filtered before venous return (75%)

old stuff goes to the heme

spleen breaks down old RBCs and sends it to the urine and feces

how do most pathogens enter the body?

through the gastrointestinal and respiratory tracts

what is MALT

mucosa associated lymphoid tissue

lymphoid tissue in mucous membranes throughout the body—GI, respiratory, urogenital tracts

protects the systems

largest collections found in tonsils, Peyer’s patches, and appendix

what are tonsils

gathers and removes pathogens in air, food, and drink

palatine tonsils, lingual tonsils and pharyngeal tonsils

where are each of the tonsils found

palatine tonsils—largest and most often infected, found in the back of the throat

lingual tonsils—under the tongue

pharyngeal tonsils—behind the nose

Peyer’s patches

clusters of lymphoid follicles in the wall of the ileum

appendix

offshot of the first part of the large intestines

3 ½ inch tube off of the secum (lower right abdomen)

destroys pathogens in food and drink

Thymus

bilobed organ found beneath the sternum

where T cells mature and learn what to attck

teaches immunocompetence and self-tolerance

what are the steps for lymphocyte development, maturation, and activation

Origin

Maturation

Seeding secondary lymph organs

Antigen encounter and activation

Proliferation and differentiation

Origin

both B and T lymphocyte beginner cells come from red bone marrow

maturation

T (thymus) cell and B (bone marrow) cells learn immunocompetence and self-tolerance

Seeding secondary lymph organs

the lymphocytes leave the thymus or bone marrow and plant themselves into secondary organs and circulate through blood and lymph

antigen encounter and activation

lymphocyte is activated when its antigen receptors bind to an antigen

proliferation and differentiation

creates an army of themselves

colonal expansion