Lymphatic System

Question 1

functions of lymphatic system (3)

Answer 1

• fluid balance: 10% fluid released into tissues by capillaries drains back through lymphatic vessels
• filtration: filters out antigens
• immune response: specific (adaptive) defense; produces, matures, maintains lymphocytes

Question 2

lymph

Answer 2

interstitial fluid that is drained from the tissues

travels in vessels (lymphatics)

Question 3

lymphatics

Answer 3

lymph vessels that direct the collected lymph into the venous system

Question 4

primary lymphoid organs and tissue

Answer 4

bone marrow - b cells
thymus gland - t cells

produce and mature lymphocytes

Question 5

secondary lymphoid organs and tissue

Answer 5

spleen
appendix
lymph nodes
tonsils
MALT

-activate lymphocytes - filtration and immune response

Question 6

clonal proliferation

Answer 6

activated and sensitized to attack specific foreign antigen, give multiple copies of activated tissue

Question 7

lymph capillaries (terminal lymphatics)

Answer 7

• closed-end structures
• composed of overlapping endothelial cells with incomplete basement membrane
• overlapping allows for larger openings than cardiac, allows large solutes (proteins, viruses, cells) into lymph
• anchoring filaments (microfilament like fibers and elastin fibers that connect to ECM)

Question 8

collecting lymphatics

Answer 8

• larger lymphatic vessels are like veins in structure but thinner walls
• all have overlapping endothelium and incomplete basement membrane
• larger vessels have thin layer of smooth muscle and an adventitial layer
• MANY valves - at high risk for backflow

Question 9

2 ways lymphatics exist

Answer 9

superficial vessels in areolar connective tissue
or
deep lymphatics with cardiovascular support to muscle and other organs

Question 10

how does lymphatic circulation begin

Answer 10

lymph capillaries filtering lymph from interstitial fluid

-trunks drain into one of 2 collecting ducts (right or left (thoracic)

Question 11

right lymphatic duct

Answer 11

collects from right side of body superior to diaphragm

Question 12

thoracic (left) lymphatic

Answer 12

collects from left side above diaphragm and entire lower body
more than right lymphatic

Question 13

how does the lymphatic system return fluid to the venous circulation

Answer 13

through connections to subclavian veins

Question 14

cisterna chyli

Answer 14

where all lymphatic from lower body is drained into - lower limbs and abdominopelvic drained here

Question 15

primary lymphatic organ that receives immature T cell lymphocytes from the bone marrow

Answer 15

thymus

Question 16

thymus structure

Answer 16

• fibrous protective capsule where internal extensions (septa) divide the gland into lobules
• each lobule arranged with an outer cortex layer and an inner medulla

Question 17

what does the cortex of the thymus contain

Answer 17

thymic epithelial cell (TEC) aggregates that regulate T cell maturation

• TEC act to form thymic blood barrier

Question 18

process of all immature T cells

Answer 18

enter through cortex, undergo 2 step selection process, if successful then they leave through the medulla to enter circulation

Question 19

journey through the thymus is…

Answer 19

rough - about 90% do not make it through the thymus at the end of selection

Question 20

immature T cells enter the thymus cortical layer as

Answer 20

double negative cells - do not possess CD4 or CD8 receptors

Question 21

mhc II

Answer 21

cd4

t helper cells

Question 22

mhc I

Answer 22

cd8

cytotoxic t cells

Question 23

exposure to signaling from thymic hormones results in

Answer 23

double positive cells

have both cd4 AND cd8

Question 24

as t cells migrate through the cortex they show binding affinity for

Answer 24

either mhc I or mhc II

Question 25

cells that fail to bind in thymus

Answer 25

are ignored and allowed to die

Question 26

negative selection

Answer 26

as T cells migrate to the medulla, exposed to antigens and self-markers - any that bind with high affinity are subject to apoptosis - they cannot tolerate "self" - intolerant cells are selected against to protect body from autoimune responses - cells that survive go into circulation

Question 27

bone marrow

Answer 27

b cells do not do positive selection, do something similar to negative selection - ensure they will tolerate self - go through maturity in bone marrow - once released go to secondary organs

Question 28

what is spleen composed of

Answer 28

lymphoid tissue but not served by any lymph vessels

Question 29

splenic artery

Answer 29

enters at hilium, branches, and capillaries release the blood into sinuses NOT a closed circuit of vessels in spleen

Question 30

how is the spleen protected

Answer 30

connective tissue capsule | composed of red and white pulp

Question 31

red pulp

Answer 31

has the sinuses and a reticular fiber network RBC that survive the distortion of the network return to circulation through splenic vein -contains high concentration of RBC and macrophages and scattered lymphocytes

Question 32

what does the spleen act as during hemorrhage

Answer 32

reservoir spleen holds less than 150cc blood

Question 33

white pulp

Answer 33

contains lymphoid tissue and has high concentration of B and T lymphocytes

Question 34

macrophages in sinuses

Answer 34

recycle old RBCs that rupture when passing through reticular network

Question 35

lymphocytes in red pulp

Answer 35

screen for foreign antigens and recruit additional lymphocytes from the white pulp

Question 36

where can you find a high concentration of lymph nodes

Answer 36

throat, GI, groin | places where you are more likely to get an infection

Question 37

lymph node organization

Answer 37

more organized than red or white pulp, it has follicles subcapsule: for afferent vessel bringing interstitial fluid connective tissue forming trabeculae - give follicles outer area: cortex: all follicles have germinal areas - naive b and t cells - produce clones of themselves here goes into medullary area, comes out efferent vessels

Question 38

flow through lymph nodes

Answer 38

- afferent vessels direct lymph to node - lymph enters subcapsular sinus- macrophages start antigen processing - antigen presented to unsensitized b cells in germinal layer of cortex - lymph flows to deep cortex and exposed to T cells - lymph enters medullary sinus which contains medullary cords containing plasma cells - fluid exits through efferent vessels nodes are filtering system for immune defense

Question 39

MALT

Answer 39

- lack a protective fibrous capsule - exist as aggregates or nodules of lymphoid tissue in areolar connective tissue -nodules concentrated in regions susceptible to pathogen entry

Question 40

examples of MALT

Answer 40

tonsils peyer's patches appendix

Question 41

2 types of immunity

Answer 41

innate and acquired

Question 42

physical barriers in innate immunity

Answer 42

``` skin mucous membranes saliva flushing action of tears and urine stomach acid ``` stop infection before it enters the body