2: chapter 20 Flashcards
what is the function of the lymphatic system?
returns 15% of fluids that leaked from blood vessels back to the blood
what does the lymphatic system consists of? (3 things)
- network of lymphatic vessels (lymphatics)
- lymph- fluid in vessels
- lymph nodes-cleanse lymph
what do lymphoid organs and tissues do ?
- provide a structural basis of immune system
- house phagocytic cells and lymphocytes
what are examples of lymphic organs/tissues?
- spleen
- thymus
- tonsils
- lymph nodes
- lymphoid tissues, nodules, and MALT
What are lymphatic vessels also known as
lymphatics
what is the function of he lymphatic vessels/lymphatics
- return interstitial fluid and leaked plasma proteins back into the blood
how much interstitial fluid and leaked plasma proteins do you lose a day?
3L
once interstitial fluid enters lymphatics what is it then called?
lymph
what direction does lymph flow?
toward the heart
what kind of system are the lymphatic vessels?
one way system
what do lymph vessels/ lymphatics include?
- lymphatic capillaries
- collecting lymphatic vessels
- lymphatic trunks and ducts
what do lymphatic trunks and ducts do?
return to the subclavian vein
lymphatic capillaries are similar to blood capillaries except:
- very permeable
- endothelial cells overlap loosely to form one way minivalves
- increased ECF volume opens minivalves
how do pathogens travel throughout the body?
lymphatics
*what are lymphatic capillaries absent from?
- bones
- teeth
- bone marrow
- CNS
lymphatic vessels are similar to veins except:
- thinner walls
- more internal valves
- anastomose more frequently
how many ducts can lymph be delivered into?
- 2
- right lymphatic duct
- thoracic duct
how does lymph deliver into the right lymphatic duct
- drains right upper arm and right side of head and thorax
- smaller pathway
how does lymph deliver into the thoracic duct
- thoracic duct arises as cisterna chyli; drains rest of body
- larger pathway
where is lymph emptied and where does it reenter?
lymphatic ducts empty lymph into venous and reenters into the subclavian vein
what are lymphocytes known as?
the warriors of the immune system
where are lymphocytes from
red bone marrow
what do lymphoid cells mature into?
- T cells (T lymphocytes)
- B cells (B lymphocytes)
what do T cells and B cells protect against
antigens
what is an antigen
- anything the body perceives as foreign
- examples: bacteria, bacterial toxins, viruses, mismatched RBC’s, cancer cells
what is the function of T cells
- manage immune system
- “mark for destruction”
- attack and destroy infected cells
what is the function of B cells
- produce plasma cells (which secrete/produce antibodies)
what do plasma cells secrete/ produce
antibodies
what do macrophages do
- fight foreign substances
- help activate T cells
what do dendritic cells do
- capture antigens and deliver them to lymph nodes
- activate T cells “later”
what do lymphoid tissues do
- houses and provides a grow site for lymphocytes
- surveillance for lymphocytes and macrophages
what kind of tissue is lymphoid tissue
reticular connective tissue - loose
what does lymphoid tissue diffuse
diffuses lymphoid tissue of lymphoid cells and reticular fibers in every body organ
describe lymphoid follicles
solid spherical bodies of tightly packed lymphoid cells and reticular fibers
where are lymphoid follicles located
- germinal centers of proliferating B cells
- may form part of larger lymphoid organs
- isolated aggregations of Peyer’s Patches, ileum, small intestine, and appendix
what are lymphoid follicles also known as
nodules
where are lymph nodes located
- embedded in connective tissue
- clusters along lymphatic vessels
- near body surface in inguinal, axillary, and cervical regions
*where are lymph nodes highly concentrated
- cervical
- axillary
- inguinal
what are the functions of the lymph nodes
- filter lymph- destroy microorganisms and debris
- immune system activation’s- activated and mount attack against antigens
what are some antigens the lymph nodes attack
- bacteria
- viruses (intracellular parasite)
- fungi
- protozoans (large) - (mallard, giardia)
what is the structure of a lymph node
- vary in shape and size but most are bean shaped
- has a capsule and trabeculae
what are the two histologically distinct regions of a lymph node
- cortex (outer) (B cells)
- medulla (inner)
what does the cortex of a lymph node contain
- follicles with germinal centers, heavy with dividing B cells
where does T cells circulate continuously
among blood, lymph nodes, and lymph
describe the medullary cord structure of a lymph node
extend inward from the cortex
what is contained in the medullary cords
- B cells
- T cells
- plasma cells
what is the largest lymphoid organ
spleen
what is the spleen served by
splenic artery and vein
where does the splenic artery and vein enter and exit
at the hilum
what are the functions of the spleen
- site of lymphocyte growth and immune surveillance and response
- cleanses blood of aged cells and platelets, macrophages remove debris
what are some additional features of the spleen
- stores breakdown products of RBC’s (ex. iron)
- stores blood platelets
- site of fetal erythrocyte production (makes RBC’s for fetal)
- contains lymphocytes, macrophages, and erythrocytes
what are the structures of the spleen?
- white pulp
- red pulp
what structure makes up majority of the spleen
red pulp
where is white pulp found?
- around central arteries
- sometimes veins
what is white pulp mostly consisted of
lymphocytes
when is the functions of the thymus most important
early in life
where is the thymus located
found in neck and partially overlies the heart
when is the thymus most active?
during childhood
does the thymus increase or decrease in size?
increase
when does the thymus stop growing?
during adolescence and gradually atrophies
does the thymus have any function after it atrophies
still produces immunocompetent cells, slowly
what are most thymic cells
lymphocytes
what does the cortex contain
rapidly diving lymphocytes and scattered macrophages
what is the thymic corpuscle involved in
regulatory T cell development
how does the thymus differ from other lymphoid organs
- contains no follicles
- does not directly fight against antigens
- functions strictly in T cell maturation
why doesnt the thymus contain follicles
because it lacks B cells
what is the thymus known as
“bootcamp”
“training”
what does it mean when T lymphocytes become immunocompetent
- fully trained
- ready for deployment
what is MALT
mucosa- associated Lymphoid tissue
where is MALT located
in lymphoid tissues throughout the body
what does MALT do
protects from pathogens
what are the largest collections of MALT
- Tonsils
- peyers patches
- appendix
where are some other examples of where MALT is located
- respiratory organs
- genitourinary organs
- rest of digestive tract
what is the simplest lymphoid organ
tonsil
what are the tonsils
- palatine (back of throat)
- lingual (tongue)
- pharyngeal (nasopharynx)
- tubal (auditory tubes)
what is the function of tonsils
gather and remove pathogens in the air and food
what do tonsils contain
follicles with germinal centers
what are crypts
caves/traps
what is the function of crypts
- trap and destroy particulate matter
- allow immune cells to build memory for pathogens
where is the peyers patches located
- in wall of distal portion of small intestine (ileum)
- similar structures are found in the appendix
what is the function of peyers patches and appendix
- destroy bacteria
- prevent bacteria from breaching intestinal wall
what happens to the number of lymphocytes at and after birth
- after: high numbers of lymphocytes
- at birth: poor
