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chapter 21

Lymphatic and immune systems
STUDY
PLAY
Immune system
not an organ system but a population of cells that inhabit all of our organs and defend the bhody form agents of disease
a population of cells espcially concentrated in the true organ system-_________
lymphatic system
lymphatic system
network of organs and vein-like vessels that recover fluid, inspect it for diesease agents, activate immune responses, and return fluid to the bloodstream
function of the lymphatic system
fluid recovery, immunity, and lipid absorption
__-___ L/day of ___and about half of the _____ _____ enters lymphatic system and then returned to the blood
2-4; water; plasma protiens
lacteals
special lymphatic vessels in the small intestine that absorb dietay lipids that are not absorbed by the blood capillaries
lymph
the recoverd fluid, clear colorless fluid, similar to plasmabut much less protiens
lymphatic vessels
transport the lymph/fluid from interstial spaces (tissues) to the bloodstream.
lymphatic tissues
composed of aggregates of lymphocytes and macrophages that populate many organs in the body
lymphatic organs
defense cells are especiallly concentrated in these organs; nodes, tonsils, thymus, spleen
lymphatic capillaries
terminal lymphatics, penetrate nearly every tissue of the body, closed at one end, cells tethered to surrounding tissue by protien filaments, sacs of thin endothelial cells that loosely overlap each other
the gaps between cells are large enough to ___
allow bacteria and cells entrance to lyphatic capilary
Endo thelium creates valve-like flaps that ___ when interstitial fluid pressure is high, and ____ when it is low
open, close
large lymphatic vessels are composed of three layers: _______-endothelium and valves, ____ elastic fibers, smooth muscles, and ___ thin outer layer
tunica interna, tunica media, and tunica externa
Two collecting ducts are the ___ and the ___
right lymphatic duct, thoracic duct
right lymphatic duct
receives lymph from right arm, right side of head and thorax, empties into right sublavian vein
thoracic duct
receives lymph from below diaphragm, left arm, left side of head, neck and thorax, empties into left subclavian vein
the thoracic duct is ___ and ____ and bings as a prominent sac in the abdomen called the _____ ____
larger, longer, cisterna chyli
lymph flows under forces similar to those that govern venous return, except no _____
pump
lymph flows at ____ pressure and ____speed compaired to venous blood
low, slower
the lympth is moved along by _____ _____ of lymphatic vessels where stretching of vessels stimulates contractions
rhythmic contractions
____ aids the flow from abdominal to thoracic cavity and flow aided by ____ ____ ____
thoracic pump; skeletal muscle pump
_____ prevent backwards flow
valves
rapidly flowing blood in subclavian veins, _________lymph which explains why exercise increases lymph flow
draws in
natural killer (nk) cell
large lyphocytes that attack and destroy bacteria, transplanted tissue, host cells infected with viruses or have turned cancerous
nk cells are responsible for
immune surveillance
T lymphocytes (T cells)
mature in thymus to become immunocompetent
B lymphocytes (B cells)
activation causes proliferation and differentiation into plasma cells that produce antibodies.
Macrophages
-develop from monocytes.
-phagocytize tissue debris, dead neutrophils, bacteria, and other foreign matter.
-antigen presenting cells (APCs).
dendritic cells
-branched, mobile APCs found in epidermis, mucous membranes, and lymphatic organs.
-alert immune system to pathogens that have breached their surface.
reticular cells
-branched stationary cells that contribute to the stroma of a lymphatic organ.
-act as APCs in the thymus
lymphatic (lymphoid) tissue
aggregations of lymphocytes in the connective tissues of mucous membranes and various organs.
diffuse lymphatic tissue
-lymphocytes are scattered, rather than densely clustered in mucous membranes and connective tissue of many organs.
-prevalent in body passages open to the exterior.
-respiratory, digestive mucosa, urinary, and reproductive tracts.
-mucosa-associated lymphatic tissue (MALT)
lymphatic nodules (follicles)
-dense masses of lymphocytes and macrophages that congregate in response to pathogens.
-constant feature of the lymph nodes, tonsils, and appendix.
-Peyer patches
Peyer patches
dense clusters in the ileum, the distal portion of the small intestine
Lymphatic organs anatomy
-have well-defined anatomical sites.
-have connective tissue capsule that separates the lymphatic tissue from neighboring tissues.
primary lymphatic organs
-red bone marrow and thymus
-site where T and B cells become immunocompetent
immunocompetent .
able to recognize and respond to antigens
secondary lymphatic organs
-lymph nodes, tonsils, and spleen
-immunocompetent cells populate these tissues
Red Bone Marrow
-red bone marrow is involved in hemopoiesis (blood formation) and immunity.
as blood cells mature in the red bone marrow...
they push their way through the reticular and endothelial cells to enter the sinus and flow away in the blood stream.
thymus
- member of the endocrine, lymphatic, and immune systems.
-houses developing lymphocytes. (T-cells)
-secretes hormones regulating their activity.
thymus anatomy
bilobed organ located in superior mediastinum between the sternum and aortic arch
the lifetime of the thymus
Very large in fetus, after age 14 begins degeneration or involution (in elderly most fatty and fibrous tissue)
trabeculae (septa) of thymus
divide the gland into several lobes.
lobes of the tymus have cortex and medulla populated by
T lymphocytes
reticular epithelial cells seal off cortex from medulla forming ___which____
blood-thymus barrier.
-isolates developing T lymphocytes from foreign antigens
the thymus produces signaling molecules__.__,__,__, and __
thymosin, thymopoietin, thymulin, interleukins, and interferon.
T -cells become immunocompetent in the __
thymus
lymph nodes
- the most numerous lymphatic organs.
two functions of the lymph nodes
-cleanse the lymph
-act as a site of T and B cell activation
anatomy of lymph nodes
-elongated, bean shaped structure with hilum.
-enclosed with fibrous capsule with trabeculae that divide interior into compartments containing stroma of reticular fibers and reticular cells.
-parenchyma divided into cortex and medulla.
-several afferent lymphatic vessels lead into the node along its convex surface.
the germinal centers of lymph nodes
where B cells multiply and differentiate into plasma cells.
lymph leaves the nodes though
one to three efferent lymphatic vessels that leave the hilum.
Lymph Node Contain
-reticular cells, macrophages that phagocytize foreign matter.
-lymphocytes to respond to antigens.
-lymphatic nodules- germinal centers for B-cell activation.
lymphadenopathy - collective term for all lymph node diseases.
lymphadenitis
swollen, painful node responding to foreign antigen.
lymphadenopathy
collective term for all lymph node diseases.
lymph nodes are common sites for__ they appear__
metastatic cancer; swollen, firm and usually painless.
tonsils
-patches of lymphatic tissue located at the entrance to the pharynx
-guard against ingested or inhaled pathogens.
each tonsil is covered with __ and have deep pits called __ lined with lymphatic nodules where pathogens enter in and encounter lymphocytes (tonsillitis /tonsillectomy).
epithelium; tonsillar crypts
three main sets of tonsils
palatine tonsils, lingual tonsils, pharyngeal tonsil (adenoid)
palatine tonsils
pair at posterior margin of oral cavity.
most often infected