Organs of Immunity

Question 1

What is one of the main functions of the lymphoid system?

2

Answer 1

To enable lymphocytes to encounter antigens

It is here that adaptive immune responses are initiated

Question 2

What does the lymphoid system consist of?

3

Answer 2

Primary lymphoid organs

Secondary lymphoid organs

Lymphatic vessels

Question 3

List the parts of the primary lymphoid organs.

2

Answer 3

Bone marrow

The thymus

Question 4

What is a primary lymphoid organ?

Answer 4

A location where cells of the immune system are generated or mature

Question 5

How is bone marrow a primary lymphoid organ?

2

Answer 5

B and T lymphocytes are produced from stem cells in the bone marrow

B lymphocytes mature in the bone marrow

Question 6

How is the thymus a primary lymphoid organ?

Answer 6

T lymphocytes mature in the thymus

Question 7

What happens to B and T lymphocytes after they mature?

Answer 7

They accumulate in secondary lymphoid organs

Question 8

List the secondary lymphoid organs.

Answer 8

Lymph nodes

Tonsils

Appendix

Spleen

Peyer’s patches

Question 9

What is a secondary lymphoid organ?

Answer 9

A location in the body where immune responses can be initiated and organised

Question 10

What do all secondary lymphoid organs contain?

4

Answer 10

Germinal centres

T-cells

B-cells

Antigen presenting cells

Question 11

What are germinal centres

Answer 11

This is where mature B cells are activated/become plasma cells

Question 12

What connects the secondary lymphoid organs to the rest of the body?

Answer 12

A vast network of lymphatic vessels

Question 13

Where are peyer’s patches found?

Answer 13

They are found in the small intestine

Question 14

What are developing cells in the thymus called?

Answer 14

Thymocytes

Question 15

Describe the structure of the thymus.

4

Answer 15

It is an encapsulated organ

It consists of two lobes of glandular tissue

The lobes are divided into lobules by septae

Each lobule consists of a densely cellular cortex and a less cellular medulla

Question 16

How many lobes does a thymus have?

Answer 16

Two

Question 17

What divides the thymus lobes into lobules?

Answer 17

Connective tissue called septae

Question 18

Which part of the lobule is densely cellular?

Answer 18

The cortex which is on the outside

Question 19

Which part of the lobule is not densely cellular?

Answer 19

The medulla which is in the middle

Question 20

What can be found in the medulla of the thymus?

Answer 20

Hassall’s corpuscles

Question 21

What do Hassall’s corpuscles look like?

Answer 21

Rings in the medulla

Question 22

Describe the pathway of cells in the thymus.

3

Answer 22

Arterial vessels bring the undifferentiated lymphocytes to the cortex

The cells then migrate to the medulla while differentiating into mature T cells

T cells leave for the systemic circulation or the lymph nodes (by lymphatic vessels)

Question 23

What happens to 98% of thymocytes?

Answer 23

They are killed as they are either useless or potentially dangerous

Question 24

What happens to the thymus as a person gets older?

Answer 24

It becomes involuted

Question 25

what is involution?

Answer 25

The infiltration of the thymus by adipose tissue

Question 26

What do lymph nodes do?

Answer 26

They act as filters

Question 27

How do lymph nodes act as filters?

Answer 27

They contain a honeycomb structure of connective tissue filled with lymphocytes that destroy bacteria and viruses

Question 28

What happens to the lymph nodes when there is an infection?

Answer 28

They swell due to increasing numbers of lymphocytes

Question 29

How many lymph nodes does a person have?

Answer 29

Approximately 500-600

Question 30

Give five places where there are clusters of lymph nodes.

Answer 30

Underarms Groin neck Chest Abdomen

Question 31

How are lymph nodes shaped?

Answer 31

They are bean shaped

Question 32

What is a lymph node surrounded by?

Answer 32

A capsule

Question 33

What is found inside the capsule of a lymph node?

Answer 33

The fibrous capsule extends to form trabeculae

Question 34

What is the concave side of the lymph node called?

Answer 34

Hilum

Question 35

What attaches at the hilum of a lymph node?

Answer 35

The artery and vein

Question 36

What is the lymph node divided into? | 3

Answer 36

The outer cortex (B-cell zone) A paracortex (T cell zone) An inner medulla

Question 37

What is the B cell zone of the lymph node?

Answer 37

The cortex

Question 38

What is the T cell zone of the lymph node?

Answer 38

A paracortex

Question 39

How does lymph travel to a lymph node?

Answer 39

Via afferent lymphatic vessels

Question 40

Where does lymph drain into the lymph node?

Answer 40

In a space beneath the capsule called the subcapsular sinus

Question 41

How does lymph leave the lymph node?

Answer 41

Via the efferent lymphatic vessels

Question 42

What is found in the cortex of lymph nodes?

Answer 42

Lymphoid follicles

Question 43

What occurs in the lymphoid follicles?

Answer 43

Plasma cell activation and antibody production

Question 44

List the parts of a lymph node | 8

Answer 44

Cortex Paracortex Medulla Lymphoid follicles Hilum Capsule Subcapsular sinus Trabeculae