Ch.19 - The Lymphatic System Flashcards
Three parts of lymphatic system
network of lymphatic vessels (lymphatics), lymph, lymph nodes
lymph
fluid in vessels
lymph nodes
cleanse lymph
lymphoid organs and tissues
provide structural basis of immune system by housing phagocytic cells and lymphocytes
lymphoid structures
spleen, thymus, tonsils, lymph nodes
lymphatic system
returns interstitial fluid and plasma proteins back to blood
lymphatic vessels
elaborate network of drainage vessels
once interstitial fluid enters lymphatics, it is called…
lymph
lymphatic capillaries
blind-ended vessels that weave between tissue cells and blood capillaries
How are lymphatic capillaries different from blood capillaries?
more permeable; can take up larger molecules and particles that blood can’t
Increased permeability of lymphatic capillaries is caused by two specialized structures
endothelial cells overlap loosely to form one-way minivalves; MVs anchored by collagen filaments to matrix
lacteals
specialized lymph capillaries present in intestinal mucosa; absorb digested fat and deliver fatty lymph (chyle) to the blood
lymphatic trunks
formed by union of largest collectin vessels, drain large areas of body
Regions lymphatic trunks drain:
lumbar, bronchomediatinal, subclavian, jugular trunks, intestinal trunk
right lymphatic duct
drains right upper arm and right side of head and thorax
thoracic duct
drains rest of body
lymphangitis
condition in which lymphatic vessels appear as painful red lines under skin; caused by inflammation of larger lymphatic vessels that contain vaso vasorum
lymphedema
severed localized edema; caused by anything that prevents normal return of lmph to blood
immune system cells
lymphocytes
two types of lymphocytes
T cells; B cells
T cells & B cells
protect against antigens
T cells
manage immune response
B cells
produce plasma cells which secrete antibodies
other lymphoid immune cells
macrophages and dendritic cells
macrophages
phagocytize foreign substances and help activate T cells
dendritic cells
capture antigens and deliver them to lymph nodes
reticular cells
produce reticular fibers called stroma
main functions of lymphoid tissue
houses and provides proliferation sites for lymphocytes; offers surveillance vantage points for lymphocytes and macrophages as they filter through lymph
two types of lymphoid tissues
diffuse lymphoid tissue, lymphoid follicles (nodules)
diffuse lymphoid tissue
loose arrangement of lymphoid cells and some reticular fibers
lymphoid follicles (nodules)
solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers
lymphoid organs are groups into two functional categories
primary and secondary
primary lymphoid organs
areas where T and B cells mature - red bone marrow and thymus
T and B cells originate in ___ ___, but only __ cells mature there; __ cells mature in thymus
bone marrow, B, T
Secondary lymphoid organs
areas where mature lymphocytes first encounter their antigen and become activated
what are the secondary lymphoid organs?
nodes, spleen, MALT (mucosa-associated lymphoid tissue), and diffuse lymphoid tissues
lymph nodes
principal secondary organs or body
Where are most lymph nodes found?
embedded deep in connective tissue in clusters along lymphatic vessels
Two main functions of lymph nodes
cleanse the lymph; immune system activation
lymph nodes are surrounded by
external fibrous capsule
capsule fibers extend inward as ___ that divide node into compartments
trabecule
two histologically distinct regions of node
cortex, medulla
lymph enters convex side of node via
afferent lymphatic vessels
lymph travels through large ___ ___ and then into smaller sinuses found throughout cortex and medulla
subscapsular sinus
buboes
inflamed, swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy
largest lymphoid organ
spleen
the spleen is served by ___ ___ and __, which enter and exit at the ___
splenic artery, vein, hilum
Spleen Functions
site of lymphocyte proliferation and immune surveillance and response; cleanses blood of aged blood cells and platelets, macrophages remove debris
The spleen consists of two components
white pulp and red pulp
white pulp
site where immune function occurs; contains mostly lymphocytes on reticular fibers
where are white pulp clusters found?
around central arteries; appear as islands of white in a sea of red pulp
red pulp
site where old blood cells and bloodborne pathogens are destroyed
red pulp is composed of
splenic cords (reticular tissue) that separate blood-filled splenic sinusoids (venous sinuses)
In children younger than 12 years, what happens if their spleen is removed?
spleen will regenerate if a small part is left
Mucosa-associated lymphoid tissue (MALT)
lymphoid tissues in mucous membranes throughout body; protects from pathogens trying to enter body
Where are the largest collections of MALT found?
tonsils, Peyer’s patches, appendix
palatine tonsils
at posterior end of oral cavity; largest tonsils and most often infected
lingual tonsil
lumpy collection of follicles at base of tongue
pharyngeal tonsil
also called adenoids; located in posterior wall of nasopharynx
tubal tonsils
surrounded openings of auditory tubes into pharynx
tonsils function
gather and remove pathogens in food or air
tonsilar crypts
overlying epithelium invaginates; bacteria or particulate matter enters crypts, where they are trapped and destroyed
Peyer’s patches
clusters of lymphoid follicles in wall of distal portion of small intestine; also called aggregated lymphoid nodules
Peyer’s patches function
destroy bacteria, preventing them from breaching intestinal wall; generate “memory” lymphocytes
appendix
offshoot of first part of large intestine; contains a large number of lymphoid follicles
appendix functions
destroy bacteria, preventing them from breaching intestinal wall; generate “memory” lymphocytes
thymus
bilobed lymphoid organ found in inferior neck; extends into mediastinum and partially overlies heart
thymus function
functions as lymphoid organ where T cells mature
Stops growing during adolescence, then gradually atrophies
thymus
Thymus differs from other lymphoid organs in important ways
has no follicles bc it lacks B cells; doesn’t directly fight antigens
blood thymus barrier
keeps immature T lymphocytes isolated from any antigens to prevent premature activation
stroma
made up of epithelial cells, not reticular fibers; provide environment in which T lymphocytes become immunicompetent
