Lymphoid lab

Question 1

Name the lymphoid organs

Answer 1

• thymus
• lymph nodes
• spleen
• tonsils
• peyer’s patches & mucosa-associated lymphoid tissue`

Question 2

What is a primary lymphoid organ and give an example?

Answer 2

Organs where lymphocytes are formed and mature by providing an environment for stem cells to divide and mature into B and T cells

• The thymus is a primary lymphoid organ

Question 3

What are secondary lymphoid organs and list them

Answer 3

Are a series of filters that monitor the contents of extracellular fluid

Where lymphocytes are activated

• lymph nodes
• spleen
• tonsils
• peyer’s patches & mucosa associated lymphoid tissue

Question 4

Describe the general features of the thymus

Answer 4

• located in the anterior superior mediastinum
• consists of two lobes both of which have a central medulla and a peripheral cortex surrounded by an outer capsule
• thymus provides inductive environment for the development of T cells and selection of self-tolerant T cells

Question 5

Describe the general features of the spleen

Answer 5

• produces immune cells to fight antigens
• remove particulate matter and aged blood cells
• produce blood cells during fetal life

synthesises abs in white pulp

Question 6

What is white pulp?

Answer 6

Histological designation for regions of the spleen

consists entirely of lymphoid tissue

Question 7

Describe the general features of the lymph nodes

Answer 7

consists of lymphoid follicles in outer cortex, which surrounds the inner medulla on all sides except at the hilum, which makes the nodes bean shaped.

Question 8

What is the paracortex

Answer 8

immediately surrounds the medulla.

Unlike the cortex, contains an mixture of mature and immature T cells

Question 9

What is a sentinel lymph node?

Answer 9

The hypothetical first lymph node or group of nodes draining a cancer

Question 10

What is a lymph follicle?

Answer 10

dense collection of lymphocytes

Question 11

Describe the capsule of a lymph node

Answer 11

composed of dense irregular connective tissue with some plain collagenous fibers

capsule contains a rich blood supply

is thicker in some areas than others in an irregular pattern

Question 12

What is he subcapsular sinus?

Answer 12

The space between the capsule and the cortex, where lymph flows through

Question 13

Where are the T cells found in a lymph node?

Answer 13

deep cortex

Question 14

Where are B cells found in a lymph node?

Answer 14

outer cortex and medullary cords

Question 15

Describe the blood supply and drainage of the lymph nodes

Answer 15

• nodal vein
• nodal artery

= nodal vessels

enter/exit the hilum of the node

Question 16

What is Di George syndrome?

Answer 16

child born without a thymus

therefore no T cells and no cell mediated immunity

Question 17

Describe the flow of lymph through vessels

Answer 17

vessels have no valves

lymph flow aided by muscular movement that ‘milks’ lymph

Question 18

Describe mechanical filtration of lymph

Answer 18

settling tank of lymph node

rate of flow slows down in the subscapular sinus allowing filtrate to be removed from the lymph

Question 19

Describe biological filtration of lymph

Answer 19

phagocytosis by macrophages

Question 20

What histological sign is present in during an active lymphoid response?

Answer 20

presence of oval lymphoid nodules in the outer cortex

Question 21

What is a lymphoid nodule and why do they form?

Answer 21

B cell feature

• Ag enters node
• B cell with affinity will bind
• proliferation of B cells
• small > medium > large cells as they divide and get more cytoplasm

Question 22

Describe the histological features of a lymphoid nodule

Answer 22

• oval body
• light pole and dark pole
• germinal centre
• cap/carona of small lymphocytes

cap faces the source of foreign material

Question 23

Which layer of the appendix is lymphoid tissue found?

Answer 23

• bulk in submucosa

- some found in lamina propria

Question 24

Describe the histology of white pulp

Answer 24

• central arteriole adjacent to white pulp
• white when fresh, purple when stained
• T cells immediately around the arteriole
• B cell further out

Question 25

What is the time span for lymphoid nodules?

Answer 25

• appear for a few days during infection then begin to dissappear
• macrophages slower to leave, leaving a ‘reaction centre’

Question 26

Describe the epithelium of the tonsils

Answer 26

stratified squamous non-keratinised epithelium, typical of the mouth

Question 27

Describe the histology of tonsils

Answer 27

also contains skeletal muscle cells

Question 28

Which of the tonsils has distinct features?

Answer 28

Palatine tonsil contains tonsilar crypt

The crypt epithelium hugely infiltrated by lymphocytes = very difficult to see

crypt contains micro-organisms and sloughed off cells = allows lymphocytes to get good exposure to microorganism to amount a response

Question 29

Describe the histology of the thymus

Answer 29

contains partitions that breaks it into lobules

paler part = medulla
darker parts = cortex where lymphocytes are programmed

Question 30

How can you differentiate between a childs thymus and an adults?

Answer 30

• T cells activate in childhood

- thymus involutes and replaced by fatty tissue in adults

Question 31

Does the thymus engage in an immune response?

Answer 31

no - primary lymphoid organ