chapter 24 lymphatic system

lymphatic system

transports fluids and helps fight infections

what happens to excess interstitial fluid when leaked out of blood capillaries?

enters the lymph vessels

after entering the vessels the fluid is called?

lymph

• lymphatic vessels return the fluid to venous circulation

• if not removed it can accumulate and cause edema

lymphatic vessels transport?

dietary lipds

lymphatic capillaries

called lacteals absorb lipids in intestine

lymphoid organs

aid in production and maturation of lymphocytes

lymphatic system

generates immune response against antigens

lymphocytes

macrophages monitor body for foreign agents

• some of the cells produce antibodies that bind the pathogen

other lymphoid cells

• attach the antigen directly

• become memory cells to quickly attack the antigen if it appears again

lymphatic vessels network transport..

excess fluid back to the heart

lymph is carried through progressively larger vessels:

• lymphatic capillaries

• lymphatic vessels

• lymphatic trunks

• lymphatic ducts

lymphatic capillaries

are closed ended tubes interspersed among most blood capillary beds

• are not in red bone marrow and avascular tissue

• associated with the dural venous sinuses of the brain

lymphatic capillaries have overlapping..

endothelial cells that act as one-way entry flaps

• flaps are attached by anchoring filaments to nearby structures

lacteals

are specialized lymphatic capillaries located in the small intestine

• collect interstitial fluid as well as lipids and lipid-soluble vitamins

chyle

the lymph collected from gastrointestinal system

lymphatic capillaries merge to form..

lymphatic vessels

• they resemble small veins in that they have components of all three vascular tunics and possess valves

afferent lymphatic vessels

bring lymph to a lymph node

efferent lymphatic vessels

transport filtered lymph away from the lymph node

lymphatic trunks

form form merging lymphatic vessels

lymphatic ducts

form from the fusion of lymphatic trunks

right lymphatic duct

is deep to the clavicle and returns lymph at the junction of right subclavian and internal jugular veins

• it returns lymph form the right side of the head and neck, right upper limb, and the right side of the thorax

thoracic duct

the largest lymphatic vessel

• begins just inferior to the diaphragm as a rounded saclike structure called the cisterna chyli

• it collects lymph from most of the body (excluding the right lymphatic duct drainage)

• it passes through the diaphragm’s aortic opening and returns lymph into the junction between the left subclavian and internal jugular veins

lymphoid cells

perform an immune response

• some are antigen-presenting cells (APCs) - capable of presenting antigen to lymphocytes

lymphoid cell types

• macrophages

• dendritic cells

• lymphocytes

macrophages

monocytes that have left blood; engulf foreign substances and may act as APCs

dendritic cells

internalize antigens and are the main APCs

lymphocytes

most abundant lymphoid cells; three types of lymphocytes, each with a specific job in an immune response

there are three types of lymphocytes

• t-lymphocytes (t-cells)

• b-lymphocytes (b-cells)

• natural killer (nk) cells

  all three migrate through the lymphatic system and search for harmful antigens

T-lymphocytes

• make up about 70%-85% og body lymphocytes

• they express a plasma membrane coreceptor (“CD” followed by a number) than can recognize a particular antigen

There are two main groups of t-cells

• helper t-cells

• cytotoxic t-cells

helper t-cells

• oversee immune response

• contain the CD4 coreceptor and are referred to as CD4+ cells or T4 cells

• present antigens to other lymphoid cells

• secrete cytokines

cytokines

molecules that activate other lymphoid cells

cytotoxic t-cells

• contain CD8 coreceptor

• directly kill infected or tumor cells

• respond to one type of antigen only

• kill by secreting substances that cause unregulated entry into cell

• must be activated by helper t-cell

other types of t-cells..

• include memory t-cells (mount rapid response to previously encountered antigen)

• regulatory t-cells (suppress immune responses)

b-cells

• make up 15%-30% of body lymphocytes

• stimulate production of immunoglobulins (antibodies) against that antigen

b-cells activated by..

t-cells but can also be activated by independent of t-cells

• b cells then divide and become either plasma cell or memory b-cells

nk cells

• also called large granular lymphocytes

• small percentage of lymphocytes

• can kill a wide variety of infected cells and cancerous cells