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Lymphatic and immune systems

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


special lymphatic vessels in the small intestine that absorb dietay lipids that are not absorbed by the blood capillaries


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 _____


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


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.


-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.


- 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 __


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.

swollen, painful node responding to foreign antigen.


collective term for all lymph node diseases.

lymph nodes are common sites for__ they appear__

metastatic cancer; swollen, firm and usually painless.


-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

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