Module 4: Immune-Lymphatic System: Intro and Thymus

Question 1

Immune system consists of

Answer 1

lymphatic tissue, nodules, nodes, spleen, bone marrow, thymus

Question 2

point of lymphatic system

Answer 2

monitor body surfaces and internal fluid compartments and react to the presence of potentially harmful substances

Question 3

Lymphocytes

Answer 3

effector cells in the response of immune system to harmful substance

Question 4

3 lines of defence for mammals

Answer 4

1) Protective surface phenomena (first response)
- skin is protective, when skin fails (abrasion, burn, etc. other types of defence mechanisms are activated)

2) Non specific cellular responses (innate immunity)
- macrophages and neutrophils destroy pathogens in loose connective tissue after they have reached the epithelial surface. If this fails, #3 is activated

3) Specific immune responses (adaptive immunity)
- production of antibodies by lymphocytes that recognize specific characteristics of pathogen. Antibody binds to antigen to promote destruction

Question 5

cells of immune system can be found

Answer 5

disseminated throughout whole body as isolated cells, diffuse aggregations or within lymphoid organs (thymus lymph nodes, spleen)

Question 6

Lymphoid aggregations

Answer 6

found in tonsils and appendix

Question 7

Peters patches

Answer 7

lymphoid aggregations in small intestine

Question 8

Thymus

Answer 8

first lymphoid organ to appear
Most active in childhood
Begins to atrophy at puberty
In adults, it is mostly fat

Question 9

Function of thymus

Answer 9

maturation of T lymphocytes

Question 10

Thymus cortex

Answer 10

Outer, deeper staining area
Lymphocyte producing component of thymus
Epithelial reticular cells, nurse cells produce thymic hormones, thymosin (responsible for proliferation and differentiation of T lymph precursors)
Mature T lymphs leave organ through venules at corticomedullary border
Lymphatic vessels only exit the thymus, none enter

Question 11

Thymus structure

Answer 11

protected by capsule of fibrous connective tissue with septa which extends into matrix of organ and provide structural support
Septa divides thymus into lobules
Main support comes from underlying network of reticulin fibers

Cells arranged into 2 zones, Cortex and medulla

Question 12

Thymus medulla

Answer 12

inner, paler staining region
meshwork of epithelial cells (extensive pink-staining cytoplasm and large pale nuclei)
These cells termed thymic or Hassall’s corpuscles (appear in groups of keratinized epi cells that may represent degenerative phenomenon)
These cells unique to thymic medulla