W1 Haematopoietic System and Component Parts Part 2

Question 1

what are the primary lymphoid organs?

Answer 1

thymus and bone marrow (bursa of fabricus in birds) and maturation of T and B lymphocytes

Question 2

what are the secondary lymphoid organs?

Answer 2

spleen, lymph nodes, MALT/GALT, tonsils and adenoids - initiation of immune response

Question 3

what are the tertiary lymphoid organs?

Answer 3

ectopic lymphoid tissues that develop at sites of chronic inflammation in non-lymphoid organs

Question 4

what is the thymus?

Answer 4

an organ that provides environment for T cell development, it has lobes divided into lobules by trabeculae

Question 5

what parts do each lobe of the thymus have?

Answer 5

outer cortex and inner medulla

Question 6

what happens to thymocytes that are not selected?

Answer 6

they undergo apoptosis and are phagocytosed by macrophages

Question 7

what is a thymocyte?

Answer 7

an immune cell present in the thymus that undergoes transformation into a T Cell

Question 8

what is the major role of the spleen?

Answer 8

to survey the presence of foreign antigens in blood

Question 9

what is the spleen?

Answer 9

a secondary lymphoid organ that consists of a capsule with fibrous partitions (red and white fibrous pulp)

Question 10

what does the red pulp of the spleen do?

Answer 10

filters and removes damaged or aged red blood cells via phagocytosis by macrophages

Question 11

what is the role of white pulp in the spleen?

Answer 11

to bring lymphocytes together to mount immune responses against foreign antigens (B and T cells circulate in the pulp entering via terminal arterioles and leaving via blood vessels in the red pulp)

Question 12

where do T cells localise within (they interact with dendritic cells here)?

Answer 12

periarteriolar sheath (PALS)

Question 13

where do B cells localise (where they interact with specialised dendritic cells)?

Answer 13

in follicles

Question 14

what do B cells responding to antigens form? what happens here?

Answer 14

form germinal centres where they mature and differentiate

Question 15

blood components from capillaries enter tissues forming extracellular fluid that provides nutrients and gas exchange, what does this fluid drain into?

Answer 15

vessels called lymphatics

Question 16

what are lymph nodes?

Answer 16

small and bean shaped tissue aggregates at junctions of major lymph vessels, they are located within the lymphatic system to allow the surveillance of antigens and initiate the adaptive immune response

Question 17

what size are lymph nodes?

Answer 17

1-25mm, larger during infection

Question 18

what are the three parts of a lymph node?

Answer 18

cortex, paracortex and medulla (surrounded by a capsule)

Question 19

lymph carrying antigens and dendritic cells enter via what?

Answer 19

afferent lymphatics

Question 20

what do lymphocytes from the blood enter via?

Answer 20

high endothelial venules (HEV)

Question 21

do T cells migrate and localise in the paracortex or cortex?

Answer 21

paracortex (B cells in the cortex)

Question 22

lymphocytes migrate through the medulla and exit the node via what?

Answer 22

efferent lymphatics

Question 23

name three lymph nodes:

Answer 23

any three of:
submandibular
cervical
axillary
popliteal
inguinal

Question 24

what is MALT?

Answer 24

mucosal associated lymphoid tissue - diffusely distributed lymphoid tissues in lining of gastro. , resp. and urogenital tracts

Question 25

what is GALT and BALT?

Answer 25

GALT - gut-associated lymphoid tissue
BALT - bronchus associated lymphoid tissue

Question 26

what is GALT made up of?

Answer 26

peyer’s patches and isolated follicles in intestinal submucosa

Question 27

what are peyer’s patches?

Answer 27

aggregates of lymphocytes that are covered in specialised lymphoepithelium containing M cells

Question 28

do peyer’s patches have afferent or efferent lymphatics?

Answer 28

efferent

Question 29

antigens in the gut enter via M cells that then do what?

Answer 29

selectively take up particles and deliver them to lymphoid follicles - or they will be sampled by specialised dendritic cells which ‘reach’ into the gut lumen to sample anitgens

Question 30

what do the tonsil (waldeyer’s ring) and adenoids (pharyngeal tonsils) do?

Answer 30

survey the oropharyngeal and nasal cavities for foreign antigens

Question 31

what do harderian glands do?

Answer 31

survey the oculonasal region in birds

Question 32

what is the cecal tonsil?

Answer 32

a gut lymphoid tissue located in the large intestine of birds

Question 33

the appendix of dogs and cats contain a significant amount of lymphoid tissue suggesting it may function as what?

Answer 33

GALT